FIELD-TRIALS IN 1903
The extended series of shop tests which had occupied a considerable
portion of the late winter and early spring of 1903 had demonstrated
the following facts: First, with the aerodrome mounted on the
launching car, a propeller thrust of from 450 to 475 pounds could
be maintained indefinitely by the engine, and even when the engine
was delivering its full power to the propellers, the vibration was
so small as to cause no apprehension that the wings and rudder would
be made to vibrate sufficiently to produce undue strains in them.
Second, with the aerodrome suspended from the ceiling by springs
at the points at which the wings would be attached, the vibration
produced by the engine developing it’s full power was even less than
when the machine was mounted on the launching car and there was,
consequently, even less cause for concern that the wings and rudder
might be set in vibration when the machine was free in the air.
Third, the engine could be depended upon to deliver something over
52 horse-power when the five cylinders were working properly, and
even with one cylinder not working, but acting as a dead load against
the others, approximately 35 horse-power could be developed, while
with two cylinders not working at all, the three which were working
would deliver about 25 horse-power. Therefore, even assuming that two
of the five cylinders might become deranged during a flight, there
should still be sufficient power to propel the machine. These tests,
some of which had been witnessed by members of the Board of Ordnance
and Fortification, clearly demonstrated that the time had arrived
when it was safe to give the aerodrome a test in free flight. The
machine itself together with all its appurtenances and much extra
material for repairs in case of breakages, which previous experience
had shown to be almost certain, was accordingly taken from the shop
and placed on the house-boat preparatory to taking it down the river
to the point opposite Widewater, Va., which had already been selected
as the “experimental ground.”
Owing to the limited size of the shops it had been impossible to
place the wings and rudder in their proper positions on the aerodrome
and determine its balancing in a way similar to that practiced with
the models. The approximate settings for the wings and rudder had,
however, been determined by calculation from the data obtained in the
test of the quarter-size model, so that it remained only to place the
wings and a weight to represent the rudder actually on the machine
in the large space of the house-boat (which, however, was not large
enough to permit the rudder to be assembled along with the wings),
and thus check the balancing previously determined by calculation.
There were very [p256] few appurtenances which could be shifted in
balancing the aerodrome, but the proper disposition of weight had
been so accurately determined by calculation that the floats, which,
as will be seen from the various photographs, were merely cylindrical
tanks with pointed ends, and of a sufficient capacity to cause a
displacement great enough to float the aerodrome when it came down
into the water, proved sufficient ballast for shifting the center of
gravity to its proper point. The flying weight of the aerodrome was
830 pounds,[47] including the weight of the writer, which was 125
pounds. The total area of the wings or supporting surfaces was 1040
square feet, or the ratio of supporting surface to weight was 1.25
square feet per pound, which is the same as .8 pound per square foot.
After the balancing of the large aerodrome had been completed on the
house-boat, and everything else got in readiness as far as could be
done before actually arriving at the point at which the test was to
be made, the house-boat was towed down the river on July 14, 1903,
and fastened to its mooring buoy, which had been placed in the middle
of the river at a point practically opposite Widewater, Va., and
approximately forty miles from Washington. See Coast-Survey Chart,
Plate 85.
Sleeping quarters for the force of eight workmen and the regular
soldier from the United States Army, who had been detailed as a
special guard, had been provided on the boat, but owing to the lack
of space it had been found impracticable to arrange proper cooking
facilities on the boat, and it had been found necessary to arrange
to transport the workmen to Chopawamsic Island, near Quantico, Va.,
for their meals. It had been planned to use the twenty-five-foot
power launch for this purpose, but owing to the heavy storms which
became quite frequent soon after the house-boat was taken down the
river, it was found that the small launch was not sufficient, and
it was necessary to employ a tug-boat and keep it stationed there
at all times. This added very considerably to the expense of the
experiments, as the hire of this one tug-boat very nearly equalled
the pay-roll of the workmen, and while it was not expected that the
stay down the river would be so greatly prolonged as afterwards
proved the case it was felt certain that minor delays were sure to
occur and the experiments would at the very least require several
weeks.
[Illustration: PL. 85
LOCATION OF HOUSE BOAT IN CENTER OF POTOMAC RIVER, JULY 14, 1903
FROM SHEET NO. 3, U. S. COAST AND GEODETIC SURVEY CHART OF POTOMAC
RIVER, ISSUE OF 1882 SCALE 1 1-16 INCH TO STATUTE MILE]
Had it been possible to foresee the great delay which finally
occurred before the large aerodrome was actually launched, and the
great expense arising from the necessity of maintaining one or
more expensive tug-boats constantly, it is very certain that an
experimental station nearer Washington would have been selected,
even though the nearer places on the river which were available
were much less suitable, both on account of the river being much
narrower and the traffic very much heavier. In fact, at the time
that the house-boat was taken down the river on July 14, with the
expectation that the experiments with the [p257] large aerodrome
would certainly be concluded within four weeks, the expenses of the
work, which had been met from the Hodgkins Fund of the Smithsonian
Institution since the original allotment from the Board of Ordnance
and Fortification was exhausted more than a year previously, had
already made such heavy drafts on this fund that Mr. Langley was most
reluctant to draw further on it, even to the extent which seemed
necessary to meet the expenses of a month of “field-work.”
Before making the tests of the large aerodrome, it was intended to
give the quarter-size model a preliminary trial to test the balancing
which it was proposed to use on the large machine. For this test it
was planned to employ the small launching apparatus mounted on top
of the small house-boat, which had been used in the experiments with
the steam-driven models Nos. 5 and 6 in 1899, and later with the
quarter-size model in 1901. However, after arriving down the river,
it was found that the small house-boat which had been anchored at
Chopawamsic Island since the experiments in 1901 had deteriorated
to such an extent that it was unsafe to take it out into the river.
The launching apparatus for the model was, therefore, removed from
it and placed on the turn-table of the large house-boat, alongside
the launching track for the large machine. After completing this
transfer of the model-launching apparatus everything was thought to
be in readiness for a test of the quarter-size model, but upon making
a shop test of the model to make sure that its engine was working
properly, it was found impossible to get it to work at all. A few
explosions could be obtained once in a while, but very irregularly.
After spending considerable time in trying to locate the difficulty,
it was found that the commutator which distributes the high-tension
sparking current to the proper cylinder at the proper time was
short-circuited. This commutator had been made of “insulating fibre”
and had never caused any previous trouble. It was now found, however,
that the very damp atmosphere which had been experienced during the
preceding two weeks, when the fog for a large portion of the time
was so heavy that objects at a short distance across the water could
not be seen, had caused the moisture to penetrate the fibre and thus
destroy its insulating qualities. After much trouble some vulcanite
and mica were secured and a new commutator made to replace the fibre
one, and, then, after some minor difficulties had been remedied, the
engine for the model was got into good condition again. After getting
satisfactory shop tests on the model aerodrome, and having everything
in readiness for a flight, it was necessary to wait many days before
the weather was calm enough for a test. However, on August 8 the
weather quieted down and the model was launched at 9.30 a. m. into a
wind blowing about 12 miles per hour from E. SE.
Referring to Plate 86, which shows the quarter-size model mounted on
its launching car on top of the large house-boat, and which was taken
only a few [p258] minutes before the model was actually launched,
it will be noted that a board (‹A›) projects from the front of the
launching car. This board, which is mounted in a false floor of the
launching car, is so arranged that when it strikes the two blocks
(‹B›) at the end of the track it is driven backward in the car
against the triggers which prevent the uprights (‹D›), supporting
the aerodrome, from being folded down against the floor. When this
board strikes the triggers it releases them and the springs (‹C›),
which in this case were rubber bands, immediately fold the vertical
posts or uprights (‹D›) against the brace posts (‹E›), which are
immediately folded down flat against the floor of the car through
the action of the spring hinges, by which they are connected to it.
These uprights (‹D›), which support the aerodrome at the front and
rear, respectively, are not released until a fraction of a second
after the release of the clutch hook (‹F›), which is attached to
the middle upright (‹G›), and which, grasping the lower pyramid,
holds the machine down firmly against the uprights (‹D›) previously
referred to. In order to prevent the possibility of the aerodrome
being released prematurely while the car is held at the extreme
rear end of the track by the hook (‹H›), a steel pin (‹J›), which
can just be seen in the photograph, is pushed through a hole in the
board (‹A›), and into a hole in a cross-member on the bottom of the
car, thus holding the board in its proper position. After the engine
is started up one of the mechanics who has assisted in starting it
is under orders to remove the pin at the word “Ready,” and at the
word “Go” the other mechanic who has assisted in starting the engine
is under orders to release the hook (‹H›), and thus allow the car
to dash down the track. In the experiment on August 8 the mechanic
failed to remove the pin (‹J›) at the proper time, and it was only
after the machine had been released and started down the track that
it was seen that the pin had not been removed. It was then, however,
too late to stop it, so the car dashed down the track. Although the
striking of the board against the blocks caused the pin to split
the board to pieces, the launching apparatus worked perfectly and
the aerodrome started off on a perfectly even keel, the propellers
revolving at an exceedingly high rate of speed. The aerodrome flew
straight ahead for a distance of 350 feet, when it began to circle
towards the right, descending slightly as it circled. Upon completing
a quarter circle it again began to rise, flying straight ahead until
it had gone a similar distance, when it again lost headway, but
before it reached the water the engine increased its speed and the
aerodrome again rose. When the engine slowed down for the third time,
however, the aerodrome was not many feet above the river, so that
before the engine regained its normal speed the aerodrome touched the
water with its propellers still revolving, but very slowly. While
the total distance covered was only about 1000 feet, and the time
that it was actually in the air 27 seconds, yet in this brief time
it had served the main purpose for which it had been built, which
was to find out if the balancing of [p259] the large aerodrome,
which had been determined by calculation from the results obtained
with the steam-driven models, was correct. For it was assumed that
if the quarter-size model, which was an exact counterpart of the
large machine, should fly successfully with the same balancing as
that calculated for the large one, the large one could reasonably
be expected to act similarly. It was at first thought best to make
another test with the model immediately after recovering it from the
water, but by the time it could be brought into the house-boat and
the water which had got into the engine cylinders could be removed
and the engine made to work properly quite a strong wind had sprung
up and rendered further tests of the model on this day impossible.
If the launching track for the small machine could have remained
on the top of the boat without interfering with the completion of
the preparations for testing the large machine, it would have been
left there and other tests made with the model when the weather was
suitable, but as this could not be done without interfering with the
work on the large machine, and the delays with the model had already
been so great, the small track was immediately removed and the model
stored away in the house-boat for possible later tests.
At the first it was impossible to account for the engine on the
model running so irregularly and slowing down so soon after it was
launched, as it was felt very certain that the cylinders could not in
so short a time, and with the aerodrome actually moving through the
air, have heated up sufficiently to cause it. After a while, however,
one of the workmen volunteered the information that in his zeal to
fill the fuel tank completely so as to insure a long flight, he had
caused the tank to overflow so that some of the gasoline had run into
the intake pipe, and that he had noticed gasoline dripping from the
intake pipe as the machine went down the track. This excess gasoline
in the intake pipe had caused the mixing valve which controls the
quality of the explosive mixture to be improperly set, so that it
would not furnish the proper mixture when the fuel was supplied in
the proper way by the carburetor, and consequently when this excess
gasoline had evaporated, the mixture furnished to the engine was
not proper, and it consequently slowed down, there being no human
intelligence on board to correct the adjustment of the mixing valve.
A series of seven photographs of this flight of the quarter-size
model is given in Plates 87 to 93. Plate 87, taken with a kodak from
the tug-boat stationed several hundred yards directly ahead of the
house-boat, shows the machine in full flight heading directly for
the tug-boat. Although the aerodrome was about fifteen or twenty
feet higher above the level of the water than the camera, still, at
the considerable distance from which the photograph was taken, this
view would not show so much of the under side unless the machine had
been pointing upward. The photograph also proves very clearly that
at the time it was taken the machine had certainly not dropped at
all below the level [p260] at which was launched. In Plate 88 the
camera was unfortunately not well aimed, and only the front guy-post,
bearing points, float and bowsprit are visible, besides the blur of
the propellers, which, it will be noted, were moving very rapidly.
The camera with which this and the succeeding plates were taken was
one of the two special telephoto cameras belonging to the Zoological
Park, but built in the course of the aerodromic work and used where
especially rapid shutters were needed. As the shutters on these
cameras give an exposure of only 1/500 of a second, and consequently
are sufficiently rapid to show the individual feathers in a rapidly
moving bird’s wing, any distortion of the machine in flight would
certainly have been shown, but, as will be seen from the later
photographs, no distortion of any kind occurred, both the surfaces
and the framework remaining in a perfectly straight condition. Near
the bottom of Plate 88 is the tug from which Plate 87 was taken,
and a careful inspection of Plate 87 shows two persons standing on
the roof of the house-boat, below the upper works, the gentleman on
the left being Mr. Thomas W. Smillie, the official photographer of
the Smithsonian Institution, who took all of the photographs except
Plate 87, and, as stated above, used therefor the special telephoto
cameras with the rapid shutters. Plate 89 is an exceedingly good
view, and shows the propellers revolving very rapidly while Plates
90, 91 and 92 show very clearly that the speed of the propellers had
greatly decreased between the successive photographs. Plate 93 shows
the aerodrome shortly after it touched the water and had been almost
completely submerged, in spite of its floats, by the very strong tide
which was running. Though these plates show all that photographs
can, they give no adequate idea of the wonder and beauty of the
machine when actually in flight. For while the graceful lines of the
machine make it very attractive to the eye even when stationary,
yet when it is actually in flight it seems veritably endowed with
life and intelligence, and the spectacle holds the observer awed and
breathless until the flight is ended. It seems hardly probable that
anyone, no matter how skeptical beforehand, could witness a flight
of one of the models and note the almost bird-like intelligence with
which the automatic adjustments respond to varying conditions of the
air without feeling that, in order to traverse at will the great
aerial highway man no longer needs to wrest from nature some strange,
mysterious secret, but only, by diligent practice with machines of
this very type, to acquire an expertness in the management of the
aerodrome not different in kind from that acquired by every expert
bicyclist in the control of his bicycle.
[Illustration: PL. 86
QUARTER-SIZE MODEL AERODROME MOUNTED ON LAUNCHING-CAR]
[Illustration: PL. 87
QUARTER-SIZE MODEL AERODROME IN FLIGHT, AUGUST 8, 1903]
[Illustration: PL. 88
QUARTER-SIZE MODEL AERODROME IN FLIGHT, AUGUST 8, 1903]
[Illustration: PL. 89
QUARTER-SIZE MODEL AERODROME IN FLIGHT, AUGUST 8, 1903]
[Illustration: PL. 90
QUARTER-SIZE MODEL AERODROME IN FLIGHT, AUGUST 8, 1903]
[Illustration: PL. 91
QUARTER-SIZE MODEL AERODROME IN FLIGHT, AUGUST 8, 1903]
[Illustration: PL. 92
QUARTER-SIZE MODEL AERODROME IN FLIGHT, AUGUST 8, 1903]
[Illustration: PL. 93
QUARTER-SIZE MODEL AERODROME AT END OF FLIGHT, AUGUST 8, 1903]
In describing this flight immediately after it was made, Professor
John M. Manly, who took the photograph shown in Plate 87, said: “The
flight of the small aerodrome was an event which all who saw it will
remember for the rest of their lives. We were, of course, in a state
of considerable nervous excitement and tension, for, after weeks
of delay from high winds, rains, and [p261] other uncontrollable
causes, at last we had a day ideally suited to the test. This was,
to be sure, not the great test, the final test, the test of the
man-carrying flyer, but it was felt by all to be of almost equal
importance, for if the balancing of the small aerodrome was correct,
the large one would maintain its equilibrium, and the problem of
human flight would be solved practically as well as theoretically.
That the weather was now favorable for the test filled us with
excitement. Again and again the favorable moment had seemed to
come, and had gone again before we could make ready for it. The
aerodrome was rapidly carried to the upper works of the house-boat
and the observers and helpers went hastily to their positions. The
large tug-boat was stationed directly ahead, almost in the line of
flight, and about a mile from the house-boat. Signals of readiness
were exchanged, and with every sense astrain we awaited the supreme
moment. The rocket gave the starting signal, and instantly there
rushed towards us, moving smoothly, without a quiver of its wings,
with no visible means of motion and no apparent effort, but with
tremendous speed, the strange new inhabitant of the air. Onward it
moved, looking like a huge white moth, but seeming no creature of
this world, not only on account of its size, its ease of movement and
its wonderful speed, but also because of its strange, uncanny beauty.
It seemed visibly and gloriously alive as it advanced, growing
rapidly larger and more impressive. Straight at us it came, and for
a moment there was a wild fear that it would come right on and crush
itself against the ponderous tug-boat. There was a half impulse to
move the tug-boat out of its way, but the aerodrome seemed to realize
its danger and rapidly, though not abruptly or violently, as if it
had intelligence and power of self-direction, it checked its speed
and circled to the right, descending slightly. Soon it quickened
its speed again and went straight ahead for about ten seconds, when
it again checked its flight and descended, circling once more. Once
again it attempted to increase its speed and rise, but it was too
near the water, and in a few moments the waves had wet its propellers
and wings, and it sank, a poor, bedraggled creature. But the vision
of its beauty and power and seeming intelligence and life will long
remain with those who saw its flight.”
After removing the model-launching track so that the final
arrangements could be completed for testing the large machine, many
weeks of delay were experienced, almost entirely due to the unusually
bad weather conditions which prevailed, and which were unprecedented
for the time of the year. However, on September 3 the weather became
more suitable, and the aerodrome being in readiness the metal frame
of the large machine was hoisted to the top of the boat and placed
on the launching car, and the wings, rudder, etc., were then hoisted
up and properly assembled and everything made ready for a flight.
The parties with the telephoto cameras were sent to their stations
on the shore, where definite base lines had been marked out so
that with the data as to [p262] altitude and azimuth, which these
cameras automatically recorded, the speed, height, etc., of the
machine in flight could be accurately computed. After stationing the
tug-boats at proper points, so as to render assistance should the
aerodrome come down into the water at a considerable distance from
the house-boat, it was found, upon attempting to start the engine,
that for some reason it would not operate. The sparking battery which
had been placed at the extreme rear of the aerodrome was found to
be giving such a weak spark that it would not ignite the mixture
in the cylinders. Upon removing the connection which grounded the
terminal of the battery to the framework and replacing it by a large
copper wire leading up to the engine so as to decrease the resistance
of the circuit it was found that the battery still would not give
sufficient spark. A large quantity of dry cells, such as were used
for the engine, had been procured to insure against delay from
lack of batteries, but upon attempting to get a new set from this
reserve supply it was found that they, as well as the set that was
on the machine, had so deteriorated that instead of giving eighteen
amperes on short circuit they would give only three, which was not
a sufficient current to enable the engine to operate. No shop tests
on the large engine had been made since the large aerodrome had been
brought down the river, as no provision had been made for properly
supporting the aerodrome in the house-boat in such a way as to permit
the large propellers to whirl around without causing damage, and,
therefore, the batteries which had hitherto proved to be suitable had
not had any special test since they had been brought down the river.
As no batteries suitable for use were on hand, and as none could be
procured from a point nearer than Washington, the test had to be
abandoned for the day and the aerodrome removed to the interior of
the boat.
It was at first impossible to account for the rapid deterioration of
so large a number of dry cells, but it was later found that the damp,
penetrating fogs which had been experienced for nearly two months
were responsible for it, and that in order to preserve the batteries
in such a climate it was necessary to place them in metallic boxes
which could be nearly, if not quite, hermetically sealed. New
batteries were immediately procured from Washington, and before again
mounting the aerodrome on the launching track provision was made for
testing the engine inside the house-boat.
[Illustration: PL. 94
HOISTING WING OF FULL-SIZE AERODROME]
Up to this time the wings had been stored inside the house-boat by
suspending them from the ceiling, but the time required to hoist
them to the upper works on top of the boat, after the main body of
the aerodrome had been placed on the launching car preparatory to
making a flight, had added so greatly to the delay, and consequently
to the difficulty of getting the machine entirely ready for a flight
while the weather conditions remained suitable for a test, that it
was decided to build some framework on the upper works and cover it
with canvas so as to provide some boxes in which the wings could be
[p263] stored whenever it seemed probable that a flight would
soon be possible. Some of the difficulties experienced in hoisting
these wings from the interior of the boat to the upper works may be
appreciated by an inspection of Plate 94, where one of them is seen
just ready to be hoisted from the raft. Only one wing at a time could
be handled on the raft, even when there was no appreciable wind or
roughness of the water, so that in order to hoist all four wings the
raft had to be hauled around from the door at the end of the boat to
the side where the wing was hoisted, and back again four times every
time the machine was assembled preparatory to a flight. The necessity
for making occasional tests of the engine in order to make sure that
no trouble would be again experienced in having proper batteries,
etc., for the engine when the machine was again on the point of
being launched also made it imperative to remove the wings from the
interior of the house-boat, as the tremendous blasts of air from the
propellers would certainly have wrecked the wings had they remained
in the boat while the engine was being tested.
After the wings had been stored in the “wing boxes,” thorough tests
of the engine were made, and before there came another day which was
at all suitable for a trial, it was accidentally discovered that the
glued joints in the cross-ribs of the large wings had been softened
by the moisture of the fogs which had penetrated everything, and
that the joints had all opened up and left the ribs in a practically
useless condition.
It will be recalled from the description of these cross-ribs, Chapter
VI, that the rib is composed of two channel-shaped strips, the edges
of which are glued together while the strips are bent over a form
which causes the ribs to maintain the curved form desired after
the glue has hardened. Recalling these facts, it will be readily
understood that there is at all times a considerable strain on the
glued joints due to the two strips of wood trying to straighten
out, and, therefore, if the glue should at any time become softened
sufficiently to allow one strip to slide along on the other, the
joint would open up and the rib would consequently become straight.
When the construction of the hollow ribs was first contemplated it
was realized that although the hollow construction would enable the
ribs to be strong, and at the same time exceedingly light, yet it
would make it imperative that the ribs be covered with a water-proof
varnish in order to prevent the glue from being softened when the
aerodrome came down into the water, as it was expected from the first
that it would do at the end of its flight. Considerable time and
attention had, therefore, been given to this very problem of securing
a suitable water-proof varnish, and ribs coated with the varnish
which was finally used had been submerged in water for more than 24
hours in testing this very point, and no softening of the glue could
be detected after this long submergence. It had, therefore, been
felt that the ribs had been given a test which was much more severe
than any conditions which [p264] were likely to be met with, since
the aerodrome would, in no case which could be anticipated, be in
the water for so long a period as 24 hours, and no trouble from this
source need be anticipated.
In the present case, however, the moisture of the atmosphere, which
had been heavily laden with fog for several weeks, had penetrated
the varnish and softened the glue, even though the submergence of 24
hours in water had shown no effect. To construct new ribs for the
wings would have required several weeks, and the delays which had
already been experienced had by this time prolonged the stay down
the river so greatly that even under the very best conditions it
seemed hardly possible to complete the tests before the coming of
the equinoxial storms, which would make it necessary to remove the
boat from the middle of the river and place it in a safe harbor.
Something, therefore, had to be done, and that very quickly, so
that an immediate test could be made, or else the tests would have
to be delayed until the following season, or possibly postponed
indefinitely on account of the lack of funds.
Owing to the varnish with which the ribs were covered, it was
impossible in repairing them to carry out the first plan which
suggested itself of binding the ribs with a strip of cloth
impregnated with glue and wound spirally from end to end. As the wood
was so very thin, it was impossible to bind the two parts together
with wire, and even thin bands of metal driven up on the tapered
portion of the rib were not likely to draw the two strips together
without crushing the wood. What was finally done was to scrape the
edges of the two strips where the joint had opened, thereby removing
all the old glue, and after putting fresh glue on all these edges the
two strips were drawn together and bound with surgeons’ tape, which
was found to adhere very firmly even to the varnished surface.
After repairing the ribs in this manner and readjusting the guy-wires
of their framework so as to make the wing assume the correct
form, which had been slightly altered by the warping and twisting
consequent on the opening up of the ribs, everything was again in
readiness for a test in free flight, numerous tests of the engine
having meanwhile been made both with the aerodrome frame inside of
the house-boat and also when mounted on the launching track above.
The weather, which had been unprecedentedly bad all summer, now
became even worse, and although short periods of calm lasting an
hour or less occasionally occurred, there were for several weeks no
calm periods long enough for completing the necessary preparations
and making a test, although the time required for assembling the
aerodrome had been greatly shortened by building the “wing boxes”
on the superstructure, and in other ways previously described. On
several occasions when an attempt was made to utilize what appeared
to be a relative calm, the aerodrome was assembled on the launching
apparatus and everything got in readiness except the actual fastening
of the [p265] wings and rudder to it, but in every instance, before
the wings could be actually applied and a flight made, the wind
became so strong as to absolutely prohibit a test. On two occasions
when the wings were actually attached, heavy rain storms suddenly
came up and drenched the machine before the wings could be removed,
and on several occasions it was necessary to leave the entire metal
frame and engine of the aerodrome mounted on top of the boat all
night, because the heavy sea which was running made it impossible to
utilize the large raft in returning the frame to the interior of the
boat.
Finally, however, after it seemed almost useless to hope for calm
weather, what appeared to be a most propitious day arrived on October
7. The wind which had been quite high in the early morning gradually
quieted until at 10 a. m. it was blowing only about twelve miles
per hour and the indications were that it would quiet down still
more. Every energy was concentrated in getting the aerodrome ready
at the earliest possible moment, as previous experience had shown
too clearly that the conditions might be completely reversed in less
than an hour. As the tide and wind caused the boat to swing up the
river from its buoy, and thus made the launching track point down
the river, the steam tug-boat was sent down the river for a distance
of a mile or more so that, should the aerodrome come down into the
water without being able to make a return trip to the house-boat,
the tug-boat would be able to reach it quickly and render assistance
to both the writer and the machine should they need it. At 12.20 p.
m. everything was in readiness and what appeared to be the decisive
moment had arrived, when the writer, after starting up the engine
and gradually raising its speed to the maximum, and after taking the
last survey of the whole machine to insure that everything was as it
should be, finally gave the orders to release it.
Although the writer did not have the privilege of seeing it glide
down the track, as his attention was too thoroughly engaged in
insuring that he was in the proper position for reaching immediately
any of the control apparatus, either of the aerodrome or of the
engine, yet those who did witness the actual passage of the machine
down the track have said that the sight was most impressive and
majestic. No sign of jar was apparent when the machine was first
released, but with lightning-like rapidity it gathered its speed as
it rushed down the sixty feet of track, the end of which it reached
in three seconds, at which time it had attained a speed of something
over thirty-two feet per second. Just as the machine reached the end
of the track the writer felt a sudden shock, immediately followed
by an indescribable sensation of being free in the air, which had
hardly been realized before the important fact was intuitively felt
that the machine was plunging downward at a very sharp angle, and he
instinctively grasped the wheel which controls the Pénaud tail and
threw it to its uppermost extent in an attempt to depress the rear of
the machine and [p266] thereby overcome the sharp angle of descent.
Finding that the machine made no response to this extreme movement
of the tail, he immediately realized that a crash into the water was
unavoidable and braced himself for the shock. The tremendous crash of
the front wings being completely demolished as they struck the water
had hardly become apparent before he found himself and the machine
plunging downward through the water. By some instinct he grasped
the main guy-wires which were above his head, and pulling himself
through the narrow space between them freed himself from the machine
and swam upward as rapidly as possible. A few moments after reaching
the surface of the water the uppermost point of the pyramid of the
machine was seen to project from the water and he swam over and sat
down on it until a row-boat could be sent to it from the nearby
power-boat.
The first thing that the writer saw after looking around him was a
newspaper reporter, his boatman expending the utmost limit of his
power in pushing his boat ahead to be the first one to arrive.
After giving directions to the workmen regarding the recovery of
the machine, the writer returned to the house-boat to obtain dry
clothing, and although his first inclination was not to make any
statement until a complete examination could be made to determine
both the cause of the lack of success and also the extent of the
damage which had been sustained by the machine, yet owing to the very
great pressure brought to bear by the press representatives who said
that unless some statement was given out they would write their own
conclusions as to the cause of the mishap, he finally gave out the
following statement:
STATEMENT MADE BY MR. MANLY TO ASSOCIATED PRESS
“It must be understood that the test to-day was entirely an
experiment, and the first of its kind ever made. The experiment
was unsuccessful. The balancing, upon which depends the success of
a flight, was based upon the tests of the models and proved to be
incorrect, but only an actual trial of the full-size machine itself
could determine this. My confidence in the future success of the work
is unchanged. I can give you no further information. I shall make a
formal report to Secretary Langley.”
[Illustration: PL. 95
FLIGHT OF LARGE AERODROME, OCTOBER 7, 1903]
[Illustration: PL. 96
FLIGHT OF LARGE AERODROME, OCTOBER 7, 1903
PHOTOGRAPH BY T. W. SMILLIE]
After recovering the machine the foreman of the workmen (Mr. Reed)
[who together with Mr. McDonald were the only ones on top of the
boat when the launching actually took place], busied himself to
discover what had caused the jerk to the machine at the moment it was
released, which had been immediately followed by the great depression
of the front end. After some little time he discovered that the
upright guide at the extreme front of the launching car (which, as
heretofore stated, was slotted to receive a metal lug projecting from
the end of the guy-post, and thus prevent the front end of the [p267]
framework from being twisted by a side wind striking the machine
while it was still on the launching car) had been distorted, the
metal cap on it being stretched out of shape in a way which indicated
that the pin of the front guy-post had hung in the cap, and that the
guy-post was not therefore free from this part of the car when the
end of the launching track dropped. The shock which the writer felt
at the moment of launching and which had also been seen by others to
occur was thus conclusively shown to have been due to the falling
track, dragging the front end of the machine down with it. As the
machine was travelling forward and the car had been almost instantly
brought to a standstill by its buffer pistons co-acting with the
buffer cylinders at the foot of the track, this front guy-post had
been pulled backwards, and thus not only pulled the main guy-wires
of the wings backwards and thereby depressed the front edge of
the front wings so that they had no angle of inclination, but had
also bent the front end of the metal framework downward,--effects
which were discovered from the later examination of the frame and
the guy-post itself. From the instantaneous photographs which were
obtained, indisputable evidence was obtained that this was what
actually occurred. Referring to the photograph, Plate 95, which was
taken by Mr. G. H. Powell, Secretary of the Board of Ordnance and
Fortification, and which shows the machine just a few feet in front
of the point where it was actually launched, it will at once be
seen that the front end of the frame is bent downward and that the
front guy-post instead of being parallel with the rear one has been
deflected backward at the lower end through an angle of 30 degrees.
Referring further to the photograph, Plate 96, which was taken at
the same instant as the one just described, it will be seen that
even this one, which is a view of the machine as it passed almost
directly over Mr. Smillie’s head, most clearly shows the extreme
extent to which the front wings had been distorted, the rear edges of
the wings near the frame having been twisted up until they struck the
cross-frame, and the outer ends being free to twist had been forced
up very much higher.
After completing the recovery of the machine and the examination
as to the extent of the injuries it had sustained, and finding
unquestionable evidence that the accident had been caused by the
front guy-post hanging in its guide block on the launching car, the
workmen were set to work straightening out and arranging the various
parts, fittings and accessories, and cleaning up the engine which
fortunately had sustained no injury whatever. After a consultation
in Washington with Mr. Langley, who had been unable to be present at
the experiment, both concerning what had already occurred and also
what should be done regarding the future of the work, and in view
of the fact that the statement which the writer had given to the
press representatives, immediately after the accident, had been made
before there had been time to make an examination of the machine
itself, it was decided that it would be best to give to the press
[p268] a short statement to correct the earlier one, and Mr. Langley
accordingly made public the following note:
“Mr. Langley states that he was not an eye witness of the experiment
at Widewater yesterday, having been detained in Washington by
business, but that on the report of Mr. Manly, immediately in
charge, he is able to say that the latter’s first impression that
there had been defective balancing was corrected by a minuter
examination, when the clutch, which held the aerodrome on the
launching ways and which should have released it at the instant of
the fall, was found to be injured.
“The machinery was working perfectly and giving every reason to
anticipate a successful flight, when this accident (due wholly to
the launching mechanism) drew the aerodrome abruptly downward at the
moment of release and cast it into the water near the house-boat.
The statement that the machine failed for lack of power to fly was
wholly a mistaken one.
“The engine, the frame and all the more important parts were
practically uninjured. The engine is actually in good working order.
The damage done was confined to the slighter portions, like the
canvas wings and propellers, and these can be readily replaced.
“The belief of those charged with the experiment in the ultimate
successful working of the machine is in no way affected by this
accident, which is one of the large chapter of accidents that beset
the initial stages of experiments so novel as the present ones.
It is chiefly unfortunate in coming at the end of the season when
outdoor work of this sort is impossible.
“Whether the experiments will be continued this year or not has not
yet been determined.”
In view of the many inaccurate accounts published in the daily press
at the time of this experiment, special attention is directed to the
fact that even under the enormous strain to which the aerodrome was
subjected, due to its striking the water at an angle of approximately
forty-five degrees and at a speed certainly not less than forty miles
an hour, no bending or distortion of any kind was found in the frame
after it was recovered, except that a slight depression at the front
had been produced by the lower guy-post catching on the launching
car, as previously described. This is very clearly seen in Plate 97,
Fig. 1, which shows the aerodrome being hoisted from the water, and
in Plate 97, Fig. 2, which shows it just afterwards resting on the
raft, the wings, tail and rudder having been completely demolished by
towing it through the water to the house-boat from the place where it
struck the water. This single distortion, therefore, was in no way a
result of the strains experienced by the frame either while it was
in the air or when it struck the water. Some of the press reports,
and, in fact, some of the accounts published in the scientific press,
stated that the aerodrome frame had proved so weak that it broke
while the machine was in the air, and that this was the cause of the
accident. Nothing could be farther from the actual facts than this,
for though there were many things connected with the machine which
could not be properly tested until it was actually in the air, yet
the strength of the frame had been most thoroughly [p269] tested in
the shops prior to the trial, and it had been found that with the
frame supported only at the extreme front and rear, no appreciable
deflection was produced upon it by the concentrated weight of four
men at the center, even when they simultaneously jumped up and
down on it. That the aerodrome frame was amply strong was further
evidenced by the fact that in the later trial, hereafter described,
no injury was sustained by the frame even when the machine turned
over in mid-air and struck the water flat on its back. In fact, no
point regarding the aerodrome is more certain than that the frame was
more than strong enough for its purpose.
Plates 98 to 100 show the aerodrome in the water from the moment
after it arose and the writer, who had extricated himself while it
was plunging down through the water and beat it to the surface,
had swum over to it and sat down on the upper pyramid to await a
row-boat, until the machine was taken in tow by the tug-boat.
As the weather conditions were continually growing worse, owing
to the lateness of the season, it was decided that it would be
absolutely impossible to undertake to keep the house-boat down the
river until the aerodrome could be repaired and another test made,
and the writer accordingly returned to Quantico on the following
day, expecting to take the tug-boat from there to the house-boat
and complete arrangements for bringing everything to Washington.
On reaching Quantico, however, it was found that a most violent
storm was raging on the river, and had, in fact, been increasing
in violence since the evening of October 7, immediately following
the trial. On account of the storm it was impossible to reach the
house-boat or to get into communication with the workmen, who had
sought refuge at the hotel at Clifton Beach, as the tug-boat itself
was not at the point at which it was expected to be found, and, in
fact, it had not been seen by any of the river people since the
morning of October 8, when it was seen taking the workmen from the
boat to Clifton Beach. Two days later, or October 11, when the storm
had subsided and the tug-boat, which had been blown many miles
down the river, was able to return the workmen to the house-boat,
it was found that the storm had made a complete wreck of all the
row-boats, the power-launch, and the large raft. The row-boats had
been completely demolished on the beaches, the launch had been broken
from its moorings to the house-boat and driven ashore some four miles
down the river, where it was found with the deck torn completely
off, a large hole stove in it amidships, and the engine seriously
damaged, while the raft had been very seriously damaged on the beach
many miles down the river. After making temporary repairs to the raft
and getting it launched, it was used as a floating dock for making
temporary repairs on the power-launch; both were then returned to
their moorings at the house-boat and everything got in readiness
for towing the house-boat to Washington, and this was finally
accomplished on October 12. [p270] Even while the boat was en route
some of the workmen were busily engaged in the repair of the damaged
parts, the others having been sent ahead to Washington to begin work
on the construction of new wings, so that another trial could be had
at the earliest moment that the weather would permit.
One extra pair of wings was on hand, but these had been stored in the
house-boat while it was down the river, and the damp weather, which
had caused such serious damage to the cross-ribs of the wings which
were actually used, had also so seriously affected the ribs of these
extra wings that it was necessary to discard some of them and repair
the others. An extra Pénaud tail was on hand, as well as a steering
rudder, and it was estimated that unless some unforeseen delay
occurred the aerodrome would be ready for flight in three weeks.
After making a careful examination of the places on the river which
seemed most available for an experiment, it was finally decided to
make the next test just off the Potomac Flats, at the junction of
the main body of the river and the Eastern Branch, the traffic on
this part of the river, which would have been more dangerous and
troublesome during the summer, being quite light at this time of the
year. By making the experiment at this point it was possible to leave
the house-boat at its dock until the weather seemed suitable and then
have a tug-boat tow it to the exact point, which would be determined
by the state of the wind and the tide.
After more completely examining the condition of the framework of
the machine, and discussing and maturely deliberating on the causes
which had led to the accident of October 7, the writer advised Mr.
Langley not to make any changes either in the machine itself or in
the launching apparatus, except to remove the small lug from the
metal rod which projected from the end of the guy-post, and which
by catching in its guide on the launching car had been the sole
cause of the accident. The aerodrome was accordingly repaired so
as to reproduce exactly the conditions which obtained at the time
of the previous experiment, except for this slight change, and it
was again ready for trial by the middle of November. The weather,
however, at this time was very variable, there being at times
comparatively quiet periods which lasted for only an hour or less,
which was not sufficient time for procuring a tug-boat and towing
the boat to the proper point, and then assembling the aerodrome and
making a trial. However, after many days waiting, what appeared
to be an exceptionally quiet day occurred on December 8, the wind
quieting down by noon to such an extent that practically a dead calm
prevailed. Vigorous search was immediately instituted for a tug-boat
to tow the house-boat to the point selected, but it was very late in
the afternoon before one could be procured, and by the time the boat
arrived at the proper place darkness was descending and a strong
[p271] and exceedingly gusty wind had sprung up, and it seemed
almost disastrous to attempt an experiment.
[Illustration: PL. 97
AERODROME BEING RECOVERED, OCTOBER 7, 1903]
[Illustration: PL. 98
AERODROME IN WATER, OCTOBER 7, 1903]
[Illustration: PL. 99
AERODROME IN WATER, OCTOBER 7, 1903]
[Illustration: PL. 100
AERODROME IN WATER, OCTOBER 7, 1903]
However, the funds which had been appropriated by the Board of
Ordnance and Fortification had been exhausted nearly two years
before, and all the expense since that time had been met from a
special fund of the Smithsonian Institution. But, owing to the
heavy drains which the work had made upon this fund, Mr. Langley
felt unwilling to draw further upon it, and since there were no
other funds available from which to meet the expenses which would
be incurred by postponing the experiments until spring, it was
decided that it was practically a case of “now or never,” and
although the river was full of large blocks of floating ice several
inches thick, which added enormously to the danger involved in the
experiment, the writer decided to make the test immediately so that
the long-hoped-for success, which seemed so certain, could be finally
achieved.
After considerable delay, due to the great difficulty of properly
assembling the huge wings in the strong and gusty wind, into which
the boat could not be kept directly pointed, owing both to the
strong tide which was running and to the fact that the wind itself
was rapidly varying through as great a range as ninety degrees, and
after many minor delays, due to causes too numerous to mention, the
aerodrome was finally ready for test.
The wind was exceedingly gusty, varying in velocity from twelve to
eighteen miles per hour and shifting its direction most abruptly and
disconcertingly, so that the aerodrome was at one moment pointed
directly into it and at the next moment side gusts striking under the
port or starboard wings would wrench the frame severely, thus tending
to twist the whole machine from its fastenings on the launching car.
After starting up the engine and bringing it to full speed, the
writer gave the signal for the machine to be released, and it started
quietly, but at a rapidly accelerated pace, down the launching track.
Exactly what happened, either just before or just as the aerodrome
reached the end of the track, it has been impossible to determine,
as all the workmen and visitors had gone to their stations on the
various auxiliary boats, except the two workmen (Mr. Reed and Mr.
McDonald) who had been retained on top of the boat to assist in the
launching. It had grown so dark that the cameras of Mr. Smillie, the
official photographer, were unable to get any impression when he used
them, owing to the extreme rapidity of the shutters with which they
were equipped. Fortunately, one photograph of the machine while still
in the air was secured, which shows the result of what had occurred
in the launching and before any further damage had been caused by its
coming down into the water, but the all-important question as to just
what caused the accident which did occur remains to a certain extent
a mystery. [p272]
Mr. Reed, the foreman, who was qualified to observe accurately, not
only through his having worked continuously for many years on the
machines, but also from his having witnessed the numerous tests of
the models, states that from his position near the rear end of the
launching track he noticed that at a point about ten feet before
the machine reached the end of the track the Pénaud tail seemed to
have dropped at the rear end in some inexplicable way so that it
was dragging against the cross-pieces of the track, and that at the
next instant, when the car reached the end of the track, he saw the
machine continue onward, but the rudder and whole rear portion of the
frame and the wings seemed to be dragging on the launching car. Mr.
McDonald, the head machinist, states that he had his attention so
concentrated on the engine, which he noticed was working perfectly
and driving the propellers at a higher rate of speed than he had ever
before seen it do, that he did not see anything happen until he saw
the machine shoot upward in the air, gradually attaining a vertical
position with its bow upward, where it was sustained for a few
moments by the upward thrust of the propellers. After a few moments,
however, the strong wind, which was blowing from twelve to eighteen
miles an hour directly ahead and acting against the wings which were
now vertical, drove the machine backwards towards the house-boat,
and he saw it come down into the water on its back, with the writer
gradually righting himself in accordance with the turning of the
machine until he was finally hidden from view by the machine coming
down on top of him. The witnesses on the tug-boats seem not to have
been able to perceive exactly what occurred. All unite in stating
that something seemed to happen to the machine just a few feet before
the launching car reached the end of the track, but what it was they
could not say. Everyone who saw the accident and who was sufficiently
familiar with the construction of the machine to be able intuitively
to form an idea as to just what was taking place was so very close
to the machine that when the accident happened everything seemed to
merge into one vision, which was that of the whole rear of the wings
and rudder being completely destroyed as the machine shot upward at
a rapidly increasing angle until it reached the vertical position
previously mentioned.
The writer can only say that from his position in the front end of
the machine, where he was facing forward and where his main attention
was directed towards insuring that the engine was performing at its
best, he was unable to see anything that occurred at the rear of
the machine, but that just before the machine was freed from the
launching car he felt an extreme swaying motion immediately followed
by a tremendous jerk which caused the machine to quiver all over,
and almost instantly he found the machine dashing ahead with its
bow rising at a very rapid rate, and that he, therefore, swung the
wheel which controls the Pénaud tail to its extreme downward limit
of motion. Finding that [p273] this had absolutely no effect, and
that by this time the machine had passed its vertical position and
was beginning to fall backwards, he swung himself around on his arms,
from which he supported himself, so that in striking the water with
the machine on top of him he would strike feet foremost. The next few
moments were for him most intense, for he found himself under the
water with the machine on top of him, and with his cork-lined canvas
jacket so caught in the fittings of the framework that he could
not dive downward, while the floor of the aviator’s car, which was
pressing against his head, prevented him from coming upward. His one
thought was that if he was to get out alive he would have to do so
immediately, as the pressure of the water on his lungs was beginning
to make itself seriously felt. Exerting all of the strength he could
muster, he succeeded in ripping the jacket entirely in two and thus
freeing himself from the fastenings which had accidentally held him,
he dived under the machine and swam under the water for some distance
until he thought he was out from under the machine. Upon rising to
the surface his head came in contact with a block of ice, which
necessitated another dive to get free of the ice. Upon coming to the
surface of the water he noticed Mr. Hewitt, one of the workmen, just
about to plunge in; before he could call out to indicate he was safe,
Mr. Hewitt had heroically plunged in with the expectation of diving
under the machine where he believed the writer to be entangled.
Finding the house-boat was being rapidly shoved upon him, imperilling
the life of both himself and Mr. Hewitt, besides the safety of the
aerodrome, the writer gave orders that the tug-boat reverse and tow
the house-boat away. Then, with the assistance of a row-boat, he
reached the house-boat, where willing hands drew him on board and
assisted him into dryer and warmer clothing.
Meanwhile, it had become quite dark, and when the writer went outside
to see about the aerodrome he found that the men on the tug-boat, in
their zeal to render assistance, had fastened a rope to the rear end
of the machine, at the same time pulling it in the direction in which
the front end was pointed, and through their ignorance had forced it
down into the muddy bottom of the river and broken the main framework
completely in two, thus rendering it absolutely impossible with the
facilities at hand to remove it from the water to the interior of
the boat. It was finally necessary to tie the wrecked machine to the
stern of the house-boat and have the boat towed to its dock where the
mast and boom were assembled and the wrecked machine hoisted from
the water. This was finally accomplished about midnight, when the
workmen, who had been working at a fever heat all day, were glad to
close up the work for the day, which had proved so unfortunate.
[Illustration: PL. 101
ATTEMPTED LAUNCHING OF AERODROME, DECEMBER 8, 1903
ENLARGEMENT OF PHOTOGRAPH BY THE WASHINGTON STAR]
As has already been remarked, darkness had descended to such an
extent that the light was not strong enough to give photographs
with the very rapid shutters with which Mr. Smillie had his cameras
equipped, and that, therefore, [p274] incontrovertible evidence,
which the instantaneous photographs had given as to just what
had occurred to the machine in the accident of October 7, was in
this case unfortunately lacking. It was at first thought that no
photographs had been obtained while the machine was actually in
the air, but it was later found that by some rare fortune the
photographer for ‹The Washington Star› had secured a photograph,
which, while small, showed very distinctly some decidedly interesting
facts. An enlargement of this photograph is shown in Plate 101, by
the kind permission of ‹The Washington Star›. Referring to this
photograph, it will be seen that at the moment it was taken the
machine was practically vertical in the air, and it confirms the
testimony of the eye witnesses, and also the writer’s impression
that the machine was maintained in a vertical position for several
moments by the upward thrust of the propellers. It will also be seen
that the Pénaud tail has been completely demolished and is hanging as
a limp roll of cloth, which the strong wind has deflected backwards
towards the house-boat, the port rear wing has broken its main ribs,
both where they are attached to the main frame and also about midway
the length of the wing, the outer end being partially folded towards
the frame. The starboard rear wing has also broken both of its main
ribs at the point where they are joined to the frame, and they have
also broken at a point about one-third their length from the frame,
the outer end being likewise folded towards the frame. By a still
more careful inspection, it will also be seen that the port front
wing is apparently uninjured, while the starboard front wing has
broken the middle main rib at a point between the sixth and seventh
cross-ribs, and while it cannot be distinctly seen at first that
the front main rib has also broken at the same point very careful
inspection will show that this is the case, as the sixth and seventh
ribs, showing as faintly darker lines in the photograph, are seen to
be displaced, so that they are together and actually crossing each
other. It will furthermore be seen that both front wings have been
pressed upward by the wind until their tips near the inner ends are
in contact with the cross-frame. This could not have happened unless
the front guy-post had given away either by bending or breaking. The
fact that it has given way is further evidenced by a more careful
examination of the extreme front end of the machine, where it will be
seen that the bowsprit and the curved tubes which form the extreme
end of the steel frame have been bent from a straight line with
reference to the main frame. This bending of the bowsprit and the
curved tubes could be produced only by the front guy-post coming in
contact with some obstruction on the launching car as the machine
left it. It is known very certainly that the rear end of the machine
came in contact with the launching car, as the car itself shows a
very deep gash in the wooden cross-piece at its center, which was
produced by the port-bearing point at the rear striking it. As this
bearing point was elevated five feet above the cross-piece of the
launching car, and was also six feet six inches to [p275] the rear
of the point where the wood is torn, this rear-bearing point must
have travelled downward at an angle of approximately thirty-eight
degrees in order for the bearing point to strike the car at this
point. As the lower end of the rear guy-post was only eighteen inches
above the cross-piece of the launching car, it, of course, would be
broken before the bearing point could descend so much. As has been
previously stated, Mr. Reed, who was at the rear of the launching
track, states very positively that the rudder was dragging on the
track at least ten feet before the launching car reached the front
end of the track where the machine was actually launched. There
are several ways in which the rudder could have gotten down on the
track, but positive information is lacking. If it was dragging on
the track, as Mr. Reed states (and from his extended experience and
rather acute powers of observation I should place great credence in
his report), the subsequent demolition of the guy-posts succeeded by
the destruction of the rear wings and serious injury of the front
ones is easily explained. If the dropping of the rudder on the track
occurred from the breaking of the upper rudder post, over which the
upper control wire passed, the lower vertical surface would first
come in contact with the track, and the destruction of this part
would certainly occasion subsequent destruction of the horizontal and
upper vertical surfaces of the rudder, leaving the central rib of
the rudder still attached to the frame, and upon the machine being
released from the car a few moments later this destroyed rudder would
easily catch in the launching car and pull the aerodrome down on it,
and thus cause the destruction of the guy-posts, wings, and so forth.
If the dropping of the rudder was caused primarily by its main rib
breaking loose from its connection with the frame, the rudder would
still be dragged along behind the machine by the wire cords through
which it was operated, and the subsequent launching of the machine
would still give the rudder every chance to catch in the launching
car and drag the machine down on it.
It can therefore be said that, while positive information is lacking,
there is very strong evidence that the accident in the launching
was due to the rudder becoming entangled with the launching track
owing to the breakage of some part of the mechanism by which it was
connected to the main frame.
It is of importance to note that the photograph furnishes
incontrovertible evidence that the main frame of the machine was in
no way injured, except for the slight bending of the forward curved
extension, and that, therefore, the accident was in no way due to
the weakness of the frame. The main frame was not even injured by
the machine coming down in the water on its back, and the later
damage was entirely caused by the combination of the ignorance of the
tug-boatmen and the darkness in which they were working, when they
attempted to tow it to the rear of the house-boat so that it could be
removed from the water. [p276]
On the day following the trial a very careful inspection was made
in the hope of obtaining some more definite information as to just
what caused the accident, but the serious injury to the machine
caused by the tug-boatmen breaking it in the water had so greatly
tangled things up that it was impossible to tell anything about
it. The workmen were immediately put to work removing fittings
from the broken wings, rudder, etc., and dismounting the engine,
which was immediately reassembled on its testing frame and found to
be absolutely uninjured. The transverse frame of the machine was
comparatively uninjured, the damage done by the men on the tug-boat
being the breaking of the machine in two at a point just back of the
cross-frame, together with the consequent destruction of the bearing
points, “trestle,” and certain fittings by which the main guy-wires
were attached to the main tubes and pyramids.
The situation which now existed was most distressing and
disheartening. Mr. Langley felt that he could not approve of further
expenditures from any Smithsonian fund, and the Board of Ordnance and
Fortification of the War Department having been severely criticised
on the floors of Congress for its original allotment for the work,
deemed it inexpedient to incur a possible curtailment of the funds
annually placed at its disposal for general experimental work through
a manifestation of continued interest in the flying machine.
As has already been stated, representatives from the Board of
Ordnance and Fortification of the War Department were present at
both tests of the large aerodrome; on October 7 Major Montgomery
M. Macomb and Mr. G. H. Powell, and on December 7 General W. F.
Randolph accompanied by Major Macomb and Mr. Powell, represented the
War Department, and Dr. F. S. Nash, at that time Contract Surgeon,
U. S. A., was officially present at both trials to render medical
assistance should it be needed.
By permission of the War Department, the official report of the tests
submitted by Major Macomb to the Board of Ordnance and Fortification
is here made public:
Enc. 1st to 3d end’t, BOF 6191.
REPORT
Experiments with working models which were concluded August 8 last
having proved the principles and calculations on which the design
of the Langley aerodrome was based to be correct, the next step
was to apply these principles to the construction of a machine of
sufficient size and power to permit the carrying of a man, who could
control the motive power and guide its flight, thus pointing the
way to attaining the final goal of producing a machine capable of
such extensive and precise aerial flight, under normal atmospheric
conditions, as to prove of military or commercial utility.
Mr. C. M. Manly, working under Prof. Langley, had, by the summer of
1903, succeeded in completing an engine-driven machine which under
favorable [p277] atmospheric conditions was expected to carry a man
for any time up to half an hour, and to be capable of having its
flight directed and controlled by him.
The supporting surface of the wings was ample, and experiment showed
the engine capable of supplying more than the necessary motive power.
Owing to the necessity of lightness, the weight of the various
elements had to be kept at a minimum, and the factor of safety in
construction was therefore exceedingly small, so that the machine
as a whole was delicate and frail and incapable of sustaining any
unusual strain. This defect was to be corrected in later models
by utilizing data gathered in future experiments under varied
conditions.
One of the most remarkable results attained was the production of a
gasoline engine furnishing over fifty continuous horse-power for a
weight of one hundred and twenty pounds.
The aerodrome, as completed and prepared for test, is briefly
described by Prof. Langley as “built of steel, weighing complete
about seven hundred and thirty pounds, supported by one thousand and
forty feet of sustaining surface, having two propellers driven by a
gas engine developing continuously over fifty brake horse-power.”
The appearance of the machine prepared for flight was exceedingly
light and graceful, giving an impression to all observers of being
capable of successful flight.
On October 7 last everything was in readiness, and I witnessed the
attempted trial on that day at Widewater, Va., on the Potomac. The
engine worked well and the machine was launched at about 12.15 p. m.
The trial was unsuccessful because the front guy-post caught in its
support on the launching car and was not released in time to give
free flight, as was intended, but on the contrary, caused the front
of the machine to be dragged downward, bending the guy-post and
making the machine plunge into the water about 50 yards in front of
the house-boat. The machine was subsequently recovered and brought
back to the house-boat. The engine was uninjured and the frame only
slightly damaged, but the four wings and rudder were practically
destroyed by the first plunge and subsequent towing back to the
house-boat. This accident necessitated the removal of the house-boat
to Washington for the more convenient repair of damages.
On December 8 last, between 4 and 5 p. m., another attempt at a
trial was made, this time at the junction of the Anacostia with the
Potomac, just below Washington Barracks.
On this occasion General Randolph and myself represented the Board
of Ordnance and Fortification. The launching car was released at
4.45 p. m., being pointed up the Anacostia towards the Navy Yard.
My position was on the tug Bartholdi about 150 feet from and at
right angles to the direction of proposed flight. The car was set
in motion and the propellers revolved rapidly, the engine working
perfectly, but there was something wrong with the launching. The
rear guy-post seemed to drag, bringing the rudder down on the
launching ways, and a crashing, rending sound, followed by the
collapse of the rear wings, showed that the machine had been wrecked
in the launching, just how, it was impossible for me to see. The
fact remains that the rear wings and rudder were wrecked before the
machine was free of the ways. Their collapse deprived the machine
of its support in the rear, and it consequently reared up in front
under the action of the motor, assumed a vertical position, and then
toppled over to the rear, falling into the water a few feet in front
of the boat. [p278]
Mr. Manly was pulled out of the wreck uninjured and the wrecked
machine was subsequently placed upon the house-boat, and the whole
brought back to Washington.
From what has been said it will be seen that these unfortunate
accidents have prevented any test of the apparatus in free flight,
and the claim that an engine-driven, man-carrying aerodrome has been
constructed lacks the proof which actual flight alone can give.
Having reached the present stage of advancement in its development,
it would seem highly desirable, before laying down the
investigation, to obtain conclusive proof of the possibility of free
flight, not only because there are excellent reasons to hope for
success, but because it marks the end of a definite step toward the
attainment of the final goal.
Just what further procedure is necessary to secure successful flight
with the large aerodrome has not yet been decided upon. Professor
Langley is understood to have this subject under advisement, and
will doubtless inform the Board of his final conclusions as soon as
practicable.
In the meantime, to avoid any possible misunderstanding, it should
be stated that even after a successful test of the present great
aerodrome, designed to carry a man, we are still far from the
ultimate goal, and it would seem as if years of constant work and
study by experts, together with the expenditure of thousands of
dollars, would still be necessary before we can hope to produce an
apparatus of practical utility on these lines.
M. M. MACOMB,
Major Artillery Corps.
WASHINGTON, January 6, 1904.
The attitude of the Board of Ordnance and Fortification, with
reference to rendering further financial assistance to the work, is
clearly shown by the following extract from the official report of
the Board on October 6, 1904, to the Secretary of War:
THE LANGLEY AERODROME
Early in the year 1898 a board composed of officers of the Army
and Navy was appointed to examine the models and principles of the
aerodrome devised by Dr. S. P. Langley, Secretary of the Smithsonian
Institution, and to report whether or not, in its opinion, a large
machine of this design could be built, and, if so, whether it would
be of practical value.
The report of this board was referred to the Board of Ordnance and
Fortification for action, and Doctor Langley was invited to appear
before the Board and further explain the proposed construction.
In view of the great utility of such a device, if a practical
success, the Board, on November 9, 1898, made an allotment of
$25,000 for the construction, development, and test of an aerodrome
to be made under the direction of Doctor Langley, with the
understanding that an additional allotment of the same amount would
be made later. On December 18, 1899, the additional allotment of
$25,000 was made.
The construction of the machine was delayed by Doctor Langley’s
inability to procure a suitable motor, which he was finally obliged
to design. The aerodrome was completed about July 15, 1903, and
preparations for its test were made at a point in the Potomac River
about 40 miles below Washington. [p279]
Preliminary arrangements having been completed and tests made of
a quarter-size model, the first attempt at actual flight with the
man-carrying aerodrome was made on October 7, 1903.
On this occasion there were present on behalf of the Board, Major M.
M. Macomb, Artillery Corps, and Mr. G. H. Powell, clerk of the Board.
Major Macomb in his report to the Board stated that--
“The trial was unsuccessful because the front guy-post caught in its
support on the launching car and was not released in time to give
free flight, as was intended, but on the contrary, caused the front
of the machine to be dragged downward, bending the guy-post and
making the machine plunge into the water about 50 yards in front of
the house-boat.”
This accident necessitated the removal of the house-boat to
Washington for the more convenient repair of damages. The repairs
having been completed, on December 8, 1903, another attempt at a
trial was made, this time at the junction of the Anacostia and the
Potomac Rivers. General W. F. Randolph and Major Macomb, members of
the Board, and Mr. Powell, were present. Major Macomb reported as
follows:
“The launching car was released at 4.45 p. m. . . . The car was set
in motion and the propellers revolved rapidly, the engine working
perfectly, but there was something wrong with the launching. The
rear guy-post seemed to drag, bringing the rudder down on the
launching ways, and a crashing, rending sound, followed by the
collapse of the rear wings, showed that the machine had been wrecked
in the launching, just how, it was impossible for me to see.”
March 3, 1904, the Board stated that it was not “prepared to make an
additional allotment at this time for continuing the work,” whereupon
Doctor Langley requested that arrangements be made for a distribution
of the aerodrome material procured jointly from funds allotted by
the Board and by the Smithsonian Institution. Doctor Langley was
informed that all of the material would be left in his possession and
available for any future work that he might be able to carry on in
connection with the problem of mechanical flight.
That this refusal of the Board of Ordnance and Fortification to
render further assistance to the work was due to the fear that such
action would result in a curtailment of their appropriation by
Congress is clearly shown by the following extract from the official
report of the Board on November 14, 1908, to the Secretary of War:
AERIAL NAVIGATION
For a number of years the Board has been interested in the subject
of aerial navigation, and as long ago as 1898 made allotments to
carry on experiments with a machine of the heavier-than-air type,
under the direction of the late Dr. S. P. Langley, Secretary of
the Smithsonian Institution, who had made exhaustive experiments
in aerodynamics,[48] and who had demonstrated the practicability
of mechanical flight by the successful operation of engine-driven
models.
The many problems and mechanical difficulties met with in the
development of the full-size machine have been set forth in the
various published statements[49] [p280] of Doctor Langley, and the
unsuccessful outcome of the experiments is too well known to require
reiteration. It may be said, however, that at the time of the trials
the Board was of the opinion that the failure of the aerodrome to
successfully operate was in no manner due to the machine itself, but
solely to accidents in the launching apparatus, which caused the
wreck of the aerodrome before it was in free flight.
Doctor Langley considered it desirable to continue the experiments,
but the Board deemed it advisable, largely in view of the adverse
opinions expressed in Congress and elsewhere, to suspend operations
in this direction.
These adverse opinions expressed in Congress were wholly due to the
bitter criticism by the newspapers, whose hostility was engendered
by Mr. Langley’s refusal to admit their representatives to the
shops and house-boat where the work was in progress. Mr. Langley
had at all times tried to make his position in the matter clear to
the newspapers, but, on August 19, 1903, at the time of one of his
visits to the experimental station near Widewater, Va., he found the
newspaper representatives so persistent in their misrepresentations
of his reasons for excluding them that he gave out the following
statement, which was published at that time:
SMITHSONIAN INSTITUTION, WASHINGTON, D. C.,
August 19, 1903.
TO THE PRESS: The present experiments being made in mechanical
flight have been carried on partly with funds provided by the Board
of Ordnance and Fortification and partly from private sources,
and from a special endowment of the Smithsonian Institution. The
experiments are carried on with the approval of the Board of Regents
of the Smithsonian Institution.
The public’s interest in them may lead to an unfounded expectation
as to their immediate results, without an explanation which is here
briefly given.
These trials, with some already conducted with steam-driven flying
machines, are believed to be the first in the history of invention
where bodies, far heavier than the air itself, have been sustained
in the air for more than a few seconds by purely mechanical means.
In my previous trials, success has only been reached after initial
failures, which alone have taught the way to it, and I know no
reason why the prospective trials should be an exception.
It is possible, rather than probable, that it may be otherwise now,
but judging them from the light of past experience, it is to be
regretted that the enforced publicity which has been given to these
initial experiments, which are essentially experiments and nothing
else, may lead to quite unfounded expectations.
It is the practice of all scientific men, indeed of all prudent men,
not to make public the results of their work till these are certain.
This consideration, and not any desire to withhold from the public
matters in which the public is interested, has dictated the policy
thus far pursued here. The fullest publicity, consistent with the
national interest (since these recent experiments have for their
object the development of a machine for war purposes), will be given
to this work when it reaches a stage which warrants publication.
(Signed.) S. P. LANGLEY.
Although it was impossible to immediately find funds for actively
continuing the work, the writer finally, after some delay, persuaded
Mr. Langley to allot a small sum from a limited fund which personal
friends had some time previously placed at his disposal for use in
any experiments he might wish to make. This small sum was used to
meet the expense of the workmen who were kept employed long enough to
completely repair the main frame so that, should further experiments
be possible at a later time, there would be no danger of important
parts and fittings having been lost in the meantime, and even if no
further experiments were made the frame would be in such condition
that others could profit from an examination of it, the frame itself
embodying the solution of many important problems which had cost much
time and money.
In the spring of 1904, after the repairs to the main frame were
well under way, the writer on his own initiative undertook to see
what could be done towards securing for Mr. Langley’s disposal the
small financial assistance necessary to continue the work; but he
found that while a number of men of means were willing to assist
in the development of the aerodrome, provided arrangements were
made for later commercialization, yet none were ready to render the
assistance from a desire to assist in the prosecution of scientific
work. Many years prior to this Mr. Langley had had some very tempting
propositions made to him by certain business men with a view to
carrying on the work in a way that would lead to later commercial
development. He had never patented anything previously in his life,
and although many friends had urged that it was only proper that he
should patent whatever of value had been developed in connection with
the aerodromes, he steadfastly refused to do so. He had given his
time and his best labors to the world without hope of remuneration,
and he could not bring himself at his stage of life to consent to
capitalize his scientific work. Success seemed only a step away, and
his age was such that any delay in achieving success increased the
probability of his not living to see it, but he maintained positively
and resolutely that, if neither the War Department nor others felt
sufficient interest in the work to provide the small amount of funds
necessary to continue the experiments, and they therefore could
be continued only by his giving in and permitting his work to be
capitalized, he would have to deny himself the hope of living to see
the machine achieve success.
The result is well known to all.
PRESENT STATUS OF THE WORK
The completely repaired frame of the large machine is now stored
in one of the workshops at the Smithsonian Institution. The large
engine, the steam-driven models Nos. 5 and 6, and the quarter-size
model, driven by the three [p282] horse-power gasoline engine, are
on exhibition at the U. S. National Museum. The launching-car and
a small amount of materials have also been stored away. The large
house-boat, the construction and maintenance of which proved such a
serious drain on the finances, and the preservation of which would
have entailed the continuance of heavy fixed charges, has been turned
over to the War Department and sold, as has also the power-launch and
other paraphernalia which it seemed useless to preserve.
The writer is firmly convinced that the aerodrome is not only correct
in principle but that it possesses no inherent faults or weaknesses,
and that the success which the work deserves has been frustrated by
two most unfortunate accidents in the launching of the machine. Other
plans of launching, several of which were studied out during the
early stages of the work on the large machine, would have avoided the
accident which did occur, but, of course, might have produced others
possibly even more disastrous, but which could be determined only by
actual trial. But even recognizing certain fundamental weaknesses
of the launching mechanism as used, he believes that there is no
inherent reason why the machine should not have been successfully
launched, and that the accidents which proved so disastrous in the
two experiments were not such as should cause a lack of confidence in
the final success of the aerodrome.
It might be of interest to add that the writer is now preparing to
resume the work at the earliest opportunity, and that the machine
will be used in practically the form in which it existed at the two
previous experiments, though a slight change will be made permitting
experiments over the land rather than the water. The only thing that
prevents an immediate resumption is the pressure of private business
matters.
Before closing this record the writer wishes to acknowledge the very
valuable assistance in the work rendered by Mr. Richard Rathbun,
Assistant Secretary of the Smithsonian Institution, through his
moral support and interest in it at all times, and especially during
the trying days of the summer of 1903; by Captain I. N. Lewis, who,
while Recorder of the Board of Ordnance and Fortification from 1898
to 1902, manifested keen interest in the work and gave it his moral
support before the Board; by Professor John M. Manly, who devoted
the whole of the summer of 1903 to it; and by Professor W. G. Manly,
who devoted a large part of the summer of 1903 to assistance in the
preparation for the actual field-trials of the aerodrome.
Mention must also be made of the very loyal and valuable services
rendered by Mr. R. L. Reed, the very efficient foreman of the work
during the last ten years of its progress, to whom much credit is due
for his perseverance and skill in overcoming many of the difficulties
which presented themselves, as well as to Mr. G. D. McDonald, Mr.
C. H. Darcey, Mr. F. Hewitt, Mr. R. S. Newham [p283] and the other
employees who labored faithfully for the several years they were
engaged on it.
BLÉRIOT MACHINE OF
1907 ON LANGLEY TYPE
Since completing the preparation of this Memoir, the writer’s
attention has been called to some very interesting tests made at
Issy by M. Louis Blériot with a machine of the Langley type. These
tests confirm in such a practical manner the conviction that the
large aerodrome would have flown successfully had it not been wrecked
in launching that it has seemed well to here quote an interesting
description of them published in the “Bollettino della Società
Aeronautica Italiana, August, 1907,” under the title “Il nuovo
aeroplano Blériot,” a translation of which is as follows:
THE NEW BLÉRIOT AEROPLANE
The Blériot IV in the form of a bird, of which we spoke at length
in No. 4 of the Bulletin of this year, does not appear to give good
results, perhaps on account of its lack of stability, and Blériot
instead of trying some modifications which might remedy such a
grave fault, laid it aside and at once began the construction of
a new type, No. V, adopting purely and simply the arrangement of
the American, Langley, which offers a good stability (see Bulletin
11–12, November to December, 1905, pages 187 and 188).
The experiments, which were commenced a month ago, were first
completely negative, because the 24 HP. motor would not turn the
propeller, which was 1.80 m. in diameter and 1.40 m. pitch.
By advice of Captain Ferber, Blériot reduced the pitch of his
propeller to 0.90 m., so that the motor could give all its force.
This modification was an important one for his aeroplane. From
that moment every trial marked an advance. On July 12, he made a
flight of 30 m., and the aviator was able to show that the lateral
stability was perfect. On July 15, the trial was made against a wind
of 6 miles an hour, but gave good results. He made a flight of 80
m., showing, however, that the hind part of the aeroplane was too
heavy. In this flight he arose as high as a second story, and on
landing the wheels and one propeller were somewhat damaged.
On July 24, repairs having been completed, a new trial was made.
This time, in order to remedy the defect in the balance, Blériot
had moved his seat forward about 80 cm. The correction was too
great, for on that day the aeroplane, although the hind part arose,
was not able to leave the ground. On July 27, after having mounted
the seat on wheels as skiffs, Blériot resumed the trials and made
a flight of 120 m., at first moving his seat back and then, after
getting started, bringing it forward. Blériot had not provided this
aeroplane with an elevating rudder, but, following the example
of Lilienthal, changed the center of gravity of the apparatus by
moving his own person, and after having established the proper angle
remained immovable on his seat. In order to arise or descend, the
aviator made use of the spark lever, thus varying the number of
turns of the propeller.
During a second trial on the same day, having accidently reached
the limit of the aviation field, Blériot, without allowing himself
to be surprised and obliged to descend, decided to attempt a turn
by maneuvering the steering rudder [p284] and to return again to
the center of the field. With marvelous precision, the aeroplane
began to describe a circle of about 200 m. radius, inclining as if
on a banked track. Having finished the flight, he quickly regained
his balance still in the direction of the wind, but on account of a
slight movement of the aviator, the aeroplane fell to such an extent
that he was obliged to land. He landed gently and without shock,
rolling on his wheels.
On August 1, he made another flight of 100 m. in 6-1/2 seconds; and
on the 6th, one of 265 m. with one interruption. While the attention
of the pilot was distracted for a moment, the aeroplane, which was
flying at a height of 2 or 3 m. above the ground, touched the soil
with its sustaining wheels at the end of 122 m. and then immediately
arising, covered the remaining 143 m. at a height of 12 m. Blériot,
moving forward too quickly, caused the aeroplane to descend swiftly
to the ground, and the shock broke the axle and the blades of the
propeller were bent. In order to confirm this account, we reproduce
what was said in the “Auto” of August 7, 1907.
“M. Blériot, continuing the trials of his aeroplane yesterday,
surpassed the superb results which he had already obtained. The
trial took place at 2 o’clock in the afternoon on the aviation field
of Issy. After a sustained flight of about 122 m. at a height of 2
m., the aeroplane touched the ground, without stopping, however, and
set out again almost immediately at a height of 12 m. and traversed
about 143 m. M. Blériot, who for the time had no other means of
balancing but by moving his body, then moved a little forward to
stop the ascent. The aeroplane plunged forward, and in the fall the
propeller was damaged and the axle broken.
“M. Blériot, whose courage as a sportsman equals his learning
as an engineer, was fortunately uninjured. An inspection of the
apparatus showed that one blade of the propeller was bent, which
was sufficient to prevent the maneuver made by the aviator having
its desired effect and contributed to the fall. The engine will be
repaired without difficulty and the trials will be resumed Friday.”
On August 10, he made a flight of 80 m., but the motor was not in
perfect order, so Blériot did not make other trials. He decided,
however, to substitute definitely a 50 HP. motor for the 24 HP.
motor with which he made all the experiments above reported, which
were of a character to encourage the most sanguine expectations.
Ferber advised Blériot to adopt an elevating rudder also, because
the effect produced by changing the position of the center of
gravity, although efficacious is very difficult and delicate to
control.
The conclusion of an article by Ferber in “Nature” of August 10, is
worthy of note. He says: “Let us remark, in conclusion, how fruitful
is the method of personal trial which we have always advised in
preference to any calculation. This year, with his fourth apparatus,
Blériot has not met with any damage to his aeroplane. He made the
trials himself and they quickly led to results, because each trial
gave him an exact idea of what was to be corrected. That is the
condition of success.”
[p285]
APPENDIX
STUDY OF THE AMERICAN BUZZARD AND THE “JOHN CROW”
In the preparation of this Memoir, the writer has deemed it best to
generally omit any mention of plans and ideas which were brought
forth in the work, unless constructions or tests in accordance with
them were carried to a sufficient extent to admit of some definite
conclusion regarding them. However, owing to the important part
played by the warping of the supporting surfaces, or the variation
in the angle of auxiliary surfaces, in the methods of preserving the
equilibrium of practically all flying machines of the present day, it
may be of interest to here add a short mention of the direction in
which plans along this line were originally proposed in this work.
Mention has already been made of the importance which Mr. Langley
attached to the study of the works of the great master-builder,
Nature, though recognizing at the same time that owing both to the
difference in the forces and methods of construction possible to man,
it was not in general possible for him to produce the best results by
attempting to too closely imitate the methods or plans of Nature.
Mr. Langley considered it not practicable or best to attempt to
imitate the details of construction of the flying mechanism of
birds. At the same time, he strongly believed that much was to be
learned from them about the practical side of the art of balancing,
and he therefore spent a great deal of time both in analyzing the
methods practiced by the birds in preserving their equilibrium and
in criticizing his own plans in this direction in the light of what
Nature would seem likely to do if she had to construct a flying
creature on such a large scale. In carrying on his investigations in
the art as practiced by the birds, he made a trip to Jamaica during
the early weeks of 1900, in order to study the species of buzzard
which are so numerous and tame there and are known locally as the
“John Crow.” After his return from this trip he wrote the following
very interesting letter to Mr. Robert Ridgway, requesting certain
data regarding the American buzzard, which he wished to compare with
some data on the “John Crow” which he had obtained on this trip:
MARCH 29, 1900.
DEAR MR. RIDGWAY:
I have just returned from Jamaica, where among other occupations,
I have been studying the evolutions of the buzzard locally called
the “John Crow,” a soaring bird which is almost as much superior in
skill to our buzzard as that is to a barn-yard fowl in its power of
keeping itself in the air without flapping its wings, in what is
very nearly a calm.
I have observed particularly the following points with the Jamaica
specimen (which I can only give, however, approximately), and I
should like to have you give corresponding ones for our Washington
buzzard if you can oblige me. [p286]
I note here that the measurements were made on a live bird and that
it was impracticable to get the separate weight of the wings except
by estimate, but the two wings may be estimated collectively as
1-1/4 lbs., the whole weight being 2-3/4 lbs. to 3 lbs.
Approximate values:
Weight of the bird complete, 3 pounds.
Length of bird, 23 inches.
Spread of wings from tip to tip, 5 ft. 5 in.
Complete curtate area of both wings (that is, the area of the shadow
of the bird’s wings when these are fully extended under a vertical
sun) is 600 square inches, or nearly 4 sq. ft., consequently each
square foot of the bird’s sustaining surface carries 3/4 lbs.
Diedral angle nearly 150°.
When the bird is soaring in a nearly calm atmosphere, which it
inexplicably does,--soaring I mean nearly in line of the observer’s
eyes and coming directly to of going directly away from him,--it
presents nearly the following appearance:
[Illustration: FIG. 1--Jamaica, Mch. 22, 1900. “John Crow.” Sketch
soaring horizontally, by W. H. Holmes. Weight 3 lbs. Total wings
area = 546 in. Perpendicular distance ‹c› below ‹a› ‹b› = 3.3 in. =
√(546)/7 = ‹CP›_2−‹CG›_2.]
[Illustration: FIG. 2--Another.
‹CP›_2−‹CG›_2 = 3.3 in. = √(546)/7.]
FIGS. 1 and 2.--Type sketches of wings by Holmes from a mean of
positions taken from his own sketches and photographs, and also from
sketches and photographs by Langley.
[Illustration: FIG. 3.--Type sketch of same birds, average type,
position of wings.--S. P. Langley
‹CP›_2−‹CG›_2−3.6 in. = √(546)/6.5.]
[Illustration: FIG. 4.--Average typical position of wings in soaring
gull. From memory by S. P. Langley. (The scale here may be taken
‹approximately› at 1/13).]
[p287]
I must preface what follows by a little statement of the things
which particularly interest me here and which are not a naturalist’s
ordinary concern.
First, I want to know the ‹CG› of the bird when in flight. You will
understand that though there is but one center of gravity (here
symbolized as ‹CG›), it may be considered (1) with reference to its
position on the horizontal plan of the bird with wings extended,
when it will always be found somewhere in the medial vertical plane,
passing through the body, and usually nearly at a certain point with
reference to length, the position thus considered being called ‹CG›,
or (2) the position of the same ‹CG› with reference to a vertical
plane passing transversely through the medial line, the position
thus considered being called ‹CG›_2. In the latter case you will
understand that the ‹CG› which is that of the whole body, wings and
all, will be carried more or less upward when the wings are thrown
high up, and will be carried temporarily downward when the wings are
at their lowest point of the stroke. It would have a certain position
when the bird was at rest and another position when it was soaring
and the wings were above the body.
The soaring bird is chiefly held upward by the pressure of the air
under each wing, and just as the common center of gravity is a
point where all the efforts of gravity are supposed to be centered,
so there is a common center of pressure, or one point where all
the efforts of the upper pressure of the air may be supposed to be
centered, and it will be clear, on very little consideration that
this latter point must be always nearly in a vertical line through
the ‹CG›, and usually above it. Call it ‹CP›.
‹CG›_1 and ‹CP›_1 are then, the symbols of ‹CG› and ‹CP› as referred
to the horizontal plane. ‹CG›_2 and ‹CP›_2 are the symbols for the
corresponding ones when referred to their position in the vertical
plane.
I shall be glad to explain to you, if you are not familiar with it,
the simple method of finding the ‹CG›_1 and ‹CG›_2. It consists in
bending the wings into just the position that they would ordinarily
occupy above the body in plain soaring flight, keeping them there by
a very light bent stick or wire, then hanging the bird up by a line
attached to the tip of one wing, and see where this line would pass
through the body of the bird, for the ‹CG› will be somewhere in this
line. After marking then, on the body of the bird its position, hang
it up a second time by the head or tail and note again where the new
vertical line runs in the new position. There is but one ‹CG› and but
one point in which two straight lines can cross, and that will be
the ‹CG› necessarily. Note with all care just where this is above or
below the center of the body of the bird.
As for the ‹CP› for either wing, that may be nearly found by tracing
the wing on a flat piece of thick paper or cardboard strong enough
not to bend much--cutting out the tracing and balancing it well on
the point of a pencil--the point about which it balances is very near
‹CP›_2 or the center of pressure in the vertical plane. There is such
a point of course in each wing, and when they are thrown up in the
actual position that they have in calm soaring flight, we may suppose
a horizontal line drawn between them, and it is the distance from
this horizontal line to ‹CG›_2 compared with the area of the wings or
with the distance between their extended tips which we want to know,
which gives the vertical distance which the ‹CG› is below the ‹CP›,
the thing we want to know.
It will be very convenient also to have a wing dissected from the
body and the wing itself held in about the soaring curve by a bit of
light stick balanced on a pencil point, which will give the ‹CG› of
the wing as distinct from that of the body. However, the three things
I principally want, beside a sketch or [p288] photograph of the bird
from about its own level coming directly toward or going directly
away in soaring flight, are these:
Approximate weight of the bird,--and approximate tracing of its
extended wing with the area, so that we can tell the area of the
supporting surface relative to the weight, and finally, the distance
between ‹CP›_2, and ‹CG›_2, which is obtainable by the process which
I have explained.
I am afraid that what I have just been describing at such length
may have a certain obscurity to you, but if you will give me an
opportunity, I shall be pleased to illustrate it with the actual
experiment when the bird is hung up by a string, and you will see
that it is in reality simple.
Referring to the sketches on page 3 of this communication, ‹a› and
‹b› correspond to the centers of pressure on either wing where the
upward pressure of the air distributed over each wing may be supposed
to be gathered in a single point. This, as I have said, is called
the center of pressure with reference to the vertical flight, and
its symbol is ‹CP›_2, while the horizontal dotted line between them
represents the level of ‹CP›_2, from the best estimate that I could
make when the wings are in their natural position of soaring. It is
evident that this line passed far above the body of the vulture, and
if (the corresponding symbol for the height of the center of gravity
being ‹CG›_2), the ‹CG›_2, of the entire bird be taken, it will be
found to lie nearly in the point ‹c›. Where ‹c› is in the present
case, I could not determine exactly in my hasty examinations in the
live bird, but I assume that it is about 1/2 way between the central
horizontal axial line of the bird’s body and the upper portion. I
repeat that it is important to me to know what the vertical distance
is between ‹CP›_2 and ‹CG›_2 in each specimen of soaring bird. I may
observe in illustration that in the common sea-gull, it is nearly as
shown in the faint sketch; that is to say, that the corresponding
line ‹a› ‹b› in the soaring gull passes distinctly through the upper
part of the body, and the distance down to the ‹CG›_2 of the whole in
the gull is almost nil, while in the buzzard it is very considerable
as shown by the corresponding distance in the “John Crow.”
Now, what I want to get from you is the corresponding figures for
an average specimen of our Washington buzzard. If you will kindly
have one killed and weighed while fresh, and before the rigor-mortis
has set in, first noting the position of its wings when soaring in
a calm, and (if possible) when coming toward you or going away in
about a horizontal plane with your eye, in which position the wings
will be elevated and bent somewhat as in the case of the above sketch
of the “John Crow”; if you will kindly do this, so as to give me
corresponding facts with reference to the buzzard, namely weight,
area of extended wing surface, distance between tips as bent up in
ordinary flight, distance between ‹extended› tips, ‹the quantity›
‹CP›_2−‹CG›_2, and also will make such a tracing of the buzzard’s
wing as Mr. Manly will show you of the “John Crow’s,” I shall be
obliged.
My impression is that the buzzard is a considerably heavier bird
than the “John Crow,” without, however, very much greater spread of
wing. I may observe that when the wings of the Jamaica bird were
spread out, they were spread quite to their utmost extent, and the
distance between the tips of the terminal feathers was much greater
than when in flight. I wish you would kindly also add the scientific
name of the “John Crow,” with any particulars that you would think of
interest.
If there be any special expenses incurred in the preparation of this
memorandum, including the time of a photographer, I will direct them
to be paid from the Smithsonian fund. [p289]
If you could get Mr. Holmes (who made most of the sketches and all
of the photographs of the “John Crow”), to try and do something like
this for your buzzard, especially getting such a photograph of it ‹in
flight›, as will give the position of its center of gravity relative
to the center of pressure on the wings, it would add very greatly to
the value of your memoranda, and I think Mr. Holmes takes so full and
intelligent an interest in the subject, that he might be pleased to
give his help.
Very truly yours,
S. P. LANGLEY,
‹Secretary›.
MR. ROBERT RIDGWAY,
Smithsonian Institution,
Curator, Division of Ornithology, U. S. National Museum, Washington,
D. C.
In response to this request, Mr. Ridgway submitted the following very
interesting information:
SMITHSONIAN INSTITUTION,
UNITED STATES NATIONAL MUSEUM
WASHINGTON, D. C., October 16, 1900.
PROF. S. P. LANGLEY,
Secretary, Smithsonian Institution.
SIR:
I have the honor of submitting herewith the data obtained by Mr.
Rolla P. Currie concerning measurements, etc., of the common Turkey
Buzzard (‹Cathartes aura›) of the United States, as requested by you
in your letter of March 29, last.
The difficulties in the way of securing these data, already
explained by me in previous communications, are responsible for the
delay in submitting them.
Hoping that this material may prove of use to you, I am,
Very respectfully,
R. RIDGWAY,
‹Curator, Division of Birds›.
MEMORANDA IN REGARD TO THE TURKEY BUZZARD (SECOND SPECIMEN)
1. ‹Weight›.--1850 grammes.
2. ‹Area of outstretched wings›.--641 square inches. (Computed from
three sheets of tracings, ‹A›_1 and ‹A›_2 comprising the entire area
of both wings; ‹B›, a single wing.)
‹Note›.--As the bird was in process of moult, one of the large wing
quills, as shown by the tracings and compo-board patterns, is but
partially developed, thus slightly modifying the results obtained.
Its length, if full grown, would be nearly the same as that of the
quill just above it.
3. ‹Distance between the tips of these wings›.--5 feet, 8.7 inches.
4. ‹Distance between the tips of the same wings when the bird is in
horizontal soaring flight›.--Estimating the dihedral angle of the
wings to be 150°, and elevating the wings so as to make this angle,
the distance between their tips [p290] measures 5 feet, 5.7 inches,
or 3 inches less than when fully extended in the horizontal plane.
5. ‹The position of the center of pressure of the wing›.--This is
indicated on two compo-board patterns, ‹C› and ‹D›. ‹C› was made
from a fully extended wing, while ‹D› was made from the wing in the
soaring position. The centers of pressure of the wings are about
2 feet, 0.5 inches apart, or 1 foot, 0.25 inches from the central
point of the bird’s body.
6. ‹The position of the center of gravity of the soaring
bird›.--(Length of buzzard, 26 inches.) The center of gravity of
the soaring buzzard in the horizontal plane, CG_1, was found to lie
9-1/2 inches behind the tip of the beak and 16-1/2 inches in front
of the tip of the tail.
The center of gravity of the soaring bird in the vertical plane,
‹CG›_2, was found to lie 2.8 inches above the ventral point of the
body and 1.6 inches below the dorsal point, the depth of the bird’s
body at ‹CG›_1, being 4.4 inches.
In determining the center of gravity, the bird was frozen in the
soaring position, its wings making a dihedral angle of 150°. It
was then hung up, first horizontally and then vertically, and
balanced till the line from which it was suspended coincided with a
plumb-line placed in front of it; the measurements were then made.
The bird was afterwards, and while still frozen, hung up in the same
way in Mr. Smillie’s photographic room, and exposures made by him
in both positions. These photographs, ‹E›_1 and ‹F›_1 were enlarged
to natural size, and measurements made on the enlargements yielded,
as nearly as could be determined, the same results as when taken
directly upon the bird.
As determined by measurements upon the buzzard in soaring position,
the center of gravity was found to be 2.65 inches below the center
of pressure (estimating the center of pressure to be at the bend of
the wing); or, employing the compo-board pattern in a corresponding
position, the distance was seen to be a small fraction of an inch
less.
7. ‹The position of the root of the wing›.--This is indicated on the
tracing A_1.
‹a.› (Depth of the body on a vertical line with root, 3.5 inches.)
The root lies 1.6 inches below dorsal line, 1.9 inches above ventral
line.
‹b.› (Length of body, 26 inches.) The root lies 7.6 inches behind
tip of beak, 18.4 inches in front of tip of tail.
8. ‹The dihedral angle between the wings›.--The photographs taken
previously were not sufficiently large or distinct to enable us to
determine this with exactness. It was estimated, however, as 150°,
and experiments were made on this basis.
9. ‹The center of gravity of the dissected wing›.--This was found,
‹first›, for the wing having all the muscles, up to the ball and
socket joint, intact. One of the wings was frozen in the soaring
position and its center of gravity found by balancing on a point.
Its position was marked by a wire thrust through the wing at this
place, and the wing (‹H›) is preserved in formalin. This position
is also marked on a special tracing, ‹I›. It lies 6 inches from the
base of the humerus bone (root of wing). ‹Secondly›, it was found
for the wing denuded of all muscle. Its position was marked on
the other wing of the bird, which is preserved dry, spread in the
soaring position. It lies 9-3/4 inches from the base of the humerus.
[p291]
10. ‹The weight of the dissected wing›.--
‹a.› With all muscle up to the ball and socket joint intact, 325
grammes.
‹b.› With all muscle removed, 190 grammes.
Weight of muscle, therefore, 135 grammes.
‹The position of the root of the tail›.--
‹a.› In the horizontal plane, 11.8 inches in front of the tip of the
longest tail feather; 14.2 inches behind tip of beak.
‹b.› In the vertical plane: (depth of body from ventral point below
root of tail to a point directly above, which is on a level with the
highest point of the back, 2.5 inches.) 1.5 inches above ventral
point, 1 inch below dorsal point.
‹Weight of tail›.--With muscle, 40 grammes; ‹without› muscle, 30
grammes. Weight of muscle, therefore, 10 grammes.
EXHIBITS ACCOMPANYING THESE MEMORANDA
[Illustration: EXHIBIT E_1.--Turkey Buzzard suspended in soaring
position. (R. P. Currie.)]
‹A›_1 and ‹A›_2. Two sheets, comprising a tracing of the entire
turkey buzzard with fully outstretched wings. From these the area
of the wings and the distance between their tips was obtained. The
position of the root of the wing and the root of the tail is also
marked on one of these sheets.
‹B.› One sheet, comprising a tracing of a single wing, and from
which the area was also computed. This area, multiplied by 2,
gives the same result as the sum of both wings on A_1 and A_2. The
compo-board pattern ‹C› was made from this tracing.
‹C.› Compo-board pattern of fully extended wing, on which the center
of pressure is indicated.
‹D.› Compo-board pattern of wing in soaring position, on which the
center of pressure is shown. [p292]
‹E›_1. Photograph of bird in soaring position, suspended
horizontally.
‹E›_2. Same, enlarged to natural size.
‹F›_1. Photograph of bird in soaring position, suspended vertically.
‹F›_2. Same, enlarged to natural size.
‹G.› Tracing of wing in soaring position, from which the compo-board
pattern ‹D› was made.
[Illustration: EXHIBIT F_1.--Turkey Buzzard suspended vertically in
soaring position. (R. P. Currie.)]
‹H.› Wing preserved in formalin, on which the center of gravity is
recorded.
‹I.› Tracing of wing ‹H› when frozen in soaring position, on which
the center of gravity is marked.
‹J.› Wing with muscle removed, on which the center of gravity is
shown.
Several persons connected with the Smithsonian Institution and U.
S. National Museum have contributed towards securing the results
herewith submitted. Among them, I desire especially to mention Mr.
W. H. Holmes, Mr. [p293] F. A. Lucas, Mr. N. R. Wood, and Mr. R.
L. Reed. Mr. Holmes superintended the experiments in connection
with ‹No. 6› (finding the bird’s center of gravity), and by his
suggestions and criticisms helped me in many other particulars. The
photographs and enlargements were made by Mr. T. W. Smillie.
Respectfully submitted,
ROLLA P. CURRIE,
‹Aid, Division of Insects, acting in the Division of Birds›.
OCTOBER 16, 1900.
The feats of airmanship performed by the “John Crow” seemed to
greatly impress Mr. Langley and shortly after this trip he wrote the
following letter to the writer:
SMITHSONIAN INSTITUTION
WASHINGTON, D. C., April 16, 1900.
DEAR MR. MANLY:
I am reminded of the consequence that I have, in connection with
Mr. Chanute and perhaps Mr. Huffaker, attached in the past to the
possibility of directing the bird, and consequently the flying
machine, by the mere inflection of the wing, that is, by changing
its angle; and you recall to me that Mr. Huffaker at one time
proposed to arrange a wing, with some provision of a spring, which
should enable it to change its angle automatically. . . . .
I have been noting this ability to guide by the slight inflection
of the wing, in my studies of the Jamaica buzzard, and am ready
to say that I think, while the quarter-sized working model of the
great aerodrome is building, it will be worth while to make some
arrangement of the frame or wing-holder which will make it possible
to test this idea. I will endeavor to work out something of the
kind more in detail myself, but whatever it is, it will apparently
involve the ability of the wing to rotate about a line passing
nearly through it lengthwise, and an allowance for this; if not in
the wing itself, then in the wing-holder; will need to be made while
the present model is under construction.
I will request you to especially look out for this, as far as you
can on these indications.
Very respectfully yours,
S. P. LANGLEY,
‹Secretary›.
The instructions and suggestions contained in this letter and in many
conferences on the subject were never carried out by the writer, on
account of the extreme pressure of the work already on him which
had for its object, not the production of a flying machine which
would embody all of the control which we wished it to have, but
which would be burdened only with such devices and arrangements as
would enable it to transport a human being, and thus demonstrate the
practicability of human flight.
[p294]
SECRETARY LANGLEY’S INSTRUCTIONS TO ASSISTANTS
SMITHSONIAN INSTITUTION, WASHINGTON, D. C., November 30, 1895.
DEAR SIR:
The following instructions are to replace those of May 13, 1895:
1. The ‹minimum› fraction of its own “flying weight” (that is,
weight complete with initial water and fuel), which the aerodrome
shall lift on the pendulum, is 50 percent,[50] under such engine
power as can certainly be gotten up in the field and maintained
during forty seconds from the time the aerodrome is let go.
The blast, the pumps, and all other essential parts must, in other
words, be in such a condition that steam enough for this lifting
over 50 per cent of weight can be gotten up readily and surely
in the field and in a time which will still leave at least forty
seconds’ supply.
2. The ‹minimum› relation of supporting area to weight in any
aerodrome constructed hereafter, is to be two feet to the pound,[50]
and the minimum of power at the rate of one steadily-maintained
horse power[50] at the brake under ordinary conditions, to not over
twenty-two pounds (ten kilos) of flying weight. In absence of a
brake determination horse power may be taken--
H. P. = (revs. per min. at rest × pitch ×
diameter (in ft.) × thrust (in lbs.)) / 33,000.
These rules do not apply to No. 5, but they do to No. 6, which is to
be built over, if necessary, to meet them.
3. In balancing an aerodrome, unless otherwise instructed, set wings
at a root angle of either 10°, 7°, or 5°, after being certain from
previous inversion and sanding, that the tip angle in motion will
not differ from this root angle as much as 5°.
The object in balancing any aerodrome with a single pair of wings
is to be able to bring the ‹c g›_2 under their ‹c p›_2 without any
reference to the tail, which supports nothing, unless specially
ordered. But as this condition cannot now be obtained in Nos. 5
and 6, these at any rate, and perhaps future aerodromes, are to
carry a second pair of wings. When this second pair of wings is of
nearly equal size with the first it is to be assumed in preliminary
adjustments for weight and center of pressure, that the second pair
has two-thirds the lifting efficiency per unit area of the first.
Calling the whole distance from the mean center of pressure of
the wings to the center of gravity ‹M›. ‹M› is to have a definite
relation to the breadth of [p295] wings from tip to tip (‹b›) and
total fore and aft length (1), which is provisionally fixed at M =
√(bl)/8, and the line of thrust is to be not over one-fourth the way
from ‹c p›_2 to ‹c g›_2.
Generally speaking the front pair of wings will be fixed in position
and the adjustment for balancing made by moving the rear pair.
The individual weights of all parts checked by lump weighing are
to be given by the caretaker (Mr. Huffaker), under the general
scheme shown in the note. The work on the aerodromes being divided
into two classes, viz.: metal work and all which is not metal, the
two in charge of this work (Mr. Reed and Mr. Maltby) are severally
responsible for knowing the weight in grammes of any of the parts
they have put into their work, giving these weights to Mr. Huffaker,
together with any data for filling out the annexed tables,[51] on
his request.
Until further orders, Mr. Huffaker is charged with the
responsibility of seeing that these conditions are met before
any aerodrome is boxed, and will keep the record of weights of
the aerodromes and their principal parts as already completed,
in a book, to be preserved in your keeping, which will also be
arranged to show with signed ‹photographs› and descriptions, and
with sketches where needed, the condition and weight (as far as
constructed) of every aerodrome, and of any new construction of any
part, on the first of each month.
Particular attention is directed to the preceding paragraph, and to
the need that evidence of a definite character is to be obtained and
preserved of everything already done, and being done.
Without special orders to the contrary, you will not authorize the
boxing of any aerodrome which does not, to your knowledge, meet
these conditions.
Each aerodrome is to have the following parts in duplicate or in
triplicate:
2 pairs wings;
2 pairs tails;
2 pairs light silk covered rudders;
3 pairs wheels;
with any other parts in duplicate or triplicate, which experience
has shown to be necessary.
Mr. Reed will not box any aerodrome till a certificate from Mr.
Huffaker can be put on the inside cover, with the list of contents,
showing what the conditions are as to weight, wing area, power,
etc., and the person in the field charged with the duty of launching
the aerodrome (at present Mr. Reed), is authorized not to let it go
unless he is satisfied that it has a full forty seconds’ supply of
steam. [p296]
I am satisfied that a great deal of time is lost in putting
the aerodrome together for flight, owing to the absence of any
preliminary drill in doing this. Before it goes into the field the
whole is to be completely boxed, and then taken out from the box
and set up on the clutch, and steam gotten up for flight. All this
is to be done in the shop before the final boxing, and provision is
to be made so that no wiring or adjusting of parts is to be done in
the field which can possibly be avoided by forethought in the shop.
The tail-piece, for instance, is to be bushed with brass, so that it
will always come into the same place, and make a tight fit, in spite
of wetting or shrinking, in the steel tube, where it is to go into a
guide-way with a bayonet spring, or a like contrivance for setting
it at once securely into position.
The mean positions of the wings and tail are to be laid out
in some way permanently on the mid-rod, but every guy-rod or
adjustable piece is to be arranged so as to fit at once securely and
permanently in its position without wiring or like slow process.
Very truly yours,
S. P. LANGLEY,
‹Secretary›.
W. C. WINLOCK, Esq.,
Assistant in Charge,
Smithsonian Institution.
A copy to be communicated to:—
Mr. Huffaker,
Mr. Reed,
Mr. Maltby.
FOOTNOTES.
[37] “The Flying Machine” ‹McClure’s Magazine›, June, 1897.
[38] One noted astronomer and mathematician re-affirmed this opinion
as late as 1900 and even stated that man could not hope to construct
a flying machine capable of sustaining a weight as great as our
largest birds, knowing that even at that time the model Aerodromes
Nos. 5 and 6 had already done more than this.
[39] These wings are described in Chapter VI, pp. 191.
[40] See “Experiments in Aerodynamics.” It will be recalled that in
the experiments with the “plane-dropper” there was a greatly reduced
lifting power with superposed planes when their distance apart was
one-half the width the planes, unless a speed of about 42.5 feet a
second was obtained. In the above tests with the superposed wings,
the speed was only from twenty to twenty-two feet a second at the
time of launching, and as the distance between the surfaces was only
one-half as great as their width, it is not surprising that the
lifting power should not be as great as with the “single-tier” wings.
[41] In fact the setting of the tail at a negative angle and
fastening it to the frame by an elastic or spring connection was only
begun in 1896, and while it proved to be the key to the solution
of the problem of automatic longitudinal stability, yet it was not
at that time so recognized, although the first real test of the
aerodromes after the elastic connection and negative angle of the
tail were adopted resulted in the epoch-making flight of No. 5 on May
6. By comparing the angle of the tail on No. 5 in Plate 27A, Part I,
with the angle of the tail on No. 6 in Plate 27B, Part I, it will be
seen that while the first had an angle of much less than 5 degrees,
the latter had an angle of about 15 degrees. But the wooden springs
changed so that it was not accurately known what the angle really was
at the time at either flight in 1896.
[42] The drawings, Plate 55, which illustrate many of the fittings
used on the frame, show the guy-wires as attached by means of loops
twisted in their ends, these drawings having been made before the
final plan of attaching the wires had been devised.
[43] See explanation of system of locating points in Part I, Chap.
II, p. 15.
[44] See Balancing of Engines, by Archibald Sharpe.
[45] Except for a ten minute stop to renew the supply of lubricating
oil and change the sparking batteries.
[46] See foot-note, page 249.
[47] The weight was afterwards increased to 850 pounds due to
repairing the wings and adding more sparking batteries.
[48] See Experiments in Aerodynamics, Smithsonian Contributions to
Knowledge, Vol. 27, Washington 1891.
[49] Researches and Experiments in Aerial Navigation, Smithsonian
Publication No. 1809, Washington, 1908.
[50] All these minimum permissible conditions are connected by the
tacit assumption that the supporting area is not greatly over 2 ft.
to the pound of weight. If for instance the weight were increased by
larger wings or more wings, furnishing a much greater supporting area
per pound, these conditions would not necessarily apply.
[51] These tables were later designated as “Data Sheets.” Several
copies, with the data duly entered on them, are given in this
appendix, and the form which Mr. Langley included in this letter is
therefore not repeated here.--EDITOR.
[p297]
DATA SHEETS.
DATA SHEET No. 1.
Weight of Aerodrome No. 5, as photographed on May 11, 1896.
Certified to by R. L. Reed, May 6, 1896.
---------------------------------------+----------+-------------+
Parts. | Sizes. | Weight. |
---------------------------------------+----+-----+------+------+
|‹m.›|‹ft.›|‹gr.› |‹lbs.›|
1 Frame, including everything of | | | | |
metal, permanent and undetachable, | | | | |
such as bed-plate, cross-rods for the | | | | |
support of propellers, bearing points | | | | |
for clutch, etc. | | | 2443| |
| | | | |
2 Engine, gears, shafts, etc. | | | 1110| |
| | | | |
3 Pump, pump shaft | | | 231| |
| | | | |
4 Hull covering | | | 350| |
| | | | |
5 Gasoline tanks, valves | | | 178| |
| | | | |
6 Smokestack | | | 342| |
| | | | |
7 Float | | | 275| |
| | | | |
8 Reel | | | 77| |
| | | | |
9 Wing clamps, 235; clamp for | | | | |
guy-posts, 29 | | | 264| |
| | | | |
10 Other things, counter | | | 75| |
| | | | |
11 Burners | | | 360| |
| | | | |
12 Boilers | | | 651| |
| | | | |
13 Separators, steam gauge, pipe to | | | | |
engine | | | 540| |
| | | | |
14 Exhaust pipe | | | 143| |
| | | | |
15 | | | | |
| | | | |
16 | | | | |
| | | | |
17 Wings (without clamp) | | | 1950| |
| | | | |
18 Tail (without clamp) | | | | |
| | | | |
19 Rudder | | | 350| |
| | | | |
20 Guy sticks, each, 57 | | | 114| |
| | | | |
21 Propellers | | | 800| |
| | | | |
22 Extra length of midrod, 308; drop | | | | |
piece for rudder, 40 | | | 348| |
| | | | |
23 Wood Bowsprit | | | 74| |
| | | | |
24 Other things | | | | |
| | | | |
25 | | | | |
| | | | |
26 | | | | |
| | | | |
27 Fuel (at starting flight) | | | 200| |
| | | | |
28 Water (at starting flight) | | | 900| |
| | | | |
29 | | | | |
| | | | |
30 | | | | |
| | | | |
31 Sundries unknown | | | | |
| | | | |
32 | | | | |
| | | | |
33 | | | | |
| | | | |
34 Total flying weight | | |11,775| 26 |
| | | | |
35 | | | | |
| | | | |
36 | | | | |
| | | | |
37 | | | | |
| | | | |
38 Total area of support (not | | | | |
including tail) sq. ft. | |68 | | |
| | | | |
39 Total area of support in feet, | | | | |
divided by total flying weight in lbs. | | 2.6 | | |
| | | | |
40 Total area of horizontal tail sq. | | | | |
ft. | | | | |
| | | | |
41 Total area of rudder (vertical) | | | | |
sq. ft. | | 6 | | |
| | | | |
42 Horse-power at brake. Horse-power | | | | |
by formula* .72 | | 7 | | |
| | | | |
43 Minimum pressure during 40 secs. | | | | |
lift, 150 lbs. | | | | |
| | | | |
44 Lift at pendulum (during 40 secs. | | | | |
absolute) 5772 | | | | |
| | | | |
45 Lift at pendulum (during 40 secs. | | | | |
in terms of wt.) 49% | | | | |
| | | | |
46 Minimum pressure with which wheels | | | | |
turn, 10 lbs. | | | | |
| | | | |
47 Position of center of pressure of | | | | |
wings† F. W., 1575; R. W., 1383.5 | | | | |
| | | | |
48 Time of getting up full steam, 1 | | | | |
minute | | | | |
| | | | |
49 | | | | |
| | | | |
50 Curvature of wings, 1/11 | | | | |
| | | | |
51 Root angle of wings, 9° | | | | |
| | | | |
52 Tip angle of wings, 9° | | | | |
| | | | |
53 Position of wings, Front rib on F. | | | | |
W., 1607; R. W., 1415.5 | | | | |
| | | | |
54 How guyed | | | | |
| | | | |
55 | | | | |
| | | | |
56 | | | | |
| | | | |
57 | | | | |
| | | | |
58 Position of tail | | | | |
| | | | |
59 Angle of tail | | | | |
| | | | |
60 Co-efficient elasticity of tail | | | | |
| | | | |
61 Position of rudder, center, | | | | |
1288.3; rear end, 1229.8 | | | | |
| | | | |
62 Line of thrust, 2500 | | | | |
| | | | |
63 Line of thrust, 1500 which is 9 | | | | |
cm. below the center of midrod | | | | |
| | | | |
64 Center of gravity_1 of whole, 1497 | | | | |
| | | | |
65 Center of gravity_2 2501, i. e., 1 | | | | |
cm. above line of thrust | | | | |
| | | | |
66 Center of pressure_1 of whole | | | | |
estimate, 1498 | | | | |
| | | | |
67 Center of pressure_2, 2536 | | | | |
| | | | |
68 | | | | |
| | | | |
69 | | | | |
| | | | |
70 | | | | |
| | | | |
71 | | | | |
| | | | |
72 | | | | |
---------------------------------------+----+-----+------+------+
Parts. Remarks.
1 Front end of bowsprit, 1686.3.
2 Front end of midrod, 1611.6.
5 Front edge of F. W., 1607.
8 C. of P. on F. W., 1575.
11 Back edge of F. W., 1527.
14 Back edge of cross frame, 1509.
17 Line through center of propellers, 1500.
21 C. of G., 1497.
24 Front edge of R. W., 1415.5.
27 C. of P. on R. W., 1383.5.
30 End of mid-rod, 1360.5.
33 Front end of rudder, 1343.8.
36 Back edge of R. W., 1335.5.
39 Center of rudder, 1288.3.
41 Back end of rudder, 1229.8.
* H. P. = (Rev.×diam.×pitch ratio×thrust)/33000
† This is calculated on the assumption that the center of pressure
on each wing or on pair of wings at a motion of 2000 feet per minute
is in ordinary curved wings 2-5 the way from front to rear, that for
wings of usual size the rear wings have 2-3 of the efficiency per
surface of the front ones and that the tail proper bears no part of
the weight; but if rear wing is smaller or larger this efficiency is
smaller or larger per unit of surface.
[p298]
DATA SHEET No. 2.
Weight of Aerodrome No. 6.
Certified to by R. L. Reed, November 27 and 28, 1896.
-------------------------------------------+-----------+-------------+
Parts. | Sizes. | Weight. |
-------------------------------------------+-----+-----+------+------+
|‹m.› |‹ft.›|‹gr.› |‹lbs.›|
1 Frame, including everything of metal, | | | | |
permanent and undetachable, such as bed-| | | | |
plate, cross-rods for the support of | | | | |
propellers, bearing points for clutch, | | | | |
etc. | | | 1178| |
2 Engine, gears, shafts, etc. | | | 1043| |
| | | | |
3 Pump, pump shaft | | | 190| |
4 Hull covering | | | 345| |
5 Gasoline tanks, valves | | | 306| |
6 Smokestack, 302; burner, 172 | | | 474| |
7 Float | | | 275| |
8 Reel | | | 77| |
9 Wing clamps, 238; drop piece for rudder, | | | 278| |
40 | | | | |
10 Other things | | | 156| |
11 Boiler, frames, mica cover | | | 694| |
12 Separator, steam gauge, pipe to engines | | | 535| |
13 Exhaust pipe | | | 82| |
14 | | | | |
15 | | | | |
16 | | | | |
17 Wings (without clamp), wet | | | 2154| |
18 Tail (without clamp) | | | | |
19 Rudder | | | 375| |
20 Guy sticks, each 53 | | | 106| |
21 Propellers | | | 644| |
22 Extra length of midrod | | | 398| |
23 Wood bowsprit | | | 135| |
24 Counter | | | 75| |
25 | | | | |
26 | | | | |
27 Fuel (at starting flight) | | | 250| |
28 Water (at starting flight) | | | 2350| |
29 | | | | |
30 | | | | |
31 Sundries unknown | | | | |
32 | | | | |
33 | | | | |
34 Total flying weight | | |12,120| |
35 | | | | |
36 | | | | |
37 | | | |
38 Total area of support (not including | | 54| | |
tail) sq. ft. | | | | |
39 Total area of support in feet, divided | | | | |
by total flying weight in lbs. | | 2 | | |
40 Total area of horizontal tail sq. ft.| .6 | | | |
41 Total area of rudder (vertical) sq. ft.| .6 | | | |
42 Horse-power at brake Horse-power by | | | | |
formula* | | | | |
43 Minimum steam pressure during 40 secs. | | | | 130|
lift | | | | |
44 Lift at pendulum (during one minute | | | | 7,211|
absolute) | | | | |
45 Lift at pendulum (during one minute in | | | | |
terms of wt.) | | | | |
46 Minimum pressure with which wheels turn | | | | 10 |
47 Position of center of pressure of wings†| | | | |
48 Time of getting up full steam, 75 secs. | | | | |
49 Angle of midrod with horizon, 2° 17′ | | | | |
50 Curvature of wings, 1 in 18, 1/4 from | | | | |
front | | | | |
51 Root angle of wings, 10° 30′ | | | | |
52 Tip angle of wings, 10° 30′ | | | | |
53 Position of wings | | | | |
54 How guyed | | | | |
55 | | | | |
56 | | | | |
57 | | | | |
58 Position of tail | | | | |
59 Angle of tail | | | | |
60 Co-efficient elasticity of tail | | | | |
61 Position of rudder | | | | |
62 | | | | |
63 Line of thrust 1500 | | | | |
64 Center of gravity_1 of whole, 1483.8 | | | | |
65 Center of gravity_2, 2482‡ | | | | |
66 Center of pressure_1 of whole | | | | |
estimate, 1487 | | | | |
67 Center of pressure_2, 2520 | | | | |
68 | | | | |
69 | | | | |
70 | | | | |
71 | | | | |
72 | | | | |
-------------------------------------------+-----+-----+------+------+
Parts. Remarks.
1 Front end of bowsprit, 1797.
2 Center of float in first trial, Nov.
6 Front end of midrod, 1613.7. 9 Front edge of F. W., 1595.7.
12 Center of float in flight, Nov. 28, 1896, 1575.8.
16 C. of P. on F. W., 1563.7.
19 Back edge of F. W., 1515.7.
22 Line through center
of propellers, 1500.
26 C. of G., 1484.4 (old C. of G., 1486.3).
29 Front edge of R. W., 1406.
32 C. of P. on R. W., 1374.
35 End of midrod, 1351.3
38 Front end of rudder, 1334.5.
41 Back edge of R. W., 1326.
43 Center of rudder, 1279.
46 Back end of rudder, 1220.5.
49 Reed wings, 80 cm.×185 cm. in rectangle.
53 Weight in shop, 1982 g.
56 On day of flight they weighed 2154 g. because they were damp.
60 Area 54 sq. ft.
63 Spread of wings, 359 cms. or 11′ 9-3/8″.
67 Weight of aerodrome in flight, 12,120 grs.
* H. P. = (Rev.×diam.×pitch ratio×thrust)/33000
† This is calculated on the assumption that the center of pressure
on each wing or on pair of wings at a motion of 2000 feet per minute
is in ordinary curved wings 2-5 the way from front to rear, that for
wings of usual size the rear wings have 2-3 of the efficiency per
surface of the front ones and that the tail proper bears no part of
the weight; but if rear wing is smaller or larger this efficiency is
smaller or larger per unit of surface.
‡ This is undoubtedly incorrect, as if it were true, the C. G. would
be just at the center of the separator, and this would be impossible.
Mr. Reed states that the C. G. was 2 cm. below the side frame, and if
this is correct, we would have C. G. = 2486.
[p299]
DATA SHEET No. 3.
Weight of Aerodrome No. 6, Flat Wings and Pénaud Rudder.
Certified to by Chas. M. Manly, June 7, 1899.
---------------------------------------+----------+-------------+
Parts. | Sizes. | Weight. |
---------------------------------------+----+-----+------+------+
|‹m.›|‹ft.›|‹gr.› |‹lbs.›|
1 Frame, including everything of | | | | |
metal, permanent and undetachable, | | | | |
such as bed-plate, cross-rods for the | | | | |
support of propellers, bearing points | | | | |
for clutch, etc. | | | 2867| |
| | | | |
2 Engine, gears, shafts, etc. | | | | |
| | | | |
3 Pump, 123; pump shaft, 49 | | | 172| |
| | | | |
4 Hull covering, including apron and | | | | |
piece behind separator | | | 274| |
| | | | |
5 Gasoline and air tanks, 167, 114; | | | | |
air valve, 16 | | | 297| |
| | | | |
6 Smokestack, 319; counter, 95; | | | | |
burner, 165 | | | 679| |
| | | | |
7 Float, 275; pipe from pump to | | | | |
boiler, 40 | | | 315| |
| | | | |
8 Reel, with fork and float | | | 128| |
| | | | |
9 Wing clamps, 188; guy-post clamps, | | | 212| |
24 | | | | |
| | | | |
10 Boiler, 764; steam gauge and | | | | |
connections, 79 | | | 843| |
| | | | |
11 Front lower bearing post, 75; | | | | |
clutch post, 58; rear bearing points, | | | 288| |
155 | | | | |
| | | | |
12 Separator and pipes leading to | | | | |
engines and pump | | | 502| |
| | | | |
13 Drop piece for rudder, 57; | | | 75| |
guy-post for rudder, 18 | | | | |
| | | | |
14 | | | | |
| | | | |
15 | | | | |
| | | | |
16 | | | | |
| | | | |
17 Wings (without clamp) | | | 2077| |
| | | | |
18 Superposed wings, 3448 | | | | |
| | | | |
19 Rudder | | | 323| |
| | | | |
20 Guy sticks, each 53 | | | 106| |
| | | | |
21 Propellers | | | 620| |
| | | | |
22 Extra length of midrod | | | 377| |
| | | | |
23 Wood bowsprit | | | 128| |
| | | | |
24 Canvas keel, 36; rudder, 76 | | | 112| |
| | | | |
25 | | | | |
| | | | |
26 | | | | |
| | | | |
27 Fuel (at starting flight) | | | 175| |
| | | | |
28 Water (at starting flight) | | | 1525| |
| | | | |
29 | | | | |
| | | | |
30 | | | | |
| | | | |
31 Sundries unknown | | | | |
| | | | |
32 | | | | |
| | | | |
33 | | | | |
| | | | |
34 Total flying weight | | |11,995| 26.44|
| | | | |
35 | | | | |
| | | | |
36 | | | | |
| | | | |
37 | | | | |
| | | | |
38 Total area of support (not | | | | |
including tail) sq. ft. | |54 | | |
| | | | |
39 Total area of support in feet, | | | | |
divided by total flying weight in lbs. | | 2.04| | |
| | | | |
40 Total area of horizontal tail sq. | | | | |
ft. | | 9.5 | | |
| | | | |
41 Total area of rudder (vertical) | | | | |
sq. ft. | | 7.75| | |
| | | | |
42 Horse-power at brake Horse-power | | | | |
by formula* | | | | |
| | | | |
43 | | | | |
| | | | |
44 Lift at pendulum (during one | | | | |
minute absolute) | | | | |
| | | | |
45 Lift at pendulum (during one | | | | |
minute in terms of wt.) | | | | |
| | | | |
46 Minimum pressure with which wheels | | | | |
turn | | | | |
| | | | |
47 Position of center of pressure of | | | | |
wings† 40% from front | | | | |
| | | | |
48 | | | | |
| | | | |
49 | | | | |
| | | | |
50 Curvature of wings, 1 in 18 | | | | |
| | | | |
51 Root angle of wings, 10° | | | | |
| | | | |
52 Tip angle of wings, 10° | | | | |
| | | | |
53 Position of wings--front edge of | | | | |
front wing, 1595.7; of rear wing, | | | | |
1406.5 | | | | |
| | | | |
54 How guyed--with wires from wing to | | | | |
wing on top and to guy-post on bottom | | | | |
| | | | |
55 | | | | |
| | | | |
56 | | | | |
| | | | |
57 | | | | |
| | | | |
58 Position of center of rudder, | | | | |
1279.5 | | | | |
| | | | |
59 Angle of tail, 10° | | | | |
| | | | |
60 Co-efficient elasticity of tail | | | | |
| | | | |
61 Position of rudder | | | | |
| | | | |
62 | | | | |
| | | | |
63 Line of thrust, 1500 | | | | |
| | | | |
64 Center of gravity_1 of whole, | | | | |
1484.4 | | | | |
| | | | |
65 Center of gravity_2 | | | | |
| | | | |
66 Center of pressure_1 of whole | | | | |
estimate | | | | |
| | | | |
67 Center of pressure_2 | | | | |
| | | | |
68 | | | | |
| | | | |
69 | | | | |
| | | | |
70 | | | | |
| | | | |
71 | | | | |
| | | | |
72 | | | | |
Parts. Remarks.
1 Front edge of bowsprit, 1702.7. Weight 2867 gm. for part 1
includes also part 2.
2 Center of float with small wind vane rudder, 1628.9.
6 Front edge of midrod, 1613.7.
9 Center of float with small rudder off, 1609.2.
12 Front edge of F. W., 1595.7.
15 C. of P. on F. W., 1563.7.
18 Back edge of F. W., 1515.7.
21 Line through center of propellers, 1500.
25 C. of G., 1484.4.
28 Front edge of R. W., 1406.5.
31 C. of P. on R. W., 1374.5.
34 End of midrod, 1351.8.
37 Front end of rudder, 1335.
39 Back edge of R. W., 1326.5.
42 Center of rudder, 1279.5.
45 Back end of rudder, 1221.
* H. P. = (Rev.×diam.×pitch ratio×thrust)/33000
† This is calculated on the assumption that the center of pressure
on each wing or on pair of wings at a motion of 2000 feet per minute
is in ordinary curved wings 2-5 the way from front to rear, that for
wings of usual size the rear wings have 2-3 of the efficiency per
surface of the front ones and that the tail proper bears no part of
the weight; but if rear wing is smaller or larger this efficiency is
smaller or larger per unit of surface.
[p300]
DATA SHEET No. 4.
Weight of Aerodrome No. 6, Superposed Wings and Pénaud Rudder.
Certified to by Chas. M. Manly, June 13, 1899.
---------------------------------------+----------+-------------+
Parts. | Sizes. | Weight. |
---------------------------------------+----+-----+------+------+
|‹m.›|‹ft.›|‹gr.› |‹lbs.›|
1 Frame, including everything of | | | | |
metal, permanent and undetachable, | | | | |
such as bed-plate, cross-rods for the | | | | |
support of propellers, bearing points | | | | |
for clutch, etc. | | | 2867| |
| | | | |
2 Engine, gears, shafts, etc. | | | | |
| | | | |
3 Pump, 123; pump shaft, 49 | | | 172| |
| | | | |
4 Hull covering, including apron and | | | | |
piece behind separator | | | 274| |
| | | | |
5 Gasoline and air tanks, 167, 114; | | | | |
air valve, 16 | | | 297| |
| | | | |
6 Smokestack, 319; counter, 95; | | | | |
burner, 170 | | | 584| |
| | | | |
7 Float | | | 315| |
| | | | |
8 Reel, with fork and float | | | 128| |
| | | | |
9 Wing clamps, 188; guy-post clamps, | | | | |
24 | | | 212| |
| | | | |
10 Boiler, 764; steam gauge and | | | | |
connections, 79 | | | 843| |
| | | | |
11 Front bearing point, 75; clutch | | | | |
post, 58; rear bearing points, 155 | | | 288| |
| | | | |
12 Separator and pipes to engines and | | | | |
pump | | | 502| |
| | | | |
13 Drop piece and guy-post for rudder | | | 75| |
| | | | |
14 | | | | |
| | | | |
15 | | | | |
| | | | |
16 | | | | |
| | | | |
17 Wings (without clamp), 2077; | | | | |
superposed wings | | | 3448| |
| | | | |
18 Tail (without clamp) | | | | |
| | | | |
19 Rudder | | | 323| |
| | | | |
20 Guy sticks | | | 106| |
| | | | |
21 Propellers | | | 620| |
| | | | |
22 Extra length of midrod | | | 377| |
| | | | |
23 Wood bowsprit | | | 128| |
| | | | |
24 Canvas keel, 36 | | | 36| |
| | | | |
25 | | | | |
| | | | |
26 | | | | |
| | | | |
27 Fuel (at starting flight) | | | 175| |
| | | | |
28 Water (at starting flight) | | | 1525| |
| | | | |
29 | | | | |
| | | | |
30 | | | | |
| | | | |
31 Sundries unknown | | | | |
| | | | |
32 | | | | |
| | | | |
33 | | | | |
| | | | |
34 Total flying weight | | |13,275| |
| | | | |
35 | | | | |
| | | | |
36 | | | | |
| | | | |
37 | | | | |
| | | | |
38 Total area of support (not | | | | |
including tail) sq. ft. | |87.4 | | |
| | | | |
39 Total area of support in feet, | | | | |
divided by total flying weight in lbs | | | | |
| | | | |
40 Total area of horizontal tail sq. | | 9.5 | | |
ft. | | | | |
| | | | |
41 Total area of rudder (vertical) | | 7.75| | |
sq. ft. | | | | |
| | | | |
42 Horse-power at brake Horse-power | | | | |
by formula* | | | | |
| | | | |
43 | | | | |
| | | | |
44 Lift at pendulum (during one | | | | |
minute absolute) | | | | |
| | | | |
45 Lift at pendulum (during one | | | | |
minute in terms of wt.) | | | | |
| | | | |
46 Minimum pressure with which wheels | | | | |
turn | | | | |
| | | | |
47 Position of center of pressure of | | | | |
wings†, 40% from front | | | | |
| | | | |
48 | | | | |
| | | | |
49 | | | | |
| | | | |
50 Curvature of wings, 1 in 18 | | | | |
| | | | |
51 Root angle of wings, 10° | | | | |
| | | | |
52 Tip angle of wings, 10° | | | | |
| | | | |
53 Position of wings--front edge of | | | | |
front wing, 159 | | | | |
| | | | |
54 How guyed | | | | |
| | | | |
55 | | | | |
| | | | |
56 | | | | |
| | | | |
57 | | | | |
| | | | |
58 Position of tail | | | | |
| | | | |
59 Angle of tail, 7-1/2° | | | | |
| | | | |
60 Co-efficient elasticity of tail, | | | | |
1240 grammes at center to deflect to | | | | |
the horizontal | | | | |
| | | | |
61 Position of rudder | | | | |
| | | | |
62 | | | | |
| | | | |
63 Line of thrust, 1500 | | | | |
| | | | |
64 Center of gravity_1 of whole, | | | | |
1484.4 | | | | |
| | | | |
65 Center of gravity_2 | | | | |
| | | | |
66 Center of pressure_1 of whole | | | | |
estimate | | | | |
| | | | |
67 Center of pressure_2 | | | | |
| | | | |
68 | | | | |
| | | | |
69 | | | | |
| | | | |
70 | | | | |
| | | | |
71 | | | | |
| | | | |
72 | | | | |
---------------------------------------+----+-----+------+------+
Parts. Remarks.
1 Front edge of bowsprit, 1702.7. Weight 2867 gm. includes parts 2.
2 Center of float without small wind vane rudder, 1666.1. (Center of
float with wind vane rudder on, 1627.)
8 Front edge of midrod, 1613.7.
11 Front edge of F. W., 1585.
13 C. of P. on F. W., 1563.7.
16 Rear edge of F. W., 1531.7.
19 Line through center of propellers, 1500.
23 C. of G., 1484.4.
26 Front edge of R. W., 1395.8.
29 C. of P. on R. W., 1374.5.
32 End of midrod, 1351.8.
35 Front end of rudder, 1335.
38 Back edge of R. W., 1342.5.
40 Center of rudder, 1279.5.
43 Back end of rudder, 1221.
* H. P. = (Rev.×diam.×pitch ratio×thrust)/33000
† This is calculated on the assumption that the center of pressure
on each wing or on pair of wings at a motion of 2000 feet per minute
is in ordinary curved wings 2-5 the way from front to rear, that for
wings of usual size the rear wings have 2-3 of the efficiency per
surface of the front ones and that the tail proper bears no part of
the weight; but if rear wing is smaller or larger this efficiency is
smaller or larger per unit of surface.
[p301]
DATA SHEET No. 5.
Weight of Aerodrome No. 6, Flat Wings and Pénaud Rudder.
Certified to by Chas. M. Manly, June 22, 1899.