NARRATIVE OF WEATHER OBSERVATIONS FROM AN AIRPLANE
In order to qualify as meteorologist competent to confer with aviators,
it seemed desirable to become personally acquainted with some of
the conditions that confronted them. As a matter of professional
acquirement therefore, I was glad to accept an invitation to go aloft
after the necessary official arrangements had been made with Washington.
This trip was in line with the previous endeavors of applying practical
meteorology to the science of flight and appropriately extended the
work which was begun in San Diego with Chanute and the sea-gulls
fifteen years before.
_Object of Flight._--I wished to put myself in the student’s place
and learn at first hand the practical facts he demanded from weather
observations and to acquaint myself with everything possible that might
be of value to an aviator. There were two definite things of which I
desired knowledge: first, to determine the height of the upward trend
of the sea-breeze over Point Loma which causes the mysterious “woolly”
of a score of years’ acquaintance from a yachting standpoint; second,
to observe the extent, form, and composition of the velo cloud which is
the characteristic sun-cover of California.
_Preparations for the Ascent._--Aviator Instructor Oscar Brindley
(the 1915 winner of the Curtiss trophy), in military tractor No.
50, was assigned as pilot. It may be stated here that the accepted
definition of aviator is a pilot of a flying-machine heavier than air.
The airplane used in my first flight (see Fig. 13) was made in Los
Angeles and is the present standard army model. This tractor has an
80-horsepower engine and 8-foot propeller. It is 21 feet long, has a
wing-spread of 38 feet, supporting area 364 square feet, and a flying
radius, with two persons, of 300 miles. The maximum altitude attained
with this model at San Diego was 13,000 feet. Before being placed in
service the machines are thoroughly gone over at the repair shop (see
Fig. 22), and the motors are run at full speed for twenty-four hours,
after which they are taken down and subjected to scrutiny for possible
defects. All of the struts, guys, and wires are closely examined; the
boltheads are all drilled, wired, and soldered so that no amount of
vibration will loosen them. Regardless of the length of the flight,
each machine, before going up again, is given a rigid inspection and
not until the mechanicians have tested every part is it pronounced
ready.
Not being prepared with a regulation aviation suit, I was loaned a
leather jacket by one officer, face-goggles and safety helmet by
others. I then took my place in the observer’s seat forward and was
strapped into it with the safety belt (see Fig. 12). I was cautioned to
let my body give way as the waist-controls were moved from side to side
and not pay any attention to the steering rudder wheel which had a way
of mysteriously revolving, advancing and receding.
In cranking an airplane, a certain formula is always gone through. The
mechanician at the propeller calls out, “Close!” The aviator closes
the switch and repeats the word. This short-circuits the ignition
apparatus so that no spark occurs in the cylinders. The propeller is
turned in order to introduce explosive mixtures into the cylinders.
When ready to start the mechanician says “Open!” The aviator opens the
switch and repeats the word. The charges in the cylinders then fire
when the propeller is turned.
After the engine starts, the machine is “trimmed” by helpers and
jockeyed for a favorable “take-off” into the air. (See Figs. 14, 15.)
This model of airplane climbs on a gradient 1 to 7; its minimum speed
is 41 miles per hour. In other words, if the speed is less than 41
miles per hour the machine will not fly horizontally.
_The Ascent._--The tractor was headed into a 30-mile northwesterly
wind so that the “take-off” was quick and easy; there were only a few
seconds spent rolling over the field, when the airplane left the ground
and I felt the never to be forgotten cushioning feeling of the air.
For ten seconds there was experienced a decidedly weakening nervous
chill, which occurred to me once before when making a high dive from
a spring-board. It was the sort of physiological disturbance that can
only be counteracted by immediately pulling one’s self together saying,
“_Well, here goes nothing!_” The momentary depression was immediately
followed by a corresponding elation of feeling which strange to say did
not leave me during the trip and is always associated with thoughts
of the journey. There was no dizziness, although I am peculiarly
susceptible to the least change in balance. The earth did not recede
as we progressed steadily upward; we seemed part of the earth, but
not of it. Although the airplane reached an altitude of 3,000 feet in
a comparatively few minutes, the barometer falling from 30.0 to 27.0
inches, the decreased bodily pressure was not at all noticeable.[H]
[H] Trans-American Climatic Association, 1915, 31:20, Hot
Springs, Va.
Next to the supporting quality of the atmosphere I had noticed the
70-mile blast of air as the airplane pushed its way steadily onward and
upward. Naturally, the exhaust of the motor in addition to the roar of
the wind made conversation impossible. Some airplanes have telephone
communication between observer and pilot. (See Fig. 9.) During one
flight in a machine not so equipped, the passenger noticed the breaking
of some apparatus. Knowing that it was impossible to make himself heard
he hastily scribbled the word “Accident!” on a bit of card, whereupon
the pilot shut off his engine and glided to earth.
_Two-thousand Feet above Point Loma._--Carrying out my suggestion as
to investigating the “woolly,” the pilot drove the machine straight
for Point Loma and those unseen aërial breakers. Suddenly there were
two distinct “wallops” and I felt the fuselage beneath me respond as
if struck by a stuffed club. There was evidently first a surge then
a drop, and it was the descending current of air that deprived the
airplane of the supporting medium, hence the shock. Point Loma itself,
from this altitude, and seen directly from above, looked very like a
barracuda’s backbone--long, low, and ugly. Although this peninsula (see
Fig. 21) is less than 500 feet high it so effectively deflects the
prevailing northwesterly wind that the upward surge has been noticed by
aviators at an altitude of 4,000 feet. It is no wonder then that these
descending winds, called “woollies” (from their churning the water into
isolated masses which look like tufts of wool), are dreaded alike by
yachtsmen and birdmen. They have been known to carry away topsails from
too closely venturing schooners and student aviators always give the
vicinity of Point Loma a wide berth.
_No Winds Aloft._--We had not changed our direction since leaving the
ground, but after passing over Point Loma the airplane was put sharply
on a port course. I had been expecting this and must confess, somewhat
dreaded it, innocently thinking that a 30-mile wind added to our
70-mile rate of speed would “heel” the craft to an uncomfortable angle
when the course was changed from northwesterly to southerly. What was
my astonishment to find that the putting about was unaccompanied by
any of the nautical motions such as tilting or canting. Theoretically
one may be ever so well grounded in physical laws but it seems to take
actual experience to bring their truth home to us. Of course there can
be no wind in the air; when we entered the air it was moving 30 miles
an hour in relation to the earth but as soon as we were free from the
earth the velocity of the wind had no effect on our flight. No matter
how strong the gale, so far as it concerned the airplane, if the wind
be steady no difficulty is experienced; the aviator is concerned only
by wind-shifts.
_The Velo Cloud Seen from Above._--In kindergarten days I remember that
one of the first questions I asked was “Are clouds smoke?” And this
early query was really first answered in the air. Fog on a mountain
top may be cloud, but somehow cloud free from close proximity to the
earth seems different.
The machine was put through the cloud blanket much as a horse takes
a hurdle; it seemed unlike fog and more of a palpable substance. As
we emerged, the sun was shining on it like a silvery sea with gently
undulating surfaces and it looked for all the world as supportable
as layers of cotton-wool. Many times have cloud-banks from mountain
tops been observed, yet the upper side of the velo cloud from a
flying-machine looked very different. The cloud was only four or
five hundred feet thick and extended inland a few miles in irregular
outline. The seaward edges of the velo cloud were not ragged, and
apparently paralleled the coast for 10 or 15 miles.
Such was the exhilaration and confidence the air gave that I can
understand how parachute jumpers confidently step off into space,
for to them the air is a supporting medium no more terrible than a
transparent sea to a good swimmer. I believe that the record parachute
drop was made in 1916 by Colonel Maitland, of the English Royal Flying
Corps, who descended in a parachute 10,000 feet from an airplane.
Fifteen minutes was occupied in the descent.
_Ease of Vision at 3,500 Feet Altitude._--At this altitude the ease of
vision is most remarkable. At this height, _with perpendicular vision_,
the eye is possessed of wonderful powers. In those “solitudes august
with stars” men not only “mount up with wings as eagles” but are given
the eagle’s unobstructed vision. Birds have been credited with much too
keen vision. From this height of several thousand feet every object
stood out with remarkable distinctness. Automobiles racing along the
El Cajon boulevard to Lakeside were readily picked up with the unaided
eye although 20 miles away. Looking down over the aviation field the
long compass mark and the wind-direction pennant (Figs. 19 and 20)
were easily distinguished. The bay and ocean, however, gave the most
remarkable revelation, for the bottom of the bay and the shallow ocean
shore were plainly discernible. The absence of water as well as air
refraction explains why submarines cannot hide from an airplane: one of
the army aviators told me that a submarine cannot ordinarily sink so
low that it cannot be seen from an airplane.
_Color of Landing-ground Important._--Owing to the absorption and
reflection of sunlight, there is a distinct variation in the character
of otherwise similar landing-ground. A field, dark from recent plowing
(or burning), will heat the air over it faster than will a field of
stubble, hence over the former field there will be the greater air
disturbance, and this will affect the ease of landing. Air is heated
by contact and convection. One of the aviators said that recently he
was descending, and had all but reached the ground when a localized
convectional current hurled his machine upward some distance but
immediately afterward deposited him on the ground without damage.
_Spiraling Down 3,000 Feet._--Speeding ever in wide circles the course
lay southeast over the upper part of San Diego Bay. The city of San
Diego presented the usual checkerboard appearance (Fig. 16), and
even at this altitude it would seem easy to drop an orange at almost
any point. The velo cloud was lifting and we could see the gradual
disappearance as it melted rather than drifted from North Island. (See
Fig. 17.)
The gliding descent was made from an altitude of 2,500 feet, starting
above San Diego. As the aviation school was approached, we could see a
number of machines in the air, three below and two above us, circling
about like hawks. And, like soaring birds, these machines had their
air-lanes, designated courses and levels being devoted to the different
classes of machines. The landing was made without incident and the
hour’s flight was ended.
_Outline of Meteorological Work at the Aviation School._--At the close
of the lecture detail, the attention of the student aviators was called
to the importance of their having as thorough knowledge as possible of
the fundamentals of meteorology. The application of these fundamentals
to the analysis of air conditions met with in their daily flights was
shown to be essential. Investigations as to varying wind direction were
taken up by one of the staff instructors by the use of small parachutes
to be dropped at different altitudes. (See Fig. 8.) Through the
coöperation of the local official in charge of the San Diego Weather
Bureau station, duplicate signal sheets were available from which the
student officers made their local weather maps. From these maps and
their own flights, they could arrive at some relationship between the
actual and the theoretical 3,000- and 10,000-foot level maps prepared
from the Bigelow formula, as used by the Bureau. Lectures were given
on temperature and its distribution; winds, moisture, and clouds were
also made part of the course, one of the papers of the Bureau[I] being
reprinted by the aviation school by permission of the Chief of the
Bureau and used as a textbook. The Weather Bureau furnished the station
with a standard set of meteorological instruments so that the student
officers could become perfectly familiar with the regular equipment at
the Weather Bureau stations.
[I] “Clouds of California,” Carpenter, 1914, 24, 2d ed., Ft.
Leavenworth (U. S. Army Press).
_Extending the Usefulness of the Bureau to the Aviators._--Practical
utilization by the aviators of this district of the information
possessed by the Bureau has received considerable impetus during the
past six months. During the cross-country flights of April and May,
1916, the Los Angeles station was directed by the Chief of Bureau
to furnish weather and flight conditions between San Diego and Los
Angeles. With the aid of the general weather-map data from the regular
stations, and special observations of wind, weather, and fog conditions
on the immediate coast near Los Angeles, and on Mount Wilson, it
was possible to issue satisfactory forecasts of flying conditions.
The eye-observations of fog-heights as determined by the Weather
Bureau coöperative station at the Mount Wilson Solar Observatory were
especially valuable. From this mountain (6,000 feet elevation) it
is possible on a good day to see the whole length of the coast from
Point Firmin, San Pedro harbor to Point Loma, San Diego Bay. Knowing
different levels, the observer at Mount Wilson was able to give actual
thickness and extent of the fog-belt and its past twenty-four-hour
history.