THE FUTURE OF TRANSATLANTIC FLIGHT
Although three pioneer flights were made across the Atlantic during the
summer of 1919, the year passed without bringing to light any immediate
prospect of an air service between Europe and America. Nor does 1920
seem likely to produce such a development on a regular basis.
Before a transatlantic airway is possible, much remains to be
done--organization, capitalization, government support, the charting
of air currents, the establishment of directional wireless stations,
research after improvements in the available material. All this
requires the spending of money; and for the moment neither governments
nor private interests are enamored of investments with a large element
of speculation.
But, sooner or later, a London-New York service of aircraft must be
established. Its advantages are too tremendous to be ignored for long.
Prediction is ever dangerous; and, meantime, I am confining myself
to a discussion of what can be done with the means and the knowledge
already at the disposal of experts, provided their brains are allied to
sufficient capital.
Notwithstanding that the first two flights across the Atlantic were
made respectively by a flying-boat and an aëroplane, it is very evident
that the future of transatlantic flight belongs to the airship. That
the apparatus in which Sir John Alcock and I made the first non-stop
air journey over the Atlantic was an aëroplane only emphasizes my
belief that for long flights above the ocean the dirigible is the
only useful vehicle. If science discovers some startlingly new motive
power--for example, intermolecular energy--that will revolutionize
mechanical propulsion, heavier-than-air craft may be as valuable
for long flights as for air traffic over shorter distances. Until
then trans-ocean flying on a commercial basis must be monopolized by
lighter-than-air craft.
The aëroplane--and in this general term I include the flying boat and
the seaplane--is impracticable as a means of transport for distances
over one thousand miles, because it has definite and scientific
limitations of size, and consequently of lift. The ratio of weight to
power would prevent a forty-ton aëroplane--which is approximately the
largest heavier-than-air craft that at present might be constructed
and effectively handled--from remaining aloft in still air for longer
than twenty-five hours, carrying a load of passengers and mails of
about five tons at an air speed of, say, eighty-five miles an hour. Its
maximum air distance, without landing to replenish the fuel supply,
would thus be two thousand, one hundred and twenty-five miles. For a
flight of twenty-five hundred miles all the disposable lift (gross
lift minus weight of structure) would be needed for crew and fuel, and
neither passengers nor freight could be taken aboard.
There is not in existence an aëroplane capable of flying, without
alighting on the way, the three thousand miles between London and New
York, even when loaded only with the necessary crew. With the very
smallest margin of safety no transatlantic route of over two thousand
miles is admissible for aëroplanes. This limitation would necessitate
time-losing and wearisome journeys between London and Ireland,
Newfoundland and New York, to and from the nearest points on either
side of the ocean. Even under these conditions only important mail or
valuable articles of little weight might be carried profitably.
As against these drawbacks, the larger types of airships have a radius
far wider than the Atlantic. Their only limit of size is concerned with
landing grounds and sheds; for the percentage of useful lift increases
with the bulk of the vessel, while the weight to power ratio decreases.
A voyage by dirigible can therefore be made directly from London to New
York, and far beyond it, without a halt.
Another advantage of lighter-than-air craft is that whereas the
restricted space on board an aëroplane leaves little for comfort and
convenience, a large rigid airship can easily provide first-rate
living, sleeping and dining quarters, besides room for the passengers
to take exercise by walking along the length of the inside keel, or on
the shelter deck. In a saloon at the top of the vessel no noise from
the engines would be heard, as must be the case in whatever quarters
could be provided on a passenger aëroplane.
Yet another point in favor of the airship as a medium for trans-ocean
flight is its greater safety. An aëroplane is entirely dependent for
sustentation in the air on the proper working of all its motors. Should
two motors--in some cases even one--break down, the result would be a
forced descent into the water, with the possibility of total loss on a
rough sea, even though the craft be a solid flying boat. In the case
of an airship the only result of the failure of any of the motors is
reduction of speed. Moreover, a speed of four-fifths of the maximum
can still be maintained with half the motors of an airship out of
action, so that there is no possibility of a forced descent owing to
engine breakdown. The sole result of such a mishap would be to delay
the vessel's arrival. Further, it may be noted that an airship's
machinery can be so arranged as to be readily accessible for repairs
and replacement while on a voyage.
As regards comparative speed the heavy type of aëroplane necessary to
carry an economical load for long distances would not be capable of
much more than eighty-five to ninety miles an hour. The difference
between this and the present airship speed of sixty miles an
hour would be reduced by the fact that an aëroplane must land at
intermediate stations for fuel replenishment. Any slight advantage in
speed that such heavier-than-air craft possess will disappear with the
future production of larger types of dirigible, capable of cruising
speeds varying from seventy-five to ninety miles an hour. For the
airship service London-New York direct, the approximate time under
normal conditions should be fifty hours. For the aëroplane service
London-Ireland-Newfoundland-New York the time would be at least
forty-six hours.
Perhaps the most convincing argument in favor of airships as against
aëroplanes for trans-ocean aviation is that of comparative cost. All
air estimates under present conditions must be very approximate; but
I put faith in the carefully prepared calculations of experts of my
acquaintance. These go to show that, with the equipment likely to
be available during the next few years, a regular and effective air
service between London and New York will need (again emphasizing the
factor of approximation) the following capital and rates:
Aëroplane
Airship Service[1] Service[2]
Capital required $13,000,000 $19,300,000
Passenger rate:
London-New York $240 $575
Rate per passenger:
Mile 8 cents 18 cents
Mails per ounce:
London-New York 6-1/4 cents 15-1/2 cents
These figures for an airship service are based on detailed
calculations, of which the more important are:
_Capital Charges_:
Four airships of 3,500,000 cu. ft.
capacity, at $2,000,000 each $8,000,000
Two double airship sheds at
$1,500,000 each 3,000,000
Land for two sheds and aërodromes at
$150,000 each 300,000
Workshops, gas plants, and equipment 750,000
Working capital, including spare parts,
stores, etc. 850,000
Wireless equipment 50,000
Miscellaneous accessories 50,000
-----------
Total capital required $13,000,000
-----------
Annual charge, interest at 10% $1,300,000
_Depreciation and Insurance_:
Airships.
Useful life, about 3 years.
Obsolete value, about $100,000 per ship.
Total depreciation per ship, $1,900,000 in three years.
Average total depreciation per annum for four ships
for 3 years, $2,535,000.
Airship sheds.
Total annual charge $90,000
Workshops and plant.
Depreciation at 5% per annum 17,500
Total annual charge for depreciation 2,650,000
Total annual insurance charges on airships
and plant 617,500
_Annual Establishment Expenses_:
Salaries of Officers and Crews--
4 airship commanders $20,000
8 airship officers 30,000
Total number crew hands (64) 80,000 $130,000
------------------
$130,000
Salaries of Establishment--
Management and Staff $25,000
Workshop hands, storekeepers,
etc. (50 at each shed--total 100) 100,000 $125,000
------------------
Total annual establishment expenses $255,000
_Repairs and Maintenance_:
Sheds and plant, annual charge, say, $25,000
Repairs and overhaul of airships 100,000
Total charge $125,000
----------
Total annual charges on above basis $4,947,500
Say $5,000,000
_Cost Chargeable per Crossing_:
Taking the total number of crossings per
year as 200 (London-New York)--
Proportion of annual charges per crossing $25,000
Petrol per trip, 30 tons at $125 per ton. 3,750
Oil per trip, 2 tons at $200 per ton 400
Hydrogen used, 750,000 cu. ft. at $2.50
per 1,000 cu. ft. 1,875
Cost of food per trip for crew of 19 and
100 passengers 2,000
--------
Total charge per crossing (London-New York) $33,025
The weight available for passengers and mails on each airship of the
type projected would be fifteen tons. This permits the carrying of one
hundred and forty passengers and effects, or ten tons of mails and
fifty passengers. To cover the working costs and interest, passengers
would have to be charged $240 per head and mails $2,025 per ton for the
voyage London-New York.
This charge for passengers is already less than that for the more
expensive berths on transatlantic liners. Without a doubt, with the
coming of cheaper fuel, lower insurance rates and larger airships,
it will be reduced eventually to the cheapest rate for first-class
passages on sea liners.
With a fleet of four airships, a service of two trips each way per week
is easily possible. For aëroplanes with a total load of forty tons the
weight available for passengers and mails is 2.1 tons. If such a craft
were to carry the same weekly load as the service of airships--thirty
tons each way--it would be necessary to have fourteen machines
continually in commission. Allowing for one hundred per cent. spare
craft as standby for repairs and overhaul, twenty-eight aëroplanes
would be required. The approximate cost of such a service is:
_Capital Charges_:
28 aëroplanes at $600,000 each $16,750,000
28 aëroplane sheds at $50,000 each 1,400,000
Land for 4 aërodromes 500,000
Workshops and equipments 100,000
Spare parts, etc. 500,000
Wireless equipment 50,000
-----------
Total capital required $19,300,000
Annual charge at 10% interest $1,930,000
_Depreciation and Insurance_:
Aëroplanes.
Useful life, say 3 years, as for airships.
Obsolete value, say, $30,000 per
machine. Average total depreciation
per annum for 28 machines $5,250,000
Aëroplane Sheds.
Total annual charge 60,000
Workshops and Plant.
Depreciation at 3% per annum 3,000
Total annual charge for depreciation 5,314,000
Total annual insurance charges on machinery
and plant 1,152,000
_Annual Establishment Expenses_:
Salaries of 36 pilots at $3,000 per annum $108,000
Salaries of 36 engineers at $2,000 per annum 72,000
Salaries of 12 stewards at $1,500 per annum 18,000
Salaries of establishment--
Management and staff 25,000
Workshop hands and storekeepers, etc., 100 off 100,000
--------
Total annual establishment expenses $323,000
_Repairs and Maintenance_:
Sheds and plant, annual charge, say $25,000
Repairs and overhaul to machines 50,000
--------
Total. $75,000
----------
Total annual charges on above basis $8,792,500
_Cost chargeable per crossing_:
Proportion of annual charges per crossing $7,250
Petrol used per trip, 28 tons at $125 per ton 3,500
Oil per trip, 2 tons at $200 per ton 400
Cost of food per trip for 29 passengers and
crew of seven 500
-------
$11,650
It will be seen from the above that the direct running cost is 38%,
and the overhead charges 62% of the total cost.
With a weight of 2.1 tons available on each machine for passengers and
mails twenty passengers might be carried. To cover the working costs
and interest they must be charged $575 per head. The rate for mails
would be $5,500 per ton.
Having made clear that the airship is the only means of transatlantic
flight on a paying basis, the next point to be considered is the
type of dirigible necessary. A discussion at present of the size of
the airships that will link Europe and America can be little more
substantial than guesswork. The British dirigible _R-34_, which last
year made the famous pioneer voyage between England and the United
States, is too small for commercial purposes, with its disposable lift
of twenty-nine tons and its gas capacity of less than two million cubic
feet. Experts have predicted the use of airships of five million and
ten million cubic feet capacity, with respective weights of thirty tons
and one hundred tons available for passengers and freight.
It is probable, however, that such colossi must await birth for many
years, and that a beginning will be made with moderate-sized craft of
about three million, five hundred thousand cubic feet capacity, similar
to those that serve as the basis of the estimates for a service between
London and New York. A combination of British interests is planning
to send ships of this type all over the world. These can be built
immediately, and there are already in existence suitable sheds to house
them. Details of their structure and capabilities may be of interest.
[Illustration: LUCKY JIM AND TWINKLETOE, THE MASCOTS]
[Illustration: THE TRANSATLANTIC FLIGHT ENDED WITH A CRASH IN AN IRISH
BOG]
The projected airship of three million, five hundred thousand cubic
feet capacity is capable of carrying a useful load of fifteen tons
(passengers and mails) for a distance of forty-eight hundred miles in
eighty hours, at the normal cruising speed. The total lifting power is
one hundred and five tons, and the disposable lift (available for fuel,
oil, stores, crew, passengers and freight) is sixty-eight tons. The
maximum engine power is thirty-five hundred h. p., the maximum speed
seventy-five miles an hour. The normal flying speed, using a cruising
power of two thousand h. p., is sixty miles an hour. The overall length
is eight hundred feet, the maximum diameter and width one hundred feet,
and the overall height one hundred and five feet. These particulars and
performances are based on present design, and on the results attained
with ships of two million cubic feet capacity, now in service. The
figures are conservative, and it is probable that a disposable lift
greater than that of the specifications will be obtained as a result of
improved structural efficiency.
The passenger accommodation will be such that the air journey can
be made in comfort equal to that on a first-class liner of the sea.
Apart from their comparatively small disposable lift, a main objection
to vessels of the _R-34_ type for commercial purposes is that the
living quarters are in cars slung from under the middle envelope. In
this position they are necessarily rather cramped. In the proposed
craft of three million, five hundred thousand cubic feet capacity the
passengers' quarters are at the top of the vessel. There, they will be
roomy and entirely free from the vibration of the engines. They are
reached through an internal corridor across the length of the ship, or
by elevator, from the bottom of it.
The main room is a large saloon lounge fitted with tables and chairs
in the style of a Pullman car. Around it are windows, allowing
for daylight and for an outlook in every direction. Part of it is
fire-proofed, and serves as a smoking room.
Next to, and communicating with, the lounge is the dining saloon. This
leads to a serving hatch and electrical cooking apparatus. Electrical
power is provided by dynamos driven off the main engines. Current
for electric lighting and heating of the saloons, cars and sleeping
quarters is provided by the same method.
Sleeping accommodation is in four-berth and two-berth cabins on top of
the airship and forward of the living saloons. The cabins are of the
type and size fitted on ocean-going steamers. With them are the usual
bathrooms and offices. Other conveniences are an open shelter deck at
the vessel's aft end, to enable passengers to take the air, and an
observation car, fitted below the hull and also at the aft end, so that
they can observe the land or sea directly below them.
No danger from fire need be feared. The machinery installation is
carefully insulated from the gas bags, and the quarters are to be
rendered fire-proof and gas-proof. Moreover, the amount of weight
involved by the passengers' section is so small, compared with the
weight of the machinery, fuel, cargo and stores, carried in the lower
part of the craft, that the stability of the ship for rolling is
unaffected by the novel position of the living quarters.
The ship's officers will have on the hull, towards the forward end,
a control and navigation compartment, containing the main controls,
navigation instruments, charts, and a cabin for the wireless telegraphy
installation. The windows of this car give a clear view in every
direction.
Other general specifications are:
_Hull Structure._--The shape of the hull is of the most perfect
stream-line form within the limitations of constructional requirements.
An internal keel corridor, running along the bottom of the hull,
contains all petrol and oil tanks and the water ballast.
_Outer Covering._--The outer cover is made of special weather-proof
fabric, which gives the longest possible life. This fabric is
as efficient as possible in insulating the gas from change of
temperature, and thus avoids great variations in the lift.
_Gasbags._--The gas capacity is divided up into gasbags made of
suitable rubber-proofed cotton fabric, lined with gold-beaters' skins.
Gasbags will be fitted to automatic relief valves and hand control
maneuvering valves.
_Machinery Cars._--Six machinery cars are provided, each containing
one engine installation, with a direct-driven propeller fitted at the
aft end. These compartments give the mechanics easy access to each of
the six engines, and allow them to handle all parts of the machinery.
Engine room telegraphs of the electrical type communicate between the
forward compartment and each of the machinery cars.
Whereas the living quarters and the control compartment must be heated
by electric radiators, arrangements can be made to warm the machinery
cars by utilizing the exhaust heat. The transmission gear in two of the
wing cars is to be fitted with reversing gear, so that the craft may
be driven astern. So that passengers shall not be worried by the usual
roar of the exhaust, special silencers will be fitted. The transmission
gear is also so arranged that all unnecessary clamor from it may be
avoided.
The engines run on gasoline fuel, but they have devices whereby they
can be run alternatively on hydrogen gas. They are designed to develop
their maximum power at a height of five thousand feet.
_Telephones._--Telephone communication links all stations on the
airship.
_Landing Gear._--Inflated buffer landing bags of a special type are to
be fitted underneath the Forward Control Compartment and underneath the
two Aft Machinery Cars. These enable the airship to alight either on
land or on the sea's surface.
_Wireless Telegraphy._--A powerful wireless telegraphy installation is
to be fitted in the wireless cabin in the forward control compartment.
It will have a range for sending and receiving of at least five
thousand miles.
_Crew._--Two watches would be required, taking duty in eight-hour
shifts. Both must be on duty when the craft leaves or lands. Each watch
consists of navigating officer, steersman, elevator man, four engineers
and a wireless operator. With the commanding officer and two stewards,
whose duties are not regulated by watches, the crew thus numbers
nineteen men.
Although the speed of the airship at maximum power is seventy miles
per hour, the crossing normally would be made at sixty miles per
hour, which only requires two thousand horse power, and is much more
economical in fuel. The full speed, however, can be used whenever
the ship is obliged to voyage through storm areas or against strong
head winds. By the Azores route, the time needed for the journey of
thirty-six hundred miles, at a speed of sixty miles per hour, is sixty
hours; but to allow for delays owing to adverse weather, the airship
would always carry eighty hours' fuel, allowing for a speed of sixty
miles per hour. The normal time for the journey from London to New
York, via Portugal and the Azores (thirty-six hundred miles) would be,
therefore, two and one half days. The normal time for the journey New
York to London by the direct route (three thousand miles) would be just
over two days.
The prevailing wind on the direct route is almost always from West to
East, which favors the Eastbound journey, but is unfavorable to the
Westbound journey. It is proposed that the crossing Eastward from New
York to London be made by the most direct route, advantage thus being
taken of the Westerly winds.
By making the Westbound journey on the Southerly route, via the
Coast of Portugal and the Azores, and on 35´ N. parallel of latitude
across the Atlantic, and then to New York, the voyage is made in a
region where the prevailing Westerly winds of the higher latitudes
are absent, and only light winds are encountered, generally of a
favorable direction. This route, however, adds about six hundred miles
to the distance. With a ship speed of sixty miles per hour, it would
be quicker to make the Westbound journey by the direct route if the
Westerly wind did not exceed ten miles per hour. If the wind were
greater, time would be saved by covering the extra six hundred miles of
the Southerly route and dodging the unfavorable air currents.
With four airships on the Cross-Atlantic airway, two only would be in
service at a time, so that each could lay up during alternate weeks for
overhaul and re-fit. As the time of journey between London and New York
will vary between fifty to sixty hours, each airship can easily make
two crossings or one double journey per week, thus giving a service,
with two dirigibles, of two "sailings" each way per week.
The average time table might therefore be as follows:
LEAVE LONDON ARRIVE NEW YORK
Monday morning Wednesday afternoon or evening
Thursday morning Saturday afternoon or evening
LEAVE NEW YORK ARRIVE LONDON
Monday afternoon Thursday morning
Thursday afternoon Sunday morning.
From available weather reports, it is considered that crossings are
practicable on at least three hundred days in the year. Probably a
total of two hundred crossings in the year could be maintained. Until
further study of weather conditions supplies a certain knowledge of
the best possible altitudes and latitudes, it is likely that a regular
service of two crossings each way per week will be maintained only in
the months of May to September, and that the crossings from October to
April will be irregular, the day of departure being dependent on the
weather.
Weather difficulties are likely to be much less severe than might
be imagined. Rain, hail and snow should have little influence on
the navigation of airships. An outer covering that is rainproof
and non-absorbent avoids the absorption of water and the consequent
increase of weight. Hail and snow cannot adhere to the surface of the
craft when in flight, owing to its high speed through the air; and, in
any case, the precipitation height being not more than eight thousand
feet, they can be avoided by flying above this altitude.
Fog may give trouble in landing, but during the journey an airship can
keep above it. If the terminal were enveloped by fog an arriving ship
could pass on to an emergency landing ground away from the fog-belt;
if the mistiness were slight, it could remain in the air until the
ground were visible, making use of its margin of fuel beyond the
amount necessary for the London-New York flight. Airships in fog may
be enabled to find their landing ground by means of captive balloons
or kites, and of strong searchlights from the ground. At night, the
balloons or kites could carry electric lights, with connections from
the aërodrome.
In any case, fog, rain, hail and snow are nearly always local in their
occurrence, and can be avoided by a short deviation from the usual
route. Atlantic records indicate that on the main steamship routes fog
sufficient to impede navigation does not occur on more than about
twelve days in the year.
Wind is a factor that needs more careful study in its relation to
transatlantic air navigation. In most cases, unduly strong winds can
be dodged by flying on a higher level, or by cruising on a different
course, so as to avoid the storm belt. Heavy storms, which are usually
of a cyclonic nature, rarely cover an area of more than two hundred
miles diameter. Moreover, the rate of progression of a cyclonic area
is much less than the speed of the air movement. An airship is able
to shake off a cyclonic area by a deviation from its course of not
more than two hundred miles. Once away from the storm belt, it has no
difficulty in keeping clear of it.
When higher levels of the air have been charted, there is every reason
to believe that the known movements of the Atlantic winds will be
used to shorten air journeys. There are at sea level, between certain
clearly defined latitudes, prevailing winds of constant direction. At
greater heights, also, there is in most latitudes a constant drift
which, if charted, might be useful even if winds at sea level were
unfavorable.
Although precise information is available of the prevailing and
periodic winds at sea level in various latitudes, very little
coördinated work appears to have been done in charting the prevailing
and seasonal winds in higher levels of the atmosphere. Observations
of the air currents over various localities in the United States,
England and Germany have been taken, but very little is known of the
winds above the great ocean tracts. There is a great necessity for
international research to provide data for predictions of weather
conditions in the upper atmosphere and thus enable advantage to be
taken of these higher currents.
At high altitudes, constant winds of from thirty to forty miles per
hour are common. If the prevailing directions of those were known to
airship navigators, the duration of the journey could be considerably
shortened, even if this meant taking an indirect route. It is
undesirable to fly at great heights owing to the low temperature; but
with suitable provision for heating there is no reason why flying at
ten thousand feet should not be common.
Air currents cannot be charted as exactly as sea currents; but much
valuable work can and will be done by tabulating in detail, for the
guidance of air navigators, the tendencies of the Atlantic atmospheric
drifts. Reliable charts, used in conjunction with directional messages
from wireless stations and ships, may make it possible for vessels on
the London-New York air service always to avoid troublesome winds, as
well as storms and fogs, and to reduce the percentage of risk to a
figure not exceeding that relative to sea liners.
For the rest, the excellence of the most modern engines and the fact
that one or two, or even three of them can be temporarily out of action
without affecting the airship's stability during a flight, minimize the
danger of a breakdown from loss of power. The only remaining obstacle
to reasonable safety would seem to be in landing on and departing from
the terminal during rough weather. This can be overcome by the recently
patented Vickers Mooring Gear for Rigid Airships.
The gear, designed so as to permit an airship to land and remain moored
in the open for extended periods in any weather without the use of
sheds, consists principally of a tall steel mast or tower, about one
hundred and fifty feet in height, with a revolving head to which the
craft is rigidly attached by the nose, permitting it to ride clear of
the ground and to turn round in accordance with the direction of the
wind. It is provided with a hauling-in winch and rope to bring the ship
up to the mooring point.
An elevator, for passengers and goods, runs up the tower from the
ground to the platform adjoining the nose of the airship. The
passengers reach their quarters along a passage through the vessel, and
the goods are taken down a runway. An airship moored to this mast can
remain unharmed in even the worst weather, and need be taken into a
shed only when overhaul and repairs are necessary.
In discussing the future of transatlantic flight I have confined
myself to the projected service between London and New York. There
is likely to be another route over the Atlantic--London to Rio de
Janeiro, via Lisbon and Sierra Leone. Already in London tickets are on
sale at $5,000 apiece for the first flight from London to Rio. This,
of course, is a freak price, which covers the distinction of being
in the first airship to travel from England to Brazil. If and when a
regular London-Rio service is established, the ordinary passenger rate
should be little more than the $240 estimated as the air fare on the
London-New York route.
It may be that the London-New York air service will not arrive for
many years. Sooner or later, however, it must arrive; for science,
allied to human enterprise, never neglects a big idea. It may be that,
when it does arrive, the structure of the craft and the methods of
navigation applied to them will differ in important details from what I
have indicated. I make no pretense at prophecy, but have merely tried
to show how, with the means already at hand, moderately priced air
journeys from Europe to America can be made in two to two and a half
days, with comfort, safety and a high degree of reliability. Meanwhile,
much depends on the funds available for the erection of stations for
directional wireless messages, on research into the air currents at
various levels above the Atlantic Ocean, on the courage of capitalists
in promoting what seems to be a very speculative enterprise, and on new
adaptations of old mechanical inventions.
Already hundreds of aëroplanes, as time-saving vehicles, are used
regularly in many countries for commercial traffic over comparatively
short distances--the carriage of mails, passengers, valuable freight
and urgent special journeys. When, but not until, the hundreds become
thousands, and the longer distances are as well served by airships as
are the shorter distances by aëroplanes, the world's air age will be in
sight.
[Footnote 1: For airships with gross gas capacity of 3,500,000 cubic
feet and total load of 105 tons.]
[Footnote 2: For machines with total load of 40 tons.]