Evening star. [volume] (Washington, D.C.) 1854-1972, 1931-08-30

apeed of the approved type air
planes used on our cir transport lines
has increased only about 10 miles In
four years.
Post and Gatty, Pangborn and Hern-
don, Frank Hawks and others have
dazsled the world with distance-shrink-
ing fights, and the speed Of American
non-military airplanes has been sound
ed throughout the world. Yet for the
past four years the average increase
in speed has been 21a miles per year
for all types of commercial aircraft.
Though the National Air Races, now
IN progress at Cleveland, show Ameri-
can planes which can do better than
400 miles per hour, the big transport
planes, which come into the huge
Cleveland Airport at the rate of several
every hour. still average about 10 miles
an hour faster than did the CONNER
ctal planes which were flying at the
time the air transport industry really
was beginning on large scale.
The Thompson Trophy race, annual
speed classic, which Is to close the races
on Labor day, Is expected to produce
speed In excess of 235 miles per hour.
The average speed of the transport
planes, In which hundreds fly into
Cleveland every day, however, is around
126 miles per hour.
The check on the slow development
Of speed in transport planes during .
period when increased speed was rec
oenized as one of the outstanding
necessities of modern air transporta-
ton is not merely guess work. 1t is
scientific checking, made on the basis
of the Department of Commerce ap-
proved type certificates, which must be
obtained for any type of airplane be-
fore 1t can be used commercially.
What the Records Show.
During the four years between
March, 1927, when the first approved
type certificate was issued, and this
year more than $50 different airplane
types were approved by the Aeronautics
Branch of the Department of Com
merce. The study of these 800 air.
planes representing every type flown
on American air transport lines, shows
an average high speed increase from
lit TO I26 miles per hour during the
past four years. The high speed, how
ever, Is not the speed at which the
transports NY. Their cruising speed,
which is the speed which must be
considered for transport operations, is
slower, the average being more diff
cult to ascertain. Over the four-year
period, however, the average cruising
speed has increased by approximately
10 miles per hour.
The increase in flying speed of the
transport planes has been accompanied.
necessarily, by an increase in average
landing speed. The studies of the De-
partment Of Commerce figures show
that the average increase In landing
speed during the four years has been
about three miles per hour, from an
average of 81 miles in 1927 to the pres
ent average Of so miles. Such high
speed planes as that of Hawks, several
OF which are competing in the national
air races, have landing speeds in the
neighborhood Of rs miles per hour.
The increased speed Of transport
planes has been achieved largely through
the use Of more powerful engines, though
efficiency has been increased by use of
engine cowling and better streanlining
70 obtain better speed with the same
power outlay
As might be expected, the use Of more
powerful engines has resulted in a de-
crease in power loading. This means
that for each horsepower added TO the
output Of the engine there has been a
proportionate decrease in the number
OF pounds per horsepower the plane can
carry.
Wing Leading Increases.
At the same time wing loading has
increased. In other words, the average
amount Of weight supported by each
square foot Of wing area has become
greater, Average pay load has de-
creased in proportion TO the gross weight
Of the aiTplane and the pay load has
become less in proportion TO horse
power.
Here Is found the key to the reason
for the disappointment low increase in
airplane speeds. Increase in speed is
paid for heavily by the airplane oper-
ator. As speed increases the plane be-
comes less efficient. The amount Of
horsepower must be increased greatly
with little or no increase in the amount
OF pay load which can be carried. AS
speed is increased structural weight
must be increased also to take care OF
the added strain Of high-speed flying,
still further cutting into the amount OF
useful load
Study Of the approved type certih-
Gates issued over the four-year period
shows that many airplanes originally
equipped with engines Of 200-horse-
power, for example have been revised
In design until today the same models
with the same seating capacity and pay
load. now are equipped with engines
developing as much as $50 horsepower
While the power loading was de-
creasing Department Of Commerce
specialists found, wing loading was in
creasing at almost the same rate, re-
sulting In the higher landing speeds
and more highly stressed structures.
Though the increased weight could have
been cared for by increasing the wing
area, the airplane designers. realizing
that this would reduce the speed, chose
TO keep the wing area constant, paying
toll for increased flying speed in higher
speed and higher wing losdings.
The economy Of an airplane in trans
port operation can be determined by the
ratio Of pay load TO engine horsepower.
The eirplane cost is likely to be based
pretty closely on horsepower and main
tenance and operation costs also viii
follow horsepower.
Must Cut Costs.
THE airplanes pay-load capacity,
whether it represents actual or poten-
tiaI income or merely seating space for
pleasure flying" Department Of Com
merce experts pointed out, must be in
reasonable relation TO cost Der horse
power. or air transportation in the one
case will prove 70 be a poor invest
ment and In the other an overexpensiye
pastirne."
From this standpoint airplane eff
cheney has been on the wane since the
necessity for high speeds drove the de-
signers 70 extensive modification of their
designs. Though the planes serve well
for the purpose for which they were
intendeo-the movement Of a seleol
list Of passengers at high Speeds-they
are not efnc1ent load carriers.
This has led 10 q pronounced move
ment toward larger airplanes In which
q higher percentage Of efficiency may
be obtained without sacrifices in other
directions The smallest planes, IL was
found. we're the least ef1cient, on the
basis OF the useful load they could car
At@m4r mxs~f~N
As plane sizes increased the proportion
~ I1aafnl load unon which revenues