Evening star., 1941-02-05
Plane Model Changes
Handicap Production
0fA||ison Engines
freezing Of Designs
Expected to Accelerate
Output Now, However
(I6th OF a Series.)
BY JOSEPH S. EDGERTON,
Star Aviation Editor.

BUFFALO, N. Y, Feb. 5.-One OF
the factors which may have acted to
slow up temporarily the production
of aircraft engines is that changes
are being made in the methods of
applying the power to those engines
as a result of changes in the science
of aeronautical design.
Outstanding among these changes
is the use of an extension drive shaft
between engine and propeller to
make possible Improvements in air
plane design and performance. The
Army P-39 Airacobra Pursuit air.
plane, built here by the Bell Air
craft Corp. for the United States
and Great Britain, is warplane
of revolutionary type made possible
largely as a result of relocation of
the engine.
In the Airacobra, the engine is
located behind the pilot and is con-
nected with the propeller. 9 feet
forward. by a gear driven drive
shaft. This fact has made neces-
sary some changes in design of the
airplane's power plant, the new
Allison milne, liquid-cooled engine,
built at Indianapolis by the Allison
Engineering Corp, division of
General Motors Corp.
Curtiss Also Uses Allison.
The Allison engine also is the
heart of the Curtiss P-40 Army
Pursuit airplane, built at Buffalo by
the Curtiss Aeroplane Division of
the Curtiss- Wright Corp, and by
the twin-engined Lockheed P-38
pursuit-interceptor built in Cali
fomia.
The Bell and CurtiSs single -en-
gined fighters are in production and,
because of the difference in engine
location in these two airplanes, it
has been necessary to produce
slightly different engines for them.
The Allison engine. since reaching
production stage, already has gone
through five changes. which have
resulted in design differences so
drastic as to require new model
designations. The Curtiss P-40
is powered with the Allison model
&C" engine. For the Airacobra,
however, changes had to be made in
certain of the bearings and drive
mechanism to meet the extension
shaft requirements The Airacobra
engine is model "E."
Other changes in the Allison en-
gine were made necessary by Army
orders. Each of these changes, some
apparently minor in themselves,
made necessary design changes in
a number of parts, with resulting
changes In dies, tools and produc-
tion machines. Such changes, in
escapable though they may be, mill |
tate against mass production.
Way Cleared to Speed.
Because the Allison engine, though |
the newest American production |
model aircraft engine and the first |
of the new liquid-cooled engines.
already Is taking a prominent place
IN the national defense picture. this
survey trip. primarily devoted to
engine production, has been routed
to include the two airplane factories
which now are chief markets for
the new engine-Bell and Curtiss of
Buffalo.
The survey shows that both air
planes are we'll through the pre-
liminary production phase which in
cludes the working out of bugs"
which appear in any new type of
elaborate mechanism, and have
reached a stabilized condition which
IS the basis of quantity production
and which makes possible a similar
freezing of the engines which
power them.
Apparently, therefore, the way
lnally has been cleared for the mass
of Allison engines and,
except for changes which the Army
nay order, there should be no fur
her obstacles in the way of an ALI
ION production which already has
attained the rate of more than $50
,ngines a month and is expected to
Increase steadily to peak rate of
200 a month next November.