News Letter 1941 Jul-Dec - Air Force Historical Studies Office

from 50 to 75 hours of flight tests per month
are about all a test pilot can withstand and
remain physically fit.
To calibrate an air speed meter, the teat
pilot makes at least five two-way runs aver
a measured course at an alti tude of about 25
feet. The runs are made at approximately
equal intervals between the high speed and
the minimum safe flyi~g speed of the airplane.
It 1s vitally 1.lIJportant to keep the
air speed and altimeter readings constant
during each run. If the pilot finds that
the speed has changed after entering the
course he immediately turns out and starts
over. :l:achof the runs is timed with a stopwatch.
The times, together with the indicated
air speeds and free air temperature.,
are later converted to calibration speeds by
applying temperature-pressure corrections
for the whole speed range of the airplane.
In the speed runs, the limits of precision
in determining horizontal s~eed at sealevel
or at altitude must be withln plus or minus
one per cent.
The cruising speed is determined by using
the nor~l rated power of the engine, not
to exceed a maximum of 75 per cent.
Saw-tooth climbs are so named because the
tracings on the barograph record of a properly
executed saw-tooth climb look like saw
teeth. They are employed to determine the
indicated speed at which the maximum rate
of climb occurs at different altitudes. The
maximum rate is obtained by climbing the
airplane through specified altitude ranges
a.tvarious speeds, wi th full power.
.Check climbs establisb the true rate of
climb from sea level to the airplane's service
ceiling, the point at which the rate of
climb drops off to 100 feet per minute. In
this test, the airplane is climbed steadily
to its service ceiling at the indicated
speeds established for each zone by the sawtooth
climb. Readings recorded for a check
climb are free air temperature, r. p. m.,
manifold pressure, and carburetor air temperature.
Time and pressures are recorded by a
barograph, and all data are coordinated with
pressure altitude.
The Air Corps definition of a test pilot
is a pilot who is able to run full standard
performance tests on any airplane. To measure
up, the student test pilot still has
more tests to master.
pilot first flies for 30 minutes in level
flitdlt at 2,000 feet, with military load and
full power. Then he pulls into a climb and
continues at best climbing speed to within
2,000 feet of the service ceiling. Afterward
a ground cooling test is obtained at 60 per
cent of the ground r.:o.m. permissible.
Those are the basic flight testing methods
which the rookie test pilot practices for
two or three months, and do not include the
tests of air intake and exhaust systems,
carbon monoxide tests; radio interference;
armament; navi~ution lnstruments, and nigh~
tests of lightlng equipment.
The final requirement is to fill out r.Pilot's
Observations "a lengthy questionnaire
which inquires about the airplane's controllability
stability, trim, balance, maneuverability,
interior arrangements of equipment
and contrQls, and all-around characteristics
in the air and on the ground. Approximately
157 questions must be answered.
By studying the "Manual for Test Pilots'
and talking with the other test ~ilots. the
newcomer is ready for regular fllght tests
after 10 or 12 weeks of practice. On an
average, six months more are required to
turn him into a seasoned test pilot taking
his regular turn in rotation with t~e other
test uilots in the more difficult flight
test assignments.
Due to the fatigue which follows a test
flight to extreme altitude, a test pilot is
not ordinarily expected to take more than
one high altitude flight in one day but
frequently he will take a number of dIfferent
types of airplanes up for test flights
on the same day. In one way of thinking
an Air Corps test uilot is a highly traine!
specialist- he must also be amazi~~ versatile
in tkt his next assignment for flight
test may bea 3D-ton, four-engine bomber, a
tiny half-ton short-range liaison airplane,
or any type between. Tne effective horsepower
he controls may increase from a mere
65 to 6,000 h.p. or more.
It is not uncommon to find 40 or more
different airplanes ready for flitdlt tests
at one time. Typically they would include
light, heavy and medium bombers, single- and
twin-engine pur suits, observation, photographic
and cargo airplanes, and a variety
of basic combat transition, advance, basic
and primary tra t ning airplanes.
Routine flight tests of new development
equipment are being made constantly at Wright
Field by project officers as well as test
pilots. In the equipment flight tests, the
project officer is interested primariLy in
recording the functioning of the new equipment
under maximum operating conditions.
Air Corps equipment is developed in a group
of laboratories at Wright Field. There is
an excusable misconceution that military
airplanes and equipment are manufactured
here, although none is for service use. Exr;>erimentalequipment
is fabricated only when
it cannot be obtained commercially without
undue del~.
Requests for routine flight tests of equipment
ori~nate in the Production Engineering
and the Experimental Engineering Sections.
Some of the latter's laboratories contain
laboratories within laboratories.
Involving more real hazard than some of
the more spectacular tests, take-off and
landing tests are executed under maximum
operating conditions on or near the ground.
The object is to establish the minimum distances
wi thin which an airplane can takeoff
and clear a 50-foot obstacle. and come
to a stop after landing over a 50-foot obstacle.
In the take-off tests flaps are
eet at ~arl~8 p~.itions, from lully closed
to fully open, to determine the best flap
posi tlon for a minimum run and getting the
airplane off the ground and over a 50-foot
obstacle as quickly as possible. The landing
tests are just the reverse--landing the
airplane and braking it to a stop as soon
as possible after passing over a 5D-foot
obstacle. The landing and take-off characteristics
reveal, among other things, the
minimum size of the base from which the airplane
can be operated. The Power Plant Laboratory. for instance,
consists of 25 '\U1its.each 8peci~idng in
During the engine cooling tests, the test (Continned on page 25)
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