Evening star. [volume] (Washington, D.C.) 1854-1972, 1931-10-11

study Of landing gear construction and
of regulations governing landing gear
requirements, with a view to the re-
duction Of the toll of such accidents.
Though aviation accidents caused by
structural failures constitute only a
minor portion of all accidents and
though the proportion has been grow
ing smaller from year to year, the
Aeronautics Branch has determined to
spare no efforts to reduce the number
of structural failures to the lowest
possible pint. The study has served
as a check on the efficiency Of existing
airworthiness design requirements.
The studies covered the last half OF
1880, during which period there were
a total of 103 accidents chargeable to
structural failures. OF this number all
but so were too trivial to be included
in the study. OF the so presenting
features worthy of study involved
unlicensed aircraft over which the De-
partment Of Commerce had no control
as to airworthiness. This leaves a total
OF ~ accidents which were covered in
the studies.
OF the A. accidents, total Of "a, or
TIP per cent, were due to landing
gear failures. The others were divided
as follows: Wings, 4, or 81 per cent;
floats and hulls. 2. or asa per cent;
and control surfaces, control system,
engine mount and propeller, l each,
or 2.27 per cent each.
OF the "a landing gear failures. 8
were due to collapse of the landing
gear; s to failure Of Shock-absorber
strut fittings: 6 to failure Of fuSelage
fittings; 3 to failure of welded Joints:
to failure of the shock absorber strut;
2 to wheel failure; to axle failure. In
one case bolt fell out, in another
wheel came off, was due to locking
OF a brake and l to breaking of a
brake arm.
The department pointed out that
landing gears are subjected to more
frequently repeated shocks than any
other portion of the airplane and that
frequently repeated heavy shocks may
be expected to cause fatigue of landing
gear parts and resulting failure.
Closer Research Required
The department has announced that
1t expects manufacturers to give more
careful consideration to shock -absorber
units. to stress analysis of landing
gear structures and to determinations
Of allowable loads on all members of
landing gears.
The department, It was stated, is
making a more careful study of shock
abSorber units before permitting them
to be used on licensed aircraft in the
future
IF landing-gear structural failures
continue to occur with such frequency
in spite Of more careful consideration
along the lines suggested" the depart
ment stated in its report, lit will of
course be necessary to increase the
severity Of the design conditions"
The four planes in which wing fail
ures occurred were small planes. Three
OF the failures were due to snap rolls
performed as part of acrobatic ex-
hibitions. The department is calling
for more careful analysis by manufac-
turerS of conditions of unsymmetrical
strains on wings and their supporting
structures. especially on small planes
which are likely to be subjected by
private owners to a certain amount OF
acrobatics.
The two control surface failures in
volved ailerons. One occurred in
pylon turn during a race when the |
plane struck the wash Of a ship ahead, |
inducing an aileron futter which tore
the aileron of. The other occurred in |
a 250-mile-per-h hour power drive.
In the case of floats and hulls there |
was one failure of float strut fitting /
following bad landing and one case