(a) Any additional dynamic, endurance, and operational tests, and
vibratory investigations necessary to determine that the rotor drive
mechanism is safe, must be performed.
(b) If turbine engine torque output to the transmission can exceed the
highest engine or transmission torque limit, and that output is not
directly controlled by the pilot under normal operating conditions (such
as where the primary engine power control is accomplished through the
flight control), the following test must be made:
(1) Under conditions associated with all engines operating, make 200
applications, for 10 seconds each, of torque that is at least equal to the
lesser of --
(i) The maximum torque used in meeting §29.923 plus 10 percent; or
(ii) The maximum torque attainable under probable operating conditions,
assuming that torque limiting devices, if any, function properly.
(2) For multiengine rotorcraft under conditions associated with each
engine, in turn, becoming inoperative, apply to the remaining transmission
torque inputs the maximum torque attainable under probable operating
conditions, assuming that torque limiting devices, if any, function
properly. Each transmission input must be tested at this maximum torque
for at least fifteen minutes.
(c) Lubrication system failure. For lubrication systems required
for proper operation of rotor drive systems, the following apply:
(1) Category A. Unless such failures are extremely remote, it
must be shown by test that any failure which results in loss of lubricant
in any normal use lubrication system will not prevent continued safe
operation, although not necessarily without damage, at a torque and
rotational speed prescribed by the applicant for continued flight, for at
least 30 minutes after perception by the flightcrew of the lubrication
system failure or loss of lubricant.
(2) Category B. The requirements of Category A apply except that
the rotor drive system need only be capable of operating under
autorotative conditions for at least 15 minutes.
(d) Overspeed test. The rotor drive system must be subjected to
50 overspeed runs, each 30±3 seconds in duration, at not less than either
the higher of the rotational speed to be expected from an engine control
device failure or 105 percent of the maximum rotational speed, including
transients, to be expected in service. If speed and torque limiting
devices are installed, are independent of the normal engine control, and
are shown to be reliable, their rotational speed limits need not be
exceeded. These runs must be conducted as follows:
(1) Overspeed runs must be alternated with stabilizing runs of from 1
to 5 minutes duration each at 60 to 80 percent of maximum continuous
(2) Acceleration and deceleration must be accomplished in a period not
longer than 10 seconds (except where maximum engine acceleration rate will
require more than 10 seconds), and the time for changing speeds may not be
deducted from the specified time for the overspeed runs.
(3) Overspeed runs must be made with the rotors in the flattest pitch
for smooth operation.
(e) The tests prescribed in paragraphs (b) and (d) of this section must
be conducted on the rotorcraft and the torque must be absorbed by the
rotors to be installed, except that other ground or flight test facilities
with other appropriate methods of torque absorption may be used if the
conditions of support and vibration closely simulate the conditions that
would exist during a test on the rotorcraft.
(f) Each test prescribed by this section must be conducted without
intervening disassembly and, except for the lubrication system failure
test required by paragraph (c) of this section, each part tested must be
in a serviceable condition at the conclusion of the test. (Secs.
313(a), 601, 603, 604, Federal Aviation Act of 1958 (49 U.S.C. 1354(a),
1421, 1423 1424), sec. 6(c), Dept. of Transportation Act (49 U.S.C.