spaschal on DSK3GDR082PROD with CFR

Section 29.931

14 CFR Ch. I (1-1-19 Edition)

(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 Section3 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 speed.
(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. 1655(c)))
[Amdt. 29-3, 33 FR 969, Jan. 26, 1968, as
amended by Amdt. 29-17, 43 FR 50601, Oct. 30,
1978; Amdt. 29-26, 53 FR 34216, Sept. 2, 1988]

Section 29.931

Shafting critical speed.

(a) The critical speeds of any shafting
must be determined by demonstration
except that analytical methods may be
used if reliable methods of analysis are
available for the particular design.
(b) If any critical speed lies within,
or close to, the operating ranges for
idling, power-on, and autorotative conditions, the stresses occurring at that
speed must be within safe limits. This
must be shown by tests.
(c) If analytical methods are used and
show that no critical speed lies within
the permissible operating ranges, the
margins between the calculated critical speeds and the limits of the allowable operating ranges must be adequate
to allow for possible variations between the computed and actual values.
[Amdt. 29-12, 41 FR 55472, Dec. 20, 1976]

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