title-14-part-29-sec29-927

630

14 CFR Ch. I (1–1–24 Edition)

§ 29.927

(2)

Continuous OEI power run. For

rotorcraft for which the use of contin-
uous OEI power is requested, a run at
continuous OEI torque and the max-
imum speed for use with continuous
OEI torque must be conducted as fol-
lows: For each engine, in sequence,
that engine must be inoperative and
the remaining engines must be run for
1 hour.

(3) The number of periods prescribed

in paragraph (k)(1) or (k)(2) of this sec-
tion may not be less than the number
of engines, nor may it be less than two.

(l) [Reserved]
(m) Any components that are af-

fected by maneuvering and gust loads
must be investigated for the same
flight conditions as are the main ro-
tors, and their service lives must be de-
termined by fatigue tests or by other
acceptable methods. In addition, a
level of safety equal to that of the
main rotors must be provided for—

(1) Each component in the rotor drive

system whose failure would cause an
uncontrolled landing;

(2) Each component essential to the

phasing of rotors on multirotor rotor-
craft, or that furnishes a driving link
for the essential control of rotors in
autorotation; and

(3) Each component common to two

or more engines on multiengine rotor-
craft.

(n)

Special tests. Each rotor drive sys-

tem designed to operate at two or more
gear ratios must be subjected to special
testing for durations necessary to sub-
stantiate the safety of the rotor drive
system.

(o) Each part tested as prescribed in

this section must be in a serviceable
condition at the end of the tests. No in-
tervening disassembly which might af-
fect test results may be conducted.

(p)

Endurance tests; operating lubri-

cants. To be approved for use in rotor
drive and control systems, lubricants
must meet the specifications of lubri-
cants used during the tests prescribed
by this section. Additional or alternate
lubricants may be qualified by equiva-
lent testing or by comparative analysis
of lubricant specifications and rotor
drive and control system characteris-
tics. In addition—

(1) At least three 10-hour cycles re-

quired by this section must be con-

ducted with transmission and gearbox
lubricant temperatures, at the location
prescribed for measurement, not lower
than the maximum operating tempera-
ture for which approval is requested;

(2) For pressure lubricated systems,

at least three 10-hour cycles required
by this section must be conducted with
the lubricant pressure, at the location
prescribed for measurement, not higher
than the minimum operating pressure
for which approval is requested; and

(3) The test conditions of paragraphs

(p)(1) and (p)(2) of this section must be
applied simultaneously and must be ex-
tended to include operation at any one-
engine-inoperative rating for which ap-
proval is requested.

(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)))

[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as
amended by Amdt. 29–1, 30 FR 8778, July 13,
1965; Amdt. 29–17, 43 FR 50600, Oct. 30, 1978;
Amdt. 29–26, 53 FR 34215, Sept. 2, 1988; Amdt.
29–31, 55 FR 38967, Sept. 21, 1990; Amdt. 29–34,
59 FR 47768, Sept. 16, 1994; Amdt. 29–40, 61 FR
21908, May 10, 1996; Amdt. 29–42, 63 FR 43285,
Aug. 12, 1998]

§ 29.927

Additional tests.

(a) Any additional dynamic, endur-

ance, and operational tests, and vibra-
tory investigations necessary to deter-
mine that the rotor drive mechanism is
safe, must be performed.

(b) If turbine engine torque output to

the transmission can exceed the high-
est 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 ac-
complished through the flight control),
the following test must be made:

(1) Under conditions associated with

all engines operating, make 200 appli-
cations, 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

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§ 29.935

the remaining transmission torque in-
puts the maximum torque attainable
under probable operating conditions,
assuming that torque limiting devices,
if any, function properly. Each trans-
mission input must be tested at this
maximum torque for at least fifteen
minutes.

(c)

Lubrication system failure. For lu-

brication 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 nor-
mal use lubrication system will not
prevent continued safe operation, al-
though not necessarily without dam-
age, at a torque and rotational speed
prescribed by the applicant for contin-
ued flight, for at least 30 minutes after
perception by the flightcrew of the lu-
brication system failure or loss of lu-
bricant.

(2)

Category B. The requirements of

Category A apply except that the rotor
drive system need only be capable of
operating under autorotative condi-
tions for at least 15 minutes.

(d)

Overspeed test. The rotor drive sys-

tem 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 per-
cent 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 fol-
lows:

(1) Overspeed runs must be alternated

with stabilizing runs of from 1 to 5
minutes duration each at 60 to 80 per-
cent 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 con-
ducted 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 appro-
priate methods of torque absorption
may be used if the conditions of sup-
port and vibration closely simulate the
conditions that would exist during a
test on the rotorcraft.

(f) Each test prescribed by this sec-

tion must be conducted without inter-
vening disassembly and, except for the
lubrication system failure test re-
quired by paragraph (c) of this section,
each part tested must be in a service-
able 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]

§ 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 con-
ditions, the stresses occurring at that
speed must be within safe limits. This
must be shown by tests.

show that no critical speed lies within
the permissible operating ranges, the
margins between the calculated crit-
ical speeds and the limits of the allow-
able operating ranges must be adequate
to allow for possible variations be-
tween the computed and actual values.

[Amdt. 29–12, 41 FR 55472, Dec. 20, 1976]