(a) Endurance tests, general. Each rotor drive system and rotor
control mechanism must be tested, as prescribed in paragraphs (b) through
(n) and (p) of this section, for at least 200 hours plus the time required
to meet the requirements of paragraphs (b)(2), (b)(3), and (k) of this
section. These tests must be conducted as follows:
(1) Ten-hour test cycles must be used, except that the test cycle must
be extended to include the OEI test of paragraphs (b)(2) and (k), of this
section if OEI ratings are requested.
(2) The tests must be conducted on the rotorcraft.
(3) The test torque and rotational speed must be --
(i) Determined by the powerplant limitations; and
(ii) Absorbed by the rotors to be approved for the rotorcraft.
(b) Endurance tests; takeoff run. The takeoff run must be
conducted as follows:
(1) Except as prescribed in paragraphs (b)(2) and (b)(3) of this
section, the takeoff torque run must consist of 1 hour of alternate runs
of 5 minutes at takeoff torque and the maximum speed for use with takeoff
torque, and 5 minutes at as low an engine idle speed as practicable. The
engine must be declutched from the rotor drive system, and the rotor
brake, if furnished and so intended, must be applied during the first
minute of the idle run. During the remaining 4 minutes of the idle run,
the clutch must be engaged so that the engine drives the rotors at the
minimum practical r.p.m. The engine and the rotor drive system must be
accelerated at the maximum rate. When declutching the engine, it must be
decelerated rapidly enough to allow the operation of the overrunning
clutch.
(2) For helicopters for which the use of a 2
1/2-minute OEI rating is requested, the takeoff run must be
conducted as prescribed in paragraph (b)(1) of this section, except for
the third and sixth runs for which the takeoff torque and the maximum
speed for use with takeoff torque are prescribed in that paragraph. For
these runs, the following apply:
(i) Each run must consist of at least one period of 2
1/2 minutes with takeoff torque and the maximum speed for use with
takeoff torque on all engines.
(ii) Each run must consist of at least one period, for each engine in
sequence, during which that engine simulates a power failure and the
remaining engines are run at the 2
1/2-minute OEI torque and the maximum speed for use with 2
1/2-minute OEI torque for 2
1/2 minutes.
(3) For multiengine, turbine-powered rotorcraft for which the use of
30-second/2-minute OEI power is requested, the takeoff run must be
conducted as prescribed in paragraph (b)(1) of this section except for the
following:
(i) Immediately following any one 5-minute power-on run required by
paragraph (b)(1) of this section, simulate a failure for each power source
in turn, and apply the maximum torque and the maximum speed for use with
30-second OEI power to the remaining affected drive system power inputs
for not less than 30 seconds. Each application of 30-second OEI power must
be followed by two applications of the maximum torque and the maximum
speed for use with the 2 minute OEI power for not less than 2 minutes
each; the second application must follow a period at stabilized continuous
or 30 minute OEI power (whichever is requested by the applicant). At least
one run sequence must be conducted from a simulated "flight idle"
condition. When conducted on a bench test, the test sequence must be
conducted following stabilization at take-off power.
(ii) For the purpose of this paragraph, an affected power input
includes all parts of the rotor drive system which can be adversely
affected by the application of higher or asymmetric torque and speed
prescribed by the test.
(iii) This test may be conducted on a representative bench test
facility when engine limitations either preclude repeated use of this
power or would result in premature engine removals during the test. The
loads, the vibration frequency, and the methods of application to the
affected rotor drive system components must be representative of
rotorcraft conditions. Test components must be those used to show
compliance with the remainder of this section.
(c) Endurance tests; maximum continuous run. Three hours of
continuous operation at maximum continuous torque and the maximum speed
for use with maximum continuous torque must be conducted as follows:
(1) The main rotor controls must be operated at a minimum of 15 times
each hour through the main rotor pitch positions of maximum vertical
thrust, maximum forward thrust component, maximum aft thrust component,
maximum left thrust component, and maximum right thrust component, except
that the control movements need not produce loads or blade flapping motion
exceeding the maximum loads of motions encountered in flight.
(2) The directional controls must be operated at a minimum of 15 times
each hour through the control extremes of maximum right turning torque,
neutral torque as required by the power applied to the main rotor, and
maximum left turning torque.
(3) Each maximum control position must be held for at least 10 seconds,
and the rate of change of control position must be at least as rapid as
that for normal operation.
(d) Endurance tests; 90 percent of maximum continuous run. One
hour of continuous operation at 90 percent of maximum continuous torque
and the maximum speed for use with 90 percent of maximum continuous torque
must be conducted.
(e) Endurance tests; 80 percent of maximum continuous run. One
hour of continuous operation at 80 percent of maximum continuous torque
and the minimum speed for use with 80 percent of maximum continuous torque
must be conducted.
(f) Endurance tests; 60 percent of maximum continuous run. Two
hours or, for helicopters for which the use of either 30-minute OEI power
or continuous OEI power is requested, 1 hour of continuous operation at 60
percent of maximum continuous torque and the minimum speed for use with 60
percent of maximum continuous torque must be conducted.
(g) Endurance tests; engine malfunctioning run. It must be
determined whether malfunctioning of components, such as the engine fuel
or ignition systems, or whether unequal engine power can cause dynamic
conditions detrimental to the drive system. If so, a suitable number of
hours of operation must be accomplished under those conditions, 1 hour of
which must be included in each cycle, and the remaining hours of which
must be accomplished at the end of the 20 cycles. If no detrimental
condition results, an additional hour of operation in compliance with
paragraph (b) of this section must be conducted in accordance with the run
schedule of paragraph (b)(1) of this section without consideration of
paragraph (b)(2) of this section.
(h) Endurance tests; overspeed run. One hour of continuous
operation must be conducted at maximum continuous torque and the maximum
power-on overspeed expected in service, assuming that speed and torque
limiting devices, if any, function properly.
(i) Endurance tests; rotor control positions. When the rotor
controls are not being cycled during the tie-down tests, the rotor must be
operated, using the procedures prescribed in paragraph (c) of this
section, to produce each of the maximum thrust positions for the following
percentages of test time (except that the control positions need not
produce loads or blade flapping motion exceeding the maximum loads or
motions encountered in flight):
(1) For full vertical thrust, 20 percent.
(2) For the forward thrust component, 50 percent.
(3) For the right thrust component, 10 percent.
(4) For the left thrust component, 10 percent.
(5) For the aft thrust component, 10 percent.
(j) Endurance tests, clutch and brake engagements. A total of at
least 400 clutch and brake engagements, including the engagements of
paragraph (b) of this section, must be made during the takeoff torque runs
and, if necessary, at each change of torque and speed throughout the test.
In each clutch engagement, the shaft on the driven side of the clutch must
be accelerated from rest. The clutch engagements must be accomplished at
the speed and by the method prescribed by the applicant. During
deceleration after each clutch engagement, the engines must be stopped
rapidly enough to allow the engines to be automatically disengaged from
the rotors and rotor drives. If a rotor brake is installed for stopping
the rotor, the clutch, during brake engagements, must be disengaged above
40 percent of maximum continuous rotor speed and the rotors allowed to
decelerate to 40 percent of maximum continuous rotor speed, at which time
the rotor brake must be applied. If the clutch design does not allow
stopping the rotors with the engine running, or if no clutch is provided,
the engine must be stopped before each application of the rotor brake, and
then immediately be started after the rotors stop.
(k) Endurance tests; OEI power run. (1) 30-minute OEI power
run. For rotorcraft for which the use of 30-minute OEI power is
requested, a run at 30-minute OEI torque and the maximum speed for use
with 30-minute OEI torque must be conducted as follows: For each engine,
in sequence, that engine must be inoperative and the remaining engines
must be run for a 30-minute period.
(2) Continuous OEI power run. For rotorcraft for which the use
of continuous OEI power is requested, a run at continuous OEI torque and
the maximum speed for use with continuous OEI torque must be conducted as
follows: 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 section may not be less than the number of engines, nor may it be
less than two.
(l) [Reserved]
(m) Any components that are affected by maneuvering and gust loads must
be investigated for the same flight conditions as are the main rotors, and
their service lives must be determined 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
rotorcraft, 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
rotorcraft.
(n) Special tests. Each rotor drive system designed to operate
at two or more gear ratios must be subjected to special testing for
durations necessary to substantiate 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 intervening disassembly
which might affect test results may be conducted.
(p) Endurance tests; operating lubricants. To be approved for
use in rotor drive and control systems, lubricants must meet the
specifications of lubricants used during the tests prescribed by this
section. Additional or alternate lubricants may be qualified by equivalent
testing or by comparative analysis of lubricant specifications and rotor
drive and control system characteristics. In addition --
(1) At least three 10-hour cycles required by this section must be
conducted with transmission and gearbox lubricant temperatures, at the
location prescribed for measurement, not lower than the maximum operating
temperature 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 extended to include operation
at any one-engine-inoperative rating for which approval 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)))