JAR 29.923 Rotor drive system and control
mechanism tests
(a) Endurance tests, general. Each rotor
drive system and rotor control mechanism must be
tested, as prescribed in sub-paragraphs (b) to (n)
[and (p) of this paragraph, for at least 200 hours]
plus the time required to meet the requirements of
sub-paragraphs (b)(2), (b)(3) and (k) of this
paragraph. 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 sub-paragraphs (b) (2)
and (k) of this paragraph, 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, take-off run. The takeoff
run must be conducted as follows:
(1) Except as prescribed in subparagraphs
(b)(2) and (b)(3) of this paragraph,
the take-off torque run must consist of 1 hour
of alternate runs of 5 minutes at take-off torque
and the maximum speed for use with take-off
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 rpm. 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 2½-minute OEI rating is requested, the takeoff
run must be conducted as prescribed in
subparagraph (b) (1) of this paragraph, except
for the third and sixth runs for which the takeoff
torque and the maximum speed for use with
take-off torque are prescribed in that
paragraph. For these runs, the following apply:
(i) Each run must consist of at
least one period of 2½ minutes with takeoff
torque and the maximum speed for
use with take-off 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 2½-
minutes OEI torque and the maximum
speed for use with 2½-minute OEI torque
for 2½ minutes.
(3) For multi-engine, turbine-powered
rotorcraft for which the use of 30-second/
2-minute OEI power is requested, the take-off
run must be conducted as prescribed in subparagraph
(b) (1) of this paragraph except for
the following:
(i) Immediately following any one
5-minute power-on run required by sub-
[paragraph (b)(1) of this paragraph, simulate
a failure, for each power source in turn, and]
apply the maximum torque and the
maximum speed for use with the 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 stabilised 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 stabilisation 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
JAR 29.923(b)(2) (continued)
JAR–29 SECTION 1
Change 1
1.12.99 1–E–4 1Ch. 1 (Amend. 98/1, Eff. 16.2.98)
1[be those used to show compliance with the]
[remainder of this paragraph.]
(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% of maximum
continuous run. One hour of continuous
operation at 90% of maximum continuous torque
and the maximum speed for use with 90% of
maximum continuous torque must be conducted.
(e) Endurance tests; 80% of maximum
continuous run. One hour of continuous
operation at 80% of maximum continuous torque
and the minimum speed for use with 80% of
maximum continuous torque must be conducted.
(f) Endurance tests; 60% 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% of maximum
continuous torque and the minimum speed for use
with 60% 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 sub-paragraph (b) of this
paragraph must be conducted in accordance with
the run schedule of sub-paragraph (b) (1) of this
paragraph without consideration of sub-paragraph
(b) (2) of this paragraph.
(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 endurance tests, the rotor must be
operated, using the procedures prescribed in
subparagraph (c) of this paragraph, 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%.
(2) For the forward thrust component, 50%
(3) For the right thrust component, 10%.
(4) For the left thrust component, 10%.
(5) For the aft thrust component, 10%.
(j) Endurance tests, clutch and brake
engagements. A total of at least 400 clutch and
brake engagements, including the engagements of
sub-paragraph (b) of this paragraph, must be made
during the take-off 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% of
maximum continuous rotor speed and the rotors
allowed to decelerate to 40% 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.
JAR 29.923(b)(3)(iii) (continued) JAR 29.923(g) (continued)
SECTION 1 JAR–29
Change 1 1–E–5 1.12.99
(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
sub-paragraph (k) (1) or (k) (2) of this paragraph
may not be less than the number of engines, nor
may it be less than two.
(1) Reserved.
(m) Any components that are affected by
manoeuvring 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 multi-rotor 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 multi-engine 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
[paragraph 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
[paragraph. 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 paragraph 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
[paragraph 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 sub-paragraphs
(p) (1) and (p) (2) of this paragraph must be
applied simultaneously and must be extended to
include operation at any one-engine-inoperative
rating for which approval is requested.
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