529 

Federal Aviation Administration, DOT 

§ 27.923 

is requested, 12 runs during the 10-hour 
test must be conducted as follows: 

(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 en-
gines are run at 2

1

⁄

2

minute OEI torque 

and the maximum speed for use with 
2

1

⁄

2

minute OEI torque for 2

1

⁄

2

minutes. 

(2) For multiengine turbine-powered 

rotorcraft for which the use of 30-sec-
ond and 2-minute OEI power is re-
quested, 10 runs must be conducted as 
follows: 

(i) Immediately following a takeoff 

run of at least 5 minutes, each power 
source must simulate a failure, 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, followed by applica-
tion of the maximum torque and the 
maximum speed for use with 2-minute 
OEI power for not less than 2 minutes. 
At least one run sequence must be con-
ducted from a simulated ‘‘flight idle’’ 
condition. When conducted on a bench 
test, the test sequence must be con-
ducted following stabilization at take-
off power. 

(ii) For the purpose of this para-

graph, 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 re-
peated use of this power or would re-
sult in premature engine removal dur-
ing the test. The loads, the vibration 
frequency, and the methods of applica-
tion 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. 

(f) The parts of the test prescribed in 

paragraphs (c) and (d) of this section 
must be conducted in intervals of not 
less than 30 minutes and may be ac-
complished either on the ground or in 

flight. The part of the test prescribed 
in paragraph (e) of this section must be 
conducted in intervals of not less than 
five minutes. 

(g) At intervals of not more than five 

hours during the tests prescribed in 
paragraphs (c), (d), and (e) of this sec-
tion, the engine must be stopped rap-
idly enough to allow the engine and 
rotor drive to be automatically dis-
engaged from the rotors. 

(h) Under the operating conditions 

specified in paragraph (c) of this sec-
tion, 500 complete cycles of lateral con-
trol, 500 complete cycles of longitu-
dinal control of the main rotors, and 
500 complete cycles of control of each 
auxiliary rotor must be accomplished. 
A ‘‘complete cycle’’ involves movement 
of the controls from the neutral posi-
tion, through both extreme positions, 
and back to the neutral position, ex-
cept that control movements need not 
produce loads or flapping motions ex-
ceeding the maximum loads or motions 
encountered in flight. The cycling may 
be accomplished during the testing pre-
scribed in paragraph (c) of this section. 

(i) At least 200 start-up clutch en-

gagements must be accomplished— 

(1) So that the shaft on the driven 

side of the clutch is accelerated; and 

(2) Using a speed and method selected 

by the applicant. 

(j) For multiengine rotorcraft for 

which the use of 30-minute OEI power 
is requested, five runs must be made at 
30-minute OEI torque and the max-
imum speed for use with 30-minute OEI 
torque, in which each engine, in se-
quence, is made inoperative and the re-
maining engine(s) is run for a 30- 
minute period. 

(k) For multiengine rotorcraft for 

which the use of continuous OEI power 
is requested, five runs must be made at 
continuous OEI torque and the max-
imum speed for use with continuous 
OEI torque, in which each engine, in 
sequence, is made inoperative and the 

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