627 

Federal Aviation Administration, DOT 

§ 29.923 

(ii) Absorbed by the rotors to be ap-

proved for the rotorcraft. 

(b) 

Endurance tests; takeoff run. 

The 

takeoff run must be conducted as fol-
lows: 

(1) Except as prescribed in para-

graphs (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 min-
utes at as low an engine idle speed as 
practicable. The engine must be de-
clutched 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 min-
imum practical r.p.m. The engine and 
the rotor drive system must be acceler-
ated at the maximum rate. When de-
clutching the engine, it must be decel-
erated rapidly enough to allow the op-
eration 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 take-
off torque are prescribed in that para-
graph. 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 en-
gines 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

min-

utes. 

(3) For multiengine, turbine-powered 

rotorcraft for which the use of 30-sec-
ond/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 para-
graph (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 sta-
bilized 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 con-
ducted on a bench test, the test se-
quence must be conducted 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 removals 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. 

(c) 

Endurance tests; maximum contin-

uous run. 

Three hours of continuous op-

eration 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, max-
imum left thrust component, and max-
imum right thrust component, except 
that the control movements need not 
produce loads or blade flapping motion 
exceeding the maximum loads of mo-
tions encountered in flight. 

(2) The directional controls must be 

operated at a minimum of 15 times 
each hour through the control ex-
tremes of maximum right turning 

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