628 

14 CFR Ch. I (1–1–19 Edition) 

§ 29.923 

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 posi-
tion must be at least as rapid as that 
for normal operation. 

(d) 

Endurance tests; 90 percent of max-

imum continuous run. 

One hour of con-

tinuous operation at 90 percent of max-
imum continuous torque and the max-
imum speed for use with 90 percent of 
maximum continuous torque must be 
conducted. 

(e) 

Endurance tests; 80 percent of max-

imum continuous run. 

One hour of con-

tinuous operation at 80 percent of max-
imum continuous torque and the min-
imum speed for use with 80 percent of 
maximum continuous torque must be 
conducted. 

(f) 

Endurance tests; 60 percent of max-

imum 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 contin-
uous operation at 60 percent of max-
imum continuous torque and the min-
imum speed for use with 60 percent of 
maximum continuous torque must be 
conducted. 

(g) 

Endurance tests; engine malfunc-

tioning run. 

It must be determined 

whether malfunctioning of compo-
nents, such as the engine fuel or igni-
tion systems, or whether unequal en-
gine power can cause dynamic condi-
tions detrimental to the drive system. 
If so, a suitable number of hours of op-
eration must be accomplished under 
those conditions, 1 hour of which must 
be included in each cycle, and the re-
maining hours of which must be ac-
complished at the end of the 20 cycles. 
If no detrimental condition results, an 
additional hour of operation in compli-
ance 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, assum-
ing that speed and torque limiting de-
vices, if any, function properly. 

(i) 

Endurance tests; rotor control posi-

tions. 

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 fol-
lowing percentages of test time (except 
that the control positions need not 
produce loads or blade flapping motion 
exceeding the maximum loads or mo-
tions encountered in flight): 

(1) For full vertical thrust, 20 per-

cent. 

(2) For the forward thrust compo-

nent, 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, includ-
ing the engagements of paragraph (b) 
of this section, must be made during 
the takeoff torque runs and, if nec-
essary, 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 accel-
erated from rest. The clutch engage-
ments must be accomplished at the 
speed and by the method prescribed by 
the applicant. During deceleration 
after each clutch engagement, the en-
gines must be stopped rapidly enough 
to allow the engines to be automati-
cally disengaged from the rotors and 
rotor drives. If a rotor brake is in-
stalled 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 rotor-

craft for which the use of 30-minute 
OEI power is requested, a run at 30- 

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