561 

Federal Aviation Administration, DOT 

§ 27.1521 

(i) The minimum shown during the 

type tests; and 

(ii) The minimum determined by de-

sign substantiation; and 

(2) Not more than a value determined 

under § 27.33(a)(1) and (b)(1). 

§ 27.1519

Weight and center of gravity. 

The weight and center of gravity lim-

itations determined under §§ 27.25 and 
27.27, respectively, must be established 
as operating limitations. 

[Amdt. 27–2, 33 FR 965, Jan. 26, 1968, as 
amended by Amdt. 27–21, 49 FR 44435, Nov. 6, 
1984] 

§ 27.1521

Powerplant limitations. 

(a) 

General.  The powerplant limita-

tions prescribed in this section must be 
established so that they do not exceed 
the corresponding limits for which the 
engines are type certificated. 

(b) 

Takeoff operation. The powerplant 

takeoff operation must be limited by— 

(1) The maximum rotational speed, 

which may not be greater than— 

(i) The maximum value determined 

by the rotor design; or 

(ii) The maximum value shown dur-

ing the type tests; 

(2) The maximum allowable manifold 

pressure (for reciprocating engines); 

(3) The time limit for the use of the 

power corresponding to the limitations 
established in paragraphs (b)(1) and (2) 
of this section; 

(4) If the time limit in paragraph 

(b)(3) of this section exceeds two min-
utes, the maximum allowable cylinder 
head, coolant outlet, or oil tempera-
tures; 

(5) The gas temperature limits for 

turbine engines over the range of oper-
ating and atmospheric conditions for 
which certification is requested. 

(c) 

Continuous operation. The contin-

uous operation must be limited by— 

(1) The maximum rotational speed 

which may not be greater than— 

(i) The maximum value determined 

by the rotor design; or 

(ii) The maximum value shown dur-

ing the type tests; 

(2) The minimum rotational speed 

shown under the rotor speed require-
ments in § 27.1509(c); and 

(3) The gas temperature limits for 

turbine engines over the range of oper-

ating and atmospheric conditions for 
which certification is requested. 

(d) 

Fuel grade or designation. The min-

imum fuel grade (for reciprocating en-
gines), or fuel designation (for turbine 
engines), must be established so that it 
is not less than that required for the 
operation of the engines within the 
limitations in paragraphs (b) and (c) of 
this section. 

(e) 

Turboshaft engine torque. For 

rotorcraft with main rotors driven by 
turboshaft engines, and that do not 
have a torque limiting device in the 
transmission system, the following 
apply: 

(1) A limit engine torque must be es-

tablished if the maximum torque that 
the engine can exert is greater than— 

(i) The torque that the rotor drive 

system is designed to transmit; or 

(ii) The torque that the main rotor 

assembly is designed to withstand in 
showing compliance with § 27.547(e). 

(2) The limit engine torque estab-

lished under paragraph (e)(1) of this 
section may not exceed either torque 
specified in paragraph (e)(1)(i) or (ii) of 
this section. 

(f) 

Ambient temperature. For turbine 

engines, ambient temperature limita-
tions (including limitations for winter-
ization installations, if applicable) 
must be established as the maximum 
ambient atmospheric temperature at 
which compliance with the cooling pro-
visions of §§ 27.1041 through 27.1045 is 
shown. 

(g) 

Two and one-half-minute OEI power 

operation.  Unless otherwise authorized, 
the use of 2

1

⁄

2

-minute OEI power must 

be limited to engine failure operation 
of multiengine, turbine-powered rotor-
craft for not longer than 2

1

⁄

2

minutes 

after failure of an engine. The use of 
2

1

⁄

2

-minute OEI power must also be lim-

ited by— 

(1) The maximum rotational speed, 

which may not be greater than— 

(i) The maximum value determined 

by the rotor design; or 

(ii) The maximum demonstrated dur-

ing the type tests; 

(2) The maximum allowable gas tem-

perature; and 

(3) The maximum allowable torque. 
(h) 

Thirty-minute OEI power operation. 

Unless otherwise authorized, the use of 
30-minute OEI power must be limited 

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562 

14 CFR Ch. I (1–1–24 Edition) 

§ 27.1523 

to multiengine, turbine-powered rotor-
craft for not longer than 30 minutes 
after failure of an engine. The use of 30- 
minute OEI power must also be limited 
by— 

(1) The maximum rotational speed, 

which may not be greater than— 

(i) The maximum value determined 

by the rotor design; or 

(ii) The maximum value dem-

onstrated during the type tests; 

(2) The maximum allowable gas tem-

perature; and 

(3) The maximum allowable torque. 
(i) 

Continuous OEI power operation. 

Unless otherwise authorized, the use of 
continuous OEI power must be limited 
to multiengine, turbine-powered rotor-
craft for continued flight after failure 
of an engine. The use of continuous 
OEI power must also be limited by— 

(1) The maximum rotational speed, 

which may not be greater than— 

(i) The maximum value determined 

by the rotor design; or 

(ii) The maximum value dem-

onstrated during the type tests; 

(2) The maximum allowable gas tem-

perature; and 

(3) The maximum allowable torque. 
(j) 

Rated 30-second OEI power oper-

ation.  Rated 30-second OEI power is 
permitted only on multiengine, tur-
bine-powered rotorcraft, also certifi-
cated for the use of rated 2-minute OEI 
power, and can only be used for contin-
ued operation of the remaining en-
gine(s) after a failure or precautionary 
shutdown of an engine. It must be 
shown that following application of 30- 
second OEI power, any damage will be 
readily detectable by the applicable in-
spections and other related procedures 
furnished in accordance with Section 
A27.4 of appendix A of this part and 
Section A33.4 of appendix A of part 33. 
The use of 30-second OEI power must be 
limited to not more than 30 seconds for 
any period in which that power is used, 
and by— 

(1) The maximum rotational speed, 

which may not be greater than— 

(i) The maximum value determined 

by the rotor design; or 

(ii) The maximum value dem-

onstrated during the type tests; 

(2) The maximum allowable gas tem-

perature; and 

(3) The maximum allowable torque. 

(k) 

Rated 2-minute OEI power oper-

ation. Rated 2-minute OEI power is per-
mitted only on multiengine, turbine- 
powered rotorcraft, also certificated 
for the use of rated 30-second OEI 
power, and can only be used for contin-
ued operation of the remaining en-
gine(s) after a failure or precautionary 
shutdown of an engine. It must be 
shown that following application of 2- 
minute OEI power, any damage will be 
readily detectable by the applicable in-
spections and other related procedures 
furnished in accordance with Section 
A27.4 of appendix A of this part and 
Section A33.4 of appendix A of part 33. 
The use of 2-minute OEI power must be 
limited to not more than 2 minutes for 
any period in which that power is used, 
and by— 

(1) The maximum rotational speed, 

which may not be greater than— 

(i) The maximum value determined 

by the rotor design; or 

(ii) The maximum value dem-

onstrated during the type tests; 

(2) The maximum allowable gas tem-

perature; and 

(3) The maximum allowable torque. 

(Secs. 313(a), 601, 603, 604, and 605 of the Fed-
eral Aviation Act of 1958 (49 U.S.C. 1354(a), 
1421, 1423, 1424, and 1425); and sec. 6(c) of the 
Dept. of Transportation Act (49 U.S.C. 
1655(c))) 

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as 
amended by Amdt. 27–14, 43 FR 2325, Jan. 16, 
1978; Amdt. 27–23, 53 FR 34214, Sept. 2, 1988; 
Amdt. 27–29, 59 FR 47767, Sept. 16, 1994] 

§ 27.1523

Minimum flight crew. 

The minimum flight crew must be es-

tablished so that it is sufficient for safe 
operation, considering— 

(a) The workload on individual crew-

members; 

(b) The accessibility and ease of oper-

ation of necessary controls by the ap-
propriate crewmember; and 

(c) The kinds of operation authorized 

under § 27.1525. 

§ 27.1525

Kinds of operations. 

The kinds of operations (such as 

VFR, IFR, day, night, or icing) for 
which the rotorcraft is approved are es-
tablished by demonstrated compliance 

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