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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