CS 27.1521 Powerplant limitations

ED Decision 2012/021/R

(a)     General. The powerplant limitations prescribed in this paragraph must be established so that they do not exceed the corresponding limits for which the engines are type certificated.

(b)     Take-off operation. The powerplant take-off 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 during 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 sub-paragraphs (b)(1) and (2);

(4)     If the time limit in sub-paragraph (b)(3) exceeds 2 minutes, the maximum allowable cylinder head, coolant outlet, or oil temperatures;

(5)     The gas temperature limits for turbine engines over the range of operating and atmospheric conditions for which certification is requested.

(c)      Continuous operation. The continuous 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 during the type tests;

(2)     The minimum rotational speed shown under the rotor speed requirements in CS 27.1509(c); and

(3)     The gas temperature limits for turbine engines over the range of operating and atmospheric conditions for which certification is requested.

(d)     Fuel grade or designation. The minimum fuel grade (for reciprocating engines), or fuel designation (for turbine engines), must be established so that it is not less than that required for operation of the engines within the limitations in sub-paragraphs (b) and (c).

(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 established 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 CS 27.547(d).

(2)     The limit engine torque established under sub-paragraph (e)(1) may not exceed either torque specified in sub-paragraph (e)(1)(i) or (ii).

(f)      Ambient temperature. For turbine engines, ambient temperature limitations (including limitations for winterization installations, if applicable) must be established as the maximum ambient atmospheric temperature at which compliance with the cooling provisions of CS 27.1041 to 27.1045 is shown.

(g)     Two and one-half minute OEI power operation. Unless otherwise authorised, the use of 2½-minute OEI power must be limited to engine failure operation of multi-engine, turbine-powered rotorcraft for not longer that 2½ minutes after failure of an engine. The use of 2½-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 demonstrated during the type tests;

(2)     The maximum allowable gas temperature; and

(3)     The maximum allowable torque.

(h)     Thirty-minute OEI power operation.

Unless otherwise authorised, the use of 30-minute OEI power must be limited to multi-engine, turbine-powered rotorcraft 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 demonstrated during the type tests;

(2)     The maximum allowable gas temperature; and

(3)     The maximum allowable torque.

(i)      Continuous OEI power operation. Unless otherwise authorised, the use of continuous OEI power must be limited to multi-engine, turbine-powered rotorcraft 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 demonstrated during the type tests;

(2)     The maximum allowable gas temperature; and

(3)     The maximum allowable torque.

(j)      Rated 30-second OEI power operation. Rated 30-second OEI power is permitted only on multi-engine, turbine-powered rotorcraft, also certificated for the use of rated 2-minute OEI power, and can only be used for continued operation of the remaining engine(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 inspections and other related procedures furnished in accordance with paragraph A27.4 of Appendix A of this CS-27. 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 demonstrated during the type tests:

(2)     The maximum allowable gas temperature; and

(3)     The maximum allowable torque.

(k)     Rated 2-minute OEI power operation. Rated 2-minute OEI power is permitted only on multi-engine, turbine-powered rotorcraft, also certificated for the use of rated 30-second OEI power, and can only be used for continued operation of the remaining engine(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 inspections and other related procedures furnished in accordance with A27.4 of appendix A of this CS-27. 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 demonstrated during the type tests;

(2)     The maximum allowable gas temperature; and

(3)     The maximum allowable torque.

[Amdt 27/3]