--- kind: "range" citation: "14 C.F.R. §§ 27.1503–27.1525" title: "14" from: "27.1503" to: "27.1525" count: 7 url: "https://uscodex.org/cfr/14/27.1503..27.1525" --- # §27.1503. Airspeed limitations: general. - (a) An operating speed range must be established. - (b) When airspeed limitations are a function of weight, weight distribution, altitude, rotor speed, power, or other factors, airspeed limitations corresponding with the critical combinations of these factors must be established. # §27.1505. Never-exceed speed. - (a) The never-exceed speed, VNE, must be established so that it is— - (1) Not less than 40 knots (CAS); and - (2) **Not more than the lesser of—** - (i) 0.9 times the maximum forward speeds established under [§ 27.309](/cfr/14/27.309.md); - (ii) 0.9 times the maximum speed shown under §§ [27.251](/cfr/14/27.251.md) and [27.629](/cfr/14/27.629.md); or - (iii) 0.9 times the maximum speed substantiated for advancing blade tip mach number effects. - (b) VNE may vary with altitude, r.p.m., temperature, and weight, if— - (1) No more than two of these variables (or no more than two instruments integrating more than one of these variables) are used at one time; and - (2) The ranges of these variables (or of the indications on instruments integrating more than one of these variables) are large enough to allow an operationally practical and safe variation of VNE. - (c) For helicopters, a stabilized power-off VNE denoted as VNE (power-off) may be established at a speed less than VNE established pursuant to [paragraph (a)](#a) of this section, if the following conditions are met: - (1) VNE (power-off) is not less than a speed midway between the power-on VNE and the speed used in meeting the requirements of— - (i) [§ 27.65(b)](/cfr/14/27.65.md?p=b) for single engine helicopters; and - (ii) [§ 27.67](/cfr/14/27.67.md) for multiengine helicopters. - (2) **VNE (power-off) is—** - (i) A constant airspeed; - (ii) A constant amount less than power-on VNE; or - (iii) A constant airspeed for a portion of the altitude range for which certification is requested, and a constant amount less than power-on VNE for the remainder of the altitude range. # §27.1509. Rotor speed. - (a) **Maximum power-off (autorotation).** The maximum power-off rotor speed must be established so that it does not exceed 95 percent of the lesser of— - (1) The maximum design r.p.m. determined under [§ 27.309(b)](/cfr/14/27.309.md?p=b); and - (2) The maximum r.p.m. shown during the type tests. - (b) **Minimum power off.** The minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater of— - (1) The minimum shown during the type tests; and - (2) **The minimum determined by design substantiation.** - (c) **Minimum power on.** The minimum power-on rotor speed must be established so that it is— - (1) **Not less than the greater of—** - (i) The minimum shown during the type tests; and - (ii) The minimum determined by design substantiation; and - (2) Not more than a value determined under § [27.33(a)(1)](/cfr/14/27.33.md?p=a-1) and [(b)(1)](/cfr/14/27.33.md?p=b-1). # §27.1519. Weight and center of gravity. The weight and center of gravity limitations determined under §§ [27.25](/cfr/14/27.25.md) and [27.27](/cfr/14/27.27.md), respectively, must be established as operating limitations. # §27.1521. Powerplant limitations. - (a) **General.** The powerplant limitations 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 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 paragraphs [(b)(1)](#b-1) and [(2)](#b-2) of this section; - (4) If the time limit in [paragraph (b)(3)](#b-3) of this section exceeds two 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 [§ 27.1509(c)](/cfr/14/27.1509.md?p=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 the operation of the engines within the limitations in paragraphs [(b)](#b) and [(c)](#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 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 [§ 27.547(e)](/cfr/14/27.547.md?p=e). - (2) The limit engine torque established under [paragraph (e)(1)](#e-1) of this section may not exceed either torque specified in paragraph [(e)(1)(i)](#e-1-i) or [(ii)](#e-1-ii) of this section. - (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 [§§ 27.1041 through 27.1045](/cfr/14/27.1041..27.1045.md) 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 rotorcraft 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 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 authorized, the use of 30-minute OEI power must be limited to multiengine, 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 authorized, the use of continuous OEI power must be limited to multiengine, 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 multiengine, 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 Section A27.4 of appendix A of this part and Section A33.4 of appendix A of [part 33](/cfr/14/part33.md). 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 multiengine, 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 Section A27.4 of appendix A of this part and Section A33.4 of appendix A of [part 33](/cfr/14/part33.md). 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.** # §27.1523. Minimum flight crew. The minimum flight crew must be established so that it is sufficient for safe operation, considering— - (a) The workload on individual crewmembers; - (b) The accessibility and ease of operation of necessary controls by the appropriate crewmember; and - (c) The kinds of operation authorized under [§ 27.1525](/cfr/14/27.1525.md). # §27.1525. Kinds of operations. The kinds of operations (such as VFR, IFR, day, night, or icing) for which the rotorcraft is approved are established by demonstrated compliance with the applicable certification requirements and by the installed equipment.