§ 25.107 Takeoff speeds. ( a ) V1 must be established in relation to V*EF* as follows: ( 1 ) V*EF* is the calibrated airspeed at which the critical engine is assumed to fail. V*EF* must be selected by the applicant, but may not be less than V*MCG* determined under § 25.149(e).
( 2 ) V1, in terms of calibrated airspeed, is selected by the applicant; however, V1 may not be less than VEF plus the speed gained with critical engine inoperative during the time interval between the instant at which the critical engine is failed, and the instant at which the pilot recognizes and reacts to the engine failure, as indicated by the pilot's initiation of the first action (e.g., applying brakes, reducing thrust, deploying speed brakes) to stop the airplane during accelerate-stop tests.
( b ) V *2MIN,* in terms of calibrated airspeed, may not be less than— ( 1 ) 1.13 *V* *SR* for— ( i ) Two-engine and three-engine turbopropeller and reciprocating engine powered airplanes; and
( ii ) Turbojet powered airplanes without provisions for obtaining a significant reduction in the one-engine-inoperative power-on stall speed;
( 2 ) 1.08 *V* *SR* for— ( i ) Turbopropeller and reciprocating engine powered airplanes with more than three engines; and
( ii ) Turbojet powered airplanes with provisions for obtaining a significant reduction in the one-engine-inoperative power-on stall speed; and
( 3 ) 1.10 times *V* *MC* established under § 25.149.
( c ) V *2* , in terms of calibrated airspeed, must be selected by the applicant to provide at least the gradient of climb required by § 25.121(b) but may not be less than— ( 1 ) V*2MIN*;
( 2 ) V *R* plus the speed increment attained (in accordance with § 25.111(c)(2)) before reaching a height of 35 feet above the takeoff surface; and
( 3 ) A speed that provides the maneuvering capability specified in § 25.143(h).
( d ) V*MU* is the calibrated airspeed at and above which the airplane can safely lift off the ground, and con- tinue the takeoff. V*MU* speeds must be selected by the applicant throughout the range of thrust-to-weight ratios to be certificated. These speeds may be established from free air data if these data are verified by ground takeoff tests.
( e ) V *R,* in terms of calibrated airspeed, must be selected in accordance with the conditions of paragraphs (e)(1) through (4) of this section: ( 1 ) V *R* may not be less than— ( i ) V 1 ;
( ii ) 105 percent of *V* *MC*;
( iii ) The speed (determined in accordance with § 25.111(c)(2)) that allows reaching *V* 2 before reaching a height of 35 feet above the takeoff surface; or
( iv ) A speed that, if the airplane is rotated at its maximum practicable rate, will result in a VLOF of not less than — ( A ) 110 percent of VMU in the all-engines-operating condition, and 105 percent of VMU determined at the thrust-to-weight ratio corresponding to the one-engine-inoperative condition; or
( B ) If the VMU attitude is limited by the geometry of the airplane (*i.e.,* tail contact with the runway), 108 percent of VMU in the all-engines-operating condition, and 104 percent of VMU determined at the thrust-to-weight ratio corresponding to the one-engine-inoperative condition.
( 2 ) For any given set of conditions (such as weight, configuration, and temperature), a single value of *V* *R,* obtained in accordance with this paragraph, must be used to show compliance with both the one-engine-inoperative and the all-engines-operating takeoff provisions.
( 3 ) It must be shown that the one-engine-inoperative takeoff distance, using a rotation speed of 5 knots less than *V* *R* established in accordance with paragraphs (e)(1) and (2) of this section, does not exceed the corresponding one-engine-inoperative takeoff distance using the established *V* *R*. The takeoff distances must be determined in accordance with § 25.113(a)(1).
( 4 ) Reasonably expected variations in service from the established takeoff procedures for the operation of the airplane (such as over-rotation of the airplane and out-of-trim conditions) may not result in unsafe flight characteristics or in marked increases in the scheduled takeoff distances established in accordance with § 25.113(a).
( f ) V *LOF* is the calibrated airspeed at which the airplane first becomes airborne.
( g ) V FTO , in terms of calibrated airspeed, must be selected by the applicant to provide at least the gradient of climb required by § 25.121(c), but may not be less than— ( 1 ) 1.18 *V* *SR*; and
( 2 ) A speed that provides the maneuvering capability specified in § 25.143(h).
( h ) In determining the takeoff speeds V1, VR, and V2 for flight in icing conditions, the values of VMCG, VMC, and VMU determined for non-icing conditions may be used.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-38, 41 FR 55466, Dec. 20, 1976; Amdt. 25-42, 43 FR 2320, Jan. 16, 1978; Amdt. 25-92, 63 FR 8318, Feb. 18, 1998; Amdt. 25-94, 63 FR 8848, Feb. 23, 1998; Amdt. 25-108, 67 FR 70826, Nov. 26, 2002; Amdt. 25-121, 72 FR 44665, Aug. 8, 2007; Amdt. 25-135, 76 FR 74654, Dec. 1, 2011]