(1) The takeoff path must be based on the procedures prescribed in §25.101(f);
(2) The airplane must be accelerated on the ground to V
(3) After reaching V
(b) During the acceleration to speed V 2, the nose gear may be raised off the ground at a speed not less than V
(c) During the takeoff path determination in accordance with paragraphs (a) and (b) of this section—
(1) The slope of the airborne part of the takeoff path must be positive at each point;
(2) The airplane must reach V
(3) At each point along the takeoff path, starting at the point at which the airplane reaches 400 feet above the takeoff surface, the available gradient of climb may not be less than—
(i) 1.2 percent for two-engine airplanes;
(ii) 1.5 percent for three-engine airplanes; and
(iii) 1.7 percent for four-engine airplanes.
(4) The airplane configuration may not be changed, except for gear retraction and automatic propeller feathering, and no change in power or thrust that requires action by the pilot may be made until the airplane is 400 feet above the takeoff surface; and
(5) If §25.105(a)(2) requires the takeoff path to be determined for flight in icing conditions, the airborne part of the takeoff must be based on the airplane drag:
(i) With the takeoff ice accretion defined in appendix C, from a height of 35 feet above the takeoff surface up to the point where the airplane is 400 feet above the takeoff surface; and
(ii) With the final takeoff ice accretion defined in appendix C, from the point where the airplane is 400 feet above the takeoff surface to the end of the takeoff path.
(d) The takeoff path must be determined by a continuous demonstrated takeoff or by synthesis from segments. If the takeoff path is determined by the segmental method—
(1) The segments must be clearly defined and must be related to the distinct changes in the configuration, power or thrust, and speed;
(2) The weight of the airplane, the configuration, and the power or thrust must be constant throughout each segment and must correspond to the most critical condition prevailing in the segment;
(3) The flight path must be based on the airplane's performance without ground effect; and
(4) The takeoff path data must be checked by continuous demonstrated takeoffs up to the point at which the airplane is out of ground effect and its speed is stabilized, to ensure that the path is conservative relative to the continous path.
The airplane is considered to be out of the ground effect when it reaches a height equal to its wing span.
(e) For airplanes equipped with standby power rocket engines, the takeoff path may be determined in accordance with section II of appendix E.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25–6, 30 FR 8468, July 2, 1965; Amdt. 25–42, 43 FR 2321, Jan. 16, 1978; Amdt. 25–54, 45 FR 60172, Sept. 11, 1980; Amdt. 25–72, 55 FR 29774, July 20, 1990; Amdt. 25–94, 63 FR 8848, Feb. 23, 1998; Amdt. 25–108, 67 FR 70826, Nov. 26, 2002; Amdt. 25–115, 69 FR 40527, July 2, 2004; Amdt. 25–121, 72 FR 44666; Aug. 8, 2007]