14 CFR 23.57 - Takeoff path.
For normal, utility, and acrobatic category multiengine jets of more than 6,000 pounds maximum weight and commuter category airplanes, the takeoff path is as follows:
(a) The takeoff path extends from a standing start to a point in the takeoff at which the airplane is 1500 feet above the takeoff surface at or below which height the transition from the takeoff to the enroute configuration must be completed; and
(3) After reaching VEF, the airplane must be accelerated to V2.
(b) During the acceleration to speed V2, the nose gear may be raised off the ground at a speed not less than VR. However, landing gear retraction must not be initiated until the airplane is airborne.
(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 not be negative at any point;
(2) The airplane must reach V2 before it is 35 feet above the takeoff surface, and must continue at a speed as close as practical to, but not less than V2, until it is 400 feet above the takeoff surface;
(i) 1.2 percent for two-engine airplanes;
(ii) 1.5 percent for three-engine airplanes;
(iii) 1.7 percent for four-engine airplanes; and
(4) Except for gear retraction and automatic propeller feathering, the airplane configuration must not be changed, and no change in power that requires action by the pilot may be made, until the airplane is 400 feet above the takeoff surface.
(1) The segments must be clearly defined and must be related to distinct changes in configuration, power, and speed;
(2) The weight of the airplane, the configuration, and the power must be assumed constant throughout each segment and must correspond to the most critical condition prevailing in the segment; and