Sec. 25.115  Takeoff flight path.
  
    (a) The takeoff flight path begins 35 feet above the takeoff surface at the
  end of the takeoff distance determined in accordance with Sec. 25.113(a).
    (b) The net takeoff flight path data must be determined so that they
  represent the actual takeoff flight paths (determined in accordance with Sec.
  25.111 and with paragraph (a) of this section) reduced at each point by a
  gradient of climb equal to--
    (1) 0.8 percent for two-engine airplanes;
    (2) 0.9 percent for three-engine airplanes; and
    (3) 1.0 percent for four-engine airplanes.
    (c) The prescribed reduction in climb gradient may be applied as an
  equivalent reduction in acceleration along that part of the takeoff flight
  path at which the airplane is accelerated in level flight.



  Sec. 25.117  Climb: general.
  
    Compliance with the requirements of Secs. 25.119 and 25.121 must be shown
  at each weight, altitude, and ambient temperature within the operational
  limits established for the airplane and with the most unfavorable center of
  gravity for each configuration.



  Sec. 25.119  Landing climb: All-engine-operating.
  
    In the landing configuration, the steady gradient of climb may not be less
  than 3.2 percent, with--
    (a) The engines at the power or thrust that is available eight seconds
  after initiation of movement of the power or thrust controls from the minimum
  flight idle to the takeoff position; and
    (b) A climb speed of not more than 1.3 VS.



  Sec. 25.121  Climb: One-engine-inoperative.
  
    (a) Takeoff; landing gear extended.  In the critical takeoff configuration
  existing along the flight path (between the points at which the airplane
  reaches VLOF and at which the landing gear is fully retracted) and in the
  configuration used in Sec. 25.111 but without ground effect, the steady
  gradient of climb must be positive for two-engine airplanes, and not less
  than 0.3 percent for three-engine airplanes or 0.5 percent for four-engine
  airplanes, at VLOF and with--
    (1) The critical engine inoperative and the remaining engines at the power
  or thrust available when retraction of the landing gear is begun in
  accordance with Sec. 25.111 unless there is a more critical power operating
  condition existing later along the flight path but before the point at which
  the landing gear is fully retracted; and
    (2) The weight equal to the weight existing when retraction of the landing
  gear is begun, determined under Sec. 25.111.
    (b) Takeoff; landing gear retracted.  In the takeoff configuration existing
  at the point of the flight path at which the landing gear is fully retracted,
  and in the configuration used in Sec. 25.111 but without ground effect, the
  steady gradient of climb may not be less than 2.4 percent for two-engine
  airplanes, 2.7 percent for three-engine airplanes, and 3.0 percent for four-
  engine airplanes, at V2 and with--
    (1) The critical engine inoperative, the remaining engines at the takeoff
  power or thrust available at the time the landing gear is fully retracted,
  determined under Sec. 25.111, unless there is a more critical power operating
  condition existing later along the flight path but before the point where the
  airplane reaches a height of 400 feet above the takeoff surface; and
    (2) The weight equal to the weight existing when the airplane's landing
  gear is fully retracted, determined under Sec. 25.111.
    (c) Final takeoff. In the en route configuration at the end of the takeoff
  path determined in accordance with Sec. 25.111, the steady gradient of climb
  may not be less than 1.2 percent for two-engine airplanes, 1.5 percent for
  three-engine airplanes, and 1.7 percent for four-engine airplanes, at not
  less than 1.25 VS and with--
    (1) The critical engine inoperative and the remaining engines at the
  available maximum continuous power or thrust; and
    (2) The weight equal to the weight existing at the end of the takeoff path,
  determined under Sec. 25.111.
    (d) Approach. In the approach configuration corresponding to the normal
  all-engines-operating procedure in which VS for this configuration does not
  exceed 110 percent of the VS for the related landing configuration, the
  steady gradient of climb may not be less than 2.1 percent for two-engine
  airplanes, 2.4 percent for three-engine airplanes, and 2.7 percent for four-
  engine airplanes, with--
    (1) The critical engine inoperative, the remaining engines at the available
  takeoff power or thrust;
    (2) The maximum landing weight; and
    (3) A climb speed established in connection with normal landing procedures,
  but not exceeding 1.5 VS.



  Sec. 25.123  En route flight paths.
  
    (a) For the en route configuration, the flight paths prescribed in
  paragraphs (b) and (c) of this section must be determined at each weight,
  altitude, and ambient temperature, within the operating limits established
  for the airplane. The variation of weight along the flight path, accounting
  for the progressive consumption of fuel and oil by the operating engines, may
  be included in the computation. The flight paths must be determined at any
  selected speed, with--
    (1) The most unfavorable center of gravity;
    (2) The critical engines inoperative;
    (3) The remaining engines at the available maximum continuous power or
  thrust; and
    (4) The means for controlling the engine-cooling air supply in the position
  that provides adequate cooling in the hot-day condition.
    (b) The one-engine-inoperative net flight path data must represent the
  actual climb performance diminished by a gradient of climb of 1.1 percent for
  two-engine airplanes, 1.4 percent for three-engine airplanes, and 1.6 percent
  for four-engine airplanes.
    (c) For three- or four-engine airplanes, the two-engine-inoperative net
  flight path data must represent the actual climb performance diminished by a
  gradient of climb of 0.3 percent for three-engine airplanes and 0.5 percent
  for four-engine airplanes.