Sec. 25.143 - General.

(a) The airplane must be safely controllable and maneuverable during --

(1) Takeoff;

(2) Climb;

(3) Level flight;

(4) Descent; and

(5) Landing.

(b) It must be possible to make a smooth transition from one flight condition to any other flight condition without exceptional piloting skill, alertness, or strength, and without danger of exceeding the airplane limit-load factor under any probable operating conditions, including --

(1) The sudden failure of the critical engine;

(2) For airplanes with three or more engines, the sudden failure of the second critical engine when the airplane is in the en route, approach, or landing configuration and is trimmed with the critical engine inoperative; and

(3) Configuration changes, including deployment or retraction of deceleration devices.

(c) The following table prescribes, for conventional wheel type controls, the maximum control forces permitted during the testing required by paragraphs (a) and (b) of this section:

   Force, in pounds, applied to the control
            wheel or rudder pedals              Pitch     Roll     Yaw
For short term application for pitch and roll       75       50  .......
 control_two hands available for control.....
For short term application for pitch and roll       50       25  .......
 control_one hand available for control......
For short term application for yaw control...  .......  .......      150
For long term application....................       10        5       20

(d) Approved operating procedures or conventional operating practices must be followed when demonstrating compliance with the control force limitations for short term application that are prescribed in paragraph (c) of this section. The airplane must be in trim, or as near to being in trim as practical, in the immediately preceding steady flight condition. For the takeoff condition, the airplane must be trimmed according to the approved operating procedures.

(e) When demonstrating compliance with the control force limitations for long term application that are prescribed in paragraph (c) of this section, the airplane must be in trim, or as near to being in trim as practical.

(f) When maneuvering at a constant airspeed or Mach number (up to VFC/MFC), the stick forces and the gradient of the stick force versus maneuvering load factor must lie within satisfactory limits. The stick forces must not be so great as to make excessive demands on the pilot's strength when maneuvering the airplane, and must not be so low that the airplane can easily be overstressed inadvertently. Changes of gradient that occur with changes of load factor must not cause undue difficulty in maintaining control of the airplane, and local gradients must not be so low as to result in a danger of overcontrolling.

(g) The maneuvering capabilities in a constant speed coordinated turn at forward center of gravity, as specified in the following table, must be free of stall warning or other characteristics that might interfere with normal maneuvering:

                                                                   Maneuvering bank
           Configuration                         Speed                angle in a                             Thrust power setting
                                                                   coordinated turn
Takeoff............................  V2                                   30   Asymmetric WAT-Limited.\1\
Takeoff............................  \2\V2 + XX                           40   All-engines-operating climb.\3\
En route...........................  VFTO                                 40   Asymmetric WAT-Limited.\1\
Landing............................  VREF                                 40   Symmetric for -3 flight path angle.
\1\ A combination of weight, altitude, and temperature (WAT) such that the thrust or power setting produces the minimum climb gradient specified in
   25.121 for the flight condition.
\2\ Airspeed approved for all-engines-operating initial climb.
\3\ That thrust or power setting which, in the event of failure of the critical engine and without any crew action to adjust the thrust or power of the
  remaining engines, would result in the thrust or power specified for the takeoff condition at V[INF]2[/INF], or any lesser thrust or power setting
  that is used for all-engines-operating initial climb procedures.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-42, 43 FR 2321, Jan. 16, 1978; Amdt. 25-84, 60 FR 30749, June 9, 1995; Amdt. 1-49, 67 FR 70826, Nov. 26, 2002]