[Code of Federal Regulations]

[Title 14, Volume 1]

[Revised as of January 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 14CFR25.173]



[Page 362-363]

 

                     TITLE 14--AERONAUTICS AND SPACE

 

CHAPTER I--FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION

 

PART 25_AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES--Table 

of Contents

 

                            Subpart B_Flight

 

Sec. 25.173  Static longitudinal stability.



    Under the conditions specified in Sec. 25.175, the characteristics 

of the elevator control forces (including friction) must be as follows:

    (a) A pull must be required to obtain and maintain speeds below the 

specified trim speed, and a push must be required to obtain and maintain 

speeds above the specified trim speed. This must be shown at any speed 

that can be obtained except speeds higher than the landing gear or wing 

flap operating limit speeds or VFC/MFC, whichever is appropriate, or 

lower than the minimum speed for steady unstalled flight.

    (b) The airspeed must return to within 10 percent of the original 

trim speed for the climb, approach, and landing conditions specified in 

Sec. 25.175 (a), (c), and (d), and must return to within 7.5 percent of 

the original trim speed for the cruising condition specified in Sec. 

25.175(b), when the control force is slowly released from any speed 

within the range specified in paragraph (a) of this section.

    (c) The average gradient of the stable slope of the stick force 

versus speed curve may not be less than 1 pound for each 6 knots.

    (d) Within the free return speed range specified in paragraph (b) of 

this section, it is permissible for the airplane, without control 

forces, to stabilize on



[[Page 363]]



speeds above or below the desired trim speeds if exceptional attention 

on the part of the pilot is not required to return to and maintain the 

desired trim speed and altitude.



[Amdt. 25-7, 30 FR 13117, Oct. 15, 1965]