[Code of Federal Regulations]
[Title 14, Volume 1]
[Revised as of January 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 14CFR25.173]

[Page 356]
 
                     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 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]

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