[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: 14CFR25.175]
[Page 357-358]
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. 25.175 Demonstration of static longitudinal stability.
Static longitudinal stability must be shown as follows:
(a) Climb. The stick force curve must have a stable slope at speeds
between 85 and 115 percent of the speed at which the airplane--
(1) Is trimmed, with--
(i) Wing flaps retracted;
(ii) Landing gear retracted;
(iii) Maximum takeoff weight; and
(iv) 75 percent of maximum continuous power for reciprocating
engines or the maximum power or thrust selected by the applicant as an
operating limitation for use during climb for turbine engines; and
(2) Is trimmed at the speed for best rate-of-climb except that the
speed need not be less than 1.3 VSR1.
(b) Cruise. Static longitudinal stability must be shown in the
cruise condition as follows:
(1) With the landing gear retracted at high speed, the stick force
curve must have a stable slope at all speeds within a range which is the
greater of 15 percent of the trim speed plus the resulting free return
speed range, or 50 knots plus the resulting free return speed range,
above and below the trim speed (except that the speed range need not
include speeds less than 1.3 VSR1, nor speeds
greater than VFC/MFC, nor speeds that require a
stick force of more than 50 pounds), with--
(i) The wing flaps retracted;
(ii) The center of gravity in the most adverse position (see
Sec. 25.27);
(iii) The most critical weight between the maximum takeoff and
maximum landing weights;
(iv) 75 percent of maximum continuous power for reciprocating
engines or for turbine engines, the maximum cruising power selected by
the applicant as an operating limitation (see Sec. 25.1521), except that
the power need not exceed that required at VMO/
MMO; and
(v) The airplane trimmed for level flight with the power required in
paragraph (b)(1)(iv) of this section.
(2) With the landing gear retracted at low speed, the stick force
curve must have a stable slope at all speeds within a range which is the
greater of 15 percent of the trim speed plus the resulting free return
speed range, or 50 knots plus the resulting free return speed range,
above and below the trim speed (except that the speed range need not
include speeds less than 1.3 VSR1, nor speeds
greater than the minimum speed of the applicable speed range prescribed
in paragraph (b)(1), nor speeds that require a stick force of more than
50 pounds), with--
(i) Wing flaps, center of gravity position, and weight as specified
in paragraph (b)(1) of this section;
(ii) Power required for level flight at a speed equal to (VMO
+ 1.3 VSR1)/2; and
(iii) The airplane trimmed for level flight with the power required
in paragraph (b)(2)(ii) of this section.
(3) With the landing gear extended, the stick force curve must have
a stable slope at all speeds within a range which is the greater of 15
percent of the trim speed plus the resulting free return speed range, or
50 knots plus the resulting free return speed range, above and below the
trim speed (except that the speed range need not include speeds less
than 1.3 VSR1, nor speeds greater than
VLE, nor speeds that require a stick force of more than 50
pounds), with--
(i) Wing flap, center of gravity position, and weight as specified
in paragraph (b)(1) of this section;
(ii) 75 percent of maximum continuous power for reciprocating
engines or, for turbine engines, the maximum cruising power selected by
the applicant as an operating limitation, except that the power need not
exceed that required for level flight at VLE; and
(iii) The aircraft trimmed for level flight with the power required
in paragraph (b)(3)(ii) of this section.
(c) Approach. The stick force curve must have a stable slope at
speeds between VSW and 1.7 VSR1, with--
(1) Wing flaps in the approach position;
(2) Landing gear retracted;
(3) Maximum landing weight; and
(4) The airplane trimmed at 1.3 VSR1 with
enough power to maintain level flight at this speed.
(d) Landing. The stick force curve must have a stable slope, and the
stick force may not exceed 80 pounds, at speeds between VSW
and 1.7 VSR0 with--
(1) Wing flaps in the landing position;
[[Page 358]]
(2) Landing gear extended;
(3) Maximum landing weight;
(4) Power or thrust off on the engines; and
(5) The airplane trimmed at 1.3 VSR0 with
power or thrust off.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-7, 30
FR 13117, Oct. 15, 1965; Amdt. 25-108, 67 FR 70827, Nov. 26, 2002]