[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: 14CFR25.109]
[Page 351-353]
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. 25.109 Accelerate-stop distance.
(a) The accelerate-stop distance on a dry runway is the greater of
the following distances:
(1) The sum of the distances necessary to--
(i) Accelerate the airplane from a standing start with all engines
operating to VEF for takeoff from a dry runway;
(ii) Allow the airplane to accelerate from VEF to the
highest speed reached during the rejected takeoff, assuming the critical
engine fails at VEF and the pilot takes the first action to
reject the takeoff at the V1 for takeoff from a dry runway;
and
(iii) Come to a full stop on a dry runway from the speed reached as
prescribed in paragraph (a)(1)(ii) of this section; plus
(iv) A distance equivalent to 2 seconds at the V1 for
takeoff from a dry runway.
(2) The sum of the distances necessary to--
(i) Accelerate the airplane from a standing start with all engines
operating to the highest speed reached during the rejected takeoff,
assuming the pilot takes the first action to reject the takeoff at the
V1 for takeoff from a dry runway; and
(ii) With all engines still operating, come to a full stop on dry
runway from the speed reached as prescribed in paragraph (a)(2)(i) of
this section; plus
(iii) A distance equivalent to 2 seconds at the V1 for
takeoff from a dry runway.
[[Page 352]]
(b) The accelerate-stop distance on a wet runway is the greater of
the following distances:
(1) The accelerate-stop distance on a dry runway determined in
accordance with paragraph (a) of this section; or
(2) The accelerate-stop distance determined in accordance with
paragraph (a) of this section, except that the runway is wet and the
corresponding wet runway values of VEF and V1 are
used. In determining the wet runway accelerate-stop distance, the
stopping force from the wheel brakes may never exceed:
(i) The wheel brakes stopping force determined in meeting the
requirements of Sec. 25.101(i) and paragraph (a) of this section; and
(ii) The force resulting from the wet runway braking coefficient of
friction determined in accordance with paragraphs (c) or (d) of this
section, as applicable, taking into account the distribution of the
normal load between braked and unbraked wheels at the most adverse
center-of-gravity position approved for takeoff.
(c) The wet runway braking coefficient of friction for a smooth wet
runway is defined as a curve of friction coefficient versus ground speed
and must be computed as follows:
(1) The maximum tire-to-ground wet runway braking coefficient of
friction is defined as:
[GRAPHIC] [TIFF OMITTED] TR18FE98.004
Where--
Tire Pressure=maximum airplane operating tire pressure (psi);
[mu]t/gMAX=maximum tire-to-ground braking coefficient;
V=airplane true ground speed (knots); and
Linear interpolation may be used for tire pressures other than those
listed.
(2) The maximum tire-to-ground wet runway braking coefficient of
friction must be adjusted to take into account the efficiency of the
anti-skid system on a wet runway. Anti-skid system operation must be
demonstrated by flight testing on a smooth wet runway, and its
efficiency must be determined. Unless a specific anti-skid system
efficiency is determined from a quantitative analysis of the flight
testing on a smooth wet runway, the maximum tire-to-ground wet runway
braking coefficient of friction determined in paragraph (c)(1) of this
section must be multiplied by the efficiency value associated with the
type of anti-skid system installed on the airplane:
------------------------------------------------------------------------
Efficiency
Type of anti-skid system value
------------------------------------------------------------------------
On-Off...................................................... 0.30
Quasi-Modulating............................................ 0.50
Fully Modulating............................................ 0.80
------------------------------------------------------------------------
(d) At the option of the applicant, a higher wet runway braking
coefficient of friction may be used for runway surfaces that have been
grooved or treated with a porous friction course material. For grooved
and porous friction course runways, the wet runway braking coefficent of
friction is defined as either:
[[Page 353]]
(1) 70 percent of the dry runway braking coefficient of friction
used to determine the dry runway accelerate-stop distance; or
(2) The wet runway braking coefficient defined in paragraph (c) of
this section, except that a specific anti-skid system efficiency, if
determined, is appropriate for a grooved or porous friction course wet
runway, and the maximum tire-to-ground wet runway braking coefficient of
friction is defined as:
[GRAPHIC] [TIFF OMITTED] TR18FE98.005
Where--
Tire Pressure=maximum airplane operating tire pressure (psi);
[mu]t/gMAX=maximum tire-to-ground braking coefficient;
V=airplane true ground speed (knots); and
Linear interpolation may be used for tire pressures other than those
listed.
(e) Except as provided in paragraph (f)(1) of this section, means
other than wheel brakes may be used to determine the accelerate-stop
distance if that means--
(1) Is safe and reliable;
(2) Is used so that consistent results can be expected under normal
operating conditions; and
(3) Is such that exceptional skill is not required to control the
airplane.
(f) The effects of available reverse thrust--
(1) Shall not be included as an additional means of deceleration
when determining the accelerate-stop distance on a dry runway; and
(2) May be included as an additional means of deceleration using
recommended reverse thrust procedures when determining the accelerate-
stop distance on a wet runway, provided the requirements of paragraph
(e) of this section are met.
(g) The landing gear must remain extended throughout the accelerate-
stop distance.
(h) If the accelerate-stop distance includes a stopway with surface
characteristics substantially different from those of the runway, the
takeoff data must include operational correction factors for the
accelerate-stop distance. The correction factors must account for the
particular surface characteristics of the stopway and the variations in
these characteristics with seasonal weather conditions (such as
temperature, rain, snow, and ice) within the established operational
limits.
(i) A flight test demonstration of the maximum brake kinetic energy
accelerate-stop distance must be conducted with not more than 10 percent
of the allowable brake wear range remaining on each of the airplane
wheel brakes.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-42,
43 FR 2321, Jan. 16, 1978; Amdt. 25-92, 63 FR 8318, Feb. 18, 1998]