Section 25.109

14 CFR Ch. I (1-1-19 Edition)

determined for non-icing conditions
may be used.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-38, 41 FR 55466, Dec. 20,
1976; Amdt. 25-42, 43 FR 2320, Jan. 16, 1978;
Amdt. 25-92, 63 FR 8318, Feb. 18, 1998; Amdt.
25-94, 63 FR 8848, Feb. 23, 1998; Amdt. 25-108,
67 FR 70826, Nov. 26, 2002; Amdt. 25-121, 72 FR
44665, Aug. 8, 2007; Amdt. 25-135, 76 FR 74654,
Dec. 1, 2011]

spaschal on DSK3GDR082PROD with CFR

Section 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.
(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 Section 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:

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