title-14-part-25-sec25-703

271

Federal Aviation Administration, DOT

§ 25.703

must maintain the selected positions,
except for movement produced by an
automatic positioning or load limiting
device, without further attention by
the pilots.

(b) Each lift and drag device control

must be designed and located to make
inadvertent operation improbable. Lift
and drag devices intended for ground
operation only must have means to
prevent the inadvertant operation of
their controls in flight if that oper-
ation could be hazardous.

in response to the operation of the con-
trol and the characteristics of the
automatic positioning or load limiting
device must give satisfactory flight
and performance characteristics under
steady or changing conditions of air-
speed, engine power, and airplane atti-
tude.

(d) The lift device control must be

designed to retract the surfaces from
the fully extended position, during
steady flight at maximum continuous
engine power at any speed below

9.0 (knots).

[Amdt. 25–23, 35 FR 5675, Apr. 8, 1970, as
amended by Amdt. 25–46, 43 FR 50595, Oct. 30,
1978; Amdt. 25–57, 49 FR 6848, Feb. 23, 1984]

§ 25.699

Lift and drag device indicator.

(a) There must be means to indicate

to the pilots the position of each lift or
drag device having a separate control
in the cockpit to adjust its position. In
addition, an indication of unsymmet-
rical operation or other malfunction in
the lift or drag device systems must be
provided when such indication is nec-
essary to enable the pilots to prevent
or counteract an unsafe flight or
ground condition, considering the ef-
fects on flight characteristics and per-
formance.

(b) There must be means to indicate

to the pilots the takeoff, en route, ap-
proach, and landing lift device posi-
tions.

drag devices beyond the landing posi-
tion is possible, the controls must be
clearly marked to identify this range
of extension.

[Amdt. 25–23, 35 FR 5675, Apr. 8, 1970]

§ 25.701

Flap and slat interconnection.

(a) Unless the airplane has safe flight

characteristics with the flaps or slats
retracted on one side and extended on
the other, the motion of flaps or slats
on opposite sides of the plane of sym-
metry must be synchronized by a me-
chanical interconnection or approved
equivalent means.

(b) If a wing flap or slat interconnec-

tion or equivalent means is used, it
must be designed to account for the ap-
plicable unsymmetrical loads, includ-
ing those resulting from flight with the
engines on one side of the plane of sym-
metry inoperative and the remaining
engines at takeoff power.

that are not subjected to slipstream
conditions, the structure must be de-
signed for the loads imposed when the
wing flaps or slats on one side are car-
rying the most severe load occurring in
the prescribed symmetrical conditions
and those on the other side are car-
rying not more than 80 percent of that
load.

(d) The interconnection must be de-

signed for the loads resulting when
interconnected flap or slat surfaces on
one side of the plane of symmetry are
jammed and immovable while the sur-
faces on the other side are free to move
and the full power of the surface actu-
ating system is applied.

[Amdt. 25–72, 55 FR 29777, July 20, 1990]

§ 25.703

Takeoff warning system.

A takeoff warning system must be in-

stalled and must meet the following re-
quirements:

(a) The system must provide to the

pilots an aural warning that is auto-
matically activated during the initial
portion of the takeoff roll if the air-
plane is in a configuration, including
any of the following, that would not
allow a safe takeoff:

(1) The wing flaps or leading edge de-

vices are not within the approved range
of takeoff positions.

(2) Wing spoilers (except lateral con-

trol spoilers meeting the requirements
of § 25.671), speed brakes, or longitu-
dinal trim devices are in a position
that would not allow a safe takeoff.

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272

14 CFR Ch. I (1–1–24 Edition)

§ 25.721

(b) The warning required by para-

graph (a) of this section must continue
until—

(1) The configuration is changed to

allow a safe takeoff;

(2) Action is taken by the pilot to

terminate the takeoff roll;

(3) The airplane is rotated for take-

off; or

(4) The warning is manually deacti-

vated by the pilot.

system must function properly
throughout the ranges of takeoff
weights, altitudes, and temperatures
for which certification is requested.

[Amdt. 25–42, 43 FR 2323, Jan. 16, 1978]

ANDING

EAR

§ 25.721

General.

(a) The landing gear system must be

designed so that when it fails due to
overloads during takeoff and landing,
the failure mode is not likely to cause
spillage of enough fuel to constitute a
fire hazard. The overloads must be as-
sumed to act in the upward and aft di-
rections in combination with side loads
acting inboard and outboard. In the ab-
sence of a more rational analysis, the
side loads must be assumed to be up to
20 percent of the vertical load or 20 per-
cent of the drag load, whichever is
greater.

(b) The airplane must be designed to

avoid any rupture leading to the spill-
age of enough fuel to constitute a fire
hazard as a result of a wheels-up land-
ing on a paved runway, under the fol-
lowing minor crash landing conditions:

(1) Impact at 5 feet-per-second

vertical velocity, with the airplane
under control, at Maximum Design
Landing Weight—

(i) With the landing gear fully re-

tracted; and

(ii) With any one or more landing

gear legs not extended.

(2) Sliding on the ground, with—
(i) The landing gear fully retracted

and with up to a 20

yaw angle; and

(ii) Any one or more landing gear

legs not extended and with 0

yaw

angle.

gine nacelle is likely to come into con-
tact with the ground, the engine pylon
or engine mounting must be designed

so that when it fails due to overloads
(assuming the overloads to act pre-
dominantly in the upward direction
and separately, predominantly in the
aft direction), the failure mode is not
likely to cause the spillage of enough
fuel to constitute a fire hazard.

[Amdt. 25–139, 79 FR 59430, Oct. 2, 2014]

§ 25.723

Shock absorption tests.

(a) The analytical representation of

the landing gear dynamic characteris-
tics that is used in determining the
landing loads must be validated by en-
ergy absorption tests. A range of tests
must be conducted to ensure that the
analytical representation is valid for
the design conditions specified in
§ 25.473.

(1) The configurations subjected to

energy absorption tests at limit design
conditions must include at least the
design landing weight or the design
takeoff weight, whichever produces the
greater value of landing impact energy.

(2) The test attitude of the landing

gear unit and the application of appro-
priate drag loads during the test must
simulate the airplane landing condi-
tions in a manner consistent with the
development of rational or conserv-
ative limit loads.

(b) The landing gear may not fail in

a test, demonstrating its reserve en-
ergy absorption capacity, simulating a
descent velocity of 12 f.p.s. at design
landing weight, assuming airplane lift
not greater than airplane weight act-
ing during the landing impact.

this section, changes in previously ap-
proved design weights and minor
changes in design may be substantiated
by analyses based on previous tests
conducted on the same basic landing
gear system that has similar energy
absorption characteristics.

[Doc. No. 1999–5835, 66 FR 27394, May 16, 2001]

§§ 25.725–25.727

[Reserved]

§ 25.729

Retracting mechanism.

(a)

General. For airplanes with re-

tractable landing gear, the following
apply: