Federal Aviation Administration, DOT

Section 25.493

accordance with Figure 4 of Appendix
A of this part. In this attitude - 
(a) The ground reactions must be the
same as those obtained on that side
under Section 25.479(d)(1), and
(b) Each unbalanced external load
must be reacted by airplane inertia in
a rational or conservative manner.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-91, 62 FR 40705, July 29,
1997]

Section 25.485

Side load conditions.

In addition to Section 25.479(d)(2) the following conditions must be considered:
(a) For the side load condition, the
airplane is assumed to be in the level
attitude with only the main wheels
contacting the ground, in accordance
with figure 5 of appendix A.
(b) Side loads of 0.8 of the vertical reaction (on one side) acting inward and
0.6 of the vertical reaction (on the
other side) acting outward must be
combined with one-half of the maximum vertical ground reactions obtained in the level landing conditions.
These loads are assumed to be applied
at the ground contact point and to be
resisted by the inertia of the airplane.
The drag loads may be assumed to be
zero.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-91, 62 FR 40705, July 29,
1997]

Section 25.487

Rebound landing condition.

(a) The landing gear and its supporting structure must be investigated
for the loads occurring during rebound
of the airplane from the landing surface.
(b) With the landing gear fully extended and not in contact with the
ground, a load factor of 20.0 must act
on the unsprung weights of the landing
gear. This load factor must act in the
direction of motion of the unsprung
weights as they reach their limiting
positions in extending with relation to
the sprung parts of the landing gear.

spaschal on DSK3GDR082PROD with CFR

Section 25.489

Ground handling conditions.

Unless otherwise prescribed, the
landing gear and airplane structure
must be investigated for the conditions
in SectionSection 25.491 through 25.509 with the airplane at the design ramp weight (the

maximum weight for ground handling
conditions). No wing lift may be considered. The shock absorbers and tires
may be assumed to be in their static
position.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-23, 35 FR 5673, Apr. 8,
1970]

Section 25.491

Taxi, takeoff and landing roll.

Within the range of appropriate
ground speeds and approved weights,
the airplane structure and landing gear
are assumed to be subjected to loads
not less than those obtained when the
aircraft is operating over the roughest
ground that may reasonably be expected in normal operation.
[Amdt. 25-91, 62 FR 40705, July 29, 1997]

Section 25.493

Braked roll conditions.

(a) An airplane with a tail wheel is
assumed to be in the level attitude
with the load on the main wheels, in
accordance with figure 6 of appendix A.
The limit vertical load factor is 1.2 at
the design landing weight and 1.0 at
the design ramp weight. A drag reaction equal to the vertical reaction multiplied by a coefficient of friction of
0.8, must be combined with the vertical
ground reaction and applied at the
ground contact point.
(b) For an airplane with a nose wheel
the limit vertical load factor is 1.2 at
the design landing weight, and 1.0 at
the design ramp weight. A drag reaction equal to the vertical reaction,
multiplied by a coefficient of friction
of 0.8, must be combined with the
vertical reaction and applied at the
ground contact point of each wheel
with brakes. The following two attitudes, in accordance with figure 6 of
appendix A, must be considered:
(1) The level attitude with the wheels
contacting the ground and the loads
distributed between the main and nose
gear. Zero pitching acceleration is assumed.
(2) The level attitude with only the
main gear contacting the ground and
with the pitching moment resisted by
angular acceleration.
(c) A drag reaction lower than that
prescribed in this section may be used
if it is substantiated that an effective

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