Code of Federal Regulations - Title 14

245

Federal Aviation Administration, DOT

§ 23.725

ANDING

EAR

§ 23.721

General.

For commuter category airplanes

that have a passenger seating configu-
ration, excluding pilot seats, of 10 or
more, the following general require-
ments for the landing gear apply:

(a) The main landing-gear system

must be designed so that if it fails due
to overloads during takeoff and landing
(assuming the overloads to act in the
upward and aft directions), the failure
mode is not likely to cause the spillage
of enough fuel from any part of the fuel
system to consitute a fire hazard.

(b) Each airplane must be designed so

that, with the airplane under control,
it can be landed on a paved runway
with any one or more landing-gear legs
not extended without sustaining a
structural component failure that is
likely to cause the spillage of enough
fuel to consitute a fire hazard.

this section may be shown by analysis
or tests, or both.

[Amdt. 23–34, 52 FR 1830, Jan. 15, 1987]

§ 23.723

Shock absorption tests.

(a) It must be shown that the limit

load factors selected for design in ac-
cordance with § 23.473 for takeoff and
landing weights, respectively, will not
be exceeded. This must be shown by en-
ergy absorption tests except that anal-
ysis based on tests conducted on a
landing gear system with identical en-
ergy absorption characteristics may be
used for increases in previously ap-
proved takeoff and landing weights.

(b) The landing gear may not fail, but

may yield, in a test showing its reserve
energy absorption capacity, simulating
a descent velocity of 1.2 times the limit
descent velocity, assuming wing lift
equal to the weight of the airplane.

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964; 30
FR 258, Jan. 9, 1965, as amended by Amdt. 23–
23, 43 FR 50593, Oct. 30, 1978; Amdt. 23–49, 61
FR 5166, Feb. 9, 1996]

§ 23.725

Limit drop tests.

(a) If compliance with § 23.723(a) is

shown by free drop tests, these tests
must be made on the complete air-
plane, or on units consisting of wheel,
tire, and shock absorber, in their prop-

er relation, from free drop heights not
less than those determined by the fol-
lowing formula:

h (inches)=3.6 (W/S)

⁄

However, the free drop height may not
be less than 9.2 inches and need not be
more than 18.7 inches.

(b) If the effect of wing lift is pro-

vided for in free drop tests, the landing
gear must be dropped with an effective
weight equal to

L d

+ −

(

)

[

]

(

)

where—

=the effective weight to be used in the

drop test (lbs.);

h=specified free drop height (inches);
d=deflection under impact of the tire (at the

approved inflation pressure) plus the
vertical component of the axle travel rel-
ative to the drop mass (inches);

W=W

for main gear units (lbs), equal to the

static weight on that unit with the air-
plane in the level attitude (with the nose
wheel clear in the case of nose wheel
type airplanes);

W=W

for tail gear units (lbs.), equal to the

static weight on the tail unit with the
airplane in the tail-down attitude;

W=W

for nose wheel units lbs.), equal to the

vertical component of the static reaction
that would exist at the nose wheel, as-
suming that the mass of the airplane
acts at the center of gravity and exerts a
force of 1.0

g downward and 0.33 g for-

ward; and

L= the ratio of the assumed wing lift to the

airplane weight, but not more than 0.667.

be determined in a rational or conserv-
ative manner, during the drop test,
using a landing gear unit attitude, and
applied drag loads, that represent the
landing conditions.

(d) The value of

d used in the com-

putation of

in paragraph (b) of this

section may not exceed the value actu-
ally obtained in the drop test.

(e) The limit inertia load factor must

be determined from the drop test in
paragraph (b) of this section according
to the following formula:

where—

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