**
Sec. 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
airplane, or on units consisting of wheel, tire, and shock absorber, in
their proper relation, from free drop heights not less than those
determined by the following formula:

*h*
(inches)=3.6 *(W/S)*
1/2

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

where --

*W*e=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 relative to the drop mass (inches);

*W=W*M for main gear units (lbs),
equal to the static weight on that unit with the airplane in the level
attitude (with the nose wheel clear in the case of nose wheel type
airplanes);

*W=W*T for tail gear units (lbs.),
equal to the static weight on the tail unit with the airplane in the
tail-down attitude;

*W=W*N for nose wheel units lbs.),
equal to the vertical component of the static reaction that would exist at
the nose wheel, assuming 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*
forward; and

*L=* the ratio of the assumed wing lift to the
airplane weight, but not more than 0.667.

(c) The limit inertia load factor must
be determined in a rational or conservative 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
computation of *W*e in paragraph (b) of this section may
not exceed the value actually 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 --

*n*j=the load factor developed in the
drop test (that is, the acceleration *(dv/dt)* in *g*s recorded
in the drop test) plus 1.0; and

*W*e, W, **AND** *L* are the
same as in the drop test computation.

(f) The value of *n* determined in
accordance with paragraph (e) may not be more than the limit inertia load
factor used in the landing conditions in §23.473.

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as
amended by Amdt. 23-7, 34 FR 13091, Aug. 13, 1969; Amdt. 23-48, 61 FR
5148, Feb. 9, 1996]