JAR 27.725 Limit drop test
The limit drop test must be conducted as follows:
(a) The drop height must be –
(1) 330 mm (13 inches) from the lowest
point of the landing gear to the ground; or
(2) Any lesser height, not less than 203
mm (8 in), resulting in a drop contact velocity
equal to the greatest probable sinking speed
likely to occur at ground contact in normal
power-off landings.
(b) If considered, the rotor lift specified in JAR
27.473(a) must be introduced into the drop test by
appropriate energy absorbing devices or by the use
of an effective mass.
(c) Each landing gear unit must be tested in the
attitude simulating the landing condition that is
most critical from the standpoint of the energy to be
absorbed by it.
(d) When an effective mass is used in showing
compliance with sub-paragraph (b) of this paragraph
the following formula may be used instead of more
rational computations:
where –
We = the effective weight to be used in the drop
test (lbs).
W=WM for main gear units (lbs), equal to the static
reaction on the particular unit with the
rotorcraft in the most critical attitude. A
rational method may be used in computing
a main gear static reaction, taking into
consideration the moment arm between the
main wheel reaction and the rotorcraft
centre of gravity.
W=WN for nose gear units (lbs), equal to the
vertical component of the static reaction
that would exist at the nose wheel,
assuming that the mass of the rotorcraft
acts at the centre of gravity and exerts a
force of 1.0 g downward and 0.25 g
forward.
W=WT for tailwheel units (lbs) equal to whichever
of the following is critical:
(1) The static weight on the tailwheel
with the rotorcraft resting on all wheels; or
(2) The vertical component of the ground
reaction that would occur at the tailwheel,
assuming that the mass of the rotorcraft acts at
the centre of gravity and exerts a force of 1 g
downward with the rotorcraft in the maximum
nose-up attitude considered in the nose-up
landing conditions.
h = specified free drop height (inches).
L = ratio of assumed rotor lift to the rotorcraft
weight.
d = deflection under impact of the tyre (at the
proper inflation pressure) plus the vertical
component of the axle travel (inches)
relative to the drop mass.
n = limit inertia load factor.
nj = the load factor developed, during impact,
on the mass used in the drop test (i.e., the
acceleration dv/dt in g recorded in the drop
test plus 1.0).
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