Federal Aviation Administration, DOT

Section 29.727

Section 29.691 Autorotation control mechanism.
Each main rotor blade pitch control
mechanism must allow rapid entry into
autorotation after power failure.
Section 29.695 Power boost and power-operated control system.
(a) If a power boost or power-operated control system is used, an alternate system must be immediately
available that allows continued safe
flight and landing in the event of - 
(1) Any single failure in the power
portion of the system; or
(2) The failure of all engines.
(b) Each alternate system may be a
duplicate power portion or a manually
operated mechanical system. The
power portion includes the power
source (such as hydrualic pumps), and
such items as valves, lines, and actuators.
(c) The failure of mechanical parts
(such as piston rods and links), and the
jamming of power cylinders, must be
considered unless they are extremely
improbable.
LANDING GEAR

Section 29.725 Limit drop test.
The limit drop test must be conducted as follows:
(a) The drop height must be at least
8 inches.
(b) If considered, the rotor lift specified in Section 29.473(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 paragraph (b)

h + (1  -  L )d
; and
h+d
W
n = nj e + L
W

We = W 

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 center 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 center of gravity
and exerts a force of 1.0g downward and
0.25g 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 center of gravity and exerts a
force of 1g 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 tire (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-s recorded in
the drop test plus 1.0).
[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as
amended by Amdt. 29-3, 33 FR 967, Jan. 26,
1968]

Section 29.727 Reserve energy absorption
drop test.
The reserve energy absorption drop
test must be conducted as follows:
(a) The drop height must be 1.5 times
that specified in Section 29.725(a).
(b) Rotor lift, where considered in a
manner similar to that prescribed in
Section 29.725(b), may not exceed 1.5 times the
lift allowed under that paragraph.

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Section 29.723 Shock absorption tests.
The landing inertia load factor and
the reserve energy absorption capacity
of the landing gear must be substantiated by the tests prescribed in
SectionSection 29.725 and 29.727, respectively. These
tests must be conducted on the complete rotorcraft or on units consisting
of wheel, tire, and shock absorber in
their proper relation.

of this section, the following formulae
may be used instead of more rational
computations.