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Old May 22nd 04, 12:05 PM
Byron J. Covey
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That's not exactly what it says:

Sec. 23.561

General.

(a) The airplane, although it may be damaged in emergency landing
conditions, must be designed as prescribed in this section to protect each
occupant under those conditions.
(b) The structure must be designed to [give each occupant every reasonable
chance of escaping serious injury when--]
(1) Proper use is made of seats, safety belts, and shoulder harnesses
provided for in the design;
(2) The occupant experiences the static inertia loads corresponding to the
following ultimate load factors--
(i) Upward, 3.0g for normal, utility, and commuter category airplanes, or
4.5g for acrobatic category airplanes;
(ii) Forward, 9.0g;
(iii) Sideward, 1.5g; and
(iv) Downward, 6.0g when certification to the emergency exit provisions of
Sec. 23.807(d)(4) is requested; and
(3) The items of mass within the cabin, that could injure an occupant,
experience the static inertia loads corresponding to the following ultimate
load factors--
(i) Upward, 3.0g;
(ii) Forward, 18.0g; and
(iii) Sideward, 4.5g.
(c) Each airplane with retractable landing gear must be designed to protect
each occupant in a landing--
(1) With the wheels retracted;
(2) With moderate descent velocity; and
(3) Assuming, in the absence of a more rational analysis--
(i) A downward ultimate inertia force of 3g; and
(ii) A coefficient of friction of 0.5 at the ground.
(d) If it is not established that a turnover is unlikely during an emergency
landing, the structure must be designed to protect the occupants in a
complete turnover as follows:
(1) The likelihood of a turnover may be shown by an analysis assuming the
following conditions--
(i) [The most adverse combination of weight and center of gravity position;
(ii) [Longitudinal load factor of 9.0g;
(iii) [Vertical load factor of 1.0g; and
(iv) [For airplanes with tricycle landing gear, the nose wheel strut failed
with the nose contacting the ground.]
(2) For determining the loads to be applied to the inverted airplane after a
turnover, an upward ultimate inertia load factor of 3.0g and a coefficient
of friction with the ground of 0.5 must be used.
[(e) Except as provided in Sec. 23.787(c), the supporting structure must be
designed to restrain, under loads up to those specified in paragraph (b)(3)
of this section, each item of mass that could injure an occupant if it came
loose in a minor crash landing.]


BJC


"Corrie" wrote in message
om...
"Byron J. Covey" wrote in message

. com...
The Grumman Ag Cat, among others, was designed with a stronger than

required
(for mission or for certification) cockpit section/seat/roll-over
protection/restraint system. There are numerous examples of crashes

that
pilots walked away from.


Ron Machado, in a safety seminar I went to years ago, explained how a
certificated light aircraft is designed so that if you can stop it in
as much as a tennis court, (18g decel) the cockpit will not collapse
and you can unstrap and walk away. Bruised from the belts, perhaps,
but otherwise unscathed.