曝光臺 注意防騙 網曝天貓店富美金盛家居專營店坑蒙拐騙欺詐消費者

and procedures that have been developed through
the years. The success of an emergency landing is
as much a matter of the mind as of skills.
BASIC SAFETY CONCEPTS
GENERAL
A pilot who is faced with an emergency landing in terrain
that makes extensive airplane damage inevitable
should keep in mind that the avoidance of crash
injuries is largely a matter of: (1) keeping vital
structure (cockpit/cabin area) relatively intact by using
dispensable structure (such as wings, landing gear, and
fuselage bottom) to absorb the violence of the stopping
process before it affects the occupants, (2) avoiding
forceful bodily contact with interior structure.
The advantage of sacrificing dispensable structure is
demonstrated daily on the highways. A head-on car
impact against a tree at 20 miles per hour (m.p.h.) is
less hazardous for a properly restrained driver than a
similar impact against the driver’s door. Accident
experience shows that the extent of crushable structure
between the occupants and the principal point of
impact on the airplane has a direct bearing on the
severity of the transmitted crash forces and, therefore,
on survivability.
Avoiding forcible contact with interior structure is a
matter of seat and body security. Unless the occupant
decelerates at the same rate as the surrounding
structure, no benefit will be realized from its relative
intactness. The occupant will be brought to a stop violently
in the form of a secondary collision.
Dispensable airplane structure is not the only available
energy absorbing medium in an emergency situation.
Vegetation, trees, and even manmade structures may
be used for this purpose. Cultivated fields with dense
crops, such as mature corn and grain, are almost as
effective in bringing an airplane to a stop with
repairable damage as an emergency arresting device
on a runway. [Figure 16-1] Brush and small trees
provide considerable cushioning and braking effect
without destroying the airplane. When dealing with
natural and manmade obstacles with greater strength
than the dispensable airplane structure, the pilot must
plan the touchdown in such a manner that only nonessential
structure is “used up” in the principal
slowing down process.
The overall severity of a deceleration process is
governed by speed (groundspeed) and stopping
distance. The most critical of these is speed; doubling
the groundspeed means quadrupling the total destructive
energy, and vice versa. Even a small change in
groundspeed at touchdown—be it as a result of wind
or pilot technique—will affect the outcome of a
controlled crash. It is important that the actual
touchdown during an emergency landing be made at
the lowest possible controllable airspeed, using all
available aerodynamic devices.
Most pilots will instinctively—and correctly—look
for the largest available flat and open field for an emergency
landing. Actually, very little stopping distance
is required if the speed can be dissipated uniformly;
that is, if the deceleration forces can be spread evenly
over the available distance. This concept is designed
into the arresting gear of aircraft carriers that provides
a nearly constant stopping force from the moment of
hookup.
The typical light airplane is designed to provide
protection in crash landings that expose the occupants
to nine times the acceleration of gravity (9 G) in a
forward direction. Assuming a uniform 9 G deceleration,
at 50 m.p.h. the required stopping distance is
about 9.4 feet. While at 100 m.p.h. the stopping distance
is about 37.6 feet—about four times as great.
[Figure 16-2] Although these figures are based on an
ideal deceleration process, it is interesting to note what
can be accomplished in an effectively used short stopping
distance. Understanding the need for a firm
but uniform deceleration process in very poor terrain
enables the pilot to select touchdown conditions that
will spread the breakup of dispensable structure over a
short distance, thereby reducing the peak deceleration
of the cockpit/cabin area.
Figure 16-1. Using vegetation to absorb energy.
Ch 16.qxd 5/7/04 10:30 AM Page 16-2
16-3
ATTITUDE AND SINK RATE CONTROL
The most critical and often the most inexcusable error
that can be made in the planning and execution of an
emergency landing, even in ideal terrain, is the loss of
initiative over the airplane’s attitude and sink rate at
touchdown. When the touchdown is made on flat, open
terrain, an excessive nose-low pitch attitude brings the
　
中國航空網 m.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：AIRPLANE FLYING HANDBOOK 飛機飛行手冊下(90)