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touchdown in terrain where aircraft damage is unavoidable.
Typical consequences are making a 180° turn back to the
runway when available altitude is insuffi cient, stretching the
glide without regard for minimum control speed in order to
reach a more appealing fi eld, or accepting an approach and
touchdown situation that leaves no margin for error. The
desire to save the aircraft, regardless of the risks involved,
may be infl uenced by two other factors: the pilot’s fi nancial
stake in the aircraft and the certainty that an undamaged
aircraft implies no bodily harm. There are times, however,
when a pilot should be more interested in sacrifi cing the
aircraft so that the occupants can safely walk away from it.
Fear is a vital part of the self-preservation mechanism.
However, when fear leads to panic, we invite that which we
want most to avoid. The survival records favor pilots who
maintain their composure and know how to apply the general
concepts 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
A pilot who is faced with an emergency landing in terrain
that makes extensive aircraft damage inevitable should
keep in mind that the avoidance of crash injuries is largely
a matter of:
1. Keeping vital structure (fl ight deck where the pilot
and passenger are seated) relatively intact by using
dispensable structure, such as wings, landing gear, and
carriage bottom to absorb the violence of the stopping
process before it affects the occupants.
2. Avoiding forward wing movement relative to the
carriage, allowing the mast to rotate into the fl ight deck
occupants, or the front tube to compress and break,
providing structure to impale/stab the occupants.
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 (mph) is less hazardous for
a properly restrained driver than a similar impact against the
driver’s door. Statistics indicate that the extent of crushable
structure between the occupants and the principal point of
impact on the aircraft has a direct bearing on the severity of
the transmitted crash forces and, therefore, on survivability.
Compared to an airplane, the WSC aircraft has less structure
to absorb the impact and is moving slower, but the same
principles apply.
Avoiding forcible contact with the front tube, cowling,
dashboard, or outside structure is a matter of seat and body
security with the use of seatbelts. Unless the occupant
decelerates at the same rate as the surrounding structure, no
benefi t is realized from its relative intactness. The occupant
is brought to a stop violently in the form of a secondary
collision.
Dispensable aircraft structure is not the only available energyabsorbing
medium in an emergency situation. Vegetation,
trees, and even manmade structures may be used for this
purpose. Cultivated fi elds with dense crops, such as mature
corn and grain, are almost as effective in bringing an aircraft
to a stop with repairable damage as an emergency arresting
device on a runway. [Figure 13-2] Brush and small trees
provide considerable cushioning and braking effect without
destroying the aircraft. When dealing with natural and manmade
obstacles with greater strength than the dispensable
aircraft structure, the pilot must plan the touchdown in such
a manner that only nonessential structure is “used up” in the
principal slowing down process.
It should be noted that examples presented here are not to
13-5
Figure 13-3. Stopping distance vs. groundspeed.
10
20
30
40
2 G deceleration 42 feet
10.5 feet
Headwind
Tailwind
Groundspeed
25 mph
Groundspeed
50 mph
be practiced because these situations are hazardous and can
damage the WSC and injure occupants. These examples are
shown for informational purposes, in case similar situations
arise in the future.
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 quadruples the
total destructive energy and vice versa. Even a small change
in groundspeed at touchdown, resulting from wind or pilot
technique, affects 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 means.
Most pilots instinctively—and correctly—look for the largest
　
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本文鏈接地址：Weight-Shift Control Aircraft Flying Handbook(145)