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available fl at and open fi eld 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 on aircraft carriers, and
provides a nearly constant stopping force from the moment
of hookup.
For example, assuming a uniform 2 G deceleration while
landing into a headwind with a 25 mph groundspeed, the
stopping distance is about 10.5 feet; in a downwind landing
at 50 mph groundspeed, the required stopping distance is
42 feet—about four times as great. [Figure 13-3] Although
these fi gures are based on an ideal deceleration process,
it is interesting to note what can be accomplished in an
effectively used short stopping distance. Additionally,
landing uphill reduces the stopping distance and landing
downhill increases the stopping distance. Understanding
the need for a fi rm but uniform deceleration process in very
poor terrain enables the pilot to select touchdown conditions
that spread the breakup of dispensable structure over a short
distance, thereby reducing the peak deceleration of the fl ight
deck area. A careful consideration must be made considering
wind, slope, and terrain.
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 aircraft’s attitude and sink rate at touchdown. When the
touchdown is made on fl at, open terrain, an excessive noselow
pitch attitude brings the risk of “sticking” the nose in
the ground. Steep bank angles just before touchdown should
also be avoided, as they increase the stalling speed and the
likelihood of a wingtip strike.
Since the aircraft’s vertical component of velocity is
immediately reduced to zero upon ground contact, it must
be kept well under control. A fl at touchdown at a high sink
rate (well in excess of 500 feet per minute (fpm)) on a
hard surface can be injurious without destroying the fl ight
deck structure depending on the design of the airframe and
the shock absorbing system. On soft terrain, an excessive
sink rate may cause digging in of the nose wheel with the
wing and/or WSC aircraft rotating forward into the ground,
stopping with severe forward deceleration or tumbling with
higher speeds.
13-6
Figure 13-4. Increased altitude provides increased landing options.
Ground
1,000' AGL
500' AGL
2,000' AGL
5,000' AGL
5,000 Feet AGL 80 Square Miles
Terrain Selection
A pilot’s choice of emergency landing sites is governed by
the:
• Route selected during prefl ight planning and
• Height above the ground when the emergency
occurs.
The only time the pilot has a very limited choice is during low
and slow fl ying or during takeoff if the landing approach is
always within gliding distance of the runway.
It should be understood that the amount of area for available
landing sites increases at a rapid rate with increased altitude.
[Figure 13-4] As an example, a WSC aircraft with a 5 to 1
glide ratio fl ying at 500 feet AGL has 500 feet multiplied
by fi ve feet horizontal (or 2,500 feet) radius on the ground
to select a suitable landing area. For example, use a ½
mile radius. The area of available landing spots is π x r2,
approximately 0.8 square miles. At 1,000 feet AGL, this
area would be 3.1 square miles; at 2,000 feet AGL, this is
about 12.5 square miles; and at 5,000 AGL, this is almost
80 square miles.
Additionally, fl ying in a downwind direction provides more
area to be covered while fl ying upwind reduces the amount
of area that can be covered while looking for a suitable
landing area.
If beyond gliding distance of a suitable open area, the pilot
should judge the available terrain for its energy absorbing
capability. If the emergency starts at a considerable height
above the ground, the pilot should be more concerned about
fi rst selecting the desired general area than a specifi c spot.
Terrain appearances from altitude can be very misleading
and considerable altitude may be lost before the best spot can
be pinpointed. For this reason, the pilot should not hesitate
to discard the original plan for one that is clearly better.
However, as a general rule, the pilot should not change his
or her mind more than once.
Approach
When the pilot has time to maneuver, the planning of the
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Weight-Shift Control Aircraft Flying Handbook(146)
