Due to the reduced drag in ground effect, the airplane
may seem to be able to take off below the recommended
airspeed. However, as the airplane rises out of
ground effect with an insufficient airspeed, initial
climb performance may prove to be marginal because
of the increased drag. Under conditions of high-density
altitude, high temperature, and/or maximum gross
weight, the airplane may be able to become airborne at
an insufficient airspeed, but unable to climb out of
ground effect. Consequently, the airplane may not be
able to clear obstructions, or may settle back on the
runway. The point to remember is that additional
power is required to compensate for increases in drag
that occur as an airplane leaves ground effect. But during
an initial climb, the engine is already developing
maximum power. The only alternative is to lower pitch
attitude to gain additional airspeed, which will result in
inevitable altitude loss. Therefore, under marginal conditions,
it is important that the airplane takes off at the
recommended speed that will provide adequate initial
climb performance.
Ground effect is important to normal flight operations.
If the runway is long enough, or if no obstacles exist,
ground effect can be used to an advantage by using the
reduced drag to improve initial acceleration.
Additionally, the procedure for takeoff from unsatisfactory
surfaces is to take as much weight on the wings
as possible during the ground run, and to lift off with
the aid of ground effect before true flying speed is
attained. It is then necessary to reduce the angle of
attack to attain normal airspeed before attempting to
fly away from the ground effect area. |
SHORT-FIELD TAKEOFF AND
MAXIMUM PERFORMANCE CLIMB
Takeoffs and climbs from fields where the takeoff area
is short or the available takeoff area is restricted by
obstructions require that the pilot operate the airplane
at the limit of its takeoff performance capabilities. To
depart from such an area safely, the pilot must exercise
positive and precise control of airplane attitude and
airspeed so that takeoff and climb performance results
in the shortest ground roll and the steepest angle of
climb. [Figure 5-7]
The achieved result should be consistent with the
performance section of the FAA-approved Airplane
Flight Manual and/or Pilot's Operating Handbook
(AFM/POH). In all cases, the power setting, flap
setting, airspeed, and procedures prescribed by the
airplane's manufacturer should be followed.
In order to accomplish a maximum performance takeoff
safely, the pilot must have adequate knowledge in
the use and effectiveness of the best angle-of-climb
speed (VX) and the best rate-of-climb speed (VY) for
the specific make and model of airplane being flown.
The speed for VX is that which will result in the
greatest gain in altitude for a given distance over the
ground. It is usually slightly less than VY which provides
the greatest gain in altitude per unit of time.
The specific speeds to be used for a given airplane
are stated in the FAA-approved AFM/POH. It should
be emphasized that in some airplanes, a deviation of
5 knots from the recommended speed will result in a
significant reduction in climb performance.
Therefore, precise control of airspeed has an important
bearing on the successful execution as well as
the safety of the maneuver. |
