When unexpected adverse weather is encountered by the VFR pilot, the most likely situation is that of being trapped in or above a broken or solid layer of clouds or haze, requiring that a descent be made to an altitude where the pilot can reestablish visual reference to the ground. Generally, the descent should be made in straight flight.
A descent can be made at a variety of airspeeds and vertical
speeds by reducing power, adding drag (gear and flaps), and lowering the
nose to a predetermined attitude. Before beginning the descent, it is recommended
that first the descent airspeed and the desired headings be established
while holding the wings level. In addition, the landing gear and flaps
should be positioned up or down, to help in maintaining either a slow rate
of descent, or a fast rate of descent, as desired. Establishing the desired
configuration before starting the descent will permit a more stabilized
descent and require less division of attention once the descent is started.
Rather than attempting to maintain a specific rate of descent, it is recommended
that only a constant airspeed be maintained.
|The following method for entering a descent is effective
either with or without an attitude indicator. First the airspeed is reduced
to the desired airspeed by reducing power while maintaining straight and
level flight. When the descent speed is established, a further reduction
in power is made, and simultaneously the nose is lowered to maintain a
constant airspeed (Fig. 13-2). The power should remain at a fixed (constant)
setting and deviations in airspeed corrected by making pitch changes. Jockeying
the throttle to control airspeed only adds to the pilot's workload.
If an attitude indicator is available, the pitch attitude can be adjusted by reference to the representative airplane and the artificial horizon, and then checking the airspeed indicator to determine if the attitude is correct. Deviations from the desired airspeed are
In any case, the pilot need not be concerned with slight deviations in airspeed. The main objective is to descend at a safe airspeed - well above the stall but not more than the airplane's design maneuvering speed.
While descending, directional control should be maintained by reference to the directional instruments just as described for straight and level flight. Pilots are cautioned against "chasing" the instrument pointers.
If any thought was given to the matter before starting the flight, the pilot will have at least a rough idea of the height of obstructions and terrain in the vicinity of the descent. Before starting the descent, then, a decision must be made regarding the minimum altitude to which the descent will be made.