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level to maintain a constant altitude. The nose is then raised as
the throttle is reduced to maintain a constant altitude.
As the speed decreases further, the pilot should note the
feel of the fl ight controls, pitch pressure, and diffi culty of
maintaining a straight heading with the increased side-to-side
pilot input forces required to keep the wings level. At some
point the throttle must be increased to remain level after the
WSC has slowed below it’s maximum LD speed. The pilot
should also note the sound of the airfl ow as it falls off in tone.
There is a large difference by manufacturer and model, but
the bar generally should not be touching the forward tube
at minimum controlled airspeed. For example, the control
bar would be 1 to 3 inches from the front tube at minimum
controlled airspeed. [Figure 6-21]
6-21
Control bar is moved forward,
slowing the WSC
Trim flight Minimum controlled airspeed
Power is decreased slightly
as the nose is raised to slow
to minimum controlled
airspeed
Power applied for straight-andlevel
flight at minimum
controlled airspeed
Shallow turns are performed
in level flight at minimum
controlled airspeed
Normal straight-andlevel
flight
Figure 6-21. Minimum controlled airspeed maneuver.
The pilot should understand that when fl ying below the
minimum drag speed (L/DMAX), the aircraft exhibits a
characteristic known as “speed instability.” If the aircraft
is disturbed by even the slightest turbulence, the airspeed
decreases. As airspeed decreases, the total drag increases
resulting in a further loss in airspeed. Unless more power is
applied and/or the nose is lowered, the speed continues to
decay to a stall. This is an extremely important factor in the
performance of slow fl ight. The pilot must understand that, at
speeds less than minimum drag speed, the airspeed is unstable
and will continue to decay if allowed to do so.
It should also be noted that the amount of power to remain
level at minimum controlled airspeed is greater than that
required at the minimum drag speed which is also the best
glide ratio speed and the best rate of climb speed.
When the attitude, airspeed, and power have been stabilized
in straight-and-level fl ight, turns should be practiced to
determine the aircraft’s controllability characteristics at
this minimum speed. During the turns, power and pitch
attitude may need to be increased to maintain the airspeed
and altitude. The objective is to acquaint the pilot with the
lack of maneuverability at minimum controlled airspeed, the
danger of incipient stalls, and the tendency of the aircraft
to stall as the bank is increased. A stall may also occur as a
result of turbulence, or abrupt or rough control movements
when fl ying at this critical airspeed.
Once fl ight at minimum controllable airspeed is set up
properly for level fl ight, a descent or climb at minimum
controllable airspeed can be established by adjusting the
power as necessary to establish the desired rate of descent
or climb.
Common errors in the performance of slow fl ight are:
• Failure to adequately clear the area.
• Inadequate forward pressure as power is reduced,
resulting in altitude loss.
• Excessive forward pressure as power is reduced,
resulting in a climb, followed by a rapid reduction in
airspeed and “mushing.”
• Inadequate compensation for unanticipated roll during
turns.
• Fixation on the airspeed indicator.
• Inadequate power management.
• Inability to adequately divide attention between
aircraft control and orientation.
Stalls
A stall occurs when the smooth airfl ow over the aircraft’s
wing root is disrupted and the lift degenerates rapidly. This
is caused when the wing root exceeds its critical angle of
attack. This can occur at any airspeed in any attitude with
any power setting.
The practice of stall recovery and the development of
awareness of stalls are of primary importance in pilot
training. The objectives in performing intentional stalls are to
familiarize the pilot with the conditions that produce stalls, to
assist in recognizing an approaching stall, and to develop the
habit of taking prompt preventive or corrective action.
Pilots must recognize the fl ight conditions that are conducive
to stalls and know how to apply the necessary corrective
action. They should learn to recognize an approaching stall
by sight, sound, and feel. The following cues may be useful
in recognizing the approaching stall:
　
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