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setting maintains that speed. The airplane slows several knots
below the desired speed because of a slight reduction in the
power setting. The pilot increases the power slightly, and the
airplane begins to accelerate, but at a slow rate. Because the
airplane is still in the “flat part” of the drag curve, this slight
increase in power will not cause a rapid return to the desired
speed. The pilot may need to increase the power higher
than normally needed to maintain the new speed, allow the
airplane to accelerate, then reduce the power to the setting
that maintains the desired speed.
Climbs
The ability for an aircraft to climb depends upon an excess
power or thrust over what it takes to maintain equilibrium.
Excess power is the available power over and above that
required to maintain horizontal flight at a given speed.
Although the terms power and thrust are sometimes
used interchangeably (erroneously implying they are
synonymous), distinguishing between the two is important
when considering climb performance. Work is the product of
a force moving through a distance and is usually independent
of time. Power implies work rate or units of work per unit of
time, and as such is a function of the speed at which the force
is developed. Thrust, also a function of work, means the force
which imparts a change in the velocity of a mass.
During take off, the aircraft does not stall even though it
may be in a climb near the stall speed. The reason is that
excess power (used to produce thrust) is used during this
flight regime. Therefore, it is important if an engine fails
after take off, to compensate the loss of thrust with pitch
and airspeed.
For a given weight of the aircraft, the angle of climb depends
on the difference between thrust and drag, or the excess
thrust. When the excess thrust is zero, the inclination of the
flight path is zero, and the aircraft is in steady, level flight.
When thrust is greater than drag, the excess thrust allows a
climb angle depending on the amount of excess thrust. When
thrust is less than drag, the deficiency of thrust induces an
angle of descent.
Acceleration in Cruise Flight
Aircraft accelerate in level flight because of an excess of
power over what is required to maintain a steady speed. This
is the same excess power used to climb. Upon reaching the
desired altitude with pitch being lowered to maintain that
altitude, the excess power now accelerates the aircraft to its
cruise speed. However, reducing power too soon after level
off results in a longer period of time to accelerate.
2-11
Figure 2-14. Turns.
The standard rate of turn, 3° per second, is used as the main
reference for bank angle. Therefore, the pilot must understand
how the angle of bank varies with speed changes, such
as slowing down for holding or an instrument approach.
Figure 2-14 shows the turn relationship with reference to a
constant bank angle or a constant airspeed, and the effects on
rate of turn and radius of turn. A rule of thumb for determining
the standard rate turn is to divide the airspeed by ten and
add 7. An aircraft with an airspeed of 90 knots takes a bank
angle of 16° to maintain a standard rate turn (90 divided by
10 plus 7 equals 16°).
Radius of Turn
The radius of turn varies with changes in either speed or bank.
If the speed is increased without changing the bank angle,
the radius of turn increases, and vice versa. If the speed is
constant, increasing the bank angle reduces the radius of
turn, while decreasing the bank angle increases the radius of
turn. This means that intercepting a course at a higher speed
requires more distance, and therefore, requires a longer lead.
If the speed is slowed considerably in preparation for holding
or an approach, a shorter lead is needed than that required
for cruise flight.
Coordination of Rudder and Aileron Controls
Any time ailerons are used, adverse yaw is produced. Adverse
yaw is caused when the ailerons are deflected as a roll motion
(as in turn) is initiated. In a right turn, the right aileron is
deflected upward while the left is deflected downward. Lift
is increased on the left side and reduced on the right, resulting
in a bank to the right. However, as a result of producing lift
on the left, induced drag is also increased on the left side.
The drag causes the left wing to slow down, in turn causing
the nose of the aircraft to initially move (left) in the direction
opposite of the turn. Correcting for this yaw with rudder, when
entering and exiting turns, is necessary for precise control of
　
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