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Instrument Flying Handbook
Aerodynamic Factors
Climbs and Turns

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Instrument Flying


Table of Contents

Chapter 1. Human Factors
Chapter 2. Aerodynamic Factors
Chapter 3. Flight Instruments
Chapter 4. Section I
Airplane Attitude Instrument
Using Analog Instrumentation
Chapter 4. Section II
Airplane Attitude Instrument
Using an Electronic Flight

Chapter 5. Section I
Airplane Basic
Flight Maneuvers
Using Analog Instrumentation
Chapter 5. Section II
Airplane Basic
Flight Maneuvers
Using an Electronic Flight

Chapter 6. Helicopter
Attitude Instrument Flying

Chapter 7. Navigation Systems
Chapter 8. The National
Airspace System

Chapter 9. The Air Traffic
Control System

Chapter 10. IFR Flight
Chapter 11. Emergency

For example, a pilot is on an instrument approach at 1 .3
a speed near L/Dmax, and knows that a certain power
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 1101 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.

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 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.

Like any moving object, an aircraft requires a sideward force
to make it turn. In a normal turn, this force is supplied by
banking the aircraft in order to exert lift inward, as well as
upward. The force of lift is separated into two components
at right angles to each other. (Figure 2-13) The upward
acting lift together with the opposing weight becomes the
vertical lift component. The horizontally acting lift and its
opposing centrifugal force are the horizontal lift component,
or centripetal force. This horizontal lift component is the
sideward force that causes an aircraft to turn. The equal and
opposite reaction to this sideward force is centrifugal force,
which is merely an apparent force as a result of inertia.

Forces In Turn.
Figure 2-13. Forces In Turn.

The relationship between the aircraft's speed and bank angle
to the rate and radius of turns is important for instrument
pilots to understand. The pilot can use this knowledge to
properly estimate bank angles needed for certain rates of
turn, or to determine how much to lead when intercepting
a course.

Rate of Turn
The rate of turn, normally measured in degrees per second,
is based upon a set bank angle at a set speed. If either one of
these elements changes, the rate of turn changes. If the aircraft
increases its speed without changing the bank angle, the rate
of turn decreases. Likewise, if the speed decreases without
changing the bank angle, the rate of turn increases.

Changing the bank angle without changing speed also causes
the rote of turn to change. Increasing the hank angle without
changing speed increases the rate of turn, while decreasing
the hank angle reduces the rate of turn.