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Instrument Flying Handbook
Aerodynamic Factors
Coordination of Rudder and Aileron Controls

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Instrument Flying
Handbook

Preface

Table of Contents

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

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

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
Operations

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 airspeed of 90 knots takes a bank
angle of' 16° to maintain a standard late 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 tile 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
the airplane when flying on instruments. The pilot can tell if
the turn is coordinated by checking the ball in the turn—and—
slip indicator or the turn coordinator. (Figure 2-15)

As the aircraft banks to enter a turn, a portion of the wing's
vertical lift becomes the horizontal component; therefore,
without an increase in back pressure, the aircraft loses altitude
during the turn. The loss of vertical lift can be offset by
increasing the pitch in one-half bar width increments. Trim
may be used to relieve the control pressures; however, if used,
it has to be removed once the turn is complete.

In a slipping turn, the aircraft is not turning at the rate
appropriate to the bank being used, and the aircraft falls to
the inside of the turn. The aircraft is banked too much for the
rate of turn, so the horizontal lift component is greater than
the centrifugal force. A skidding turn results from excess of
centrifugal force over the horizontal lift component, pulling
the aircraft toward the outside of the turn. The rate of turn
is too great for the angle of bank, so the horizontal lift
component is less than the centrifugal force,

The ball instrument indicates the quality of the turn, and
should be centered when the wings are banked, If the ball
is off of center on the side toward the turn, the aircraft is
slipping and rudder pressure should be added on that side to
increase the rate of turn or the bank angle should be reduced.
If the ball is off of center on the side away from the turn,
the aircraft is skidding and rudder pressure toward the turn
should he relaxed or the bank angle should be increased,
If the aircraft is properly rigged, the ball should be in the
center when the wings arc level; use rudder and/or aileron
trim if available,

The increase in induced drag (caused by the increase in angle
of attack necessary to maintain altitude) results in a minor
loss of airspeed if the power setting is not changed.

Turns
Figure 2-14. Turns

 

2-11