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Instrument Flying Handbook
Helicopter Attitude Instrument Flying
Straight-and-Level Flight

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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

During performance of a maneuver, there is sometimes
a failure to anticipate significant instrument indications
following attitude changes. For example, during level off
from a climb or descent, a pilot may concentrate on pitch
control, while forgetting about heading or roll information.
This error, called omission, results in erratic control of
heading and bank.

In spite of these common errors, most pilots can adapt well to
flight by instrument reference after instruction and practice.
Many find that they can control the helicopter more easily
and precisely by instruments.

Instrument Interpretation
The flight instruments together give a picture of what is
happening. No one instrument is more important than the
next; however, during certain maneuvers or conditions,
those instruments that provide the most pertinent and useful
information are termed primary instruments. Those which
back up and supplement the primary instruments are termed
supporting instruments. For example, since the attitude
indicator is the only instrument that provides instant and
direct aircraft attitude information, it should he considered
primary during any change in pitch or bank attitude. After
the new attitude is established, other instruments become
primary, and the attitude indicator usually becomes the
supporting instrument.

Aircraft Control
Controlling a helicopter is the result of accurately interpreting
the flight instruments and translating these readings
into correct control responses. Aircraft control involves
adjustment to pitch, hank, power, and trim in order to achieve
a desired flight path.

Pitch attitude control is controlling the movement of
the helicopter about its lateral axis. After interpreting
the helicopter's pitch attitude by reference to the pitch
instruments (attitude indicator, altimeter, airspeed
indicator and vertical speed indicator (VSI)), cyclic control
adjustments are made to affect the desired pitch attitude. In
this chapter, the pitch attitudes depicted are approximate
and vary with different helicopters.

Bank attitude control is controlling the angle made by the
lateral tilt of the rotor and the natural horizon. Or the movement
of the helicopter about its longitudinal axis. After interpreting
the helicopter's bank instruments (attitude indicator, heading
indicator, and turn indicator), cyclic control adjustments are
made to attain the desired bank attitude.

Power control is the application of collective pitch with
corresponding throttle control, where applicable. In straight-
and-level flight, changes of collective pitch are made to
correct for altitude deviation if the error is more than 100
feet, or the airspeed is off by more than 10 knots. If the error
is less than that amount, a pilot should use a slight cyclic
climb or descent.

In order to fly a helicopter by reference to the instruments, it
is important to know the approximate power settings required
for a particular helicopter in various load configurations and
flight conditions.

Trim, in helicopters, refers to the use of the cyclic centering
button, if the helicopter is so equipped, to relieve all
possible cyclic pressures. Trim also refers to the use of pedal
adjustment to center the ball of the turn indicator. Pedal trim
is required during all power changes.

The proper adjustment of collective pitch and cyclic friction
helps a pilot relax during instrument flight. Friction should
be adjusted to minimize overcontrolling and to prevent
creeping, but not applied to such a degree that control
movement is limited. In addition, many helicopters equipped
for instrument flight contain stability augmentation systems
or an autopilot to help relieve pilot workload.

Straight-and-Level Flight

Straight-and-level unaccelerated flight consists of maintaining
the desired altitude, heading, airspeed, and pedal trim.

Pitch Control
The pitch attitude of a helicopter is the angular relation of
its longitudinal axis to the natural horizon. If available, the
altitude indicator is used to establish the desired pitch attitude.
In level flight, pitch attitude varies with airspeed and center of
gravity (CG). At a constant altitude and a stabilized airspeed,
the pitch attitude is approximately level. [Figure 6-2]

 
6-3