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Pilot's Handbook of Aeronautical Knowledge
Flight Controls

Autopilot

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Pilot's Handbook of Aeronautical Knowledge

Preface

Acknowledgements

Table of Contents

Chapter 1, Introduction To Flying
Chapter 2, Aircraft Structure
Chapter 3, Principles of Flight
Chapter 4, Aerodynamics of Flight
Chapter 5, Flight Controls
Chapter 6, Aircraft Systems
Chapter 7, Flight Instruments
Chapter 8, Flight Manuals and Other Documents
Chapter 9, Weight and Balance
Chapter 10, Aircraft Performance
Chapter 11, Weather Theory
Chapter 12, Aviation Weather Services
Chapter 13, Airport Operation
Chapter 14, Airspace
Chapter 15, Navigation
Chapter 16, Aeromedical Factors
Chapter 17, Aeronautical Decision Making

Appendix

Glossary

Index

Adjustable Stabilizer
Rather than using a movable tab on the trailing edge of the
elevator, some aircraft have an adjustable stabilizer. With this
arrangement, linkages pivot the horizontal stabilizer about its
rear spar. This is accomplished by use of a jackscrew mounted
on the leading edge of the stabilator. [Figure 5-23]

adjustable stabilizer
Figure 5-23. Some airplanes, including most jet transports, use an
adjustable stabilizer to provide the required pitch trim forces.

On small aircraft, the jackscrew is cable operated with a trim
wheel or crank. On larger aircraft, it is motor driven. The
trimming effect and flight deck indications for an adjustable
stabilizer are similar to those of a trim tab.

Autopilot

Autopilot is an automatic flight control system that keeps an
aircraft in level flight or on a set course. It can be directed by
the pilot, or it may be coupled to a radio navigation signal.
Autopilot reduces the physical and mental demands on a pilot
and increases safety. The common features available on an
autopilot are altitude and heading hold.

The simplest systems use gyroscopic attitude indicators and
magnetic compasses to control servos connected to the flight
control system. [Figure 5-24] The number and location of
these servos depends on the complexity of the system. For
example, a single-axis autopilot controls the aircraft about the
longitudinal axis and a servo actuates the ailerons. A threeaxis
autopilot controls the aircraft about the longitudinal,
lateral, and vertical axes. Three different servos actuate
ailerons, elevator, and rudder. More advanced systems often
include a vertical speed and/or indicated airspeed hold mode.
Advanced autopilot systems are coupled to navigational aids
through a flight director.

Basic autopilot system
Figure 5-24. Basic autopilot system integrated into the flight
control system.

The autopilot system also incorporates a disconnect safety
feature to disengage the system automatically or manually.
These autopilots work with inertial navigation systems,
global positioning systems (GPS), and flight computers to
control the aircraft. In fly-by-wire systems, the autopilot is
an integrated component.

Additionally, autopilots can be manually overridden. Because
autopilot systems differ widely in their operation, refer to the
autopilot operating instructions in the Airplane Flight Manual
(AFM) or the Pilot's Operating Handbook (POH).

Chapter Summary

Because flight control systems and aerodynamic characteristics
vary greatly between aircraft, it is essential that a pilot
become familiar with the primary and secondary flight
control systems of the aircraft being flown. The primary
source of this information is the AFM or the POH. Various
manufacturer and owner group websites can also be a
valuable source of additional information.

 

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