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Pilot's Handbook of Aeronautical Knowledge
Flight Controls

Flight Control Systems

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Pilot's Handbook of Aeronautical Knowledge



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




The rudder controls movement of the aircraft about its vertical
axis. This motion is called yaw. Like the other primary control
surfaces, the rudder is a movable surface hinged to a fixed
surface, in this case to the vertical stabilizer, or fin. Moving
the left or right rudder pedal controls the rudder.

When the rudder is deflected into the airflow, a horizontal
force is exerted in the opposite direction. [Figure 5-15] By
pushing the left pedal, the rudder moves left. This alters the
airflow around the vertical stabilizer/rudder, and creates a
sideward lift that moves the tail to the right and yaws the nose
of the airplane to the left. Rudder effectiveness increases with
speed; therefore, large deflections at low speeds and small
deflections at high speeds may be required to provide the
desired reaction. In propeller-driven aircraft, any slipstream
flowing over the rudder increases its effectiveness.

The effect of left rudder pressure.
Figure 5-15. The effect of left rudder pressure.

The V-Tail design utilizes two slanted tail surfaces to perform
the same functions as the surfaces of a conventional elevator
and rudder configuration. The fixed surfaces act as both
horizontal and vertical stabilizers. [Figure 5-16]

Beechcraft Bonanza V35.
Figure 5-16. Beechcraft Bonanza V35.

The movable surfaces, which are usually called ruddervators,
are connected through a special linkage that allows the control
wheel to move both surfaces simultaneously. On the other
hand, displacement of the rudder pedals moves the surfaces
differentially, thereby providing directional control.

When both rudder and elevator controls are moved by the
pilot, a control mixing mechanism moves each surface the
appropriate amount. The control system for the V-Tail is
more complex than that required for a conventional tail. In
addition, the V-Tail design is more susceptible to Dutch roll
tendencies than a conventional tail, and total reduction in
drag is minimal.

Secondary Flight Controls
Secondary flight control systems may consist of wing flaps,
leading edge devices, spoilers, and trim systems.

Flaps are the most common high-lift devices used on aircraft.
These surfaces, which are attached to the trailing edge of
the wing, increase both lift and induced drag for any given
AOA. Flaps allow a compromise between high cruising speed
and low landing speed, because they may be extended when
needed, and retracted into the wing's structure when not
needed. There are four common types of flaps: plain, split,
slotted, and Fowler flaps [Figure 5-17]

Five common types of flaps.
Figure 5-17. Five common types of flaps.