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at times may also require inputs to compensate for
propeller torque. Rudder sensitivity and effectiveness
are directly proportional to the velocity of airflow over
the rudder surface. Consequently, many gyroplane
rudders are located in the propeller slipstream and
provide excellent control while the engine is developing
thrust. This type of rudder configuration, however, is
less effective and requires greater deflection when the
engine is idled or stopped.
HORIZONTAL TAIL SURFACES
The horizontal tail surfaces on most gyroplanes are
not controllable by the pilot. These fixed surfaces, or
stabilizers, are incorporated into gyroplane designs to
increase the pitch stability of the aircraft. Some gyroplanes
use very little, if any, horizontal surface. This
translates into less stability, but a higher degree of
maneuverability. When used, a moveable horizontal
surface, or elevator, adds additional pitch control of the
aircraft. On early tractor configured gyroplanes, the
elevator served an additional function of deflecting the
propeller slipstream up and through the rotor to assist
in prerotation.
COLLECTIVE CONTROL
The collective control provides a means to vary the
rotor blade pitch of all the blades at the same time, and
is available only on more advanced gyroplanes. When
incorporated into the rotor head design, the collective
allows jump takeoffs when the blade inertia is sufficient.
Also, control of in-flight rotor r.p.m. is available
to enhance cruise and landing performance. A simple
two position collective does not allow unlimited control
of blade pitch, but instead has one position for prerotation
and another position for flight. This is a performance
compromise but reduces pilot workload by simplifying
control of the rotor system.
Figure 17-3. Foot pedals provide rudder control and operation is similar to that of an airplane.
18-1
rotating portion of the head to the non-rotating torque
tube. The torque tube is mounted to the airframe
through attachments allowing both lateral and longitudinal
movement. This allows the movement through
which control is achieved.
FULLY ARTICULATED ROTOR SYSTEM
The fully articulated rotor system is found on some
gyroplanes. As with helicopter-type rotor systems, the
articulated rotor system allows the manipulation of
Coning Angle—An angular
deflection of the rotor blades
upward from the rotor hub.
Undersling—A design characteristic
that prevents the distance
between the rotor mast axis and
the center of mass of each rotor
blade from changing as the
blades teeter. This precludes
Coriolis Effect from acting on the
speed of the rotor system.
Undersling is further explained
in Chapter 3—Aerodynamics of
Flight, Coriolis Effect (Law of
Conservation of Angular
Momentum).
Gyroplanes are available in a wide variety of designs
that range from amateur built to FAA-certificated aircraft.
Similarly, the complexity of the systems integrated
in gyroplane design cover a broad range. To
ensure the airworthiness of your aircraft, it is important
that you thoroughly understand the design and operation
of each system employed by your machine.
PROPULSION SYSTEMS
Most of the gyroplanes flying today use a reciprocating
engine mounted in a pusher configuration that drives
either a fixed or constant speed propeller. The engines
used in amateur-built gyroplanes are normally proven
powerplants adapted from automotive or other uses.
Some amateur-built gyroplanes use FAA-certificated aircraft
engines and propellers. Auto engines, along with
some of the other powerplants adapted to gyroplanes,
operate at a high r.p.m., which requires the use of a reduction
unit to lower the output to efficient propeller speeds.
Early autogyros used existing aircraft engines, which
drove a propeller in the tractor configuration. Several
amateur-built gyroplanes still use this propulsion configuration,
and may utilize a certificated or an uncertificated
engine. Although not in use today, turboprop
and pure jet engines could also be used for the propulsion
of a gyroplane.
ROTOR SYSTEMS
SEMIRIGID ROTOR SYSTEM
Any rotor system capable of autorotation may be utilized
in a gyroplane. Because of its simplicity, the most widely
used system is the semirigid, teeter-head system. This
system is found in most amateur-built gyroplanes.
[Figure 18-1] In this system, the rotor head is mounted
on a spindle, which may be tilted for control. The rotor
blades are attached to a hub bar that may or may not
　
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