conventional elevator system for this purpose.
a device designed to reduce lift on the wing whenever it
However, aircraft that operate in the higher speed
is extended into the airstream. With this system, control
ranges usually have a movable horizontal stabilizer.
stick movement will cause the left or right flaperon to
Both types of systems are discussed in the following
rise into the airstream and the opposite flaperon to
text.
remain flush with the wing surface. This causes a
decrease of lift on the wing with the flaperon extended
ELEVATOR CONTROL SYSTEM.--A typical
and results in a roll.
conventional elevator control system is operated by the
control stick in the cockpit, and is hydraulically
SPOILER/DEFLECTOR.--Many aircraft use a
powered by the elevator power mechanism. The
combination aileron and spoiler/deflector system for
operation of the elevator control system is initiated
longitudinal control. The ailerons are located on the
when the control stick is moved fore or aft. When the
trailing edge of the outer wing panel and, unlike most
stick is moved, it actuates the control cables that move
aircraft, can be fully cycled with the wings folded. The
the elevator control bell crank. The bell crank transmits
spoiler/deflector on each wing operates in conjunction
the movement to the power mechanism through the
with the upward throw of the aileron on that wing. They
control linkage. In turn, the power mechanism actuates
are located in the left- and right-hand wing center
a push-pull tube, which deflects the elevators up or
sections, forward of the flaps. The spoiler extends
down. If the hydraulic system fails, the cylinder can be
upward into the airstream, disrupts the airflow, and
disconnected. In this condition the controls work
causes decreased lift on that wing. The deflector
manually through the linkage of the mechanism to
extends down into the airstream and scoops airflow
actuate the elevators.
over the wing surface aft of the spoiler, thus preventing
airflow separation in that area.
HORIZONTAL STABILIZER CONTROL
A stop bolt on the spoiler bell crank limits
SYSTEM.--Horizontal stabilizer control systems are
movement of the spoiler to 60 degrees deflection. The
given a variety of names by the various aircraft
deflector is mechanically slaved to the spoiler, and can
manufacturers. Some aircraft systems are defined as a
be deflected a maximum of 30 degrees when the spoiler
unit horizontal tail (UHT) control systems, while others
is at 60 degrees. The spoilers open only with the upward
are labeled the stabilator control system. Regardless of
movement of the ailerons.
the name, these systems function to control the aircraft
pitch about its lateral axis.
Longitudinal Control Systems
The horizontal stabilizer control system of the
aircraft shown in figure 2-6 is representative of the
Longitudinal control systems control pitch about
systems used in many aircraft. The slab-type stabilizer
the lateral axis of the aircraft. Many aircraft use a
13.
Negative bobweight
7.
Load-relief bungee
1.
Control stick
14.
Clean and dirty switches
8.
Stabilizer actuator
2.
Flap drive gearbox
15.
Electrical trim actuator
9.
Stabilizer support shaft
3.
Trim transmitter
16.
Static spring
10.
Stabilizer
4.
Artificial feel bungee
17.
Stabilizer shift mechanism cables
11.
Stabilizer position transducer
5.
Stabilizer shift mechanism
12.
Filters
6.
Walking beam
Figure 2-6.--Horizontal stabilizer system.
2-7
