NOTE: Installation and removal of the fixtures,
pins, and blocks should not require excessive force.
Slight pressure is permissible because of the system
tolerance and temperature effects on the aircraft.
Always refer to the MIM for tolerance information.
Figure 16-18 shows the throwboard used to check
the travel of a horizontal stabilizer. The throwboard is
held in place by two wingnut attachment screws.
Before tightening these screws, the throwboard is
positioned so that the alignment hole at the zero-degree
mark is in line with the alignment screw in the aircraft
Control surface throws may be measured in
degrees and minutes or inches and fractions. Figure
16-19 provides an example of an aileron throw
indication in degrees (°) and minutes (`). The
protractor scale is calibrated in 30-minute increments.
The indicator reads 3 degrees 40 minutes obtained as
Figure 16-19.--Aileron throw protractor indications.
3. Add 3 degrees 30 minutes and 10 minutes to get
1. Read 3 degrees 30 minutes, as shown on the
the true indication of 3 degrees 40 minutes up travel.
Each mode of operation that was affected by
2. Since the indication mark does not fall directly
alignment or malfunction and subsequent repair action
on the calibrated mark of the protractor scale, look for
must be operationally checked, and the success of the
the closest alignment of indicator and protractor
checkouts verified by a qualified quality assurance
calibrated marks in the direction of indicator travel.
representative. All maintenance, including alignment,
Read the value from the 0-minute mark on the indicator
adjustment, operational testing, and component
to the closest alignment, which, in this example, is 10
replacement, must be in accordance with the
instructions provided in the applicable MIM.
Q16-20. What must be done to a flight control
hydraulic component when it is found to be
Q16-21. When an aircraft has a discrepancy with the
flight controls system, when is the aircraft
released for further flights?
Q16-22. What corrective action often results in a
repeat discrepancy or loss of aircraft?
Q16-23. Maintenance of the primary flight control
power actuator is generally beyond the
capability of what maintenance level?
Q16-24. What will ensure proper response of a flight
CONTROL SYSTEMS MAINTENANCE
LEARNING OBJECTIVE: Recognize the
maintenance procedures for cable and
push-pull rod (rigid control) systems.
Figure 16-18.--Stabilizer throwboard installation.