of operation to verify system integrity. Quality
TROUBLE ANALYSIS
assurance inspection during repair progression,
Trouble analysis of the flight control systems
testing, and of the end product is a must. When
requires the same systematic approach as any other
prescribed in the applicable periodic maintenance
hydraulic system. In many instances, malfunctions are
information cards, test flight requirements are
written off with incorrect corrective actions on the
mandatory. The test flight pilot is briefed by a qualified
maintenance action form (MAF). Corrective action
quality assurance representative regarding the nature
labeled "Could Not Duplicate" or "Replaced
of the discrepancy and corrective action taken.
Suspected Component" often results in a repeat
POWER ACTUATOR MAINTENANCE
discrepancy or loss of the aircraft. You should be very
thorough in determining the cause of a malfunction.
Maintenance of primary flight control surface
Trouble analysis of the flight controls will require
power actuators is generally beyond the capability of
complete cooperation with other work centers that are
organizational maintenance-level activities. Removal
involved in the operational checkouts. Most flight
of hydraulic components and associated linkages on
control systems have electrical input, as well as
the power actuators will destroy critical adjustments.
mechanical input from autopilot, automatic flight
Readjustment requires special tooling, jigs, and other
control systems, or stabilizing augmentation systems.
e q u i p m e n t ava i l a b l e o n l y a t i n t e r m e d i a t e - o r
Inputs occasionally cause erratic and/or misleading
depot-level maintenance facilities. When a power
aircraft flight characteristics. Flight characteristics can
mechanism has been isolated as the cause for flight
be misinterpreted, and the resultant write-up in the
system malfunction, it is removed. It is forwarded with
aircraft discrepancy portion of the aircraft flight record
the accompanying paperwork to the supply activity for
book may be vague or misleading. To gain further
disposition.
i n s i g h t r e g a r d i n g t h e va g u e d i s c r e p a n c y, t h e
maintenance crew should question the pilot who
RIGGING AND OPERATIONAL CHECKS
experienced the malfunction.
Procedures for rigging flight control systems vary
Isolating the mechanical and hydraulic portion of
with each type of aircraft. Applicable MIMs provide a
the flight control system from systems that provide
list of tools, special equipment, preparatory
automatic input will serve to pinpoint the actual
considerations, and step-by-step instructions for
problem
area.
The
MIM
provides
rigging systems.
troubleshooting/trouble analysis aids and appropriate
schematics. The MIM allows for the systematic
On some aircraft, the system rigging divides into a
checking out of the system and associated
series of sections, such as the control stick, control
components. In some MIMs these aids are general in
mechanism, power control actuator, and cables. If only
nature and limited to the more common causes of
that section of the system has been affected, it may not
failure. Several MIMs combine the operational
be necessary to rig the complete system.
checkout procedures with trouble analysis aids. Steps
Pushrods, bell cranks, and idlers are installed so
of the checkout procedures are performed in rigid
that end play is eliminated. They should be free to
sequence, and any discrepancy must be corrected
rotate without binding. Cables should be inspected for
before proceeding to the next step.
corrosion, broken strands, and proper tension. Correct
A thorough knowledge of the system involved and
cable tension is necessary to obtain proper response of
consistent use of the mechanical and hydraulic
the control surface. Low cable tension may cause
schematics will expedite the trouble analysis process.
sluggishness, free play, and flutter of the control
Excessive time required for troubleshooting should be
surface. Excessively high cable tension will cause
documented on a separate VIDS/MAF. This will
increased system friction and may result in damage to
separate the actual repair time from troubleshooting
pulleys, bell cranks, or the cable itself.
time. Separate VIDS/MAFs provide more accurate
A variety of fixtures, pins, and blocks are available
input information to the Maintenance Data Reporting
for performing alignment and rigging checks on flight
System.
control systems. Neutralizing (locking the controls and
When the malfunction has been determined and
linkage in a predetermined position), as described in
corrected, the complete system should be
the aircraft MIM, is required during the alignment and
operationally tested. Testing should occur in all modes
adjustment of the flight controls.
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