5.4 Flight Control Systems, Rigging, and Travel
Key Takeaways
- Primary controls move the aircraft about its axes, while secondary and auxiliary controls change trim, lift, drag, or handling.
- Cable tension, control stops, bellcranks, pulleys, push-pull tubes, torque tubes, and turnbuckles must be inspected as a system.
- Rigging requires current instructions, calibrated tools, neutral references, correct travel limits, and independent verification of direction of movement.
- A small rigging error can create a large flight risk because it may reverse a control, reduce travel, or cause binding under load.
Flight Controls: Rigging the Whole System
Flight controls translate pilot input into movement of surfaces such as ailerons, elevators, rudders, stabilizers, flaps, spoilers, tabs, and other devices. The Airframe ACS expects you to identify components, inspect condition, and understand rigging. The risk is direct: a control system that is installed backward, out of travel, loose, or binding can make an aircraft unsafe immediately.
Primary controls are usually associated with roll, pitch, and yaw. Secondary or auxiliary controls may trim forces, change lift, increase drag, or help high-lift operation. The exact system depends on the aircraft, so study the principles but rely on the aircraft maintenance manual for limits, rig pins, neutral points, and travel checks.
Cable systems include cables, pulleys, fairleads, pressure seals, turnbuckles, guards, connectors, and control stops. Push-pull and torque-tube systems use rods, rod ends, bellcranks, bearings, brackets, and hardware. The technician must inspect each part and the whole path. A pulley that turns smoothly by hand may still be misaligned. A cable that meets tension may still be routed incorrectly.
A disciplined rigging workflow looks like this:
- Read the aircraft procedure completely before moving hardware.
- Confirm the aircraft is supported, powered, or depressurized as required.
- Set cockpit controls, surfaces, tabs, and rigging pins to the specified neutral positions.
- Use a calibrated cable tensiometer when cable tension is required.
- Adjust only the specified locations and secure turnbuckles, jam nuts, and safety devices.
- Verify control direction, full travel, stops, freedom from binding, and cockpit indication.
- Have a second qualified check when the task or local procedure requires it.
Cable tension is sensitive to temperature, cable size, and system design. A cable tension chart is used because the correct value is not a single guess. Too little tension can allow slack, backlash, pulley jump, or poor control feel. Too much tension can overload bearings, brackets, pulleys, and structure. The ACS risk elements specifically call out cable tension charts and tensiometer use because these errors are common and consequential.
Control stops are another test favorite. Stops normally limit travel to protect the surface and system. If the stop is bypassed or adjusted incorrectly, a cable, actuator, or surface may become the limiting part. That can damage the aircraft and may not be obvious until the control reaches an extreme position.
Troubleshooting flight controls starts with the complaint but follows the system. Heavy controls may come from tension, bearing friction, interference, poor lubrication, or misalignment. Unequal travel may come from rigging, stops, incorrect rod length, or distorted structure. A control that moves the wrong direction after maintenance is a critical failure, not a minor adjustment.
On the exam, choose answers that preserve positive control. Use current data, calibrated tools, specified rigging points, full-travel checks, and documentation. Avoid answers that adjust by feel, skip control-direction verification, or treat a binding control as acceptable because it moved once.
Why is a cable tension chart used during flight-control maintenance?
What must be verified after reconnecting a primary flight control?
What is a likely result of excessive cable tension?