Cables, surfaces, rigging

Six procedures. Cable swaging technique is in GEN-E Procedures Procedure 6 and GEN-E Hands-on; this unit applies it.

Procedure 1 — Inspect control cables (S5)

1. Identify the runs and where each passes over pulleys, through fairleads and near structure. Wear concentrates there.
2. Pass a cloth along the cable. Broken wires snag it — this finds them faster and more reliably than looking.
3. Inspect at pulleys: move the surface through its travel so the cable that normally sits on the pulley is exposed.
4. Look for broken wires, wear flats, corrosion, kinks, and birdcaging near terminals.
5. Check pulleys turn freely and are not worn or grooved, and that fairleads are not worn through more than the allowed amount.
6. Assess against the manual's limits — broken-wire criteria are stated per length and per location.

Check — inspect the cable where it normally sits on the pulley, which means moving the controls. A cable inspected only in its resting position is inspected everywhere except where it wears.

Failure — running a bare hand along a cable to find broken wires. It works, and it is how mechanics cut their hands.

Procedure 2 — Measure cable tension (R1, R5, supporting S6)

1. Note the ambient temperature at the aircraft.
2. Find the tension specified for that cable at that temperature in the manual's chart.
3. Select the correct riser for the cable size on the tensiometer.
4. Fit the tensiometer at a point specified for measurement — not over a pulley, not near a terminal.
5. Read, and convert using the calibration table for that instrument.
6. Take at least two readings at different points in the run.

Check — two readings at different points should agree. If they do not, something is binding — a pulley, a fairlead, a guide — and the tension you have is not the tension throughout the run.

Failure — reading the chart at the wrong temperature, or using the wrong riser. Both give a plausible number (AF-C Concepts §3).

Procedure 3 — Adjust and secure a cable (S6)

1. Slacken both turnbuckles in an opposed pair before adjusting either.
2. Adjust to bring both tension and surface neutral toward correct together — they interact (AF-C Concepts §5).
3. Check that no more than three threads are exposed at either end of each turnbuckle.
4. Re-measure tension at temperature.
5. Safety the turnbuckles by the approved method, and safety anything else the procedure requires.
6. Check surface travel afterwards. Adjusting tension moves it.

Check — look at the exposed threads on both ends of every turnbuckle. More than three means insufficient thread engagement, and it is visible from a distance once you know to look.

Failure — adjusting one turnbuckle to correct tension and never re-checking travel.

Procedure 4 — Remove and reinstall a control surface (S4)

1. Record the rigging state before disturbing anything — travel, tension, tab position, and the number of exposed threads on adjacent turnbuckles.
2. Support the surface before removing hinge hardware. Control surfaces are heavier and more awkward than they look, and dropping one damages both it and you.
3. Remove hardware, bagging and labeling by location — hinge bolts, bushings and washers are frequently not interchangeable (GEN-F Concepts §5).
4. On reinstallation, fit the correct hardware in the correct positions, torque per the manual.
5. Check hinge freedom and freeplay through full travel.
6. Re-check balance if anything was added or removed, including paint (AF-C Concepts §1).
7. Re-rig and re-check travel and direction.

Check — move the surface through full travel by hand before connecting the controls. It must be free, with no binding at any point and no interference at the stops.

Procedure 5 — Check and adjust control surface balance (S8, S11)

1. Remove the surface and support it on the balancing fixture at the hinge line, per the manual.
2. Ensure it is in the specified condition — trim tab fitted or removed, hardware fitted, paint cured, no residual fluids.
3. Measure the moment about the hinge line as the procedure specifies.
4. Compare against the limits, which are usually expressed as a moment, not a weight.
5. Adjust by adding or removing balance weight at the specified location only.
6. Record the result.

Check — refinishing changes the balance. Paint is mass added behind the hinge line, it moves the surface toward flutter, and the amount is not negligible (GEN-G Concepts §2). That much is physics and holds for any surface.

Whether a re-check is required, and against what limits, is in the aircraft's data. Not every surface is mass-balanced, and the manufacturers who require a check after refinishing specify how it is done. Assuming a check is never needed and assuming one is always needed are both wrong — the first misses a surface moving toward flutter, the second substitutes a habit for the approved procedure. Establish what the data requires for that surface.

Failure — checking balance with the surface in the wrong configuration. The limits assume a specific fit, and a missing tab or fastener invalidates the measurement.

Procedure 6 — Rig a control system (K10, S1, S13, S7)

1. Configure the aircraft as the manual requires — jacked or on the ground, controls locked or free, surfaces supported.
2. Fit rig pins at the specified locations to establish neutral.
3. Adjust push-pull rods and turnbuckles to bring the surfaces to neutral, working the procedure's order.
4. Set tension at temperature (Procedure 2).
5. Check travel in both directions with a travel board or protractor, against the limits.
6. Check the stops — the surface must reach the stop, and the stop must limit it, not the cable or the control column.
7. Remove rig pins.
8. Check direction of movement, at the control, in the cockpit, for every axis.
9. Safety everything, and check freeplay.

Check — step 8 is the check, and it is not optional. Sit in the cockpit and move each control while watching the surface. Left stick, left aileron up. Reversed controls have killed people, and a reversed system passes every tension and travel check.

Failure — assuming direction because you did not disconnect anything that could reverse. Check it anyway, every time, after any work on the system.

The checks, collected

License

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