PAPI Check Stick for Alignment & Verification

A PAPI check stick is a field inspection and verification accessory, a purpose-designed mechanical reference that gives a repeatable physical reference between the PAPI light unit and the established aiming reference. It helps maintenance personnel identify units that have moved, been disturbed or need re-alignment. It is an inspection aid, not a substitute for the complete commissioning process.

It is used for new PAPI commissioning, periodic inspection, post-maintenance checks after light-unit replacement or adjustment, fault investigation when red/white indications are inconsistent, checks after accidental disturbance or impact, verification after foundation or mounting work, and after severe weather. It is particularly useful where repeatable field checks are needed without relying solely on pilot observation.

A PAPI projects sharply defined optical sectors, so a small mechanical movement can change the indication. Sources of alignment change include mounting hardware movement, vehicle or maintenance-equipment impact, foundation settlement, pavement rehabilitation, accidental disturbance during grass cutting, replacement of optical assemblies and incorrect previous maintenance adjustment.

No, they are complementary, not interchangeable. Use the check stick for a rapid alignment check, a digital inclinometer for numerical angular measurement, a clinometer for manual angle verification, an alignment telescope for optical line-of-sight alignment, and a manufacturer-approved aiming device for the full PAPI aiming procedure. For higher-accuracy commissioning, combine them: survey reference, PAPI aiming device, alignment telescope, check stick, then final verification.

A check stick is not an independently standardised airport lighting device. It is best specified as compatible inspection equipment for the selected PAPI and aiming method, not as a universal FAA-certified measuring instrument. Some manufacturers' L-880/L-881 maintenance manuals list a check stick as part of the bubble-level aiming kit and recommend it for routine alignment checks, so follow the manual for the installed model.

The workflow is reference, check, measure, adjust, re-check and record: use the approved reference point, runway datum and PAPI settings, check whether the unit is still in its established alignment, quantify any discrepancy with a clinometer, inclinometer, aiming device, telescope or survey, make a controlled mechanical adjustment per the manufacturer's procedure, repeat the verification and record the final settings, date, equipment ID and corrective work.

A unit out of alignment gives pilots a wrong slope indication, so treat the PAPI as unserviceable and report it under the airport procedure until it is corrected and re-verified. After realignment or unit replacement, the authority may require a flight inspection or a notified unserviceability before the PAPI returns to service. A PAPI that is still lit is not proof that it is aligned, because the excessive-tilt cut-out in FAA-qualified units operates only beyond a fraction of a degree.

Do not force the unit into position. First confirm that the check-stick reference is correct, the PAPI installation reference is unchanged, the inspection equipment is undamaged, the approved aiming angle is correct, the mounting hardware is secure and the survey reference is still valid, then perform a controlled re-alignment.

Inspect it before use for bending, cracks, loose components, worn reference surfaces, corrosion and damaged fittings. Do not use it as a lever, avoid excessive force, do not use visibly damaged equipment and do not modify reference dimensions in the field. Clean it as specified, store it where its geometry cannot distort, and keep equipment identification and dimensional verification records, with the verification interval set by the airport's maintenance system or the manufacturer.

A non-repeatable result can come from incorrect positioning, damaged reference surfaces, loose hardware, the wrong PAPI reference, contamination between surfaces or a bent accessory. If the unit is aligned but the indications are inconsistent, the issue may not be mechanical alone: a check stick finds physical misalignment but cannot verify every photometric or optical parameter, so also check optical contamination, lens or filter damage, light-source condition, unit aiming and elevation, and electrical output.

Provide the PAPI manufacturer and model, installed equipment configuration, existing aiming-device type, existing check-stick type if available, the PAPI installation drawing, alignment procedure, latest maintenance manual, runway reference information, the required inspection procedure and existing survey or reference-point details.