What is a PAPI inspection?
A walk along the wing bar to check that all four units are clean, sound, lit equally, clear of obstruction and still set at their angles.
A PAPI works only if every unit shows the right colour at the right angle. A PAPI inspection checks each of the four units for the things that would spoil that signal: a dirty or cracked lens, water inside the housing, a loose or damaged mount, a dim or failed lamp or LED, a damaged cable or connector, grass, snow or debris in front of the unit, and a unit that has moved away from its elevation setting.
Unlike an edge light, each PAPI unit is one step of a four-step signal. A single unit that is dark or dim gives the pilot a false slope indication at its angle, so a fault on one unit is treated as a defect on the whole approach aid. The four units should also look equal in brightness and colour from the approach.
Findings are recorded in the inspection log, and any defect is corrected and re-checked before the unit is returned to service. Alignment checked by inclinometer is confirmed after any work that could disturb the unit, and the complete signal is verified at commissioning and by flight inspection.
Frequently Asked Questions
Q1What is a PAPI inspection?
A routine check of the PAPI wing bar to confirm that every unit is clean, undamaged, correctly mounted, lit at the right intensity, free of obstructions in its beam, and still set at its specified elevation angle. It combines a visual check with simple operational and alignment checks.
Q2What is checked on each PAPI unit?
The lens for dirt, cracks and condensation, the housing and seals, the mounting and frangible coupling, the lamp or LED output, the cable and connector at the base, the ground in front of the unit for vegetation, snow or debris, and the elevation setting of the unit.
Q3Why does one failed unit matter so much?
Each unit is one step of the four-step signal. A unit that is dark or dim shows the wrong colour pattern at its angle, so the pilot reads a false slope indication. For this reason a PAPI unit fault is dealt with as a defect on a visual approach aid, not as a single lost light.
Q4How is the elevation setting checked?
The tilt of each unit is measured with a suitable inclinometer on its reference surface and compared with the specified setting angle for the approach slope, following the manufacturer's procedure. The overall signal is confirmed at commissioning and by flight inspection.
Q5How often is a PAPI inspected?
The interval is set by the airport's maintenance programme and the applicable regulation. Quick visual checks are normally more frequent than detailed inspections of alignment and electrical condition. Always follow the current programme and the manufacturer's instructions.
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