Airport (A)PAPI Calibration By Dewhurst Airfield Services

Description

THE REQUIREMENT
EASA Easy Access Rules for Aerodromes Regulation (EU) No. 139/2014 Paragraph CS ADR-DSN.S.895 Serviceability levels states that a system of preventative maintenance of visual aids should be employed to ensure lighting & marking serviceability. It further refers to ICAO Doc 9137 Airport Services Manual Part 9 & that in turn states in Paragraph 2.5.5 that visual approach slope indicators should be checked for vertical alignment at least twice monthly.

The UK Civil Aviation Authority CAP168 Chapter 6 Paragraph 6.200(2) is more specific & states that the vertical alignment of each PAPI unit should be checked once every week to a tolerance of one minute of arc & verified by inspection with a suitable instrument & flight check at least twice a year. Clinometers are intended to be used for a quick check & should not be used for alignment adjustments.

THE PROBLEM
The conventional method of aligning & commissioning a PAPI system is to use a mechanical inclinometer placed within the PAPI unit, on the side of the PAPI unit or on the PAPI frame. This method assumes that the framework & light beam are co-incident & have not been distorted through transport, installation or even throughout use. PAPI units can also be damaged during use by high winds & debris, & by grass-cutting or snow clearing equipment. It is possible that the clinometer checks do not adequately report changes to the light output & transition angle of the red / white signal.

THE SOLUTION
Dewhurst Airfield Services Ltd can provide a proven reliable optical method to accurately check the elevation alignment for all types of PAPI. Using this optical method, the actual elevation transition angles as viewed by the pilot can be identified providing a verified clear & correct signal.

THE METHOD
The physical positions of the PAPI’s with reference to the runway & threshold are checked & recorded.

A theodolite is positioned in front of the PAPI being checked & adjusted so that the transition point can be determined. All light signals within each PAPI unit are checked for co-incident transition; discrepancies highlighted & investigated to see if they can be easily corrected. For example, we have found on occasion that filters have become loose or are not properly located, or that the horizontal is not level.

Transition angles are measured & recorded & checked against the required setting angle & those obtained previously by the inclinometer.

If the angle measured does not agree with the required angle, the theodolite is adjusted to the correct angle & the PAPI unit adjusted to suit. The inclinometer reading is then noted, so that airfield maintenance staff can check as normal each week for any further change.

Finally all observations & measurements are recorded for future reference & CAA audit.

Please contact us should you like to discuss PAPI checking for your airport/airfield or receive a no-obligation quotation.