SAE ARP4087D Wing Inspection Lights – Design Criteria

SCOPE

This SAE Aerospace Recommend Practice (ARP) is intended to cover the external lights on fixed wing aircraft for illuminating the wing leading edge and engine nacelles and the upper surfaces of the wing. The addition of an ice detection system should be implemented when the areas to inspect are not visible from the aircraft cockpit. It is not intended that this Recommended Practice require the use of any particular light source such as Halogen, LED or other specific design of lamp.

Purpose

The purpose of this document is to set forth basic considerations and criteria which should be observed when designing wing inspection lights for all aircraft.

SAE Publications

J1330
Photometry Laboratory Accuracy Guidelines

ARP5414
Aircraft Lightning Zoning

ARP6253
LEDs and Aircraft Applications

Code of Federal Regulations(CFR)

Code of Federal Regulations Title 14, Part 25 and 121.
Some applicable sections may include, but are not limited to the following:

14 CFR PART 121.341 Equipment for operations in icing conditions

14 CFR PART 121.629 Operation in Icing Conditions

14 CFR PART 25.1403 Wing Icing Detection Lights

14 CFR PART 25.1397 Color Specifications

RTCA Publications

DO-160
Radio Technical Commission for Aeronautics (RTCA), Environmental Conditions and Test Procedures for
Airborne Equipment(latest applicable revision).

U.S. Government Publications

MIL-DTL-7989 Covers, Light-Transmitting, for Aeronautical Lights, General Specification for

GENERAL PROVISIONS

As described in Part 25.1403 and Part 121.341, unless operations at night are known or forecast icing conditions are prohibited by an operating limitation, a means must be provided for illuminating or otherwise determining the formation of ice on the parts of the wings that are critical from the standpoint of ice accumulation. Any illumination that is used must be a type that will not cause glare or reflection that would handicap crewmembers in the performance of their duties.

Wing inspection lights are used to illuminate the wing leading edges, engine nacelles, upper and/or lower wing
surfaces, and any other external surfaces so that they may be visually inspected by the flight crew and/or ground personnel for ice accumulation or any other critical conditions at night or daytime (such as during low light ambient conditions). Inspection may be performed when the aircraft is on the ground, or in-flight, with and without fuel.
Therefore, the wing deflection range during flight under all various conditions (i.e., as affected by air loads) needs to be considered for the lamp design.

NOTE: it may also be appropriate to use existing airport lighting for the inspection of snow/ice accumulation.

When aircraft geometry permits, over wing inspection lights are recommended to illuminate the upper wing surfaces so that they may be visually inspected for snow/ice accumulation primarily during ground inspection.

On military aircraft the wing inspection lights may be used to provide visual reference to the boom operator in aerial refueling. In this case, it may be desirable to increase the illuminated areas on the inboard upper and/or lower surfaces of the wings.

The lights shall be designed to provide proper illumination for the crew members, but care shall be taken in the design and installation location so that they will not cause objectionable glare or halation that might handicap crew members in the performance of their duties as required in Part 121.629 i.e., for the pilot or the dispatcher can determine that the wings, control surfaces and other critical surfaces as defined in the certificate holder’s program are free of frost, ice or snow.

Aircraft geometry shall dictate the size, number, and location of lights required to perform the intended function(s).

Illuminance

The recommended minimum illuminance for wing leading edge is 21.5 lux (2.0 ft-c) measured normal to the
incident light. See Figure 1 and Figure 2. The aircraft’s surface finish and reflectance properties should be
considered when validating photometric performance. Also, the lights should be evaluated to insure that minimum intensities are achieved at the maximum viewing distances with respect to the flightcrew.

The recommended minimum illuminance for wing leading edge applies to all possible wing positions (in-flight or on the ground, loaded with fuel).

The recommended minimum illuminance for engine nacelles is 5.3 lux (0.5 ft-c) measured normal to the incident light. See Figure 1.

The recommended minimum illuminance for wing upper surfaces is 107.5 lux (10.0 ft-c) measured normal to the incident light. See Figure 2.

The light beam should be shaped and directed to provide a reasonably uniform ilumination of the wing surfaces.

Color

The color should be aviation white as defined in Part 25.1397. Deviations are acceptable.

LISUN following instruments fully meet SAE ARP4087D Wing Inspection Lights – Design Criteria