SAE ARP582D Lighting, Integral, For Aircraft Instruments: Criteria for Design of Red Incandescent Lighted Instruments

SCOPE:

This SAE Aerospace Recommended Practice(ARP) covers the general requirements and test procedures for illuminating systems for integrally lighted aircraft instruments in order to provide (a)uniformity of illumination within each instrument, (b) legibility of instrument presentation under daylight or integral light, and (c) uniformity of illumination between instrument displays.

Purpose:

The purpose of this document is to recommend certain basic considerations and criteria which the designer should observe when designing a system of red integral lighting for aircraft instruments.

Lighting Tests:

Instrument Calibration: With an approved photometer (or one that is calibrated in accordance with the manufacturer’s instructions and NIST traceable), the calibration shall be accomplished using a brightness source or reference within the range of the test. When a photometer is used as part of the test equipment, the following calibrations and checks shall be verified within a year prior to taking a measurement:

– Measure spot size of 0.004 to 0.007 in as the minimum.

– Having a focus no less than 4 in from the front of the lens.

– Minimum full scale sensitivity to 0.1 fL.

– A stability of ±2% combined zero and sensitivity drift over an 8 h period after a 15 min warm-up.

– Having a polarization error of less than 1%.

– Being able to locate a spot being measured with maximum error or 0.002 in.

– Having a readout with a resolution of no less than 0.1% of full scale.

– For colorimetric trim, a maximum correction IPL Red light (3215 Red versus 2856 Kelvin): of ±10% of filter transmittance.

– For colorimetric trim, a 4-filter tristimulus colorimetric capability with a maximum error for any Blackbody (lamp) color temperature ±0.005 x and y from 1800 to 2856 Kelvins when calibrated at 2856 degrees Kelvin for an ambient temperature excursion of 70 F ± 5 F.

Color Measurement: Apply 5V±2% (or applicable voltage ±2%) to the lighting terminals. All measurements shall be made in completely dark surroundings. With a photometer that has been calibrated in accordance to 4.2.4.1, focus on a red portion of the illuminated indicator. The value should conform to Table 1, 3.1.9.

Brightness Measurements: Calibrate the photometer with a brightness source. Focus the photometer on a lighted portion of the indicator and take a reading (R1). Insert an NBS filter No.3114 in the optical path between the instrument and the photometer without changing focus and take a reading (R2). Compute the ratio of (R2) divided by (R). Enter this ratio into the CCF-3114 graph on the “X” coordinate and determine the value “Y.” The true brightness of the indicator is given by multiplying (R) by “Y.” The values should conform to Table 1, 3.1.9.

Stray Light: Stray alight should be checked to determine that the instrument meets the requirements of 3.1.8.

Contrast: The illumination for the contrast measurements should be furnished by uniform, diffused, artificial illumination. Contrast measurements should be taken with no coverglass or other transparent surface in front of the presentation. Several brightness measurements of the indicia and of the background should be taken with the axis of the brightness meter perpendicular to the surface being measured. An average of the indicia and background readings should be used to determine conformance to the contrast values of 3.1.11.

Dielectric: The instrument should be checked to assure conformance to the requirements of 3.1.6.

LISUN following instruments fully meet SAE ARP582D Lighting, Integral, For Aircraft Instruments: Criteria for Design of Red Incandescent Lighted Instruments

LMS-6000 Portable CCD Spectroradiometer