MIL-PRF-38039D
4.5.6 Lighting.
4.5.6.1 Visibility and legibility. Visibility (i.e., brightness) measurements shall be made
with a Pritchard 1980A Photometer or equivalent. The brightness levels shall comply with MIL-
STD-411 except the high brightness requirement shall be replaced with the following contrast
requirement. When the indicators are energized with a rated voltage (5V), and subjected to a
diffused white (5000-6000 K) light environment of 10,000 fL measured at the indicator, the
indicator shall exhibit a contrast of 1.0 or greater. Contrast shall be calculated according to the
following equation:
C = (B2 - B1)/B1
Where C = contrast
B1 - average brightness of the unlighted portion
B2 = average brightness of the light portion.
Low brightness measurements shall be made in completely dark surroundings. All legends shall
be sharply defined and readable when viewed from within the frustum of an imaginary cone, the
sides of which make an angle of 60o with a perpendicular to the center of the display, and the
plane of which has the same area as the aperture of the display enclosure.
4.5.7 Environmental testing. Environmental testing shall be planned and conducted
using the guidance in RTCA/DO-160. At the conclusion of each test, and during the low
temperature tests, the system shall operate satisfactorily. The test systems shall satisfy the
visibility and legibility test before and after the environmental tests. Altitude, acceleration, and
solar radiation testing shall be done in accordance with an industrially accepted test method (see
6.2).
4.5.7.1 Low temperature test. The system shall be subjected to a low temperature test in
accordance with RTCA/DO-160, Section 4, Category A3, Ground Survival Low Temperature
Curve, and temperature of -54oC.
4.5.7.2 High temperature test. The system shall be subjected to a high temperature test
in accordance with RTCA/DO-160, Section 4, Category A3, Ground Survival High Temperature
Curve, except the maximum temperature shall be +85oC.
4.5.7.3 Vibration test. The system shall be subjected to a vibration test in accordance
with RTCA/DO-160, Section 8, Standard Sinusoidal Vibration Test Procedure, Figure 8-4,
Curve Y. Each circuit shall be operated under both dim and bright conditions during this test.
There shall be no flickering of the lights, and all fastening hardware shall be secure.
4.5.7.4 Shock test. The system shall be subjected to a shock test in accordance with
RTCA/DO-160, Section 7 at a peak of 15 g and nominal duration of 0.011 second.
4.5.7.5 Humidity test. The humidity test shall be conducted in accordance with
RTCA/DO-160, Section 6, Category C.
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