Downloaded from https://www.everyspec.com MIL-STD-81OD I-3.2.3 Procedure III - Oual@atlon t-. . . . Qualification can be accomplished either with a single test which combines all the appropriate environmental stresses or with a series of separate tests: It is not’recommended to run all environmental stresses in separate tests. When the use of separate environ- mental tests is selected, the following single and combined environment stress tests are recommended: vibration; a combined temperature, altitude, and humidity teat; and a combined supplemental cooling airflow-with humidity, temperature, and mass flow rate as test parameters.
The following guidance is recommended for each separate test. 19 July 1983 I-3.2.3.1 Vibratio~. Use the test conditions and durations.recommended in method 514 of MIL-STD-81O for qualification testing. :. I-3.2.3.2 Temperature-aMe-humiditv test. This test is for the conditions inside an equipment bay or cockpit. Identify the maximum and minimum tempera- ture to be experienced in anticipated deployment by the item to be tested.. Identify the maximum and minimum temperatures under which the test item is ~ expected to’operate. These temperatures can be obtained from the analysis outlined in paragraph I-3.2.2 of procedure II.
If such an analysis was not” accomplished, tables 520.O-V and 520.O-VI and figure 520.0-4 can be used. The values in tables 520.O-V and 520.O-VI are based on measured data and are representative of extreme temperature conditions (air temperature, not equipment temperature). Therefore, there is reasonable”confidence that these test levels will sufficiently stress the test item. from the analysis outlined in paragraph I-3.2.2. Often the altitude (air pressure) ins?de a cockpit or equipment bay is different from that outside the aircraft because of cabin pressurization. If an analysis has not been done, use maximum flight altitude or, if unknown, use 16 km (52,500 ft.).
The maximum altitude to be experienced by the.item to be tested should come The recommended durations of stress exposure in table 520.O-VI are based upon anticipated extreme-case exposure durations. It is not recommended to force the test item to reach thermal stability. As would happen in actual usage, the mass of the test item will determine how close the test item will get to-the impo,9edtemperature. The humidity stress is based upon reasonable levels that can be experienced in actual usage.
Unless analysis such as outlined in paragraph,I-3.2.2 of procedure II shows that the’equipment bay or cockpit environment is signi- ficantly more or lees humid, the level shown in table 520.O-V is recommended. ,. ,2 I-3.2.3.3 ~1-coo ~.-.,~.~ JEas.5flow rate. and temneratura m. This test is.for supplemental cooling airflow that flows directly through an equipment system. The temperature, humidity and mass flow rate can be determined frem”an analysi? as outlined in paragraph I-3.2.2 of‘procedure II. If such “an analysis is not available;the levels in table 520.O-V‘and ,. combined as shown in table 520.O-VI and figure 520.0-5 are recommended. I-3.2.3.4 Electrical str~.
Unlese otherwiee def?ned, use tke electrical stress conditions outlined in paragraphs I-3.2.2 .9.1 and I-3.2.2.9.2 as applicable. METHOD 520.0 ,. 19.JuIY 1983 520.0-16