Downloaded from https://www.everyspec.com MIL-STD-810D 19 “July 1983 aircraft do not cool equipment with ECS air, thus the equipment sees only ambient humidity conditions.) For the purposes of this test, whenever the cold day environment is being simulated, humidity will be uncontrolled, but less than or equal to the dew temperature shown in table520.0-111. For the hot environment, dew temperatures will be less than or equal to values shown in table 520.0-111. In the case of the warm moist day, dew temperatures will be greater than or equal to the values found in table 520.0-111 up to 10km. Above 10 km, the dew temperature shall be less than or equal to the values found in table’520.0-111.
If the platform has an ECS, the design specifioationg for ‘the water separator shall be used to define humidity conditions for the warm moist day. When the effioienoy of the ECS is unknown, the aPProximetio9 technique put forth above should be used. Note: The formation of free water on the test items during combined environment testing can be a normal condition. It will occur whenever the temperature of the test item is cooler than the dewpoint,temperature of the“air being delivered by the ECS or from ram airflow. This is normal and a realistio condition. I-3.2.2.8 AJ&.itudestre~.
Altitude simulation should be employed when there I is reason to believe that systemperformance may be affeoted by variation in air Pi.essure. Examples of such situations are: hermetioally sealed,units that use PF-.assurizedcooling parts to maintain sufficient heat transfer, vacuum cdpone,nts where the seal is maintained by air pressure, and units where change in air p,re~~uremav cause aroin= or change of cOmoonent values. When altitude effect is to be te~ted~ the alt~ttidestr~sg, or r~duced atmospheric pressure variatir~ns,shall be applied according to the miesion PrOfileS selected for test.
,’~healtitude,’or reduced pressure, is initially applied at the simulated airCraft takeoff and ‘continuesat the pressure changes corresponding tO the Various flight phases from climb-out to landing. The ‘rateof change of Preseutw? should reflect the climb or descent rate of the aircraft while PerfOrtrjing‘the varioua flight mission phases. The ‘maximumPressure (minimum used for “thetest shall be that of ground elevation at the test site. I-3.2.2.9 1 stre~. Electrical streeses are deviations of the equipmentts electric supply parameters at the equipment terminals from their nominal values.
The test procedure must assure that all electrical stresses occurring during normal operation in service (mission profile) are simulated the required extent. to It is not the purpose of this test method to simulate extremes specified for special situations or to take the place of special electrical stress teSte. Special conditions, like emergency operation of certain aircraft equipment within the ‘electrical/electronicsystem, ‘shallbe simulated only on request.
Depending upon the requirements and the availability of data, the simulation may cover the range from the exact reproduction of the specificelectric supPly conditions within a epecial aircraft for a.specific mission profile, down to a standardized simplified orofile for KeneI’aliZedaDPliCatiOnS. The following conditions and effects must be taken-into consideration to they affect the operation and reliabilityy”of.the equipment determine whether to be tested. ~THOD 520.0 19 July 1983 520.0-14