Downloaded from https://www.everyspec.com MIL-STD-81OC 10 March 1975 :’.. TEMPERATURE-ALTITUDE METHOD 504.1 1. PURPOSE. The temperature-altitudetest is conducted to determine the abil~equipment to operate satisfactorilyunder simultaneouslyapplied varying conditions of low pressure and high/low temperature. The equipment category, as used in this method, is determined by the required altitude operating range and the required sea level continuous operating temperature delineated in table 504.l-I. 1.1 General effects.
Deleterious effects to be anticipated include leakage of gases or fluids from sealed enclosures, rupture of pressurized’containers, congealing of lubricants, cracking or rupture of materials due to contraction or expansion, short circuiting of electrical wiring and other damaging effects which might be expected from exposure to any of the above environments singly. In addition, equipment dependent on a convection type cooling system may be affected due to the reduction of efficiency of heat dissipation in less dense air. 2. APPARATUS. Temperature-altitudechamber and auxiliary thermal sensors tiithassociated recording devices (see note (a)). 3. PROCEDURES 3.1 Procedure 1.
The test item shall be prepared in accordance with General Requirements, 3.2. In general, the testing schedule outlined in table 504.l-II shall be followed. However, each step in table 504.1-II represents a condition which the test item may encounter in service; therefore, each step may be applied independently of the others. For operating conditions other than those specified in table 504.l-I, the alternate temperature-altitudeconditions in figures 504.1-1, 504.1-2, 504.1-3, or 504.1-4 shall be used.
When changing chsmber conditions from those required for one step to those required for any other step, in the sequence given in table 504.1-11 or in any sequence, the rates of temperature and pressure changes may be the maximum attainable by the chamber, but these rates shall not exceed l° C (1.8”F)per second for airborne equipment or 10”C (18”F) per minute for test equipment and O.5 inch of mercury per second. Pressures for altitude tables are contained in U. S. Standard Atmosphere supplement, 1966. 504.1-1 METHOD .504.1 10 March 1975