I 1- Downloaded from https://www.everyspec.com MIL-STD-81OD 19 July 1983 Climatic temperature estimates may be incorporated into the test by selecting a representative group of fixed temperature offsets which add to or subtrsct from the standard composite mission temperature profile. By having these Offsets represent equiprobable temperature intervals, a full climate set of these temp- erature profiles can simulate the whole temperature system which the st.Ore could experience. A sample composite mission temperature profile climatic set is shown in figure 523.0-4.
Note that the profiles are clustered around,the standard value to reflect the higher frequency of operations in more;”tempera- ture climates. For practical test operation, each test cycle (One”c0mP09ite mission) will trace a composite temperature profile, start-ingand endirigat a resting temperature. The resting period between consecutive test cycles should be sufficient to allow internal store temperature to stabilize, thus simulating the ground time occurring between,service missions. A climatic Set Of teat cycles will consist of a sequence of test cycles”(usually 6 to 15) in which the composite mission temperature pattern”ie offset stepwise upward and downward from zero offset.
Figure 523.0-5 illustrates a typical offset sequence for an 8-cycle climatic set. To provide uniformity and consistency from one teat to the next, it is important that several full climate seta be completed before the expected Mesn-Time-To-FaiIure of the atore is reached. A test minimum of five aets is recommended. ,, ..... I-3.4.2 ofile. A composite mission vibration profile may be generated by determining the dynamic pressures during each stable segment of aircraft flight (refer to I-2.5),. A rough profile can now be constructed. The perioda of changing temperature will usually also be periods of changing’q since both are dependent on aircraft altitude and velocity.
However, since vibration in the laboratory may be changed’almost instantaneously (not with lag, like temperature) and is more easily controlled at fixed levels, the i profile ia usually laid out a? series of steps. Figure 523.0-6 shows a typical compositemission dynamic pressure profile matching the corresponding figure 523.0-7 temperature profile. Data from instrumented flights is used to determine the spectral envelope for various mission phases and the translation’ from q to vibration level. The simplified vibration profile shows intensity only. The spectrum enV,elOPe and the suatial distribution (including directivity) of the vibration are additional variables that,,when uncont~olled.
can ~ause error in the simulation process. “Experimentaladjustment should achieve a reasonable correlation between captive-flights and from the store under be ~one in the test c,hamberso as to accelerometer vibration records from test. I-5 ~ ,. :? a. Meeker, D .B. and Piersol, A.G., Vibroacouatic Environments,” Reliability \!AcceleratebReliability”Testing under Design for Vibracoustic Environments, s. b. Dantowitz, A., Hirschberger, G., and Pravid10, D., “AnalYsis of Aeronautical Equipment Environmental Failures, N Air Force Flight Dynamics Laboratory, TR-71-32, May ~971. ASME AMD-VO1. 9, New York, NY 1974. c. Meeker, D .B. and Everett, w.D., NU.S.
Navy Experience OQ tie Effects of Carrier-Aircraft”Environment on Guided Missiles,” AGARD conference o proceedings No. CP270, May 1979. -.. MRTHOD 523~’O 19 July 1983 523.0-6