Downloaded from https://www.everyspec.com MIL-STD-810D 19.July 1983 Apply broadband vibration to the atore using an input store-mounted forward accelerometer response spectrum The input level shall be 6dB down from the calculated forward accelerometer. spectrum”shape of the from paragraph I-3.2.7a. response level of the accelerometera, in the direction of applied vibration, exceed the applied input vibration by 6dB or greater. There may be different frequencies for the forward and aft accelerometers. Identify those frequencies at which the store-mounted .
Peak or notch the applied input spectrum until both the forward- and aft- mounted accelerometer in the direction of applied vibration at their respective frequencies identified above equal or exceed the required test levele determined.from paragraph I-3.2.7a. .. It may be necessary to move the points of attachment between shaker and store until locations are found where both ends of the store are simultaneously excited to their respective test levels. The off-axia accelerometer response (those accelerometers 91Jdegrees to the aPPlied vibration) should be examined.
For each frequency where the responee of an off-axis accelerometer is above in-axis reapcnse levels, the following actions are suggested. For each of these frequencies, calculate the ratio of required to observed levels for each accelerometer which was in the direction of vibration (in-axis) and those perpendicular (off-axis) accelerometers which have excessive levels. Average these ratios for each frequency. The input vibration spectrum may then be adjusted so that, at each of these frequencies, their respective average value is equal to unity. 1-3.2.8 Jkteua’v 7B t instaed in ,. extertiv carried stcr~.
Equipment installed within an externally carried store will experience a broadband vibration spectrum that depends chiefly on the captive-carry response of the store. Vibration testing, whenever possible should be based on in-flight measurements. If satisfactory flight measurements are not available, functional tests may be derived from figure 514.3-33 and table 514.3-VI. NOte that the test levels for equipment installed in stcres are the same as the response test levels cf assembled stores. The response of the store is the input vibration to an item installed in the stare.
If buffet-manuever and free-flight conditions can occur for the’store into which the equipment will be installed, vibration test spectra need to be developed for each condition. a. k vela. If sufficient measured data does not exist, use figure 514.3-33 and refer to I-3.2.7. Vibration testing of equipment to be installed in externally carried jet aircraft stores ehould be input-controlled testing (see I-4.2.6). b. -t dura~. Refer to I-4.3, I-4.6, I-4.7, I-4.8 and I-4.9 for test duration and endurance test criteria. c. lest aet~. Use I-4.11 for setup. METHOD 514.3 19 July 1983 514.3-51