Downloaded from https://www.everyspec.com MIL-STD-81OC (2) Constant percentage bandwidth analyzer (a) Filter bandwidth = pfc = one-tenth of center frequency maximum, (O.Ifc) where p = percentage and f= = analyzer center frequency (b) Analyzer averaging time = T = ~, minimum (pfc)2 (c) Analysis sweep rate (logarithmic)= R = ~ or ~ (Hz/second),maximum, whichever is smalleri c. Digital power spectra”ldensity analysis system employing quantization techniques providing accuracies corresponding tO the abOve apprOach. Accelerometer(s)employed for test level control shall be mounted in accord- ance with 4.2.
Where more than one accelerometer is employed for test level control, the,power average of the several accelerometer signals shall be used as the test level signal control. 4.6 Procedures 4.6.1 Procedure 1. Equipment installed in airplanes or helicopters. (Categoryb.1 or c.) b b.1 eauiument. uroceed r 4.6.1.1 Part 1. For category . . 4.5.1.2, and 4.5.1.3. The test levels and t~m~ durations shall be as speci-” fied in table 514.2-11 and figure 514.2-2. For category c equipment, proceed the same as in 4.5.1.1. the same as in 4.5.1.3 only. The test levels and time schedules shall be as specified in table 514.2-111 and figure 514.2-3. 4.6.1.2 Part 2.
For category b.1.equipment, test items normally provided with vibr=isolators shall be vibrated in accordance with 4.5.1.1, 4.5.1.2, and 4.5.1.3 with the vibration isolators removed but including any other required holding devices. The test levels and time durations shall be as specified. in table S14.2-11 and figure ,514.2-2. For category c equipment, proceed the same as in 4.5.1.3 only with the vibration isolators removed but including any other holding devices. The test levels and time schedules shall be as specified in table 514.,2-IIIand figure 514.2-3. 4.$5.2 Procedure IA. Random vibration test for equipment installed in jet airplanes..
(Not for turboprop aircraft or jet powe+ed helicopters.~ The random vibration environment which occurs at equipment 1ocations in jet aircraft stems from four printipal sources: a. Turbulent aerodynamic airflow along external surfaces of the aircraft structure. 514.2-7 METHOD 514.2 .