Downloaded from https://www.everyspec.com MIL-STD-81OC b, c. Piersol, A. G., “Vibration and Acoustic Test Criteria for Captive Flight of Externally Carried Aircraft Stores, !!AFFDL-TR-71-158,Wright-Patterson AFB, Ohio, December 1971. d. Bur~hard, A., I!Captive Flight Acoustic Test Criteria for Aircraft StOres)“ Shock and Vibration 8ulletin No. 43, Part 3 (pP 113-126), NRL, Wash., DC., June 1973. 4.6.3.2 Procedure IIB. Assembled externally carried airplane stores 4.6.3.2.1 Purpose. This vibration test is performed to determine that the assembled store as a system is constructed to withstand and perform in the expected dynamic environment.
The nature of this test is to simulate the lower frequency vibratory environment of the store by application of vibra- tory energy at discreet points. To insure that the vibratory test levels reflect the inflight vibratory levels, the selection of the test points and vibration input levels are determined by the response of the store. Procedure II of Method 515.2, acoustic testing for assembled exte~aLIY carried aircraft stores, shall also be conducted to simulate the higher frequency distributed aerodynamical1y induced vibratory environment. Acous- tic testing is not required if the minimum value of f. of 4.6.3.2.3 is greater than 1,200 Hz.
Procedure 11A of this method”shall be used when individual equipment items such as fuzes, electronic equipment, etc. , need to be tested separately from the whole store. 4.6.3.2.2 Accelerometer placement. Accelerometers to monitor the vibratory response of the store shall be mounted on two relatively hard points or rings within the store: one in the nose section and one in the aft section. For stores such as bombs with nonintegral tail cones, the aft section mount- ing point shall be in the aft most section of the main body of the store. At each mounting p~int or ring, two accelerometersshall be mounted - one in the vertical and one in the lateral plane.
(Longitudinaldirection is along the axis of the store. The vertical direction shall be considered as perpendicular to the longitudinalaxis and contained in a plane passing through the mounting lugs.) 4.6.3.2.3 Test levels. The test frequency spectrum for each store mounted monitoring accelerometer shall be determined from figure 514.2-4A and the values of table 514.2-IV. GenerallY, the test spectrum for the forward accelerometerswil1 be different from that of the aft accelerometers. Test levels for both a functional and endurance test shall be determined. The value of f. used in figure 514.2-4A for this test shall be defined as follows: f.
= (t/R2) x 105 + 100 Hz for stores with circular or elliptical cross-sections 514.2-11 METHOD S14.2