Downloaded from https://www.everyspec.com MIL-STD-810C 10 March 1975 METHOD 519.2 GUNFIRE VIBRATION, AIRCRAFT 1. PURPOSE. The gunfire vibration test is conducted to simulate the rela- tively brief but very intense vibration fields resulting from blast pressure fields generated by repetitive firing guns mounted in, on or near the air- craft stmcture. This method applies to gun pod configurationsand may also be used for helicopter gunships. 2. APPARATUS. Vibration shaker system with peripheral eq~ipment and instrumentation. 3. CRITERIA FOR APPLICATION.
The most severe vibration field results, primarily, from blast pressure pulses that transfer to the aircraft primary structure inducing a vibration field of maximum intensity near the gun muzzle region. This field, in an inverse relationship, decreases sharply as a function of the distance from the gun muzzle. Because of this marked varia- tion; guns, physical locations, and ballistic parameters should be carefully and accurately identified prior to application of this test method.
In no case s~ould this test method be substituted for conventional vibration tests but if the maximum test spectrum level of the gunfire configuration is equal to or less than the other specified vibration test levels the gunfire method need not be conducted. b 3.1 Sensitive equipment. Equipments found most susceptible to gunfire are those equipments that are usually located within a 3-foot radius of the gun muzz1e and are mounted on the structural surface exposed to the gun blast. Prime examples are UHF antennas of the blade, V, and the flush-mounted configurations,including their bracketry, coaxial connectors, and cables.
Next in order of failure susceptibility is equipment mounted on drop-down doors and access panels, equipment mounted in cavities adja- scentto and near the aircraft surface structure, and finally, equipment located in the interior of the vehicle. Typical vulnerable equipments in these latter categories are auxiliary hydraulic and power units (including mounting bracketry), switches, relays, IR, photographic, communication and navigation equipment and radar systems; including items either shock or hard mounted. 3.2 Equipments associated with mounting structures.
Equipments are classified in accordance with the structure to which they are attached and are identified as either.equipments mounted on primary structure or as equipments mounted on secondary structure. 519.2-1 METHOD 519.2 B 10 March 1975