THE US ARMY IS TO test-fire laser and ballistic weapons against experimental composite-helicopter tail-booms in a combined test programme with Boeing aimed at improving helicopter battlefield-survivability.
The directed-energy weapon tests will be conducted at Wright Patterson AFB, Ohio, using lasers representative of projected threats such as slewed-beam lasers. Ballistic tests, involving armour-piercing incendiary and 23mm high-explosive incendiary (HEI) weapons, will be carried out at the US Army's Aviation Applied Technology Directorate (AATD), Fort Eustis, Virginia.
The weapons will be fired at two "soft-" and two "hard -"skin cylindrical-specimen helicopter tail-booms now being made by Automated Dynamics from thermoplastic-composite materials. The soft-skin specimens will act as a pressure-relief mechanism against HEI rounds to minimise fragmentation damage to other parts of the structure. The soft-skin designs have minimal skin thickness, with crack arrestors made from cylindrical straps.
The hard-skin, or "brute-force", approach provides damage tolerance by containing the area of the damage and is based mainly on increased skin-thickness to maintain structural integrity. The additional layers of skin add about 4.5kg to the hard-skin design, compared with that of the soft skin. The addition of crack-arrestor straps to the soft skin adds just under 0.5kg.
Structural tests will be performed to ultimate loads before the specimens are fired upon. They will be tested again after the threat damage, to assess residual strength up to design-limit load. The booms fired on by the laser will receive battle-damage repair before being tested to structural failure.
Data from the tests will support the Boeing/Sikorsky RAH-66 Comanche as well as other helicopter programmes. Boeing Defense Space Group's Helicopters division, which teamed on the programme in 1993 with AATD and the Aviation and Troop Command, also provided data from similar work carried out in the early 1970s with the YUH-61. This indicated that cylindrical booms are more resilient to peak over-pressures.
Source: Flight International
