Tech Briefs

B-52/Missile Sustainment Group adopts AFRL-developed hydraulic fluid.

An AFRL-developed fire-resistant hydraulic fluid recently completed a B-52 flight test, and based on successful test results, systems engineers from Oklahoma City Air Logistics Center (OC-ALC) will adopt the fluid (MILPRF- 87527) for use in over 90% of the aircraft's hydraulic systems. OC-ALC engineers will conduct further tests to determine whether they can also convert the hydraulic systems controlling the B-52's landing gear and wingtip protection struts to the fire-resistant fluid. AFRL expects the improved fluid's higher flash point and reduced flammability to increase the B-52 aircraft's survivability and overall operational safety. Further, the fluid's associated thermal stability measurements and fluid film thickness data indicate it performs well over extended periods of time in hightemperature environments and in temperatures as low as -65°F.

The B-52 long-range, heavy bomber (AF photo)
Air Combat Command's B-52 is a longrange, heavy bomber that performs a variety of missions (see figure). The bomber can fly at high subsonic speeds at altitudes up to 50,000 ft and can carry nuclear or conventional ordnance. In a military conflict, the B-52 can perform air interdiction, offensive-counter air, and maritime operations. During Operation DESERT STORM, B-52s delivered 40% of all weapons dropped by coalition forces.

Hydraulically actuated mechanisms are responsible for a large number of aircraft functions, including highly sophisticated flight control, landing gear operation, and accessory door actuation. Systems designers also employ hydraulic fluids to lubricate aircraft systems, cool heat-generating components, and otherwise function in highpressure hydraulic systems near a variety of ignition sources. In the past, the B-52 used a flammable, petroleum-based hydraulic fluid (MIL-PRF-5606) because it could operate at -65°F, a capability required for some deployments.