Wire strike protection system
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The wire strike protection system (WSPS) (Developed for the OH-58 / Bell 206 in 1979) is a system of components designed to mitigate the risk of wire strikes while flying helicopters at nap-of-the-earth altitudes, as well as takeoffs and landings.
The system is mounted around the front of many U.S Marine Corps, U.S Navy, U.S Air Force, U.S Army, and some civilian helicopters. The larger CH-46 and CH-47 tandem rotor helicopters have no WSPS systems installed.
The WSPS system appears as two guidance swords at the upper and lower front of the cabin protruding forward at 45° above and below the horizontal. In each of the inner corners to the cabin a large fixed, pair of scissors made of hardened steel is mounted whose opening angle is so small that a speedy or forced incoming steel cable is cut through.
(These swords are often mistaken for radio antennas). The entire system may include upper and lower cutter assemblies, a non-electrically conductive abrasive strip wire scoring device along the center of the divided windscreen and windshield wiper protector frames to keep wires from hanging up on wiper motor shafts. The WSPS is designed to channel a wire or cable into the cable cutter to score and weaken it as it travels into the cutter assembly and "cut" a wire before it can entangle the rotor system. The U.S. Army Safety Center at Fort Rucker, AL, claims that in a single wire strike 90% survivability is achieved by using WSPS. The more wires encountered at a given time the less likely WSPS will help the aircraft survive the encounter.
Some WSPS lower cutters have a break away tip in case of nose low ground impact.
- www.helicopterpage.com - WSPS system (How Helicopters Work)
- Safety Study of Wire Strike Devices Installed on Civil and Military Helicopters
- Wire Strike Accidents in General Aviation: Data Analysis 1994 to 2004 – Page 33
- Wire Strike Protection System, MDHS 500 Maintenance Manual
- Magellan Aerospace Announces New Bell Helicopter Wire Strike Protection System Development