High Altitude Low Opening
See also: Decompression sickness and John StappThe origins of the HALO technique date back to 1960 when the U.S. Air Force was conducting experiments that followed earlier work by Colonel John Stapp in the late 1940s through early 1950s on survivability factors for high-flying pilots needing to eject at high altitudes. Stapp, a research biophysicist and medical doctor, used himself as a human guinea pig in rocket sled tests to study the effects of very high g-forces. Stapp also resolved many of the issues involved in high altitude flight in his earliest work for the Air Force, and subjected himself to exposure to altitudes of 45,000 feet (14,000 m). Subsequently, he helped develop pressure suits and ejection seats, which have been used in jets ever since. As part of the experiments, on August 16, 1960, Colonel Joseph Kittinger performed the first high altitude jump at an altitude of 19.5 miles (31.4 km) above the Earth's surface. However, the technique was used for combat for the first time during the Vietnam War in Laos by members of MACV-SOG. SEAL Team Six of the United States Navy expanded the HALO technique to include delivery of boats and other large items in conjunction with parachutists.
The technique is used to airdrop supplies, equipment, or personnel at high altitudes when aircraft can fly above surface-to-air missile (SAM) engagement levels through enemy skies without posing a threat to the transport or load.
For military cargo airdrops, the rigged load is cut free and rolls out of the plane as a result of aircraft deck angle (AOA). The load then proceeds to fall under canopy to a designated drop zone.
In a typical HALO exercise, the parachutist will jump from the aircraft, free-fall for a period of time at terminal velocity, and open his parachute at a low altitude. The combination of high downward speed, minimal metal and forward air-speed serves to defeat radar, enabling a stealthy insertion.
Read more about this topic: High Altitude Military Parachuting, HALO
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