Low Altitude Parachute Extraction System (LAPES)
The Low Altitude Parachute Extraction System (LAPES) is not currently in use by the US Air Force (USAF) or the US Army. LAPES is one of the three methods used for Aerial Delivery. With LAPES, up to 38,000 pounds (17,000kg) of cargo is pulled from the aircraft by large cargo parachutes while the aircraft is five to 10 feet (3m) above the ground. The load then slides to a stop within a very short distance.
Sustained ground operations after a successful airborne assault may depend on resupply by means other than airlanding of supplies and follow-on forces. A primary means of resupply is the low altitude parachute extraction system. LAPES is a low-altitude method of aerial delivery. This system employs a 15-foot drogue parachute deployed behind the aircraft and attached to a towplate on the aircraft ramp. At the release point, the parachute forces are transferred from the twoplate to the ring slot main extraction parachute(s), which then extracts single or tandem platforms from the aircraft. Ground friction decelerates the load. The total distance from release to stopping point of the load depends on ground speed, size, number of extractions parachutes, weight of the load(s), and the type of terrain.
The LAPES delivery method was developed years ago to solve the problem of quickly placing cargo loads directly on the ground in areas where it would be unsafe to land the aircraft. In Vietnam, C-130s frequently used the technique to land cargoes onto runway areas and reduce the risk of mortar fire. It was also useful for spotting very heavy loads, such as armored vehicles, directly onto the ground without subjecting them to the risk of parachute failure from a higher altitude.
With the LAPES system, low means low. The transport approaches the target zone from an extremely low altitude - 2 to 10 feet above the ground. At the right moment, the loadmaster pops a large parachute, which drags the cargo pallet across rollers on the cargo bay floor and out the rear doors. One or more platforms may be released during a single pass, directly into the hands of the warfighters on the ground. Routine use of the LAPES gives real meaning to the term Agile Combat Support.
During the much longer war in Southeast Asia (in the 1960s and early 1970s) the widespread use of helicopters, for both troop and supply transport, largely supplanted the need for massive airdrops. Only in dire emergencies, during siege operations in particular when no other means of logistics support were readily available, did mass rigging come into play. Thus, relatively few Quartermaster aerial delivery units deployed to Vietnam. Among those that did, none exceeded the performance of the 109th Quartermaster Company.
Arriving in September 1966 and headquartered at Cam Ranh Bay, the 109th with its supporting detachments soon had the capacity to rig over 250 short tons of supplies daily. In April 1967, during Operation Junction City,a joint operation conducted in Tay Ninh province along the Cambodian border, the 109th delivered 503 short tons, the largest 24-hour airdrop up to that time. Later that year they began experimenting with the Low Altitude Parachute Extraction System, or LAPES technique, that entailed palleted and parachuted cargo exiting the back of the plane as it flew in just feet above the runway.
In September 1967, during the Siege of Khe Sanh, the 109th used LAPES to airdrop some 567 short tons of construction material to the Marines as they undertook a fierce pounding from the estimated 20,000 North Vietnamese regulars who had them completely surrounded and in their cross-hairs. The 109th went on to deliver more than 8,000 tons of supplies of all classes during the 78-day emergency period.
The C-17 Globemaster III passed an important milestone at the Flight Test Center on May 3, 1994. On that day, he Air Force's new jet transport successfully made its first aerial delivery using the low altitude parachute extraction system (LAPES). LAPES demands perfect stability and controllability from the delivery aircraft. The C-17 Combined Test Force at AFFTC carried out the first such test using the first production-category Globemaster III. On that day, the heavy lifter made its pass at 130 knots (about 150 mph) with its wheels just 2 feet above the south lake bed.
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