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Nineteen months after the U.S. Air Force banned lightweight pilots from flying the F-35, the service is lifting the restriction, allowing men and women across the full weight envelope to safely operate the aircraft.
At issue was a problem with the design of the F-35’s escape system that posed a significant risk of neck damage or death during ejection to pilots in the lowest weight range. The issue, discovered in the summer of 2015, led the U.S. military services to bar pilots under 136 lb. from flying the F-35.
The Air Force’s decision to lift the weight restriction, announced May 15, reflects the service’s confidence that ejection seat maker Martin-Baker and industry partners have successfully fixed the problem, a complex challenge involving both the ejection seat and F-35 helmet.
An ejection is a dangerous event even in ideal circumstances, with opportunities for injury at almost every stage. Once the pilot signals the plane to eject, a set of small explosives breach the windscreen canopy so the pilot can exit the aircraft. The pilot and seat are then launched upward via a rail system in a violent jolt that can cause back and neck injuries if the pilot is not in the correct position, with his or her head directly centered on the spine. The potential for injury is exacerbated by the weight of the F-35’s heavy helmet, which forces the pilot’s head down.
Once the pilot and seat reach the top of the rails, a rocket under the seat is ignited to lift the pilot-and-seat package free of the plane. At this point, the seat can begin pitching back and forth, a motion much like that of a rocking chair. The pilot’s physical build determines the direction and degree of the pitching motion; a tall, heavy person tends to pitch forward, while a short, light person tends to pitch back, sometimes even rotating a full 180 deg.
If a pilot’s position is too far back when the main recovery parachute deploys, a “snapping” of the head and neck can occur, leading to serious and potentially fatal neck injuries.
“Flying fighters as you know is an inherently dangerous business and ejecting from one means that something catastrophic has already taken place,” said Brig. Gen. Scott Pleus, chief of the F-35 integration office, during a Pentagon media briefing. “Our goal and the Air Force’s intent is to do everything possible to give the pilot the greatest chance of survival in the unlikely event that an ejection is required from a fighter aircraft.”
Martin-Baker and industry partners last year came up with a three-part fix to protect a lightweight pilot’s head and neck in the event of an ejection: a lighter helmet to help ease strain on the neck during the first phase of an ejection; a lightweight switch on the seat to delay deployment of the main parachute; and a fabric panel sewn between the parachute risers that will protect the pilot’s head from moving backward during the parachute opening, called a “head support panel” or HSP.
“These modifications combined allowed us to open up the pipeline across the entire planned pilot weight demographic of 102 to 245 lb.,” Pleus said.
Martin-Baker field teams have begun installing modification kits to the F-35 ejection seats, a company statement says. The first seat has been modified and the aircraft flew on May 4.
Retrofitting the Air Force’s full fleet of 107 F-35s with the modified seat will take about eight months, or until December-January, Pleus said.
Meanwhile, Rockwell Collins’ new “Gen III light” helmet is currently in preproduction, and will go into full production this fall. To reduce the helmet's weight, industry removed some of the strapping inside the helmet itself. Rockwell Collins also removed the external sun visor. Instead, pilots will now have two interchangeable visors, one clear and one dark.
The Pentagon’s top weapons tester has raised concerns about the new helmet, specifically that it is not practical for pilots to have to swap equipment in flight as weather or light conditions change. Another issue, Pleus acknowledged, is that there is no storage space onboard for the other visor. The Air Force is still working on a solution to that problem, he said.
“As our test pilots continue to fly with these basic preproduction helmets, they will continue to modify the tactics, techniques and procedures for where you’re going to put the external visor,” Pleus said. “We will create some sort of a storage solution that removes any opportunity for foreign object damage.”
The first lightweight F-35 pilot will begin training by year’s end and will be flying the aircraft by early 2018, Pleus said.
Отредактировано Вуду (17.05.2017 17:02:52)
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