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F-22 life support 
 
by: Ron Kraan

The system
The F-22 will be easy to fly, the manufacturers worked hard to achieve user-friendliness in the handling qualities of the aircraft. The flight-control concept of "carefree abandon" means that the pilot will never have to worry about losing control, over stressing the aircraft, or getting anything but power. There are 20 controls with 63 functions on throttles and side stick, which enable the pilot to do everything hands on.

Unusually, canopy design was part of the cockpit team's task. There is no canopy bow because of low-observability and pilot-vision requirements and the transparency is a single piece of monolithic polycarbonate with no complex curves. Bird strike testing revealed a problem when the canopy deflected and shattered the head-up display, display supplier GEC-Marconi Avionics is developing a collapsible combiner which will still work as a 600kt (1,100 km/h) blast shield. The canopy rotates down and translates forward to lock. To jettison, the canopy is pushed back and lifted off by a rocket thruster at its forward edge. The canopy does not fall but becomes a flying object and is weighted asymmetrically to ensure that it diverges from the ejecting pilots' flight path.

Modifications to the Air Force's McDonnell Douglas ACES II zero-zero ejection seat (for operation at speeds up to 1,100 km/h) in the F-22 include arm restraints and a fast-acting drogue. As the seat moves up the rails, restraint nets encapsulate the pilot, and the drogue is fired to deploy immediately the seat leaves the rails and before it can yaw. This prevents injuries that can occur if the seat is off axis when the drogue deploys. The seat is "electrified", with an electronic sequencing system, which can be tested on the ground.

The F-22 is the first program to include development of the man-mounted life-support system. The manufacturers wanted to be able to spend lots of time at high altitude and high G without wearing the pilot out. The problem was that, to protect the pilot from chemical/biological (CB) threats, he had to be wrapped in plastic. Therefore the pilot has to have thermal protection. In addition, he needed more thermal protection in case he ditched in the water. If you put CB gear, a cold-weather suit, G-suit, and thermal protection on him, you'd be lucky to get into the aircraft, let alone enable him to fly or fight, so they needed something different.

The F-22 life-support system integrates all critical components in one ensemble. In the past, these elements would have been designed separately. Those components include the on-board oxygen generation system (OBOGS); breathing regulator/anti-g system (BRAG); chemical/biological (C/B)/cold-water immersion protection garment; upper pressure garment; lower pressure garment; air-cooling garment; helmet and helmet-mounted systems including C/B goggles and C/B hood; breathing mask; and hose system. 

The gear
The resulting F-22 life-support system is divided into aircraft- and man-mounted pieces. Normalair Garrett has developed an onboard oxygen-generating source to "...fit into a small space with a peculiar shape." The UK manufacturer also developed a single breathing regulator/anti-G valve, to provide positive-pressure breathing at high altitude and high G. Man-mounted pieces include an air-cooling garment, produced by ILC of Dover, Delaware. A dedicated line feeds conditioned air to the pilot, providing a temperature range of 13-32C. This is also going to be used by pilots on the Army's RAH-66 Comanche helicopter. Over this goes the flight suit, designed by Boeing and British Columbia-based META Research. M.E.T.A. Research has designed gear for the U.S. Coast Guard, Canadian military forces, and commercial boaters and fishermen. Doubling as an immersion suit, as well as providing protection against flames and a CB environment, the integrated suit will meet with much higher pilot acceptance, Boeing says. Over the suit goes an upper pressure garment, also CB-hardened, which provides counter pressure to assist breathing and counteract G. The lower G garment incorporates a one-piece bladder for the legs and lower torso. It is still mobile enough so the pilots can fight, otherwise it would have had to be a like a full pressure suit like those used on the SR-71 says Boeing.

The helmet
The helmet now used by Air Force pilots, the HGU-55/P, meets all the prerequisites for the service's current fighters and bombers. However, for use in the F-22, it falls short in some areas. Wind forces seen during ejections, that occur at aircraft cruising speeds at 450 knots estimated air speed, cause the HGU-55/P to separate from the pilot's head thus leaving the pilot unprotected. The new helmet is built to remain on the pilot at 600 knots EAS and operations at high altitudes. The lightweight, low-lift helmet has been developed by UK-based Helmet Systems (Alpha). The Alpha HGU-86/P tested being approximately 30 percent lighter than existing systems. The HGU-86/P fits 99 percent of the Air Force's male flying population, and is being evaluated for the female flying population. Because the new helmet is lighter, with a more comfortable fit than the older one, it can be worn for longer periods of time, thus reducing fatigue. In addition, a good-fitting helmet that resists changing position while being worn is better for mounting onto it other equipment, such as specialized visors and helmet-mounted displays (HMD/JHMCS). 

Another benefit of the HGU-86/P is its emphasis on preventing hearing damage and pilot's mental fatigue. The HGU-86/P incorporates an ear-cup tensioning system that allows the helmet's ear-cup to be drawn to the head, blocking out excessive background noise and increasing the level of hearing. 
This type of noise attenuation represents a reduction in pilot workload by freeing the brain from burdensome efforts to cancel out unwanted background noise, allowing the pilot greater ability to concentrate and process information. This improved mobility and endurance for pilots. With its advanced design, the HGU-86/P helmet reduced the stresses on a pilot's neck by 20 percent during high-speed ejection compared to current helmets. The helmet also incorporates a suspension system to prevent high-G turns affecting Helmet-mounted display optics. Breathing hoses are supplied by Parker Symetrics of Newbury Park, Calif.

The mask
The HGU-86/P is currently tested with the MBU-22/P oxygen mask. This mask being a further development of the MBU-20/P. 

The future
"From a pilot's perspective, the integrated suit is better because you get used to wearing the same thing. It's already a stressful time if you have to go into combat, and it helps if the suit, mask, and helmet are already familiar and you don't need to add extra things for over water flights and CB," says Boeing chief test pilot Chuck Killberg. The Air Force has yet to buy the ensemble for production F-22s. The entire flight gear set-up is currently being tested at Brooks AFB and Edwards AFB. The gear and helmets must be available by 2004. The Air Force is considering the HGU-86/P for all its fighter aircraft.


note: Taken from, amongst others, Air Safety Magazine and altered, more info on this subject can be found in the JHMCS article.

 

"Venz" /  "Hud"  flightgear on-line 2002/2003