About two years ago, a hungry Stu Horn was driving home after a midnight landing at Jackson, Wyoming. Horn, president of Aviat Aircraft, was doctoring up a sandwich with packets of mustard and mayo, and trying to drive at the same time.
“The last time I looked, the road was straight. I was looking at the sandwich and the next thing you know, the car is off the road. 
I went into a drainage ditch, and I felt like I was rolling in the Pitts. It was pretty amazing. My last recollection was my head and my nose were an inch from the steering wheel. And then, boom, there was this big impact and the air bag came out.” Horn ended his automotive rolls by plowing into a stone wall. “Without the air bag, I would have been in serious trouble.”
Horn emerged from his close brush with death with a considerable appreciation for air-bag technology, an appreciation that will soon be expressed in the aircraft his company builds. With FAA certification now in hand, air bags may become almost as common in aircraft as they are in automobiles. The next time you buckle into a seat aboard a Boeing 777, an air bag may literally be in your lap. And now they are appearing in general aviation.
In 2001, air bags, more formally referred to as inflatable restraints, began appearing in the bulkhead-row seats of Jetstream regional airliners. Today they’re also found in Boeing and Airbus aircraft. Closer to home in the GA community, Aviat Aircraft, which makes the Husky and Pitts, was to begin offering inflatable restraints this summer, starting with the Husky. The Alarus CH2000 began installing seat belt-mounted air bags this past spring. Gippsland Aeronautics of Australia plans to offer them in its new GA8 Airvan as soon as Australian regulators give final approval. Mooney is reported to be offering air bags with its new Ovation2 DX/GX and Bravo DX/GX beginning this summer. Other manufacturers, such as Cessna and Beechcraft, are closely watching the technology, and Cirrus Design seems positively eager to offer it. Zenith Aircraft also recently committed to the technology. In five to 10 years, air bags in GA aircraft could become common, as new designs incorporate them and existing aircraft adopt them. Amsafe Aviation, which makes aviation restraint systems including air bags, believes any aircraft already flying can employ this technology.
Air-bag technology and aviation go back at least 20 years to when NASA studied air bags to help aircrews ejecting from the F-111. The Air Force needed help because so many F-111 aircrews were sustaining serious back injuries and even dying in ejections. Studies showed that the F-111 cockpit capsule, which carried the aircrew and which separated from the aircraft during ejection, was hitting the ground with far too much force, even with its parachutes properly deployed. To improve survivability, NASA developed a system of external air bags located on the bottom of the crew compartment like pillows. Equipped with blowout plugs, the system was intended to absorb impact loads like bubble wrap.
The Army adopted inflatable restraints after realizing that too many helicopter pilots were being lost in “survivable crashes,” crashes where 85 percent of the aircraft structure remained intact. Studies were showing that many helicopter aircrews were dying from injuries by impaling themselves on the cyclic control. During impact, the crews’ heads pitched forward while their seats moved downward to absorb energy. The combined movements resulted in the crews striking the top of the cyclic with their throat or face. If crews avoided being impaled, they still weren’t walking away.
Helicopter crashes tend to last longer than fixed-wing crashes and involve greater vertical impact loads while including rotational forces. In other words, helicopters drop like a rock with considerable forward motion and the spinning mass of the rotor system causes them to tumble before coming to rest.
When subjected to the forces found in a crashing aircraft, the human body proves to be surprisingly elastic and capable of movements that would make an infant cringe.
Despite a five-point harness system, helicopter flight crews can flail about like rag dolls on a string. Their arms and legs, which are unrestrained, fly about the cockpit with so much energy that bones break when they hit panels, consoles, and doors.
To reduce injuries, the Army contracted with Simula Inc. to develop and install an inflatable restraint system known as the cockpit air bag system, or CABS. CABS is slated to be installed in every helicopter in the Army fleet and may find deployment in all military branches. CABS resembles an automotive air bag system with a front-mounted main air bag in the glareshield and side air bags either above the doors or mounted to the side armor panels. When asked how much of the automotive technology was used in the system, Bob Gansman, senior product development engineer for Simula, replies, “Almost none.”
“Helicopters crash in three dimensions whereas car crashes tend to be only in two,” says Gansman. The third, or vertical dimension, rules out using automotive trigger systems and complicates the mathematical modeling in system software. Using accelerometers to detect potential crash forces, the CABS software analyzes those forces in terms of intensity and duration and takes into consideration flight conditions. The software then decides if the aircraft is experiencing turbulence, a hard landing, or a crash. If the forces meet the criteria that define a crash, the air bags deploy.
Because of vertical forces and military requirements, about the only thing that CABS has in common with its automotive cousin is the fabric of the air bag. The opposite is true when talking about another air-bag system initially designed for commercial transport aircraft called the Amsafe Aviation Inflatable Restraint, or AAIR. AAIR’s main purpose in life is to reduce fatal or debilitating head injuries in survivable crashes. Even if a head impact isn’t fatal, if a passenger is unconscious, he won’t escape.
Amsafe Aviation, with the bulk of the world market, is the 500-pound gorilla of aviation seat belts. If you’ve ever flown in an airliner anywhere in the world, you’ve most likely used one of its products. (Amsafe is also the sole supplier of seat belts to Cessna singles and Cirrus Design and supplies many GA manufacturers.) If you find yourself sitting on a bulkhead-row seat of a 777 or an Airbus 340-600, and your seat belt has a funny bulge, congratulations! You’re wearing an air bag made by Amsafe.
AAIR, like CABS, is comprised of three modules: an inflator, and air bag, and a sensor/trigger. But the CABS “sensing system is a lot different,” says Larry Williams, vice president of business development at Amsafe. “Their sensing system is much more complicated than ours” because of the vertical component in helicopter crashes. “Since airplanes crash moving forward, we only have to sense along the longitudinal axis of the airplane. So that’s a big difference. And their air bag is structurally mounted.”
In CABS, and in cars, the air bag deploys toward the passenger. “When that bag deploys,” says Williams, “anything that is in the way of the air bag is gonna move. Where our bag is different is [that] it deploys away from you and it actually has a zero operating pressure in the bag until the bag is completely full.” That means the AAIR air bag, which is mounted in the seat belt webbing, can deploy around passengers and protect everyone from a 3-year-old child to a 95-percentile adult, which makes it ideal for airline use.
FAA regulations regarding head injury require the airlines to keep extra space between seats and bulkheads so that in the event of a crash, seat belts prevent passengers from making a face plant on the hard wall of the bulkhead. “Head injury is typically related to velocity, and velocity is related to distance,” says Williams. “The farther back you sit, the more distance you have to cover” and the harder you’ll hit. AAIR will allow airlines to place seats closer to the bulkhead and add more seats. The extra space popular with long-legged travelers will disappear into airline revenues.
When AAIR deploys, because of its low pressure during inflation, it follows the path of least resistance and fills any available space. It can even deploy around passengers without lifting them up. In contrast, automotive air bags deploy at pressures that can kill children or small adults, and turn objects into projectiles.
Whereas CABS deploys like an automotive system, it has little in common with one. “The opposite is true for us,” says Williams of the AAIR. “The inflator we use is an automotive design; part of the sensing system is an automotive design. That’s the reason we get our unit cost down so low.”
The AAIR sensor system, like the CABS sensor, studies impact force in terms of intensity and duration, looking for the unique signature that identifies a crash. Hard landings and turbulence also have unique signatures that the system software can identify and rule out. The system design makes inadvertent deployments extremely unlikely, on the order of one for every 100 million flight hours.
Williams says that the GA version of AAIR will probably cost about $2,000 per seat and add about 2 pounds each. Costs and weights will vary because the system must be engineered to each aircraft type and the number of seats to be protected. The current sensor/trigger system is designed to protect a maximum of three seats. If development costs can be spread over a large number of airframes, for example, the Cessna 172, then unit costs may drop significantly.
Maintenance of the battery-powered system is expected to be minimal. Once a year, or after every 1,900 flight hours, the units will be tested to verify that the electronics and the battery are working properly. After seven years, the system is overhauled and a new battery is installed. The long battery life is attained because battery power is used only when a crash pulse is detected. Following overhaul, the system is good for seven more years, and then it must be replaced.
Williams says AAIR has strong pilot interest and informal surveys support that belief. However, not one of the surveyed pilots knew beforehand that the technology existed. Bob Gansman of Simula says, “Air bags and aviation have been around for a long time. But we’re just now exceeding the threshold of public awareness. People are only just now becoming aware of it.” One area of the aviation community that readily embraces the technology is the spouses of pilots. Says Williams, “They look at it and say, ‘You gotta have that on your airplane.’”
Amsafe believes that AAIR will be most effective in the airport environment. “About 85 percent of accidents occur at takeoff or landing,” says Williams. “This is where the aircraft is operating at its lowest speed. The fuselage or the structure of the aircraft is able to absorb a good deal of impact. If we can keep you from hitting a windscreen, or a dashboard, or a yoke, or anything else,” AAIR will substantially increase a pilot’s ability to survive.
When talking about his product and its ability to save lives, Williams’ voice takes on an edge of earnestness that borders on zealotry. Before joining Amsafe four years ago, Williams spent 25 years in the gruesome business of removing crash victims from the wreckage of aircraft and cars. His firsthand experience has made him a firm believer in the importance of air bags in general and in AAIR in particular. “I know, really and sincerely, that this device without exception will save lives.”
Aviat President Stu Horn credits his car crash with opening his eyes to the potential of air bags in airplanes. “People learn the hard way,” says Horn. “Had I not had that experience, I don’t know if I would have been as receptive to the concept.” As for the aircraft his company produces, “If we can have an enhanced level of safety in our products, I think it’s worth pursuing. If it helps one person one time, it’s worth it.” When asked if his personal aircraft will get the AAIR system, Horn doesn’t hesitate. “Absolutely.”
Beginning March 1, 2008 the Fédération Aéronautique Internationale (FAI) and the National Aeronautic Association (NAA), the governing bodies of world and United States national aviation records, will begin to recognize aircraft efficiency as a new category of world aviation records. 
