Almost 12 years ago, Congress mandated that the Federal Aviation Authority (FAA) consider new regulations to make seats tougher so they would be more likely to protect passengers in a crash landing.
After years of hearings and studies, it appears the agency is at long last getting close to a final rule that would require airlines to retrofit the vast majority of their seats within the next four years.
On Tuesday, the FAA will hold a public meeting to hash out the issue with seat manufacturers, airlines, and plane manufacturers. The public will have 30 days to comment before the rule is finalized.
The seat issue is a hot one for the FAA. The new seats may be heavier, requiring the planes to use more fuel. And, as planes get new seats, they will be taken out of service for at least a half day. Boeing estimates the vast majority of the 12,000 planes around the world will be affected. And the FAA estimates it will cost airlines in the United States almost $1 billion.
The returns for the safer seats are hard to quantify. The FAA estimates better seats will prevent 210 to 410 fatalities and 220 to 240 serious injuries over a 20 year period. Translating that into a cost benefit, the FAA says it would range from $680 million to $1.2 billion.
But the seat manufacturers maintain it's an important safety issue. "When you have occupants and pieces of the seats loose in the aircraft, it's dangerous - for example, they can block an [exit]," says Stan Desjardins, president of Simula Safety Systems Inc., a seat manufacturer in Tempe, Ariz.
In the past, seats had to hold together at nine times a person's body weight and were called 9G seats. But FAA studies found that in a "survivable" crash the loads were much higher than expected, especially on the track, the metal strip that holds the seats to the floor.
For example, in 1989 a British Midlands flight on its way to Belfast, Northern Ireland, from London's Heathrow Airport crashed in a field as it tried to make an emergency landing. After the incident, which killed 47 passengers and seriously injured 66, investigators examined the seats on the Boeing 737-400.
In one section, investigators found that only 40 percent of the wide-body plane's seats had remained fully attached to the floor. The seats in the plane were 16G seats, but Boeing estimates the passengers were under 22Gs to 28Gs during the crash. In a filing with the FAA, Boeing concluded, "All passenger seats remained attached to seat tracks where [the] floor stayed intact."
That crash and other data prompted the FAA to reconsider its seat criteria. Beginning in 1986, static tests using weights attached to a dummy in the seat were replaced with simulations in which the seat actually moves. A crash dummy is accelerated into a brick wall at a speed with the impact of 16Gs.
In the proposed new rule, the FAA wants to measure data on head impact (most who died in the British accident had fatal head injuries), knee impact, and whether the seat stays in the track.
Keeping seats in their tracks
In a survivable crash, it's critical that the seat operate correctly. According to a review of accidents between 1970 and 1983 by Civil Aeromedical Institute (part of the FAA), there were serious or fatal injuries 90 percent of the time when a seat was released from its track. The fatality rate dropped to below 25 percent when the seat stayed in its track but was damaged. If the seat was undamaged, the fatality rate was about 5 percent.
Over the years, seat manufacturers have improved seat design. For example, Simula's seats now absorb some of the energy before putting pressure on the floor attachment.
Other companies use metal that intentionally deforms or stretches. "It turns out you need some energy-absorbing quality to stay attached to the floor structure," says Mr. Desjardins.
Airbags and over-the-shoulder belts
The FAA also may require bulkhead seats (those facing a partition) to have more protection, such as airbags or improved, over-the-shoulder seatbelts.
The Air Transport Association, which represents the airlines, would not comment for this story but reportedly opposes the new rule.
Boeing, which has already submitted a document to the FAA, is not opposed to the change but wants to have its current 16G seats grandfathered in as acceptable. It also questions whether the seat manufacturers could meet the FAA's timetable. And it worries that stronger seats may require a redesign of the floor, which is designed for 9Gs.