New US Federal Aviation Administration rules on how passenger seats are to be certificated after 9 August will increase safety in the event of a fire, but force the suppliers to raise prices, say industry officials.

The rules, first being applied as special certification conditions for Boeing 737s, call for seat suppliers to ensure that the large, non-metallic (composite material) panels increasingly being used for seat backs and seat bottoms have the equivalent heat release and smoke emissions as that of similar-sized composite parts used elsewhere in the cabin.

"Large" panels are defined as those with exposed surface areas greater than 0.14m2 (1.5ft2).

Under legacy certification rules, seats, being made predominantly of metal frames and fabric covering, were not considered to be safety hazards during a post-crash fire and therefore no maximum levels were set for heat release (how much heat a component generates when it burns) and smoke emissions during a cabin fire.

Regulators, concerned over an increased use of non-traditional seat materials with no accompanying fire safety rules, first proposed the special conditions as part of Boeing's application for certification of a new 737-700 interior in 2005, later broadening the applicability to all 737s proposing the new seats, both for retrofit or forward-fit applications.

The FAA says it is developing "model-specific" special conditions "for all transport category aircraft operating under Part 121 regulations" as well. "We will continue to issue special conditions regarding this subject until Part 25 [airworthiness standards for transport category aircraft] is amended through the rulemaking process," the agency says.

Seat manufacturers such as Weber Aircraft and B/E Aerospace are increasingly using composites in seats as a way to decrease weight while maintaining the rigidity needed to pass the FAA's rigorous strength requirements.

While large composite panels used elsewhere in the cabin, for instance in overhead luggage bins, meet today's smoke emissions and heat release rules, suppliers say the seat composites, out of necessity, use different materials and do not currently meet those rules.

Seat manufacturers have begun using the composites to decrease seat weight while providing increased strength ahead of a 2009 FAA mandate that seats in new build aircraft be able to withstand 16g crash forces.

Substitute materials, they say, will have to be developed and certificated, a process officials at Weber say represents "extra costs and burden."

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Source: Flight International