The US Federal Aviation Administration is proposing to simplify the process that private aircraft owners can choose to follow to certificate the interiors of their transport category aircraft. Changes include an easing of rules for material flammability compliance and handholds throughout the interior, but an increasing of standards for fire detection, minimum aisle width, cook top design and side-facing seat testing.

The modifications, requested by the "aviation industry," come as the number of large transport category aircraft operated in non-air carrier operations has "increased substantially," says the FAA, and the costs of certificating customised interiors for such vehicles have become "significant". Further, owners are not able to amortise the expenses over a large number of aircraft as do airlines.

"Aviation industry representatives have stated that the Part 25 standards are written with only air carrier operations in mind, and have questioned whether the one level of airworthiness requirement for transport category airplanes is, in fact, appropriate for all types of operations," says the FAA.

The new safety-related rules, if implemented, will reduce the time and cost necessary to certificate cabin interiors while preserving an "acceptable level of safety" during operations, although not the same level of safety "as that afforded occupants of transport category airplanes operated by air carriers", says the FAA.

Changes include easing a requirement for a "constant handhold" configuration throughout the cabin since customised areas, like bedrooms, may not have the feature. Previously, such designs were certificated with exemptions from the rules. Also exempted today are side-facing seat testing requirements, which would be made part of the certification rules under the proposal.

Minimum aisle width, which the FAA says in some cases today "can be reduced to zero" by seats that translate toward the centre of the aircraft, will be limited to a 22.86cm (9in) minimum under the proposed rules. In terms of heat release and smoke density requirements for interior materials, the new rules will require only that operators not choosing to demonstrate those characteristics verify that the aircraft can be evacuated in 45s. The rules will also require installing a fire extinguisher in any room "not designated suitable for occupancy" during taxi, take-off and landing, and areas, like bedrooms, that can be closed off from the rest of the cabin by a door.

The FAA points out that although the overall cost of certification should be lower, certain specific areas of the voluntary streamlined rules, which would apply to aircraft that carry 60 or fewer occupants, could cost more under the proposal, including the need for more fire extinguishers, modified stoves and an additional flight attendant in certain situations.

Source: Flight International