The controversy over the FAA's 16G seat-certification rule continues to rumble on. It was introduced in FAR 25.562 Amendment 25-64 as long ago as 1988 and adopted in March 1992 under technical standard order (TSO) C127 for all new commercial aircraft.
The major bone of contention is the head-injury criterion (HIC) standard which seat manufacturers say is the most difficult with which to comply. The HIC value is computed using a formula, which takes account of impact, acceleration of the head and duration of the event. It is complicated by a requirement to test each seat position in relation to surrounding structures, to arrive at the complete "head-strike envelope". Manufacturers contend that it is extremely difficult, if not impossible, to meet the standard, especially where seats face a bulkhead, or where side-facing bench seats are involved. Airlines also take issue with the FAA's cost/benefit assessment, which they say, grossly overstates the benefits.
The FAA, bowing to pressure from the industry, is permitting manufacturers to equip aircraft with shoulder harnesses instead of having to comply with stringent injury standards. It also allows some flexibility in how rules are applied retroactively, from an earlier insistence that the seat-certification standards would have to be applied to FAR Part 25 aircraft undergoing major maintenance.
The FAA is not, however, wavering from its determination to ensure that air passengers receive the same safety considerations as those enjoyed by motorists and it plans to tighten the rules further. Within five years it is expected that seats in all aircraft will have to comply with TSO C127 requirements.
Also on the horizon - and strongly opposed by the General Aviation Manufacturers Association and the Regional Airlines Association - are the more stringent standards being considered by the FAA for commuter aircraft with less than 20 seats. These would require horizontal and vertical accelerations, of 26G and 32G respectively, as against 14G and 16G for other aircraft.
TSO C127 requires two dynamic tests using anthropomorphic test dummies, measuring a specific maximum G and velocity change. One is performed with the seat in a 60o nose up position, the second with a 10o horizontal misalignment of the seat track. Additionally, certain stipulated limits have to be met, for upper torso, pelvis, femoral and lumbar loads.
Source: Flight International
