US PASSENGER airlines will be required to retrofit their fleets with enhanced flight-data recorders (EFDRs) within about four years under a US Federal Aviation Administration proposal.

The US National Transportation Safety Board (NTSB), meanwhile, continues to criticise the FAA for acting too slowly. Its most recent concern is about the case of an Eastwind Airlines Boeing 737-200 which, in June, suffered yaw problems similar to those suspected in the unsolved 1994 USAir crash at Pittsburgh and the 1991 United Airlines accident at Colorado Springs.

Although they noted similarities, however, NTSB investigators have again been frustrated by the lack of precise data from the Eastwind aircraft's 11-parameter FDR.

The Eastwind 737 suddenly rolled sharply. The crew was able to regain control of the aircraft, but it was the fourth time that the aircraft had suffered yaw problems since 14 May. Most of the critical rudder and yaw-damper system components have been replaced, with the exception of the standby rudder-actuator.

Under the FAA's notice of proposed rulemaking, the minimum number of FDR parameters would be increased from 11 to a minimum of 17, or 18 on the oldest aircraft. The minimum for new-build aircraft, however, will be 88 parameters. Retrofit of the 4,325 affected aircraft would have to be completed within four years of publication of the final rule, expected before the end of 1996.

NTSB chairman Jim Hall says that he is "disappointed" with the FAA's proposed EFDR fitment schedule. The Board had proposed that all commercial transports receive enhanced FDRs by 1997. Furthermore, it originally urged that more than 1,000 early-model 737s be outfitted with new FDRs by 31 December, 1995.

The FAA has separated aircraft into four categories:

Category 1: nearly 2,000 aircraft with more than 30 seats (including early model 727s/737s, Lockheed L-1011s, McDonnell Douglas (MDC) DC-8/DC-9s and Fokker F28s) with 11-parameter FDRs must be upgraded to 17/18-parameter units within four years;

Category 2: about 1,400 turbofans and turboprops, including 737s/747s, Airbus A320s, MDC DC-10s, AI(R) ATR 42s, Embraer EMB-120s, now with 17-parameter FDRs, will receive 22-parameter units;

Category 3: more than 1,000 aircraft, including Boeing 757s/767s/777s, Fokker 100s, MDC MD-11s and AI(R) ATR 72s, with up to 29-parameter FDRs, will get 34-parameter data recorders;

Category 4: airliners certificated in the future, including derivatives of existing aircraft, must have 57 parameters within four years and 88 parameters thereafter.

Source: Flight International