US AIRLINES will be ordered to undertake major upgrades of flight-data recorders (FDRs) on more than 4,000 aircraft by the end of 1997 if the Federal Aviation Administration mandates a new recommendation from the National Transportation Safety Board (NTSB).

Upgrades on 739 of the US-registered Boeing 737s will have to be completed by December, with a further 3,588 aircraft in the US airline fleet having to be worked on by January 1998.

The NTSB says that present FDRs are "inadequate", and wants the minimum number of recorded data channels increased from six to cover 24 specific parameters. New-built aircraft would also have to meet improved FDR criteria, which the NTSB says will vary according to the aircraft type and number of engines, but would cover "over 100 parameters".

Boeing 737s receive special treatment in the document because the NTSB blames FDR inadequacy for the mystery still surrounding the 1991 United Airlines 737-200 catastrophe at Colorado Springs, and the difficulty in finding a solution to the similar 1994 USAir 737-300 Pittsburgh crash.

Modern FDRs, points out the NTSB, are useable not just for crash investigation, but for fleet health and incident monitoring, suggesting that data on 737 fleet in-service control behaviour might provide clues, which will help the Colorado Springs and Pittsburgh investigators.

The NTSB notes that 187 Boeing 737 flight-control incidents have been recorded between 1970 and 1994, 35 of them happening between 1990 and 1994.

As a result, the NTSB recommends that 737s with old FDRs should, by the end of this year, have the following parameters added to their existing recorder capability: lateral acceleration; and flight-control inputs and control-surface-position inputs for pitch, roll and yaw.

By 1 January, 1998, the NTSB recommendation says, Boeing 727s, Lockheed TriStars and all airliner types still in production should be fitted with FDRs with the capability of recording at least 24 specified parameters, which include the basic performance, control, aircraft attitude and engine parameters, plus other considerations such as autopilot engagement status, thrust-reverser position and angle of attack.

The FAA says that it "...fully supports the desire" to provide data, which would help reveal accident causes.

Source: Flight International