David Learmount/LONDON

Fokker has warned airline operators of a potential fault in the engine thrust-reverser systems on its Fokker 70 and 100 regional jets. This may have been a factor in the fatal TAM Brazilian Fokker 100 crash at Sao Paulo (Flight International, 6-12 November, P6).

The Netherlands civil-aviation authority (RLD) and the US Federal Aviation Administration have issued airworthiness directives (ADs) requiring operators to adopt new checks and procedures - immediately in the case of the RLD, and within 48h to comply with the FAA order.

All 90 passengers and six crew died in the 31 October crash just after take-off from Sao Paulo for Rio de Janeiro. Flight-data recorder read-outs have shown that the right engine thrust-reverser deployed inadvertently, preventing the aircraft from climbing. It crashed into houses, killing at least eight people on the ground.

A Fokker study since the accident has shown that a thrust-reverser secondary lock may remain unlocked without any indication to the crew, because of lock-actuator-relay failure. There is, as yet, no evidence that this was the cause of the Sao Paulo event.

Until a system to warn of secondary-lock failure has been devised, Fokker has produced a set of procedures for ensuring that the lock is engaged at take-off. As the operation of autothrottle take-off mode is inhibited if any reverser locks are disengaged, the procedure involves a pre-take-off test in that mode.

Fokker has also banned take-offs if the autothrottle is unserviceable, unless the reversers are de-activated. The FAAADs have made Fokker's instructions mandatory .

Source: Flight International