WASHINGTON -- The National Transportation Safety Board, based on an investigation into the May 26 explosion of a Lauda Airlines jet-iv Thailand, called on the Federal Aviation Administration to immediately review the safety of certain Boeing 767 aircraft.
The agency said Wednesday that although the investigation into the Lauda disaster was incomplete, investigators determined the jumbo jet's left engine thrust reverser engaged during flight and the crew may not have fully realized the potential danger.
Thrust reversers are deployed on landing to slow a jet once it lands. Although a jet may be able to fly with a reverser deployed, it can cause potentially dangerous aerodynamic conditions.
The Lauda Boeing 767-300ER was at 24,700 feet and northwest of Bangkok when the jet blew apart abd crashed en route to Vienna. All 213 passengers and 10 crewmembers died in the accident.
Thai officials are conducting the investigation into the cause of the disaster with the assistance of the U.S. National Transportation Safety Board and other authorities.
In a letter to FAA Administrator James B. Busey, NTSB Chairman James B. Kolstad said, 'The circumstances that led to the in-flight reverser deployment and the influence that this event had on the ability of the cockpit crew to maintain control of the airplane are not clearly understood at this time.
'However, the investigation has raised several issues which the safety board believes warrant immediate precautionary measures,' the letter said.
The NTSB is asking the FAA to review its certification of Boeing 767 aircraft equipped with Pratt and Whitney PW4000 series engines, specifically to examine the mechanical and electrical systems that control the jet engine thrust reversers.
The agency also wants the cockpit crew's reference material amended to warn that in-flight reverser deployment 'may result in severe airframe buffeting, yawing and rolling forces.'
In addition, the NTSB asks the FAA to establish specific procedures for crews to follow when a warning light goes on indicating potential failure of the thrust reverser deployment during a flight.
'The safety board is also concerned that Boeing 767 flight crew emergency procedures may not provide appropriate and timely guidance to avoid loss of flight path control in the event that the reversers deploy in flight,' Kolstad said.
Emergency procedures should include immediate cutting off of fuel and hyrdraulic and electrical power should a thrust reverser deploy during flight, the NTSB letter said.
The agency also urges the FAA to review other aircraft equipped with similar kinds of thrust reverser systems to determine if additional safety measures and training are required for aircraft besides the Boeing 767.
During the Lauda Air investigation, Boeing officials provided data demonstrating the 767 can fly with a thrust reverser deployed. However, the NTSB said such testing has not been done at higher speeds.