Air Transat Flameout Probe Winding Down
By Frances Fiorino/Aviation Week & Space Technology
20-Jun-2002 10:00 AM U.S. EDT
Air Transat Flight 236 investigators--who have collected all data on the A330-200's over-ocean double-engine flameout and reviewed reports from operations, cabin safety and technical groups--are set to begin drafting the final report, which is expected to be released by year-end.
A June 7 progress review indicates the team, led by the GPIAA Portuguese Accident Investigation Authority, has no current plans to add safety recommendations to the long list of actions taken after the Aug. 24, 2001, incident. The measures, detailed in the review, end with an unheralded Mar. 20 French DGAC recommendation on fuel-leak-detection procedures.
As a result of those actions, "There are no safety deficiency areas requiring immediate action," Frederico J. F. Serra, investigator-in-charge, concluded.
The GPIAA--along with representatives from the Transportation Safety Board of Canada (TSB), the U.K.'s Air Accidents Investigation Branch (AAIB), France's BEA, Montreal-based Air Transat, Airbus and Rolls-Royce--has begun analyzing the group reports to determine what factors combined to cause the extraordinary event with an improbable happy ending.
According to investigators, the Air Transat Flight 236 developed a "significant" fuel leak while en route from Toronto to Lisbon. Noting a lower than expected amount of remaining fuel, the flight crew opted to divert to Lajes Airport, Terceira Island in the Azores. About 135 mi. from Lajes, the A330-200's right Rolls-Royce Trent 772-211B engine flamed out. When Flight 236 was at 34,500-ft. altitude and 70 naut. mi. from Lajes, the left engine quit (AW&ST Sept. 3, 2001, pp. 34 and 36).
Capt. Robert Pichet guided the aircraft, with 13 crewmembers and 293 passengers, to a safe landing on Lajes' 10,865-ft. Runway 33. The A330's fuel tanks--which have a maximum capacity of 36,750 U.S. gal.--were empty. Sixteen passengers and two cabin-crewmembers sustained injuries, and the aircraft's fuselage and main landing gear were damaged.
Investigators soon determined that a low-pressure fuel line on the right engine failed as a result of contact with an adjacent hydraulic line, and the engine flame-outs resulted from fuel starvation.
The June 7 investigation progress report details various safety actions that were initiated after the incident, including the Mar. 20 DGAC Recommendation Bulletin that applies to all models of A330/A340 aircraft.
The bulletin emphasizes existing published Airbus operational procedures related to fuel-leak detection. For example, it recommends that fuel checks be performed when overflying waypoints or every 30 min. during cruise. That check would include verification that the amount of fuel on board and fuel consumed is consistent with the fuel quantity at departure.
The bulletin also recommends the fuel-imbalance procedure takes into account that the triggering of the "fuel imbalance" ECAM (electronic centralized aircraft monitor screen) advisory message might be the result of a fuel leak.
Referring to the fuel-leak-abnormal procedure in the A330/A340 flight manual, the bulletin underscores the importance of keeping the fuel crossfeed valve closed to prevent a leak from affecting both sides, when a leak is either not located or is not from an engine. The bulletin also recommends adding another step to the fuel imbalance procedure: either "T TANK MODE FWD" (if the trim tank is not empty), which would initiate a manual transfer of trim tank fuel, or "CTR TK XFR MAN" (if the center tank is not empty).
When fuel is automatically transferred from the tail trim tank or center tank, it goes into the lower (i.e. leaking) of the wing tanks and tends to mask a fuel imbalance. Switching the fuel transfer to manual makes the crew more aware of what the system is doing.
Previous safety actions include:
* On Aug. 24, 2001, Transport Canada initiated a Special Purpose Audit of Air Transat's maintenance and operations. The carrier conducted a review and a corrective action plan was approved, implemented and completed.
* On Aug. 29, Airbus issued an All Operators Telex (AOT) A330-73A3033 requiring a one-time visual inspection to detect any interference between fuel and hydraulic lines on A330s equipped with Rolls-Royce Trent 700-series engines.
* On Aug. 31, the U.K. Civil Aviation Authority issued AD 005-08-2001 mandating inspections of clearances between fuel and hydraulic lines recommended in Rolls-Royce's Aug. 29, 2001, Non-Modification Service Bulletin 73-D-578.
* On Sept. 7, Transport Canada issued Commercial and Business Aviation Advisory Circular 190, which recommends measures to identify fuel leaks in flight.
* On the same date, Transport Canada reinstated Air Transat's ETOPS authority for its A330s to 90 min., and on May 17, 2002, to 120 min. for all aircraft in its fleet. The carrier's A330 ETOPS authority had been suspended immediately after the incident and limited to 90 min. for other aircraft in the fleet.