Transport Canada (TC) fined Montreal-based Air Transat, the country’s largest charter airline, C$250,000 ($160,500) for improper maintenance on the Airbus A330-200 that glided to a safe landing in the Azores during a nighttime transatlantic crossing on August 24.

Preliminary reports by the Portuguese air safety board (GPIAA) point to total fuel starvation due, perhaps in part, to a leak on the number-two engine’s low-pressure fuel line. The line was apparently left too close to an adjacent hydraulic line as compliance with a Rolls-Royce Service Bulletin, SB29-C625, remained incomplete. Nine passengers and two cabin crewmembers suffered minor injuries, but the remaining 282 people on board were uninjured.

Some five hours into the flight, at 0536Z, the crew became aware of a fuel imbalance while in cruise flight at FL 390. About five minutes later the crew chose to divert to Lajes Field (LPLA), 850 mi west of their Lisbon destination, because of unexpectedly low fuel-quantity indications.

At 0548, a leak became the suspect for the deteriorating fuel supply, and the crew declared an emergency. The right engine failed at 0613 about 135 mi short of the alternate destination. Around 0626, the left engine failed and the crew advised ATC of the possibility of ditching. From FL 345, the crew began a dead-stick landing, in a fly-by-wire airliner, in night VMC.

While they blame maintenance for the cause of the close call, GPIAA investigators are looking into the possibility that the crew mishandled the fuel systems, thereby exacerbating the leak. Specifically, investigators are trying to discern whether the crew transferred fuel from the left side to the leaking right engine.

Air Transat’s A330-200 has six tanks: left and right inner wing tanks with 11,095 gal capacity each; outer wing tanks that can hold 964 gal each; a center tank with 10,979 gal capacity; and a 1,646-gal tail trim tank. The aircraft’s total capacity was 36,743 gal (246,178 lb), 60 percent of which is in the inner tanks.

Under normal conditions the fuel system operates automatically; fuel is moved from tank to tank for balance in both the longitudinal and lateral axes. Sensors trigger the fuel imbalance warning when it reaches a 6,600-lb differential. Large fuel imbalances must be transferred manually and the procedure is specified in the quick-reference handbook (QRH).

At the beginning of the balancing checklist is a notation that the crossfeed valve should remain closed if a fuel leak is suspected. Airbus divides the fuel leak checklist in the QRH into two possible scenarios: fuel leak from the engine or fuel leak from elsewhere. If the former is suspected, the recourse is to shut down the engine with the leak–an unwelcome prospect while flying at night over the ocean.

If the crew is unsure of the location of the leak, the QRH says to close the crossfeed valve, descend to between 15,000 ft and 20,000 ft, where the engines can feed by suction without vapor lock, turn on the affected engine’s ignition and shut off the boost pump. If the engine doesn’t quit, the leak is in the tank, if it does quit it means it is drawing air through a leak and the leak is from the engine side. The QRH checklist also notes that pilots can land the aircraft with one tank full and the other empty.

An Air Transat official said the crew did not know where the leak was until they were on the ground. The first officer stated the captain was controlling the airplane and that they were working through the checklists. According to GPIAA reports, the flight time from the point the crew noticed the imbalance to the second flameout was about 50 min. The aircraft was tankering extra fuel.

TC levied Air Transat’s maintenance fines for its failure to complete a required Service Bulletin and for installing mismatched parts on the incident airplane. Compliance with the Rolls-Royce SB provides adequate clearance between the hydraulic and fuel lines, according to an all-operators’ telex (AOT) issued by Airbus on August 29. Air Transat admitted the mismatching of parts when Toronto’s The Globe and Mail reported a mechanic alleged a supervisor overruled his warnings that the aircraft was unfit to fly. According to reports, the mechanics were attempting to complete the SB but could not because the parts required were not in stock. Allegedly, the supervisor told the tech to complete the installation using the procedures from a different model. Air Transat officials were forced to admit to “human error” in mismatching the parts, and the airline is currently under intense scrutiny by the Transportation Safety Board of Canada.

TC also limited the carrier’s ETOPS authority to 60 min in the A330 and 90 min in the A310 and Boeing 757. The agency also required crews to receive additional training and said it will audit the carrier. Upon compliance with TC’s standards and completion of self-initiated review, Air Transat will likely return to full ETOPS authority.