AIR TRANSAT ACCIDENT - 24 AUG 2001

Brief Details of the Accident

Flight TS 236 took off from Toronto at 0:52 UTC on Friday August 24, 2001 bound for Lisbon. There were 293 passengers and thirteen crew members on board. The aircraft was an Airbus A 330 registered as C-GITS that was manufactured in March 1999, configured with 362 seats and placed in service by Air Transat in April 1999. Leaving the gate in Toronto, the aircraft had 46.9 tonnes of fuel on board, 4.5 tonnes more than required by regulations.

At 05:36 UTC, the pilots received a warning of fuel imbalance. Not knowing at this point that they had a fuel leak, they followed a standard procedure to remedy the imbalance by transferring fuel from the port to the near-empty starboard tank.At 05:16 UTC, a cockpit warning system chimed and warned of low oil temperature and high oil pressure on engine no. 2. There is no obvious connection between an oil temperature or pressure problem and a fuel leak. Consequently Captain Piché and co-pilot DeJager suspected these were false warnings and shared their observations with their maintenance control centre, who advised them to monitor the situation.

Unknown to the pilots, the aircraft had developed a fuel leak in a fuel line to its starboard engine. The fuel transfer caused fuel from the operational side of the aircraft to be wasted through the leak in the engine on the other side. The leak, which averaged at 1 gallon per second, caused a higher than normal fuel flow through the fuel-oil heat exchanger (FOHE). The FOHE is designed to transfer heat from engine oil to fuel for both cooling and efficiency purposes. The increased fuel flow caused both the drop in oil temperature, as well as the rise in oil pressure that the pilots had observed earlier.

At 05:45 UTC, the pilots decided to divert to Lajes air base in the Azores. The crew were still unsure if they really had a fuel leak or not. They declared a fuel emergency with Santa Maria Oceanic air traffic control three minutes later.

At 06:13 UTC, while still 135 miles (217 km) from Lajes, engine no. 2 on the right wing flamed out because of fuel starvation. Captain Piché ordered full thrust from the remaining operational engine, and the plane descended to 33,000 feet (10,000 m), unable to stay at its 39,000 feet (12,000 m) cruising altitude with only one engine operating. Ten minutes later, the crew sent a Mayday to Santa Maria Oceanic air traffic control.

Thirteen minutes later, engine no. 1 also flamed out at while the aircraft was still approximately 65 nautical miles (120 km) from Lajes Air Base. Without engine power, the aircraft not only lost all thrust, but also its primary source of electrical power. The emergency Ram Air Turbine was deployed automatically to provide essential power for critical sensors and instruments to fly the aircraft. However the aircraft lost its main hydraulic power which operates the flaps, brakes, and spoilers.

Military air traffic controllers who were tracking the aircraft on their radar system guided the aircraft to the airport. While Piché flew the plane, DeJager monitored its descent rate – around 2000 feet (600 metres) per minute – and calculated that the plane had about 15 to 20 minutes left before they had to ditch the plane in the water. The crew sighted the air base a few minutes later. Piché had to execute a series of 360 degree turns to lose speed and altitude. Although they successfully lined up with Runway 33, they faced a new danger. The plane was on a final descent, going faster than optimal. Although they had unlocked the slats and deployed the landing gear, the airspeed was still too high. Additionally, the aircraft would be unable to use its thrust reversers to slow the plane during the landing.

At 06:45 UTC, the plane touched down hard 1,030 feet (310 m) down Runway 33 at a speed of approximately 200 knots (370 km/h), instead of the 170 knots (310 km/h) recommended for an unpowered landing. The aircraft bounced back into the air, but touched down again 2,800 feet (850 m) from the approach end of the runway and came to a stop 7,600 feet (2,300 m) from the approach end of the 10,000 feet (3,000 m) runway. With the operation of the emergency brakes, eight tires burst. Fourteen passengers and two crew members suffered minor injuries during the evacuation of the aircraft. Two passengers suffered serious but not life-threatening injuries.

The favourable outcome was partly attributable to the flight being rerouted at the last minute via a more southerly route across the Atlantic than initially planned, which brought the aircraft within range of the Azores.

Investigations

The Portuguese GPIAA investigated the incident along with Canadian and French authorities.

The investigation revealed that the cause of the incident was a fuel leak in the number two engine, caused by an incorrect part installed in the hydraulic system by Air Transat maintenance staff. Air Transat maintenance staff had replaced the engine as part of routine maintenance, using a spare engine, lent by Rolls-Royce, from an older model. This engine did not include a hydraulic pump. Despite the lead mechanic's concerns, Air Transat ordered the use of a part from a similar engine, an adaptation that did not maintain adequate clearance between the hydraulic lines and the fuel line. This lack of clearance — on the order of millimeters from the intended part — allowed vibration in the hydraulic lines to degrade the fuel line and cause the leak. Air Transat accepted responsibility for the incident.

Although pilot error was listed as one of the lead causes for the incident, it was the skill of the pilots, and of the military Air Traffic Controller in service at the time, 1st Sgt. José Ramos, that allowed the flight to land without fuel, causing only minor injuries to the passengers and minor damage to the airplane, which is still in service. The pilots returned to a heroes' welcome from the Quebec press.

The incident also led to the issue of Airworthiness instructions to all operators of certain types of the Airbus aircraft that stressed that crews should check that any fuel imbalance is not caused by a fuel leak before opening the cross-feed valve. The French Airworthiness Directive (AD) required all airlines operating these Airbus models to make revisions to the Flight Manual before any further flights were allowed. The FAA gave a 15-day grace period before enforcing the AD. Airbus also modified its computer systems; the on-board computer now checks all fuel levels against the flight plan. It now gives a clear warning if more fuel is being lost than the engines can consume. Rolls Royce also issued a bulletin advising of the incompatibility of the affected engine parts.