Air Transat Flight 236

Air Transat Flight 236 was a transatlantic flight bound for Lisbon, Portugal, from Toronto, Canada, that lost all engine power while flying over the Atlantic Ocean in the dark on August 24, 2001. The Airbus A330 ran out of fuel because of a fuel leak caused by improper maintenance. Captain Robert Piché, 48, and First Officer Dirk DeJager, 28, glided the plane to a successful emergency landing in the Azores, saving the lives of all 306 people (293 passengers and 13 crew) on board. This was also the longest passenger aircraft glide without engines, gliding for nearly 65 nmi. Following this unusual aviation accident, this aircraft was nicknamed the "Azores Glider".

Accident

Flight 236 took off from Toronto at 00:52 (UTC) on Friday, August 24, 2001 (local time: 20:52 (ET) on Thursday, August 23), bound for Lisbon, Portugal, with 293 passengers and 13 crew on board. The flight was flown by Captain Robert Piché, who had 16,800 hours of flight experience (with 796 of them on the Airbus A330), and First Officer Dirk DeJager, who had 4,800 flight hours (including 386 hours on the Airbus A330).

The aircraft was a two-year-old Airbus A330-243 registered as C-GITS that had first flown on March 17, 1999, configured with 362 seats and placed in service by Air Transat on April 28, 1999.

It was powered by two Rolls-Royce Trent 772B-60 engines each capable of delivering 71100 lbf thrust. Leaving the gate in Toronto, the aircraft had 46.9 t of fuel on board, 4.5 t more than required by regulations.

At 04:38 UTC (almost four hours into the flight), the aircraft began to leak fuel through a fracture that had developed in a fuel line to the no. 2 (right) engine downstream of the fuel/oil heat exchanger. At 05:03 UTC, more than four hours into the flight, the pilots noticed low oil temperature and high oil pressure on engine no. 2.

Although these readings were an indirect result of the fuel leak, the pilots had no reason to consider that as a cause. Consequently, Captain Piché suspected they were false warnings and shared that opinion with Air Transat maintenance control centre in Montreal, which advised them to monitor the situation.

There were other potential indications of fuel problems:

The fuel on board was decreasing at an unusual rate which was displayed in the Fuel-On-Board (FOB) quantity on the Engine Warning Display.

The estimated fuel on board at destination would have been showing as decreasing indicating reduced fuel range.

The full forward transfer of the fuel in the trim tank was premature given the fuel load on departure from Toronto of 46900 kg. A prolonged, 19-minute TRIM TANK XFR memo between 05:11 and 05:30, and then the TRIM TANK XFRD memo between 05:30 and 05:33 would have displayed this information.

At 05:36 UTC, the pilots received a warning of fuel imbalance.

Rather than referring to the appropriate checklists, the crew performed procedures from memory, and this resulted in the cross-feeding of fuel into an already leaking engine.

The transferred fuel was lost through the fractured fuel line, which was leaking at about 13 tonnes per hour (more than 3.6 kg/s). This caused a higher-than-normal fuel flow through the fuel-oil heat exchanger, which in turn led to a drop in oil temperature and a rise in oil pressure for the no. 2 engine.

At 05:45 UTC, the pilots decided to divert to Lajes Air Base in the Azores. Initially there was a 14-degree heading deviation from their assigned heading of 230 degrees magnetic caused by the autopilot being in true heading mode. After 2 minutes Santa Maria Oceanic air traffic control radioed "Transat 236 heavy maintain 230 magnetic heading". This transmission was not acknowledged, but the aircraft turned to the correct heading. They declared a fuel emergency with Santa Maria Oceanic air traffic control three minutes after the heading was corrected.

At 06:13 UTC, while still 150 nmi from Lajes and at 39000 ft, engine no. 2 flamed out from fuel starvation. Piché then initiated a descent to 33000 ft, which was the proper single-engine altitude for the weight of the plane at that time. Ten minutes later, the crew sent a mayday to Santa Maria Oceanic air traffic control.

Thirteen minutes later, at 06:26 UTC and about 65 nmi from Lajes Air Base, engine no. 1 also flamed out, requiring the plane to glide the remaining distance. Without engine power, the plane lost its primary source of electrical power. The emergency ram air turbine deployed automatically to provide essential power for critical sensors and flight instruments to fly the aircraft as well as enough hydraulic pressure to operate the primary flight controls (without which the aircraft would be uncontrollable).

The aircraft lost hydraulic power for the flaps, alternate brakes, and spoilers. The slats would still be powered, while the primary brakes would be able to operate a limited number of times using pressure stored in the brake accumulator. With neither engine running, there was no source of bleed air to maintain cabin pressurization. Five minutes later, at 06:31 UTC, the oxygen masks dropped down in the passenger cabin.

Military air traffic controllers guided the aircraft to the airport with their radar system. The descent rate of the plane was about 2000 ft/min. They calculated they had about 15 to 20 minutes left before they would be forced to ditch in the ocean. The air base was sighted a few minutes later. Piché executed one 360° turn, and then a series of "S" turns, to dissipate excess altitude.

At 06:45 UTC, the plane touched down hard, around 1030 ft past the threshold of runway 33, at a speed around 200 kn, bounced once, and then touched down again, roughly 2800 ft from the threshold. Maximum emergency braking was applied and retained, and the plane came to a stop after a landing run that consumed 7600 ft of the 10000 ft runway.

Because the antiskid and brake modulation systems were inoperative, the eight main wheels locked up, the tires abraded and fully deflated within 450 ft, and the wheels themselves were worn down to the axle journals during rollout.

Fourteen passengers and two crew members had minor injuries, while two passengers had serious injuries during the evacuation of the aircraft. The plane suffered structural damage to the main landing gear (from the hard touchdown and the abrasion of the locked wheels against the runway surface during the landing roll) and the lower fuselage (both structural deformation from the hard touchdown and various punctures from impact by pieces of debris shed from the main landing gear).