The full picture
What happened
The Airbus A330 was flying from Toronto to Lisbon. In the right power plant, a leak occurred: the tube installed after maintenance contacted the neighboring element, damaged and began to produce fuel.
The devices showed a growing imbalance. Following the logic of the imbalance control card, the crew opened the pumping, due to which the fuel from the service side also began to flow to the leak site. Later, one and then the second engine stopped.
The plane was closer to the Azores. After a complete loss of thrust, he planned for about 19 minutes to Lajes base. The crew paid off the extra height with maneuvers and made a hard landing. All 306 survived.
Context and mechanisms
Detailed account
Background, technical details and decisions are examined separately to avoid reducing a complex event to a single explanation.
Night line across the North Atlantic
Air Transat 236 flew from Toronto to Lisbon on an Airbus A330-243 C-GITS. There were 293 passengers and 13 crew on board. The route passed along the system of ocean tracks, where the nearest suitable airfield is at a considerable distance at certain periods. Therefore, the calculation of fuel, control of its consumption and an early decision to go to the spare are of particular importance.
A few days before the flight on the right engine Rolls-Royce Trent 700 performed a replacement. The installed temporary engine had a configuration that required a certain combination of fuel and hydraulic tubes. Due to the lack of detail and incomplete use of the service bulletin, incompatible pipelines with insufficient clearance turned out to be nearby.
During engine operation, the vibration caused the tubes to come into contact. The hydraulic line gradually scrubbed the fuel line until a crack about eight centimeters long formed. The leak did not begin as an instant rupture; it grew as it was damaged. This explains why the plane took off normally, and the critical loss has already manifested itself over the ocean.
The A330's automatic system masked the problem for a while. Fuel from the stabilizer tank moved forward, maintaining balance and replenishing the main tanks. About 3,500 kilograms were lost before the crew saw the obvious pattern. Automation did what it was designed to do, but at the same time hid the independent failure.
When the correct procedure enhances the malfunction
The first signs looked like a discrepancy between the calculated and actual amount of fuel, then as an imbalance between the wings. The crew considered the indication error because engine consumption and some other parameters did not fit into the familiar scenario. The system did not form a separate unambiguous warning “major leak on the right”.
A check card of the imbalance prescribed to open crossfeed and use fuel from a fuller tank to power the opposite engine. In the usual uneven development, this restores the balance. But in this case, the right engine received fuel through the damaged line, so pumping connected the serviceable left reserve with the leak site and increased the overall loss rate.
The crew contacted the technical center of the airline and tried to check the wing from the cabin. The night, the design of the aircraft and the absence of a visible trace did not allow to confirm the leak. This is a good example of the limitations of human diagnosis: pilots saw truthful but incomplete data, and each new symptom could be explained by several different failures.
The decision to turn to the base Lajes in the Azores was made before the engines stopped completely. It has become a major spatial barrier. Even if the diagnosis remained controversial, the plane was already reducing the distance to a suitable long strip. In emergency management, it is not always necessary to call the failure completely first; sometimes it is more important to create a safe option while the situation still allows it to be achieved.
Sixty-five nautical miles to the strip
The right engine stopped first after the fuel level fell. The flight continued on the left, but the remaining stock also left through an open scheme and was soon exhausted. At 06:26 UTC, the left engine stopped about 65 nautical miles from Lajes. The passenger A330 became a glider weighing hundreds of tons.
After the engines stopped, the main generators ceased to supply the network, and conventional hydraulic pumps lost their drive. The RAT emergency turbine automatically exited the stream. It does not create traction and does not power all systems, but supports critical electrical and hydraulic functions, allowing you to move the main controls and read the necessary devices.
The crew withstood the speed of the best planning, changing the height by a distance. On average, the A330 declined, maintaining sufficient speed to the island. The aircraft reached the area of the airfield above the required profile - the preferred position in the absence of engines, because the missing height is no longer possible to obtain, and the excess can be extinguished by turns, the release of mechanization and chassis.
The aircraft approached the base about 13,000 feet eight miles from the strip. The commander performed a full left turn and S-shaped maneuvers, then released slats and chassis. The threshold of lane 33 was crossed at about 200 knots. The first touch happened hard, the plane jumped and touched again further along the strip.
Maintenance as part of the flight
Maximum braking and lack of normal reverse thrust caused damage to tires and main racks, but the aircraft stopped within ten thousand feet of the strip. During the evacuation, several people were slightly injured; there were no fatalities. The duration of planning was about nineteen minutes and became one of the most famous examples of the flight of a wide-body liner without traction.
The investigation traced the failure back to the decision when replacing the engine. The technical staff knew about the service bulletin and the different configurations, but did not receive the document from the computer system and continued to work on the basis of partial understanding. The representative of the manufacturer was available for consultation, but he was not involved. A few small organizational compromises created physical tube contact.
After the incident, attention was focused on controlling the compatibility of parts, mandatory access to service documentation, checking gaps and independent inspection after complex work. For the crews, the fuel imbalance procedure was supplemented with the logic of checking the total number, planned flow rate, engine parameters and the possibility of leakage before the crossfeed opens.
A separate lesson is associated with the alarm. The system should not only show the level in each tank, but also help to notice the abnormal rate of disappearance of common fuel. Automatic comparison of the calculated balance with the measured one can give a warning before the imbalance becomes obvious. In ocean flight, the winning twenty minutes can decide whether the plane will reach the airfield.
Sequence
Event timeline
Rather than isolated episodes, this was an unfolding system: each stage inherited the constraints of the one before it.
- 01
The first unusual testimony
The difference in the amount of fuel between the tanks began to grow. Other parameters — including temperature and flow — gave additional signs of leakage, but the picture did not correspond to the usual scenario.
- 02
Imbalance is taken as the main problem
The crew used the alignment procedure. The pumping connected the serviceable fuel supply to the side where the leak occurred.
- 03
Decision on a reserve airfield
The plane headed for Lajes. This created an achievable goal before the situation became a complete loss of traction.
- 04
The right engine stops.
After fuel production, the right engine stopped. The flight continued on a single engine, but the remaining fuel quickly decreased.
- 05
The second engine stops.
The A330 lost all traction. The emergency turbine provided basic hydraulic functions, and the crew moved the aircraft into optimal planning.
- 06
Landing in Lajes
The plane went to the airfield with an excess of altitude, made turns for its loss and sat down with increased speed. The brake damaged the tires and racks, but the cabin remained.
More than one cause
Chain of contributing factors
An incident develops when several weaknesses come together along the same path.
Incorrect installation
Part incompatibility and insufficient inspection after maintenance have created mechanical contact and fuel line wear.
Ambiguous signs
The system showed an imbalance, but did not give the crew one clear message of "leakage". We had to collect a diagnosis from several parameters.
The procedure strengthened the refusal
The control card involved a normal imbalance, not an active leak. Formally understandable action opened the way for fuel from a serviceable wing.
Energy Management
After the engines failed, the altitude became the only energy budget: it had to be exchanged for a range, then accurately spent in front of the band.
From the flight deck
Decisions and constraints
Decisions are assessed against the information, altitude, time and aircraft condition at that moment, rather than what became known later.
Why the leak was hard to identify
The crew saw separate true readings, but the system did not combine them into a diagnosis. With a rare refusal, a person is inclined to apply the familiar procedure to the most noticeable symptom.
Why do you need an emergency turbine?
RAT utilizes a surge stream and supports critical hydraulic and electrical functions. It does not return thrust, but retains the ability to control the aircraft.
Why the landing was so fast
Without engines, it is impossible to habitually increase traction after a decrease. The crew kept the speed as an insurance against flight failure and extinguished the energy with turns and brakes already on the strip.
Summary
Investigation findings
- The leak occurred due to damage to the fuel tube after improper maintenance of the power plant.
- Fuel pumping to correct the imbalance increased the overall fuel loss.
- Timely deviation to the Azores made the airfield achievable after stopping both engines.
- The design of the A330 and the skills of the crew allowed to maintain control in long-term planning.
After the investigation
What aviation learned
A lesson becomes useful when it leads to a procedure, training, a design change or a new safety barrier.
Technical compatibility
The service should check not only the number and installation of the part, but also the physical gaps between the pipelines in all operating modes.
Diagnostics of leaks
Procedures and training have linked the imbalance to the total amount of fuel, consumption and engine parameters - so as not to pump the fuel blindly.
Planning training
A rare scenario of total loss of thrust remains part of the preparation: the speed of the best planning, the launch of the RAT, the choice of the airfield and altitude control.
Its relevance today
The diagnosis should take into account the overall balance, not a single signal.
Air Transat 236 was an example of a diagnostic trap: the procedure exactly matched the visible message, but not the actual physical process. The modern approach teaches to compare the local imbalance with the total amount of fuel, the expected flow rate, engine parameters and time. If the amount disappears faster than the plan, simply aligning the tanks does not solve the problem.
For maintenance, this is proof of the value of configuration control. The compatibility of a part cannot be determined by whether it has been physically installed. You need an up-to-date newsletter, correct numbers, set gaps and independent verification after launch. The oral confidence of an experienced specialist does not replace the manufacturer’s documentation.
Finally, successful planning shows the role of early conservative decision. The crew was unsure of the diagnosis, but had already turned to the Azores. In a rare and deteriorating situation, the creation of an achievable airfield is more important than the desire to first get the perfect explanation for each reading.
Planning physics does not turn a heavy liner into a light glider, but gives the crew a manageable altitude budget. The speed of the best quality, wind, mass, operation of the emergency turbine and the energy needed to release mechanization determine the achievable area. Therefore, dispatching assistance should quickly free the airspace and transfer distances, and the crew should not spend a reserve of altitude on unnecessary maneuvers. In Lazhesh, this calculation had to be completed with a sharp turn and a hard braking already above the strip.