Figure: Fuel Pipe Crack, from Portugal Accident Investigation Final Report, Figure 4.

Eddie Sez:

The pilots did an excellent job gliding their airplane to a safe landing, not a single occupant was injured. Now, having said that, how did the airplane lose all that fuel and end up becoming a glider? There is an old Air Force joke seems to apply: "Excellent job recovering from the spin, lieutenant! Now how did you get into the spin in the first place?"

The accident report omits a few key points and there is a lesson for all pilots in the end.

  • Air Transat insisted the aircraft return to service with a new engine and wrong hydraulic pump despite a mechanic's protest. The hydraulic pump caused a hydraulic line to abrade a fuel line which caused a fuel leak from the right engine several hours into the flight. Air Transat admitted as much and was fined heavily.

  • The first hint of a problem was an unusual oil pressure high, oil temperature low combination in the right engine. The problem wasn't covered in the flight manual. The crew concluded it was probably an indication problem. It wasn't.

  • Hours later they got a fuel imbalance warning, showing the left wing heavy. All previous fuel checks showed normal fuel usage. The flight manual warned not to cross flow if a fuel leak was suspected, but since all prior fuel checks were normal, they did not suspect a problem and commenced a fuel transfer from the left wing to the right.

  • It is said that a fuel crossflow on the Airbus 330 happens very quickly and effectively, but for this crew it did not. They chalked this up as another computer problem. They should have looked at their total fuel quantity and realized they were losing fuel faster than they were burning it, it had to be going someplace. And yet they left the crossflow open. They were transferring all fuel on the airplane to the leak in the right engine.

  • Both engines eventually flamed out and the ended up gliding the airplane 85 nm to Lajes, Azores for a successful engine-out landing. Both pilots were lauded as heroes.

  • The Airbus checklist was changed to more strongly prohibit cross flow with a fuel leak suspected.

I've had a few fuel leaks over the years, the worst of which was in a Boeing 707, story retold here: Flight Lessons / B-707 Fuel Bath Tub. My first concern is usually fire and then to the age-old question: do I have enough fuel to make it to land? Whenever you crossflow you need to make sure all of the fuel that is leaving a tank arrives at the other tank. If the total fuel decreases more than your fuel burn, you have a problem.

In older aircraft that I have flown, fuel burns in each engine can vary appreciably and having to transfer fuel is routine. In the newer aircraft, having a fuel imbalance is uncommon. In either case, it should not be a set and forget procedure, it needs to be monitored closely. If you suspect a leak in the engine, it needs to be shut down to stop the fuel loss and to prevent a fire.

The G450/G550 FMS measures fuel burn at the engine. If it differs appreciably from the fuel decrease in the tanks, you have some investigating to do. See G450 Abnormal Procedures / Fuel Leak Inflight for more on this.

What follows are quotes from the sources listed below, as well as my comments in blue.


Accident Report


Narrative

[Portugal Accident Investigation Final Report, §1.1.3]

[Portugal Accident Investigation Final Report, §1.16.2]

[Portugal Accident Investigation Final Report]


Probable Cause

Figure: Right engine fuel and hydraulic lines, from Portugal Accident Investigation Final Report, §1.6.3.

[Portugal Accident Investigation Final Report, §3.1]

  1. The replacement engine was received in an unexpected pre-SB configuration to which the operator had not previously been exposed.

  2. Neither the engine-receipt nor the engine-change planning process identified the differences in configuration between the engine being removed and the engine being installed, leaving complete reliance for detecting the differences upon the technicians doing the engine change.

  3. The lead technician relied on verbal advice during the engine change procedure rather than acquiring access to the relevant SB, which was necessary to properly complete the installation of the post-mod hydraulic pump.

  4. The installation of the post-mod hydraulic pump and the post-mod fuel tube with the pre-mod hydraulic tube assembly resulted in a mismatch between the fuel and hydraulic tubes.

  5. The mismatched installation of the pre-mod hydraulic tube and the post-mod fuel tube resulted in the tubes coming into contact with each other, which resulted in the fracture of the fuel tube and the fuel leak, the initiating event that led to fuel exhaustion.

  6. Although the existence of the optional Rolls-Royce SB RB.211-29-C625 became known during the engine change, the SB was not reviewed during or following the installation of the hydraulic pump, which negated a safety defence that should have prevented the mismatched installation.

  7. Although a clearance between the fuel tube and hydraulic tube was achieved during installation by applying some force, the pressurization of the hydraulic line forced the hydraulic tube back to its natural position and eliminated the clearance.

  8. The flight crew did not detect that a fuel problem existed until the Fuel ADV advisory was displayed and the fuel imbalance was noted on the Fuel ECAM page.

  9. The crew did not correctly evaluate the situation before taking action.

  10. The flight crew did not recognize that a fuel leak situation existed and carried out the fuel imbalance procedure from memory, which resulted in the fuel from the left tanks being fed to the leak in the right engine.

  11. Conducting the FUEL IMBALANCE procedure by memory negated the defence of the Caution note in the FUEL IMBALANCE checklist that may have caused the crew to consider timely actioning of the FUEL LEAK procedure.

  12. Although there were a number of other indications that a significant fuel loss was occurring, the crew did not conclude that a fuel leak situation existed – not actioning the FUEL LEAK procedure was the key factor that led to the fuel exhaustion.

See Also:

Abnormal Procedures & Techniques / Maintenance Malpractice

Normal Procedures & Techniques / Crew Resource Management

Normal Procedures & Techniques / Situational Awareness


References

May Day: Flying on Empty, Cineflix, Episode 6, Season 1, 8 October 2003 (Air Transat 236)

Portugal Accident Investigation Final Report, All Engines-out Landing Due to Fuel Exhaustion, Air Transat, Airbus A330-243 marks C-GITS, Lajes, Azores, Portugal, 24 August 2001