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.
I've had a few fuel leaks over the years, the worst of which was in a Boeing 707, story retold here: 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 Fuel Leak Inflight for more on this.
Everything here is from the references shown below, with a few comments in an alternate color.
Figure: Fuel Pipe Crack, from Portugal Accident Investigation Final Report, Figure 4.
Later investigation revealed "scratches and scores were directionally aligned and that they would have been caused by repeated contact from a blunt instrument, such as a screwdriver being inserted between the tubes in order to force clearance between them.
[Portugal Accident Investigation Final Report, §1.16.2]
The engine oil indications were the unusual combination of low oil temperature, low oil quantity, and high oil pressure. The assumed the issue was a computer indication problem, not an engine problem. [§126.96.36.199]
The fuel logs had shown normal fuel burns during the first four hours of the flight, the last normal reading having taken place at 04:57 [¶188.8.131.52].
Two cardinal rules of transferring fuel between tanks should be (1) make sure the fuel imbalance isn't being caused by a leak so you can avoid "feeding the leak," and (2) confirm the fuel is getting to where it should be going. In this case, the fuel leak was in the engine itself and the crossfeed was indeed feeding the leak.
This did not have the desired effect, since the right engine continued to consume fuel. The correct action would have been to shut the engine down.
If the problem was indeed with the computers, no fuel transfer would have been needed and they could have verified the imbalance with lateral trim requirements.
Figure: Right engine fuel and hydraulic lines, from Portugal Accident Investigation Final Report, §1.6.3.
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
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