Photo: BobMil42
Airbus A340 Fuel Dumping in progress
Why pilot dump fuel during an emergency?
Prior to hanging up my uniform as a captain on the Boeing 777 in 2006, I encountered an emergency which potentially could have led to a depressurization if not properly handled.
We could have ended up like the Helios Airways accident where cabin depressurization incapacitated the crew, leaving the plane to fly on autopilot until it ran out of fuel and crashed near Athens, Greece. 121 lives were lost in this deadliest aviation accident in Greek history.
I took over a flight from New York at Stockholm for Kuala Lumpur. As I climbed past 10,000 feet, the forward cargo door warning light came on. We then referred to the abnormal check list for ‘DOOR FORWARD CARGO’.
The check list informed us that the forward cargo door was not closed, latched and locked. This could possibility lead to the cargo door being dislodged and the aircraft depressurized.
It called for an immediate level off at a safe altitude or 8000 feet. We then discussed the best course of action and made the decision to return to Stockholm Airport to fix the problem.
We took off at a weight of about 293 tons but the maximum landing weight was around 213 tons. As such, we were overweight and had to dump about 80 tons in order to touch down safely.
This limitation is imposed for structural and performance reasons. We informed the control tower and were directed to a specific airspace over the Baltic Sea to jettison the fuel.
At a dumping rate of around 2 tons per minute, it took us about 40 minutes in the holding pattern before we landed safely below the maximum landing weight.
Dumping fuel can be expensive but landing overweight can be just as costly. Nevertheless, aircraft can and do land overweight in some critical emergencies.
Only bigger planes such as the Airbus A380’s and Boeing 777’s have dumping facilities. Smaller planes like the Airbus A320’s or Boeing 737’s do not need such a system due to their lighter weights and shorter range.
When performing fuel dumping, the captain must consider whether the emergency faced would render the plane unsafe due to time wasted as happened on Swiss Air Flight 111 where 229 passengers died when the captain was attempting to dump fuel during a fire.
For medical emergency, the commander would also have to consider if the time spent dumping fuel would deprive the passenger involved of urgent medical attention.
Fuel jettisoned normally above 5,000 feet will completely vaporize before reaching the ground. However, there is no restriction at lower altitudes if it is considered necessary due to extreme emergencies.
If fuel dumping is not carried out, a pilot can still land overweight, but the plane will need to undergo a maintenance inspection.
Engineers would look for obvious signs of any damage caused such as wrinkled skins, popped fasteners or bent components prior to releasing the plane for further service.
See a video on fuel dumping here