Expert: Capt Paul - 9/24/2006

Question
I've always wondered how airliners can dump large amounts of fuel (during an emergency, for example) and not cause environmental problems. Do very large amounts of jet fuel simply evaporate?

For example, the following from the WSJ:

The incident also focused renewed attention on an age-old issue in aviation -- safety versus economics. An emergency landing would have required dumping $30,000 of fuel,  

Answer
Hi,
First I’ll provide the answer regarding “How” the fuel is dumped.  The simple answer is, that we pump is out a tube located in the outboard end of each wing.  Typically, we will only dump the amount required to get the aircraft’s weight down to its landing limitation.

Even with the failure of an engine, we are typically able to climb to a reasonably high level.  For example, a heavily loaded and heavily fueled aircraft could most likely climb to at least 10000 feet.  At that height – and heights considerable lower – most of the dumped fuel will simply evaporate before it contacts the earth’s surface.

That said, in the interest of public safety, we don’t dump fuel over populated areas, in fact, in many places there are designated fuel dumping areas, and Air Traffic Control (ATC) will restrict the use of any airspace in the vicinity of a “Fuel Dump” in progress. (Anouther aircraft flying into a freshly dumped bunch of fuel would really mess up your day).

Next, is the question of Safety over Economics.  Most of the other Captains that I know have the same thoughts on this.  All things being equal, we will attempt to operate in the most cost effective manner possible.  But, when safety is in question, the economics factor is thrown out the window.  

Above economics; convenience; comfort; and even the law, Safety of all persons, and the aircraft, is always the first priority.

Personally, if I had to sacrifice $30,000 of fuel to ensure the UNCOMPROMISED safety of the passengers; persons on the ground; the crew; and the aircraft, trust me, I'll do it without an ounce of guilt.  

I hope that this answers your question.  If not, feel free to write back and I’ll provide more details.

Cheers