Dumping fuel

I was watching a documentary about the engine explosion on the Qantas A380 over Singapore that happened earlier this year.They apparently dumped about 40-50 tons of Av Gas to lighten the plane for landing.

I know this is the usual practice in these situations but dumping that amount of fuel into the air must have some pretty bad repercussions for those who live in the vicinity, human and non human.

I know we have some aviation types here in the forum, I wonder what your take on this is?

From what I've been told by our flight test pilots, the fuel vaporizes and evaporates before it ever gets to the ground. In fact I seem to recall one of our producers doing a video about this and that the fuel never making it to the ground was one of the main points of the video.

I've been on planes that dumped fuel a couple of times, once during a 757 production test flight in which the fuel dump system was routinely tested, and once on a Lufthansa flight out of Frankfurt when the 747-400 took a large bird into the #1 engine on takeoff which bent the hell out of a bunch of fan blades. We were headed for Vancouver and the plane had a lot of fuel on board so we had to dump a lot to get down to the plane's maximum landing weight. We flew around for the better part of an hour doing this.

In each case, while the fuel is streaming out of the wingtip dumps pretty heavily I could see that it was being "blasted' into droplets pretty fast.

Jet fuel is very fine kerosene , av gas went out with round motors and propellers.

Our NATOPs required a min altitude of 6000 ft to dump fuel. It is gone before it hits the ground. Better than a concentrated impact sight.

I always heard that the dumped fuel vaporized before ground contact, too. We had a fuel dump valve on the Sabreliner 40 to get down to landing weight faster if needed in an emergency. Never had to use it, though. The later model corporate jets I'm familiar with no longer had that capability. If an overweight landing occurs, inspections of aircraft components and wheel/brake replacement were required.

Apparently a KC-135 tanker can dump an impressive amount of fuel / cargo very quickly. Buddy of mine was crew on an Air Force KC-135 tanker. They lost an engine on takeoff after passing the point of "no return" (must take off). While the plane will fly with one less engine, clearing the fence at the end of the airport was done with nothing to spare. They went around and immediately landed. In my buddies words, "We were dumping cargo as fast as we could the whole way around; killed a whole lot of grass".

Ted