Fuel jettison questions

[PAPA FOX!]

1) What is the minimum altitude in which fuel will evaporate when dumped?

2) At what rate can most heavies jettison fuel?

3) Even when fuel evaporates before it hits the surface isn't it still a problem if other aircraft are flying below since the exhaust could spark the flammable vapors?

 

[scoreboard]

Temperature dependent. If the temp is 70's or greater, it should evaporate if dumped above 10,000ft agl. Below zero, it may not evaporate at all if dumped above 30,000ft agl.

Now I know it gets colder up higher, I'm talking ground level temp then standard lapse rate.

JP-8 is really bad, Some Jet A with certain modifiers are equally poor at evaporating.

Interesting point, JP-8 was sold as the "safe" fuel to military because it's flash point is so high it won't light even with a match to it. In reality, the reason JP-8 was formulated was to reduce evapoartion out of fuel tanks on the ground. Problem is, it is a very carcinogenic compound as compared to old fashioned JP-4.

 

[stupidpilot]

DC-10 with just the main pumps is about 5000#/min all main & aux pumps about 5800#/min. Although there is a bit of argument on the exact numbers.

 

[MD11Drvr]

We figure 5000lbs/min at the carrier I work for on the MD-11 but it is really closer to 5800/min just like the DC-10.

 

[bigboeings]

1200kilos per min in 767.

 

[bustinmins]

The 727 will dump at 2300 lbs per minute.