Fuel stats when dumping

[5milesbaby]

Does anyone know how long it takes dumped fuel to totally evaporate? Does an odour linger and can this be smelt by any following a/c that fly through the vapour? And finally is there a MAXIMUM altitude above which certain a/c types cannot dump?

I ask this as an ATCer trying to broaden current knowledge so I'm aware of the minimum FL's etc. We're told standard separation can be applied but it just seems a little risky to me :uhoh:

Any replies appreciated, 5mb :ok:

[Brian Fantana]

A coulpe of points I have found from the B767 FCTM :

- fuel jettison above 4,000ft AGL ensures complete fuel evaporation.
- downwind drift of fuel may exceed one mile per 1,000ft of drop.
- Avoid jettisoning fuel in a holding pattern with other planes below.

BF

[5milesbaby]

Cheers Brian, I read somewhere when I did a forum search on this topic that fuel normally descends at 500ft/min so from your stuff I guess that it'll take a max time of 8 minutes to totally evaporate from your 2nd point that "fuel jettison above 4,000ft AGL ensures complete fuel evaporation". Just gives me an idea of where not to point a/c behind one thats unloading its tanks!

Is there any chance of following a/c igniting dumped fuel they fly through or is it a case that they'll just suffer an engine surge?

[411A]

L1011....dump rate 2000kg/minute.

A much better alternative, land overweight, if the situation is urgent.
Why?
Ask (if they were still with us) the SR111 crew that had severe problems off the Canadian coast some time ago.

[BelArgUSA]

Fuel dump for a return with heavy takeoff weights is a subject of common practice in simulator training. Fine and dandy... I never fail to have crews practice one of these for initial/recurrent training in simulators. However, in classroom, we never fail to discuss (and often practice, in simulators) an "immediate return" at maximum takeoff weight, well above maximum landing weight. I do not know any type of aircraft unable to land above maximum landing weight. It is a part of FAR 25 certification.
xxx
747-200/300 -
Textbook maximum takeoff and landing weights, and considerations are -
Maximum takeoff weight 377,800 kg - Maximum landing weight 285,700 kg.
Fuel dump of 92,000 kg amount would take 38 minutes.
Your Vref will be 152 KIAS...
If you elect to do as above, who cares where and how high... it is an emergency...
If you do it in holding, some say to maintain a slight rate of climb.
Sorry if your seafood will taste bad. In any case, it takes care of your local mosquito problem...
xxx
If "dire" emergency -
Immediate return situation, could be at some 365,000 kg...
Your Vref will be 182 KIAS...
Recommend you open Xfer valves of RES tanks nº 2 and nº 3 if any fuel.
And dump immediately if able, even if in traffic pattern for return.
Stop jettison when 500 feet AGL on short final...
Any runway length (even wet) of 10,000 feet can handle such speed/weight conditions.
An overweight landing inspection takes 30 minutes by flight engineer.
Captain paperwork 2 hrs, and 10 phone calls to operations and maintenance.
Also change the crew's undies, as likely.
Besides, keep the "good stuff" in the tanks, at OPEC rates of $100/barrel of crude.
xxx
On our takeoff/landing cards, on reverse side (landing side), we always note both Vrefs applicable -
One with maximum landing weight, one with immediate return as discussed.
It is our SOP, we do not even "brief" about this - it is clearly understood.
xxx
My only experience of heavy landing was with a DC8-63F near maximum takeoff weight, as per decision given by phone patch to my (then) operations manager. Was an uneventful approach and landing (in EDDF, mid-1980s) - The only surprise was that it took very little power to maintain the rather high Vref required by the weight. I had expected high power settings, but it turned out to be the opposite. I brief that fact in the 747 class sessions.
xxx
:)
Happy contrails

[skiesfull]

B747's - if you can take-off from a runway, then you should be able to land back on it at the same weight (minus burn-off) -autoland not recommended.
Boeing has, I believe, approved overweight landings for most occurences requiring an urgent landing - subject of course to the landing distance available being equal to or greater than the landing distance required. It's expensive stuff to throw away! An overweight landing inspection should not take too long, provided a low 'G' touchdown was achieved (obtained from the ACMS for the -400).