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View Full Version : Fuel Dumping capability- when & what acft?


Herc Jerk
29th Mar 2004, 02:41
Transitioning from the Herc to 737NG and while studiously studying the fuel system chapter i found that i had finished the chapter without a hint of dump pumps, dump valves, or even dump masts. At this stage my brain kicked into high gear and, by a simple process of deduction, i concluded that there is no fuel dumping capability on the 737... smart huh?

Why not? Or then, why?

Both acft are 2nd segment limited under certain conditions.
Both can TOFF well in excess of their MLW.

There is the provision for "overweight landings" in the 73, but, although not said in so many words, there are landing graphs for the Herc that cover all weights up to MTOW. In the event of an over weight landing an inspection would be required (i assume, but am not trained in the arts of fixing), the same as the 73.

In the Herc, during every TOFF near to 155,000lbs you would invariably find the FE's hands hovering near those dump pumps. BUT our 2nd seg WAT limit was not predicated on this.

So what requires the installation of a dump system?
Both these acft are very similar in weight, the -700 is the closest approx to the Herc.
Is it a 4 eng vs 2 eng thing?
Has it got to do with the fact that the Herc can carry so much of it's payload as fuel (almost 65000lbs/14hrs of fuel w/externals)?
Or is it more so old technology/added luxury (?!)/military hold over...?

As a final question for interests sake, what other large acft do/don't have fuel dumping?

HJ

80/20
30th Mar 2004, 05:47
Yes you are right no fuel dumping in the 737.
An overweight landing requires an inspection - which might be permitted as a simple pilot walk-around if the landing was not hard. This is defined in the maintenance manual and subject to company procedures.

Advisory landing information in the QRH can also be used to calculate overweight info.

Used to fly various 4-engine heavy jets that all had dumping...

*Lancer*
30th Mar 2004, 11:27
Some 767s don't have dumping capability

jones the steam
30th Mar 2004, 11:58
Herc, you can dump fuel on Mr Lockheed's other big 4 engine beestie, the Electra. I was really surprised to hear that it is not possible to dump with most modern machines. It is great to have that capability should it be required, and a bit worrying that if you were to have a major problem with no means of dumping, you'd be stuck with tonnes of fuel on board....

Herc Jerk
31st Mar 2004, 00:06
Agreed Jonesy . I had just assumed that all acft had it. Serves me right for assuming!

Could it be more a 2 eng Vs 4 eng structural thing in that an over weight landing with fuel in the wings PLUS the weight of those extra two engines outboard will be more likely to overstress the spra/wing box should one accomplish a less than smooth touchdown... God help us..?

But then Lancer just said some 76s can dump... so i'm grasping at straws here.

So far;
For:
Herc, B767, Electra
Against:
B737, B767

Flight Detent
2nd Apr 2004, 02:40
Are you all absolutely sure there's no B737s with a fuel dump capability??

Cheers

Hawker-rider
2nd Apr 2004, 05:23
That reminds me of a B52-IP once answering me the same question...

With the gear down and the speedbrakes out, give it max power and just fly around for a while, that's the way you dump fuel, there's no hole big enough to drain fuel out off, besides the engines themselves


Funny one

BizJetJock
2nd Apr 2004, 19:52
Under JAR-25 I think there is a requirement to be able to reach max landing weight within a specified time of takeoff, so some aircraft require a dump facility to do this and some don't.

Interestingly, the Challenger series have a fuel dump system for the tail tank which is purely for maintaining the c of g in the event of not being able to transfer it. People have got into trouble using it to try and lighten the aircraft (not very effective - 1250lbs or 3150lbs depending on the model) and getting themselves out of the forward c of g limit with the subsequent landing problems.