Fuel jettison locations
Thread Starter
Joined: Feb 2006
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From: Brighton
Fuel jettison locations
A question for my ATC colleagues.
I was just wondering where the preferred locations for fuel jettison would be in the southern UK, in the event an aircraft needed to return to the departure aerodrome.
For example, if we were departing from LHR 27 L/R on a CPT SID, or if off 09L/R
on a DET SID. Any info greatly appreciated.
Warm regards.
I was just wondering where the preferred locations for fuel jettison would be in the southern UK, in the event an aircraft needed to return to the departure aerodrome.
For example, if we were departing from LHR 27 L/R on a CPT SID, or if off 09L/R
on a DET SID. Any info greatly appreciated.
Warm regards.
Joined: Jan 2008
Posts: 17,688
Likes: 2,030
From: Reading, UK
Bear in mind also that a significant number of present-day aircraft don't have a fuel dump capability. They will typically stooge around at 10,000 feet in order to burn off enough fuel to get down to MLW, assuming the emergency isn't severe enough to justify an overweight landing.
Joined: Dec 2000
Posts: 2,132
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From: on the golf course (Covid permitting)
Just to put things into perspective.
A B747-400 would normally dump above 6000ft altitude, and yes preferably over the sea, however lets run some numbers. No fuel dump with flaps between 1 and 5 - personally I would have chosen flaps up. Minimum flaps up speed after a max weight take off is about 280 kts. The published dump rate is a max of 2000 kgs/minute
So, in one minute:
Aircraft travels 280kts = 8462 metres (280/60 * 1852)
Distance between jettison nozzles ~ 40 metres
Area covered = 338,480 sq metres (8462 * 40)
Jettison rate = 2000 kgs/min
Concentration at ground = 0.006 kg/sq metre (6 grammes)
Of course this assumes that the fuel comes down vertically without dispersion and evaporation. I would imagine the dispersion rate would be vast, even from 6000ft and I doubt that more than 1% of that would actually reach a given sq metre, ie less than 1/10th of a gramme.
A B747-400 would normally dump above 6000ft altitude, and yes preferably over the sea, however lets run some numbers. No fuel dump with flaps between 1 and 5 - personally I would have chosen flaps up. Minimum flaps up speed after a max weight take off is about 280 kts. The published dump rate is a max of 2000 kgs/minute
So, in one minute:
Aircraft travels 280kts = 8462 metres (280/60 * 1852)
Distance between jettison nozzles ~ 40 metres
Area covered = 338,480 sq metres (8462 * 40)
Jettison rate = 2000 kgs/min
Concentration at ground = 0.006 kg/sq metre (6 grammes)
Of course this assumes that the fuel comes down vertically without dispersion and evaporation. I would imagine the dispersion rate would be vast, even from 6000ft and I doubt that more than 1% of that would actually reach a given sq metre, ie less than 1/10th of a gramme.
Joined: Mar 2001
Posts: 308
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From: etha
There are no actual hard fast rules about this, just guidelines and you can read the UK guidelines here which is a link to the UK MATS Part 1 (CAP493). Open the PDF document and Section 5, Chapter 1 - Aircraft Emergencies Part 13 is all about Fuel Jettisoning.
The basics are to attempt to fuel jettison above 10000ft, however if not practicable to try and at least be 7000ft during winter and 4000ft during summer.
The basics are to attempt to fuel jettison above 10000ft, however if not practicable to try and at least be 7000ft during winter and 4000ft during summer.
