PDA

View Full Version : A340 Fuel jettison on ground?


max_motoring
10th Dec 2009, 21:46
Dear All,

I am an A340 F/O under instruction, actually this was my second flight. The instructor asked me what happen if I press the fuel jettison pushbutton on the overhead panel while the aircraft is on ground, energized but with the engines not running.
I said that according to the FCOM 1 ( 1.28.10 page 22) it says nothing about jettison fuel on ground, only refers inflight at whatever altitude, even with slats and landing gear down the fuel will be jettisoned. But says absolutelly nothing if you press the those pushbuttons on ground.
Please, can somebody tell me what will happen? Thank you guys! :)

TyroPicard
11th Dec 2009, 10:49
Hi Max
FCOM 1 says the Jettison system "Makes it possible to jettison fuel in flight". It does NOT say "and on the ground". My experience of Airbus FCOM... they often leave out the word "only" when it would be really useful! Also..
1. It would be madness to make it possible on the ground.
2. There would be a big caution in the FCOM if it were possible.

Caution: I am not A340-rated......

max_motoring
11th Dec 2009, 15:06
Hi Tyro,

Thank you for your opinion mate, totally agree about jettison fuel on the ground as is unnecessary to do so. I would like to have an official written page or document to scrub in the instructor face until I got tired. Thank you Tyro! :)

groundfloor
11th Dec 2009, 16:55
What a "TURKEY"..The instructor that is..What a really useful piece of information:\.. Ask him what has 7 knots - the escape rope...:}

Dual ground
11th Dec 2009, 17:08
Max Motoring

May I suggest you ask the same question in the Engineers and Technicians forum?

Anyone who has access to the AMM could almost certainly provide a definite answer and possibly an AMM reference to back it up.

Iceman49
11th Dec 2009, 18:36
Does the term "negative training" come to mind?

763 jock
11th Dec 2009, 19:50
Has this "instructor" joined very recently? Perhaps ex Jet Airways.:E

What possible scenario would have you dumping fuel whilst on the ground when the engines are shut down?

jettison valve
11th Dec 2009, 20:12
It^s been a while since I had a look at 28-31 but: I don^t remember air/ground signal changes anything in the jettison system. Therefore, I would put my money on "yes, you can dump fuel on the ground".

Need to look at the schematics, though, to confirm.

Cheers, J.V.

Dual ground
11th Dec 2009, 20:22
Wouldn't surprise me. I'm 99% sure you can on the 747, but it's a while since I worked on them.

CV880
11th Dec 2009, 23:05
No data regarding A340 in hand but a quick check of a 747 classic and 744 AMM I have on my computer shows there is NO air/ground signal and that jettison system will work on the ground.
Once had a helpful mechanic accidentally jettison some fuel on a CV880 during overnight maintenance. Thought he was helping me by leak checking a jettison pump he had just replaced but didn't realise that in doing so he had pumped some gas out of the RH nozzle.

FE Hoppy
12th Dec 2009, 01:22
You definitely can on the Nimrod but you need an engine running to pressurise the tanks. There was a trick to close a leaky NRV in the vent system using nitrogen and blue roll. If neither was available pulling the dump valve cb's starting up an engine and hitting the dump switches would also close the faulty NRV.

Warning: make sure you pull the correct CBs as failure to do so could dump 2000lb of fuel on the apron in malmo with a bbc tv crew on board to see it happen!


Note: the contents of this post are probably completely fictional and not based on any real people or events and should not replace any published procedures in the AFM.

spannersatcx
12th Dec 2009, 08:33
As long as DC buses are powered and the CB's all set then nothing stopping you from jettisoning fuel on the ground.

Seems like it was actually a good question from the instructor then!

groundfloor
12th Dec 2009, 09:51
"Nothing to stop you from jettisoning on Ground as long as the bus`s are powered and the cb`s are in" - this is an Airbus:

1. It does not have a simple air/ground system but goes through about 9 phases from starting to shutting down that are advertised to the flight crew - there may and probably are more!!

2. Numerous: functions, warnings, auto functions are inhibited in these phases... A simple example if the Taxi camera is left on on the Pilots Flight Display during take-off it will change over to the flight display at 70 kts (camera function inhibited) ...Some Engine auto shut down functions are inhibited in flight..etc.

Unless this Instructor had the answer chapter and verse to his question and or the purpose was to illustrate something along the above lines?? The original poster has not enlightened us.

My answer. The fuel jettison is a guarded red switch - why on earth would I press it on the ground? If you forget it on during dumping for an overweight landing what will happen? Thats a relevant queston...:ok:

spannersatcx
12th Dec 2009, 12:33
To carry out an operational test on the ground the only cb's you have to pull are for the fuel pumps, this prevents fuel pressure forcing the fuel out, you do get some fuel out though. There are no other factors involved from what I can see, doors don't have to be closed, eng's don't have to be running, no forced logic to get it anywhere but on the ground. Which says to me yes it can be done.

Why? because it's airbus!:eek:

grease7
12th Dec 2009, 13:00
On the 744 it's standard practise to operate the jettison valves on ground during a lightning strike inspection. You just have to wait untill there is no pressure in the fuel manifold:}

max_motoring
12th Dec 2009, 19:26
The instructor said later that you can jettison on the ground the same way as you can pull the fire handle and discharge the bottles even if the aircraft is only battery supplied. In this case (aircraft with ext power on), you press the jettison pushbuttons and the STBY fuel pumps starts running, all x valve are open and there is no protection to stop you. the conlcusion: there is no logic, but you can jettison on the ground.
But this my conclusion only, I will ask an A340 engineer and then I will post again. Thank for your opinions mates!
:)

Dual ground
12th Dec 2009, 21:25
Maybe as it is an emergency system the logic is "keep it simple" . The simpler it is, the less can go wrong with it , the more likely it is to work when you need it.

There is no need to make things "idiot proof" if they are not designed to be used by idiots is there?

Makes sense to me as a technician/mechanic/whatever I'm called these days.

spannersatcx
12th Dec 2009, 21:58
I will ask an A340 engineer and then I will post again I am one, see above ^^^^

galaxy flyer
12th Dec 2009, 22:09
Not Airbus qual'd, but why on Earth would you want to fuel jettison on the ground, hence why isn't the fuel jettison system wired through the WOW sensor? Unless Airbus wanted us to demo fuel dumping to the BBC, of course.

Sorry FEHoppy

GF

Dual ground
12th Dec 2009, 22:36
Spannersatcx and CV880 have confirmed that both Boeing and Airbus follow the same design philosophy. I reckon there is a reason for it, as I mentioned 2 posts ago.

Can anyone confirm that any aircraft that they operate/maintain has a fuel dump system with air/ground switching?

One Outsider
12th Dec 2009, 22:43
Of course fuel jettison on ground will be possible. As there is no operational reason to do so but certainly a maintenance reason, there will be no inhibit.

Dual ground
12th Dec 2009, 22:54
There would be no problem with getting around an air/ground inhibit on the system for maintenance purposes, we do it all the time.

I don't think that would be a good enough reason for a lack of air/ground switching. I personally think that there is no inhibit because of design requirements.

FE Hoppy
13th Dec 2009, 03:25
CS 25.1001 Fuel jettisoning system

Defines the design requirements and there is nothing in there to suggest a need to operate on the ground.

Panama Jack
13th Dec 2009, 03:54
Does the term "negative training" come to mind?

Exactly!!! Another example of a stuuuuuuuuuupid question being asked in aviation-- not unlike "How many Circuit Breakers/ Antennaes are installed on this aircraft?" :ugh:

Perhaps a more practical question would have been-- "if the cute little R4 attendant only weighs 59kg, could she sit on the fold out table in front of you without exceeding its structural load limit?" :hmm:

TinyTim2
15th Dec 2009, 10:27
on most aircraft the reason there is no safety systems ( air/ground etc ) is to allow jettisons in the most dire emergancy , loss of power etc . B767 and A340 can jettison on the ground and yes it has happened , and it take some time to stop it , I've seen a B767 dump 2k on the hanagr floor ...........