Gravity cross feeding -A320 family
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Hi CMpilot1,
I disagree. See FCOM, PRO-ABN-28 Fuel, Gravity Fuel Feeding.
"F NO FUEL LEAK AND FOR AIRCRAFT HANDLING:
If no fuel leak, and for flight with only one engine running (this engine being fed by gravity), apply the following :
FUEL X FEED...... ON
BANK ANGLE...... 1° WING DOWN ON LIVE ENGINE SIDE
The fuel from the wing tank on the engine running side is used.
RUDDER TRIM USE
Use rudder trim to maintain constant course and neutral stick.
WHEN FUEL IMBALANCE REACHES 1 000 kg (2 200 lb):
BANK ANGLE...... 2° or 3° WING DOWN ON LIVE ENG SIDE
Use fuel from the opposite wing tank, until fuel imbalance is reduced to 0."
since gravity fuel is not possible using cross-feed.
"F NO FUEL LEAK AND FOR AIRCRAFT HANDLING:
If no fuel leak, and for flight with only one engine running (this engine being fed by gravity), apply the following :
FUEL X FEED...... ON
BANK ANGLE...... 1° WING DOWN ON LIVE ENGINE SIDE
The fuel from the wing tank on the engine running side is used.
RUDDER TRIM USE
Use rudder trim to maintain constant course and neutral stick.
WHEN FUEL IMBALANCE REACHES 1 000 kg (2 200 lb):
BANK ANGLE...... 2° or 3° WING DOWN ON LIVE ENG SIDE
Use fuel from the opposite wing tank, until fuel imbalance is reduced to 0."
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Hi Goldenrivett!
I can see that you have quoted my statement from post #18. Please go through my post #20 also. Whatever you have mentioned in your post #21, I have quoted exactly the same thing in my post#20 along with my interpretation. Please go through it once again and offer your comments...
I can see that you have quoted my statement from post #18. Please go through my post #20 also. Whatever you have mentioned in your post #21, I have quoted exactly the same thing in my post#20 along with my interpretation. Please go through it once again and offer your comments...
CMpilot1: Airbus write checklists to cover multiple scenarios.
In your case 1 why do you think they would require 1 degree of bank if the offside pumps were still functional? The answer is you wouldn't need any bank if the pumps were working.
The QRH has been written to also cover your case 2 - improbable as it may be!
Thus the bank angle introduces a pressure "head" difference between the two wing tanks and allows the fuel to transfer via the cross feed valve. The QRH goes on to say increase the bank to 2-3 degrees if the imbalance is getting worse.
Airbus have a variation on this cross wing fuel transfer using bank angle on the A330 to get around the failure closed of the cross feed valve. Slightly different plumbing but same principle.
As others have pointed out - this is a very unlikely scenario on a A320 operation.
In your case 1 why do you think they would require 1 degree of bank if the offside pumps were still functional? The answer is you wouldn't need any bank if the pumps were working.
The QRH has been written to also cover your case 2 - improbable as it may be!
Thus the bank angle introduces a pressure "head" difference between the two wing tanks and allows the fuel to transfer via the cross feed valve. The QRH goes on to say increase the bank to 2-3 degrees if the imbalance is getting worse.
Airbus have a variation on this cross wing fuel transfer using bank angle on the A330 to get around the failure closed of the cross feed valve. Slightly different plumbing but same principle.
As others have pointed out - this is a very unlikely scenario on a A320 operation.
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Hi CMpilot1!
What don't you understand about "Use fuel from the opposite wing tank, until fuel imbalance is reduced to 0."?
Please go through it once again and offer your comments...
Last edited by Goldenrivett; 9th Jun 2015 at 19:39.
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I posted once about this issue.
Basically I was wondering what did "WHEN TK FUEL RQRD" exactly means.
If you stay at high level to deaereate the fuel, the problem you have is that, although the total fuel on board is usable, an amount of it would have to be used on one engine only, as the wing with pumps on would deplete at some point before the pumpless wing.
This would be a problem only if the imbalance is high and the flight has to divert and/or use part of the final reserve.
So I guess that a way to handle this problem would be: to recalculate a minimum diversion fuel so that losing the pumps-on wing engine due to fuel starvation would not occur. If you estimate to have more than that on arrival, you can continue to destination. If you don't, you could still proceed, if a landing is assured and all that.
Basically I was wondering what did "WHEN TK FUEL RQRD" exactly means.
If you stay at high level to deaereate the fuel, the problem you have is that, although the total fuel on board is usable, an amount of it would have to be used on one engine only, as the wing with pumps on would deplete at some point before the pumpless wing.
This would be a problem only if the imbalance is high and the flight has to divert and/or use part of the final reserve.
So I guess that a way to handle this problem would be: to recalculate a minimum diversion fuel so that losing the pumps-on wing engine due to fuel starvation would not occur. If you estimate to have more than that on arrival, you can continue to destination. If you don't, you could still proceed, if a landing is assured and all that.
Microburst2002: Surely, if the fuel is fully de-aerated then it is not necessary to use the pumps at all and the QRH procedure for imbalance can be used. In other words you would only restrict your range if you continued to use pumps on one side only.
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If you have 2 t in the left side and reaching 0 in the right hand side due to the fact that you developed a large imbalance and have been forced to divert and hold, how do you crossfeed? Left side pumps failed, so right hand pumps pumped for a while and now you have the imbalance. When the wing with the pumps, which is the lighter wing, depletes the remaining fuel before the left wing does. How do you use the other wing fuel by gravity now?
Last edited by Microburst2002; 12th Jun 2015 at 18:30.
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Ok, ok
So we would have to accept that one engine would starve if you had to use all the fuel on board when you still had fuel. Not a good situation.
So I would manage it like I said: a revised minimum diversion fuel and end of the story.
I don't think you can develop too large an imbalance in that scenario anyway, but it could happen (being very unlucky) that you needed all of your fuel that very same day.
So we would have to accept that one engine would starve if you had to use all the fuel on board when you still had fuel. Not a good situation.
So I would manage it like I said: a revised minimum diversion fuel and end of the story.
I don't think you can develop too large an imbalance in that scenario anyway, but it could happen (being very unlucky) that you needed all of your fuel that very same day.
Microburst2002: You still seem incapable of grasping that you would not necessarily "lose an engine" whilst still having fuel available. Several postings have tried to explain this to you to no avail. What more can one say?
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Dear Meikleour
If this thread clarifies anything at all about the matter, I am a transexual who worships Satan.
Now, back to the matter:
QRH lines regarding a bank angle are exclusively dedicated to the one-engine case (they refer to the "live" engine).
Exclusively is exclusively. Not a coincidence!
I mean: Imagine that you have a large fuel imbalance, and now the left side is too low on fuel because you diverted and had just the minimum legal on arrival and then suffered a subsequent delay, and you are now in a mayday fuel situation and then you open the crossfeed valve and bank the airplane to perform a "gravity fuel xfeed" to prevent the left engine from starving, and then… The right engine flames out because it is on gravity and that bank doesn't help with the X FEED open. Just imagine...
Could that happen? I don't know, personally!
But I know that the procedure is very clear that: FUEL XFEED….OFF
I would not open it and bank the airplane, thus totally inventing a new procedure.
What I would do is just to revise my minimum diversion fuel and then to decide if either to continue or divert so as to land with at least the revised final reserve.
If this thread clarifies anything at all about the matter, I am a transexual who worships Satan.
Now, back to the matter:
QRH lines regarding a bank angle are exclusively dedicated to the one-engine case (they refer to the "live" engine).
Exclusively is exclusively. Not a coincidence!
I mean: Imagine that you have a large fuel imbalance, and now the left side is too low on fuel because you diverted and had just the minimum legal on arrival and then suffered a subsequent delay, and you are now in a mayday fuel situation and then you open the crossfeed valve and bank the airplane to perform a "gravity fuel xfeed" to prevent the left engine from starving, and then… The right engine flames out because it is on gravity and that bank doesn't help with the X FEED open. Just imagine...
Could that happen? I don't know, personally!
But I know that the procedure is very clear that: FUEL XFEED….OFF
I would not open it and bank the airplane, thus totally inventing a new procedure.
What I would do is just to revise my minimum diversion fuel and then to decide if either to continue or divert so as to land with at least the revised final reserve.
Last edited by Microburst2002; 13th Jun 2015 at 12:24.
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Microburst
You have a point. Most posts take it for granted that you must continue your FL and the flight to destination. Maintaining cross feed till impossible situation develops and then try to find a solution does not fit in any decision making tools. Initially when the failure occurs do the ECAM but after that a situational decision needs to be taken from your options. As Tubby elaborated the scenario if you were above FL300 then you can descend to FL300 and stop cross feed. That is the point you were asking WHEN TANK FUEL RQRD. Failed one side pumps and low fuel on the good side due to cross feed is definitely not an option. A diversion needs to be considered. As you rightly pointed out there is no cross feed procedure on two engines. If your company can accept a flame out on good pump side due to starvation and gravity feed on the live engine side then you can try all these methods.
You have a point. Most posts take it for granted that you must continue your FL and the flight to destination. Maintaining cross feed till impossible situation develops and then try to find a solution does not fit in any decision making tools. Initially when the failure occurs do the ECAM but after that a situational decision needs to be taken from your options. As Tubby elaborated the scenario if you were above FL300 then you can descend to FL300 and stop cross feed. That is the point you were asking WHEN TANK FUEL RQRD. Failed one side pumps and low fuel on the good side due to cross feed is definitely not an option. A diversion needs to be considered. As you rightly pointed out there is no cross feed procedure on two engines. If your company can accept a flame out on good pump side due to starvation and gravity feed on the live engine side then you can try all these methods.
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If you have to be careful with your maneuvering (AVOID NEGATIVE G FACTOR) I don't think it is a good idea to bank the airplane and open the X FEED. That might reduce the pressure in the engine LP pump. If the X FEED is closed I guess the bank angle would be OK, but who knows…
The point is that I would minimize procedure invention. QRH "over interpretation" is also a bad thing, but that's a sin we all commit from time to time
The point is that I would minimize procedure invention. QRH "over interpretation" is also a bad thing, but that's a sin we all commit from time to time
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OK, what I think:
Before any gravity feed, you will have FUEL L (R) TK PUMP 1 + 2 LO PR. You select cross feed and ignition and the affected pumps OFF. And then…
WHEN TK (affected) FUEL RQRD: TK(AFFECTED)FEED.......................................GRVTY ONLY
L2 Apply GRVTY FUEL FEED procedure, (Refer to PRO-ABN-28 GRVTY FUEL FEEDING). Fuel from the affected tank may be used immediately if there is no ceiling limitation for gravity fuel feeding.
When is required? This is your decision!
Is fuel in the center tank available with operative C. T. Booster pumps? How much?
Taking into consideration the center tank fuel availability and the time above FL300, for how long will you have to maintain what level to be able to star the gravity feed procedure?
How much imbalance will develop in the cross feed configuration for that time?
What will be the final conditions when in gravity feed and the same fuel flow is demanded from both wing tank? Total usable fuel, imbalance, final altitude, position, other aircraft systems, range, etc?
Maybe you have to descend immediately to FL 150, maybe you can maintain FL370, maybe you can maintain FL370 if you cross feed for 5 min and you will develop just 200kg imbalance, maybe…who knows.
Then, standard decision making.
Only in the very unlikely situation that you have dual fuel pumps failure + both on the same tank + one engine inop + the failed pumps on the live engine side:
Just for aircraft handling when imbalance reaches 1000 kg (and no fuel leak), you could use the bank technique (even you can fly the A320 with any imbalance).
IMHO.
Before any gravity feed, you will have FUEL L (R) TK PUMP 1 + 2 LO PR. You select cross feed and ignition and the affected pumps OFF. And then…
WHEN TK (affected) FUEL RQRD: TK(AFFECTED)FEED.......................................GRVTY ONLY
L2 Apply GRVTY FUEL FEED procedure, (Refer to PRO-ABN-28 GRVTY FUEL FEEDING). Fuel from the affected tank may be used immediately if there is no ceiling limitation for gravity fuel feeding.
When is required? This is your decision!
Is fuel in the center tank available with operative C. T. Booster pumps? How much?
Taking into consideration the center tank fuel availability and the time above FL300, for how long will you have to maintain what level to be able to star the gravity feed procedure?
How much imbalance will develop in the cross feed configuration for that time?
What will be the final conditions when in gravity feed and the same fuel flow is demanded from both wing tank? Total usable fuel, imbalance, final altitude, position, other aircraft systems, range, etc?
Maybe you have to descend immediately to FL 150, maybe you can maintain FL370, maybe you can maintain FL370 if you cross feed for 5 min and you will develop just 200kg imbalance, maybe…who knows.
Then, standard decision making.
Only in the very unlikely situation that you have dual fuel pumps failure + both on the same tank + one engine inop + the failed pumps on the live engine side:
Just for aircraft handling when imbalance reaches 1000 kg (and no fuel leak), you could use the bank technique (even you can fly the A320 with any imbalance).
IMHO.
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As I said the discussion is based on at all cost maintaining the current FL by cross feeding to deareate and then how to deal with the resultant imbalance. This is known as conformity bias where you look for data that conforms your decision rather than for information that would contradict it. Nobody is willing to take the option of descending to FL300 and stop the cross feed. If any one cares to look in the manual he will find that the difference in LRC FF at ISA+10 for a GW of 60 Tons between 370 and 300 is 8kg/HR/Eng. Just use gravity feed on failed side at FL 300.
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Yes, just follow the procedures (avoiding unnecessary or premature descents to any gravity feeding level, perhaps avoiding it at all).
Then, for the fuel management question I would take into account that if there is a significant imbalance, some of the fuel would be usable only after one engine starved, so I would consider increasing my final reserve in that amount. THen I would make my decisions based on that. If I have enough to continue, go on, other wise go somewhere else.
Then, for the fuel management question I would take into account that if there is a significant imbalance, some of the fuel would be usable only after one engine starved, so I would consider increasing my final reserve in that amount. THen I would make my decisions based on that. If I have enough to continue, go on, other wise go somewhere else.
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Hi Microburst2002,
If I anticipated that I might starve one of my engines of fuel, despite having sufficient fuel on board, then I'd attempt to fuel balance whilst gravity feeding both engines using the one wing low technique. I couldn't make matters any worse and might avoid shutting an engine down.
some of the fuel would be usable only after one engine starved,