A320 L+R Wing Tk Lo Lvl

[rudderrudderrat]

Can somebody please explain the logic behind this Airbus ECAM procedure?

The ECAM asks for the fuel X feed to be selected OFF (Closed). However the QRH procedure on every other aircraft I've flown, has told me to Open the Fuel Crossfeed.

If I have had an engine failure and FOB = 1500 kgs (750 each side), provided there is no fuel leak - I'd have considered the fuel imbalance (or opened fuel X feed on older versions) completed the Engine Shut down, and cleared the ECAM.

The L+R Wing Tk Lo Lvl ECAM will then ask me to turn the fuel pumps on and close the X feed (OFF).

Apart from the Fuel Pump Low Pressure warning, what other timely ECAM alert do I get that I'm about to run out of fuel with 750kgs still remaining in the other wing tank?

Suppose I manage to land with 1 ton final reserve fuel remaining (as shown on FOB indication) I'd only have 250 kgs feeding my good engine (that's about 7 mins endurance).

Where am I going wrong? :confused:

[TyroPicard]

Abnormals are written for one failure/caution/warning only - i.e. this procedure assumes two engines running. L+R WING TK LO LVL happens at approx 30 mins. fuel remaining.. I would hazard a guess that closing the x-feed is requested to prevent simultaneous flame-out.

I would keep the fuel x-feed open in your scenario with one engine shut-down - it is one of those situations where common sense must prevail. And you are not going wrong - you are displaying good technical understanding.

[rudderrudderrat]

Hi TyroPicard.

I agree I would definitely keep the X feed open. But surely there should be a QRH or an OEB to advise me?

Every other aircraft I've flown had a Low Fuel Contents procedure which ensured all the fuel was available to all my engines - even when Engine Out.

[Microburst2002]

The after ENG SHUT DOWN ECAM procedure calls for opening the XFEED, so I guess this is overriding the LOW FUEL XFEED shut.

As for the reason to shut the valve (2 eng)... Who knows!

[TyroPicard]

But surely there should be a QRH or an OEB to advise me?With an engine shut down ECAM has advised you to "MONITOR FUEL IMBALANCE" (implying "carry out the FUEL IMBALANCE procedure if required). Old ECAM standard requests FUEL X-FEED OPEN. As MB2002 points out this is a more serious problem than the fuel level and those actions take precedence.. think of FUEL LEAK which says "do not open crossfeed even if requested by another procedure" .. ECAM can be wrong! Pilots are paid to be right, not to follow blindly the wrong move because the book says so.

Every other aircraft I've flown had a Low Fuel Contents procedure which ensured all the fuel was available to all my engines - even when Engine Out.As does the A320 when OEI - but when on two engines Airbus choose to isolate them in a low fuel situation for reasons best known to themselves.

To expand on Abnormals are written for one failure/caution/warning onlyif you write a procedure for every possible combination of faults the cockpit really would be full of manuals without room for a pilot...

[911slf]

Tyropicard

"if you write a procedure for every possible combination of faults the cockpit really would be full of manuals without room for a pilot..."

...especially if you are forbidden to use a laptop, as some US politicians would want:)

[rudderrudderrat]

I'm still confused.

It appears from your replies that originaly, the Engine Failure ECAM told me to OPEN (select ON) the X Feed and that this procedure took precedence over the Low Fuel contents ECAM.

So now my ECAM says "Monitor Fuel Imbalance" which apparently means do the imbalance QRH checklist. No where in this check list does it say turn all the fuel pumps on and leave the cross feed open. It asks me to close the X feed when the balance is complete.

As far as I can see, at present, we don't have a published Low Fuel Contents procedure when Single Engine. We seem to rely only on crew awareness.

It appears that the change in the ECAM from "Open X Feed" to "Monitor Fuel Imbalance" has been tripped up by an error in L+R Wing Tk Lo Lvl ECAM procedure. I think the error is the Fuel X Feed should be selected On (Open) not Off (Closed).

What does the A330 Low Fuel Contents procedure say?

[Microburst2002]

That is a very good point.

The IMBALANCE......MONITOR ecam action in the SHUT DOWN procedure is quite ambiguous.

It is just a monitor advice, not a prompt to carry out the inmbalance procedure as such. Besides, it is not required to carry out this procedure if there isn't a fuel imbalance advisory.

I had this advisory once. The captain decided not to carry out the procedure before the advisory came for that note in the procedure even though we had detected quite an important umbalance. After an hour, we had a permanent bank angle and some sideslip. Then the advisory was triggered.

So it is left to the pilot to decide on wether to open the xfeed valve or keep it shut.

Therefore, in the double tank low fuel caution we should shut off the XFEED unless the MONITORing of the fuel umbalance suggests opening it before an engine flames out. In case of a previous eng fail, I guess the sensible thing to do is open the valve.

[CaptainProp]

I believe it a matter of "We think you may have screwed up so initially - Turn X-Feed OFF". ie "You have low level light because you have a leak that you did not recognize". Once you have isolated left / right fuel and confirmed that no fuel leak exists THEN you can consider turning X-Feed ON.

CP

[TyroPicard]

Three days to discuss what to do with one switch with only 30 minutes fuel remaining :ugh:
You know you are short of fuel , and are at some point in descent or approach. Consider OEI and L+R TK LO LVL in the two possible combinations.

ONE: L+R TK LO LVL caution appears. ECAM actions completed. Then an engine fails. Run ECAM and at FUEL IMBALANCE ... MONITOR you check for leaks and turn X-FEED to ON if no leak. All the fuel is available to the live engine.

TWO: OEI, ECAM actions complete. Because of the fuel imbalance the X-FEED is ON and two wing tank pumps are OFF in the low tank. L+R TK LO LVL caution appears, you run ECAM...
ALL TK PUMPS ... ON (sensible)
FUEL X FEED ... OFF !! Not sensible so you leave it ON, because the procedure is written for a serviceable aeroplane and you apply common sense.
All the fuel is available to the live engine.

Your priority is to land the a/c before you run out of fuel!!!

rudderrudderrat
Apologies if I sound like 411A but... Still confused? Volunteer for extra training or hand your licence in.
It appears that the change in the ECAM from "Open X Feed" to "Monitor Fuel Imbalance" has been tripped up by an error in L+R Wing Tk Lo Lvl ECAM procedure.They are completely separate procedures based on an otherwise serviceable a/c. This applies to all manufacturers. Air Transat 330 crew followed (old) ECAM without monitoring fuel imbalance. The current procedure is safer.
I think the error is the Fuel X Feed should be selected On (Open) not Off (Closed).ISTR that eg B747 fuel x-feed was opened with low fuel state to cope with pumps being uncovered on a go-around? This may not apply to A320? And if you do run out of fuel would you like simultaneous flame-outs or have them (say) two minutes apart?

[rudderrudderrat]

Thanks MB2002 and Capt Prop for your logical views.

TyroPicard - I don't intend to run out of fuel - but to land with more than 30 mins useable fuel with both engines running, or more than 15 mins useable fuel with one engine out.

It would be good to have a logical Low Fuel Contents ECAM procedure which satisfies both.

[rudderrudderrat]

Hi,

I just found this link from Airbus :

http://www.smartcockpit.com/data/pdfs/flightops/flyingtechnique/Operation_With_Minimum_Fuel.pdf

So when FUEL L+R Wing Tank Lo Lvl is triggered - why does the A330 request Wing X Feed On (Open), the A340 request X Feed 1,2,3,4 On - but the A320 request Fuel X Feed Off (Closed)?

I'm still hoping someone can enlighten me.

[TyroPicard]

rudderrat
Pages 16 and 17 of that .pdf link show technical differences between A320 and LR types - I don't know enough to say if that is the reason for the difference in X-FEED management.

Regarding TyroPicard - I don't intend to run out of fuel - but to land with more than 30 mins useable fuel with both engines running,you are discussing L+R TK LO LVL, this warning occurs with 30 minutes of fuel remaining.

[Idle Thrust]

I'm surprised that nobody has mentioned Air Transat at Lajes.

[TyroPicard]

Are you calling me a nobody?

[rudderrudderrat]

Hi TP,

you are discussing L+R TK LO LVL, this warning occurs with 30 minutes of fuel remaining.

According to the presentation that's an approximate figure. Depending on the aircraft variant and landing weight - our 30 mins reserves are typically about 1 Ton. Many of our fuel flight plans predict landing with about 1500 kgs - hence my original concern at the start of this thread.

Presumably we have to consider an engine failure at the worst point on the intended flight? For our short haul operations - our fuel management problem is a point on the final approach if the crew elect to fly a Go Around.

[Mäx Reverse]

In this context it is important to understand AIRBUS' approach with regard to certifying operation with low fuel levels.

They say that according to flight planning requirements you arrive your destination with minimum diversion fuel, go around, divert to alternate and arrive there with only final reserve fuel remaing, i.e. an endurance of 30 minutes which translates into roughly 1.0 - 1.2 tons on the A319/A320.

A go-around at the alternate is not taken into account from a fuel-management point-of-view although 1000 kg FOB would enable you to go around, fly a short radar vectored pattern and land with at least 400 kg remaining.

AIRBUS says Final Reserve Fuel is only for Holding and now take your seats: If you go around or otherwise exceed +10° of Pitch you might flame out any one or even both engines.

As mentioned above, as going around at the alternate is not figurde into minimum fuel requirements, there's nothing in the books with regard to this, remember 'it's the best aeroplane in the world'. :ooh:

The only small hint is in System Limitations / Fuel, as the min. FOB for takeoff is 1.500 kg or just the warning Threshold for L+R Wing Tk Lo Lvl. Nice try, uh ??!

Back on Topic:

It's a certification requirement that for Take-Off and Landing both engines may NOT be feeded from the same tank as it might be the case with Fuel X-Feed open depending on the outlet pressure of the fuel pumps. That's in my opinion the reason for NOT opening X-Feed with both wing tanks low level.

BRGDS, Max

[nnc0]

If you go around or otherwise exceed +10° of Pitch you might flame out any one or even both engines.

Where does it say that?

[Mäx Reverse]

That was admitted to our flight safety departement 'off the record', there's nothing in the book as AIRBUS deems it operationally insignificant - Insane!

BRGDS, MAX

[rudderrudderrat]

Hi Max, This is from the link I've posted above in this thread. Page 17. The aircraft would never have been certified otherwise.

A318/A319/A320/A321
The pumps located in the collector cell pick up fuel directly from the bottom of the pump canister.

FUEL L + R WING (INR) TK LO
A330/A340
The pumps located in the collector cell pick up fuel directly from the bottom of the pump canister. Jet pumps and clack valves ensure that the collector cells are maintained full.
NO RESTRICTION IN G LOAD
NO RESTRICTION IN PITCH

[Mäx Reverse]

I'm well aware of this document and as I stated above AIRBUS officially only states that there are no restrictions operating with low fuel levels. Unfortunately this only applies for manoeuvres within certification requirements and demonstrating a go-around with 30 minutes FOB is neither required nor is the fuel for it figured in the fuel-calculation as you can see on the first pages of the AIRBUS-document.

If you seriously buy the AIRBUS statement please tell my at which fuel level (if not 750 kg per tank) you would accept the possibility of a flame out with 17.5° of pitch and 25° Bank from a technical point of view. 500 kg? 200 kg? 100 kg?

And all the Boeing aircraft with notes in the book to the extend that 'pitch should be limited as much as possible' in low fuel situations seem to be pretty ill-engineered in comparision to our french plastic jet.

BRGDS, Max

[rudderrudderrat]

Hi Max,

In FCOM 3.01.28 "Minimum Fuel Quantity for TakeOff : 1,500 Kgs provided Wing Tk Lo Lvl warning must not be displayed on ECAM for takeoff." (Presumably this restriction is to prevent the ECAM ding before T.O. Inhibit.)

So if it's certified for 1500 kgs on Take Off - what's the difference in pitch during a G.A.?

Surely a balanced turn with 30 degs bank will have no effect - because the fuel will only sense an increase in g and still lie in the same position in the tank?

As for the minimum fuel before one of the main tank fuel pumps uncover - I don't know. But I thought the other pump's inlet should remain covered until the fuel was exhausted - else it would be described as unuseable fuel.

[nnc0]

Somebody at airbus said off the record that....

Those kind of things need to be taken with a grain of salt.

Physically, the collector cells lie between ribs 1 and 2, the upper and lower skins, with a one way valve for (inner) wing tank fuel to flow into the collector cell but not out. The cells have 2 pumps, fore and aft placed in opposite corners.

Once the fuel resides in a collector cell, the only way it exits that cell is through a pump to an engine. (It won't slosh/drain over to the other wing in a steep turn)

FIT would need to read 0 before the engine would flame out.

Having said all that, I understand that you can in fact flame out the engine but you would need to hold an fairly excessive angle in pitch and roll attitude or high g load for more than a few minutes, or be inverted.

[Mäx Reverse]

In FCOM 3.01.28 "Minimum Fuel Quantity for TakeOff : 1,500 Kgs provided Wing Tk Lo Lvl warning must not be displayed on ECAM for takeoff." (Presumably this restriction is to prevent the ECAM ding before T.O. Inhibit.)

So if it's certified for 1500 kgs on Take Off - what's the difference in pitch during a G.A.?

That's exactly my point: A go-around is just an inflight take off regarding attitudes and accelerations and if your FOB is below 1.500 kg then you're walking on thin ice.

Cheers, MAX