Playing with Fire

[nawarren 83]

Hi All,

 

This evening I took off from LPPG with full fuel load, I think 145 tonnes or so. After take off I decided to have  a little fun and set a Right engine fire. I followed the ECL (awesome detail) all the way through, shut down and secured the engine. All the while on auto pilot.

 

Then set up a hold to fuel dump for return back into Paris. The fuel dumping began and was going to take approx. 1 hr. All going well so far. I had an eicas fuel imbalance message appear after a few mins. No problem as this is due to having only the Left engine burning fuel. Again I followed the ECL, which told me to open the cross bleeds and turn off Left fuel pumps to allow Right fuel pumps to use the fuel in right tank to even up the imbalance.

 

Now as part of the engine fire checklist I turned on the APU, this uses fuel pump left fwd. So even though I had turned off both left hand fuel pumps the fwd left was still running. Due to this I was unable to cure the fuel imbalance and by the time fuel dumping had got down to MLW the imbalance was 5 tonnes.

 

Does anyone know if I am missing something, is this what should happen? I did think I could sort it by switching APU off but didn't think that was a safe option!

 

Hope this rambling makes sense and would love to hear from anyone with any ideas.

 

Cheers

 

Neil

 

[gatetothesky762 7]

Good evening, I think it is normally one of the tasks of the co-pilot must make a small calculation must put more fuel in the left than on the right before proceeding to the unloading of fuel to compensate for the consumption of the clearance and left engine on the left pumps ... not sure of the procedure but it is easier to realize in a simulator like FSX, the first fuel balance (roughly 3/4 left and 2/4 right), 2nd jettison. repeat operation as many times as necessary ...

[Lionking777 0]

Hi, I have posted similar posts trying to get the attention of someone in the know at PMDG. The fuel imbalance behavior is definitely not normal. The fuel flow on single engine is way to high and the FUEL IMBALANCE caution is triggered too soon. I think that this is caused by an unusually high fuel flow of the operating engine.

By the way, my day job is flying the real T7 and I am amazed at how accurate most of this sim has turned out.

[nawarren 83]

Hi Guys,

 

Thanks for your replies. I agree this is one hell of an acurate 777 simulation! Good to hear real world pilots opinions.

 

Gatetothesky762, i'm not sure what you mean. I tried correcting the fuel balance both with fuel dump on and off, did not make any difference. The issue I have is with APU running the Left Fwd pump is on automatically and therefore uses fuel from left fuel tank, which doesn't allow the fuel to be rebalanced.

 

Cheers

 

Neil

[nawarren 83]

Hi all

 

Has this issue been fixed in SP1?

 

Cheers

 

Neil

[77west 139]

I don't believe it is an issue.

 

As stated in another thread, the 777 can land with any imbalance, the advisory is there more for normal ops than emergency situations. Hell, it can land well over MLW if you really need it to.

[tcas_climb 45]

The issue wasn't the imbalance itself, the issue was that the APU running prevents the right engine from feeding from the left tank while the left engine is off thereby preventing the imbalance to be corrected with the APU running.

 

Also I could be mixing this up with another aircraft, but I'm pretty sure the 777 has a limit to the amount of fuel imbalance it can land with.

[scandinavian13 5,192]

If nobody submitted a ticket, then it wasn't guaranteed to be seen.  I don't recall seeing it on any of the lists, but there were a bunch of lists, and a bunch of items on those lists.

 

If anyone feels they have found a bug: ALWAYS submit a ticket, unless you don't truly care if it gets fixed...

[tcas_climb 45]

I thought it was submitted by the op, will check if it was changed in a few minutes and ask them about it if not.

[nawarren 83]

Hi Kyle,

 

When i first mentioned it, one of the posters said he had submitted a ticket. I will have another look at it when i get some time and submit a ticket, I wasn't sure if this is correct behaviour or not. If someone on the team could comment on this we may find out this is correct A/C logic. It just seemed illogical to my small brain :mellow: in that in a certain situation you are unable to correct a fuel imbalance.

 

Cheers

 

Neil

[nawarren 83]

Hi all,

 

Looking at the list of fixes in SP1 I saw this:

 

 0002893: [systems - Fuel] Fuel Balance issues EO (rsrandazzo) - resolved

 

So this may be fixed, when I next get a chance I will load up a full fuel load, take off, fail right engine, start APU, and begin fuel dump, and carry out fuel imbalance ECL when required and see what happens.

 

Cheers

 

Neil

[FLXMCT 0]

Gents,

 

during my testing I found the issue with APU forcing L FWD pump to run fixed. 

Now -in the air- the DC pump takes over for supplying the APU fuel.

 

But during testing I found another issue I have already submitted a ticket for and which was acknowledged by support team.

 

For simplicity I will quote the support ticket I have submitted, should you be interested.

 

 

Fuel Jettison - Balancing

During jettison operation, when trying to balance fuel with the RH main tank the lower level tank ( so RH FWD and AFT pumps off) the RH engine is not supplied via the crossfeed as it should be accompanied with FUEL PRESS ENG R amber EICAS caution.

Opposite operation works fine (noticed that SP1 fixes L FWD pump not switching off when APU is running). The same issue is also observable with fuel in the CTR tank.

 

Best regards

Luke

[nawarren 83]

Hi there,

 

I have set up a flight with max fuel approx 145 tonnes, set a VR cut on Number 2 engine. Took off, followed ECL for no:2 engine shutdown. Started APU, then started a fuel dump. Very quickly led to a fuel imbalance,more fuel in left tank, less fuel in right tank. Followed fuel imbalance ECL, opened both crossfeed valves, turned off both left fwd and aft fuel pumps. Still left fwd fuel pump stayed on (i presume because its feeding APU). Therefore the left fwd fuel pump was feeding ENG 1 and APU and no fuel was being rebalanced. DC fuel pump in left tank was not on, different to the first picture in above post. Am I doing something wrong here?

 

I would post screenshots, but can't figure out how!

 

Cheers

 

Neil