Hi,

 

I've come up with this few times. I don't know if this is really a bug or a feature but it's rather annoying. So here's how it goes (as an example, I use 105tn of fuel):

 

I usually use the ground operations mode and I'll input my planned fuel there so the ground ops refuels my plane while I'm doing my preparations. However, for perf calculations I'll type the fuel manually on the PERF INIT page so it shows like 105.0tn MANUAL while the plane is still refueling. Ok, so far we are still going by the book. Now, if you are taking a huge amount of fuel, it might take for an hour to refuel. I usually use a fast 35min ground ops turn time, as that is more than enough for me. So I'll end up with the ground ops finishing its job and notice, I still need like 50 tons more of fuel. So, I'll go to the FS Actions Menu -> Fuel menu and input 105.0 there so I have the fuel I need.

 

However, here's the problem. I already have 105.0 set in the FMC manually and let's say I have 55tn on board and now I type 105.0 in the fuel menu, which adds me 50tn. This will show on the PERF INIT page as 155.0tn. And you easily forget to change the fuel to calc on the PERF INIT page after this.

 

Now, to put it in short; if you have 100tn set manually on PERF INIT while you actually have 50tn on board, and after that you set 100tn on fuel menu, your PERF INIT will show 150tn and ruin all your perf calculations.

 

The ground ops was just an example of how I encountered this. But theactual  problem is adding fuel from fuel menu while fuel amount is set manually. 

 

I was wondering could this be changed so that the fuel, that you have set in PERF INIT page, will remain the same even after modifying the actual fuel amount from the FS Actions Menu

 

 

I've come up with this few times. I don't know if this is really a bug or a feature but it's rather annoying. So here's how it goes (as an example, I use 105tn of fuel):

 

So there's a pinned thread that says "READ BEFORE POSTING."  It is here:

http://forum.avsim.net/topic/418750-pmdg-777-issue-tracking-thread-read-before-posting/

 

It's a good idea to read things that say "READ BEFORE POSTING."

 

...because you would've seen this:

 

Found / Fixed / Added for Future Update:

[...]

- Fuel imbalance/disagree on second flight without shutting FSX down.

 

 

...and it would've saved you all that typing.

No, i think he is talking about this, but in the reverse, instead of removing fuel, he is adding fuel.

 

 

Edit: start the video from 23 minutes.

So there's a pinned thread that says "READ BEFORE POSTING."  It is here:

http://forum.avsim.net/topic/418750-pmdg-777-issue-tracking-thread-read-before-posting/

 

It's a good idea to read things that say "READ BEFORE POSTING."

 

...because you would've seen this:

 

 

...and it would've saved you all that typing.

 

1) I did read  Ryan's issue thread. Twice.

2) I did notice the mentioned bug.

3) I've been reading the thread often.

 

 

I haven't looked for that bug but considering that it is related to a second flight, I didn't see it having anything to do with this. This is not affected by which flight it is. If it causes an EICAS message, I wouldn't know about it because I took off and flew for an hour with a wrong fuel setting and didn't get any warning. This is strictly a change of manually set fuel in the fmc perf init page, when it is changed from fs actions fuel page AFTER it has been manually entered into perf page.

 

To tell you the truth, honestly I have no idea how you linked these together? Or perhaps Ryan should have noted that this bug is not caused just by flying a second flight but that you can do it anytime you want.

So Joona i do not think it is a bug, as Kyle said in his video when you manually enter a figure, say for example 50, even though the fuel quantity is saying 150, you are telling the FMC to read or see that 150 in the tanks as 50, then when you add fuel to the tanks on top of the 150 thats already in there, the FMC sees the increase in quantity and adds whatever amount you added to the tanks, to the FMC manual entry.

Bryan, you might be right. That's why I wrote in my second sentence:

 

 

I don't know if this is really a bug or a feature but it's rather annoying.

 

Because I find it annoying and I was wondering if it could be changed

 

 

.PS. And I was thinking that in case it was a bug, it was better to post here as I didn't see a mention in Ryan's thread. 

 

 

To tell you the truth, honestly I have no idea how you linked these together? Or perhaps Ryan should have noted that this bug is not caused just by flying a second flight but that you can do it anytime you want.

 

I misread what you were getting at.  I see what you're getting at now, and Bryan got it, and provided a good reference to how to handle it.

 

 

 

Because I find it annoying and I was wondering if it could be changed

 

I'm sure you could bring it up to the team via a ticket (support.precisionmanuals.com).  I don't imagine that it would be too difficult to have it automatically delete any manual fuel entry on the INIT page on fuel adjustment on the fuel page, but I didn't write the code.  I'm not sure how the real aircraft handles that situation, either.  If the real world aircraft does the same thing, I don't see it likely that it would change.

 

In any case, just delete the manual entry and everything will be fine.  Not too difficult in the end.

This sounds like a bug.

 

FMC fuel figures are either sensed, calculated or manually entered. The logic is as follows: On the ground FMC fuel is sensed (giving the same level as the EICAS readout) until the first engine is started. At this point, FMC fuel switches to "calc". It remembers what the sensed fuel level was at this time of the first engine start then continuously updates this figure by subtracting fuel as measured by the engine fuel flow sensors (the pilots can then refer to PROG page 2 to quickly compare calculated and sensed (totalized) fuel to easily identify a fuel leak). The important point here is that calculated fuel has no idea how much fuel is actually in the tanks.

 

Manual fuel entry works the same as calculated fuel; it takes a given fuel reading (except input by the pilot rather than from sensors at engine start) then uses fuel flow to update and also has no idea how much fuel is actually in the tanks. So, when then FMC is using a manually entered fuel figure and you're refuelling, it shouldn't start adding the fuel as it's loaded as described by the OP because it's not taking any information from the fuel level sensors.

Yes, it is cleared by removing the manual entry, I agree on that. However, if you remember to do that, is another story :thinking:

Yes, it is cleared by removing the manual entry, I agree on that. However, if you remember to do that, is another story :thinking:

Yes but you shouldn't have to remember. My point was that once you've entered a manual fuel load in the FMC, how much fuel is actually in the tanks is irrelevant. As such I believe you've identified a genuine bug.

 

 

Yes but you shouldn't have to remember.

 

He wasn't saying that you should (that's the whole point of this thread, honestly).  He was confirming that it clears if you remove the manual, and adding that if you don't, it causes problems.

 

 

 

As such I believe you've identified a genuine bug.

 

support.precisionmanuals.com

Ok, I sent a ticket for PMDG. Let's wait for their response :Nail Biting:

Here is a picture of the TAKEOFF REF page with wrong fuel calculations. I noted the high V speeds but I haven't flown the 777 with over 250tn weights so I was guessing that my relatively high weight was causing it. At this point I missed the GR WT which is clearly showing 378.3tn. The actual takeoff weight was 313tn (ZFW 208 + fuel 105). Also the PROG page on the FMC2 says fuel 170tn. My initial altitude was FL302 but during climb I noticed that my max crz lvl was around FL260-270. For a second I was wondering the cause for this, when I remembered the problem with fuel amount, that I had encountered earlier and confirmed from the perf init page, I had like 170tn of fuel according to the FMC. I cleared the manual entry back to calc and the normal performance was restored.

 

EDIT: sorry, uploaded wrong pic at first