Fuel usage or rather not using any fuel but still flying.

[clif737]

Doing a flight and loaded 31000 pounds of fuel (screen 1) (Screen 2) is FF or used. Fuel is not showing at all used on the gauges. (Screen 3) shows my CI which is 80 from the OPF for this flight. At this point halfway through I should have used at least 7000 pounds of fuel.  Again the gauges never show anything being used. I can even flip the fuel valves all off and the engines dont die but keep running. I have the most fuel efficient 737 in the world- but alas not realistic at all. What could be going on?

No I didnt have one heck of a tail wind either. 

 

[clif737]

also verified - Xplane still sees the full amount of fuel that I loaded at the start  - one last thing I did do a successful flight earlier but stayed in this plane and didnt reload xplane. Do I need to reload Xplane after using this 737 after just one flight?

 

Edited September 16, 2020 by clif737
changes

[Litjan]

Hi clif,

this is unusual - some observations:

Fuel loading in the 737 only works through the IXEG side-pop-out menu. You can´t load fuel through X-Plane´s fuel menu. You can see the fuel loaded in that menu, though.

When entering a PLAN fuel - this never changes. It is a value the pilots can input to PLAN a flight (i.e. if the real fuel wasn´t loaded yet). Don´t use the PLAN field - or if you do, eraze it afterwards (this will otherwise stay locked and never change the gross weight).

Switching off the fuel pumps will not starve the engines - not in a real 737, either. The engines will keep running through suction feeding, but thrust degradation at high altitude or high powersettings may occur.

Now I have to doublecheck if using a PLAN value will preclude fuel from being used - that would of course be a bug!

Normally you don´t have to reboot the aircraft after a flight - you can just go on the next one.

Cheers, Jan

Edit: I just doublechecked - using a PLAN fuel input does not affect fuel usage on my end - on the first flight. Are you running any plugins that could be affecting this? It is the first time I have heard of this problem.

 

Edited September 16, 2020 by Litjan

[clif737]

Thanks for your response. I did use the fuel load method from IXEG off the side menu. I only verified zero fuel use from the Xplane side to see not one drop was used from the sims perspective. 

[Litjan]

Thanks for getting back to me on this!

You can also enable the DATA OUTPUT field #62 (fuel weights) to readily see on screen how much fuel is in the tanks and if it is getting used.

If you can find a way to reliably reproduce our 737 to not use any fuel, please let me know! We want to fix it (or sell the technology to the airlines!! ;-)

Cheers, Jan

 

[clif737]

Well again no fuel use and nothing in plan ever today 

[clif737]

takeoff to altitude should have burned through center tank  ver 1.33

Edited September 17, 2020 by clif737
changes

[clif737]

One question I have  is the cost index off simbrief. Is that value messing with my fuel possibly? Should I be using another value?

 

[Litjan]

Hmm, no - the cost index should have nothing to do with it...could you attach your log.txt so I can check if maybe you are running some other plugin that may be interfering with this?

[clif737]

been flying this plane non stop to try to reproduce the error. It seems good now - CI does mean how fuel efficient the rout and plane is correct? I love the improvements to it. This plane is one I would recommend to anyone. 

[Litjan]

Hi clif, thanks for the nice words - I honestly have no idea what may have caused that problem for you - we pretty much use the normal X-Plane fuel usage logic for our engines...

The cost index is describing the relation between flight-time related costs (maintenance costs, crew costs) and fuel prices. In other words, if the fuel was mega-expensive and the crew works for cheap, the cost index is 0 (best fuel economy). The actual speed results from the cost index and the wind component - headwind will make you fly faster (to get out of the wind sooner) and tailwind will make you fly more slow (to coast in the tailwind longer).

If fuel is cheap, the cost index is high.

Pilots can also alter the cost-index (usually one is recommended on the flight plan) to cater for delays (fly faster to make up time) or to save fuel if they arrive early otherwise.

Cheers, Jan

 

[clif737]

Well did it to me again tonight after like 10 flights with proper fuel usage. I loaded 25000 lbs fuel and when I was fly I only used the APU fuel and nothing else. Here is my log. I also looked at data refs but I didnt see anything funky and couldn't locate one that showed fuel used. I didnt take long looking at it before getting frustrated. If you see xplane quit its because I didnt finish flight. Got to the point where an aircraft thats not pulling fuel makes the challenge pointless. Its like xplane god mode. Not getting down on this plane - I have had it a long time and its getting sooooo good. I will try sdome flights tomorrow and see how it responds. I havent had this fuel bug in other aircraft and I do run the release vulkan.

Log.txt

Edited September 24, 2020 by clif737
changes

[Litjan]

Hmm - there may be a lead in your description - do you have the APU running while you fly? Maybe there is a bug in the fuel usage code with that - I will try that on my end...

You are running two plugins that I would consider "suspect" in this case:

RealityXP and XJet.

However to really get to the bottom of this you would probably have to run a (lenghty) elimination process where you fly without any plugins to see if that fixes it - then bring in your plugins in batches to try and isolate the problem.

I believe you when you say that no other planes suffer from this, but I dare to say that few other planes have an intricate system modeling that may be affected by these plugins in the way our 737 is.

In addition this is a very isolated report - in fact it is the only report we ever had of our plane NOT using any fuel...so I deduce from this fact that it must be something unique to your setup/plugin environment. I will happily help you narrow down on the cause, of course!

Cheers, Jan

 

[Litjan]

PS: I just googled the problem a bit and it seems that there is a bug in X-Plane where if you have the "instructor operating station" open on another window, the plane will not use any fuel (as the IOS constantly "refills" your tanks). Could this be a factor in your case?

[clif737]

I dont have the instructor operating station. I had to google that to see how to do it and I dont or never have 

 

[clif737]

I also disabled the plugins you mentioned - and it did it to me again. I shut off apu after main engines start and gens on

[Litjan]

Maybe you can take a screenshot of your overhead (fuel pumps) panel when it happens the next time? Also, did you output the fuel weights (small green numbers) on screen to verify fuel is getting used (or not) on screen? I want to rule out a failure of the fuel gauges updating...

The next step would be to delete your preferences folder, and if that doesn´t help you would need to do a full re-install of X-Plane and only the 737.

These (especially the second) are big steps involving a lot of work, but I am really at a loss what could be causing this for you besides some weird corruption that happened to some of your core files...

Cheers, Jan