fuel-tanks #1 and x5 feed engines

[Retnek]

Installing 12.08b1 I see some strange interaction between the fuel-tanks and the engines,too.

After some try-and-error I re-installed the Mu-2-module and tested with the 4- and 5-blade-OEM-version. Lua-scripts or alternative acf-files to manage fuel and passengers were not installed / used.

I started with 100% in main-tank #3, empty wing-tanks #2 and #4 and 100% in tip-tanks #1 and #5. What's strange:

a) the engines get the fuel from the tip-tanks #1 and #5, later the right-hand engine switches to tank #4. The correct and only option should be the main tank #3.

b) the "auto"-option for the fuel-transfer immediately starts to balance the level of fuel between tanks #1 and #2 and #5 and #4, resp. That's strange, too, since there should be no way to transfer fuel that way. From all wing-tanks it's just one-way into tank #3. Tank #3 get some fuel from the wing-tanks, too. Sadly on top of the already 100% in the tank.

This pic was made during early climb. tanks #1 and #5 are balancing with their #2 and #4. Main tank #3 get's fuel from the wing-tanks, too, beyond it's capacity already. Engines get fuel from their tip-tanks.

 

Some minutes later #1 / #2 and #4 /#5 are balanced. tank #3 is completely overloaded and engine 2 switched from tip-tank to the wing-tank #4.

As soon as the (auto-balanced) pairs of wing-tanks are empty, the engines shut down. Main-tank isn't used and remains overloaded. One can cheat and "re-fuel" the tip-tanks in flight. Given the real-world manual it's possible to start the engines in flight. I wasn't able to re-start before my altitude was gone. It's quite a few steps, with some proper training it should be possible.

It would be kind if my findings could be checked and confirmed by others? Thanks in advance, Ulrich

 

Edited November 11, 2023 by Retnek
typo

[tkyler]

I haven't tried the Moo in 12.08 yet, but will be quite soon and will check this.  ...you're comment though

Quote

a) the engines get the fuel from the tip-tanks #1 and #5, later the right-hand engine switches to tank #4. The correct and only option should be the main tank #3.

doesn't fully make sense.   The engines get their fuel from tank 3 yes, but the fuel transfer system pumps fuel from the tip tanks to the main tank as the main tank depletes.....so you would observe no fuel coming out of the center tank #3 until the tips / outers are all empty (or the fuel transfer system is off).     ....so seems fuel transfer is correct for this point (a) you made.

Regarding tank 3 being "overloaded"...you're showing 166 gallons in screenshot 2.....and Jet-A at about 6.7 lbs/gal comes out to about 1100 lbs...which is exactly what the main fuel gauge shows....so don't quite understand your point there either.  I don't see tank 3 overloaded at all in those screenshots.

The only thing I see "odd" about those two screenshots are the outer fuel tanks (2/4) seemingly losing a small amount fuel with fuel still in the tips.

Now all that said...I certainly won't put it past X-Plane to introduce some funny business...so I certainly will double-check the fuel systems soon.

Thx.

TK

[tkyler]

Ok...that did NOT take long.   I downloaded 12.08 and without a doubt...I see what you're talking about,   the fuel transfer is definitely NOT working correctly in 12.08.  It is fine in 12.07...just checked before downloading 12.08.  I'll poke around with Laminar to see if its a bug or a "new feature" I have to now code around.

I know Laminar is getting more and more systems detail, and when they do...it usually breaks our custom stuff...because there's always some aspect to a design their generic implementations can't cover....and if they don't leave us a loophole via plugin....it can get ugly.    

Thx for reporting.

TomK

Edited November 11, 2023 by tkyler

[tkyler]

So below are the descriptions in Plane-maker of the fuel tank "role".   The tooltip on the left is 12.07...the one on the right is 12.08

Laminar definitely been playing with the fuel code...*sigh...always a fight figured this stuff out.

100.00 bucks says the tooltip on the left was written by Austin

 

12.08 IS beta....so I'll file a bug report as a start and then use other channels if I have to.

tk

Edited November 11, 2023 by tkyler

[Retnek]

Tom, tanks for checking this. It needed two Mu-2 wrecked in bad weather somewhere South of Gander. Until then the Mu-2 was my bug-free reference-plane - if  something went wrong, it was my fault. Later I stumbled over the part in Austins video where he proudly presents his code simulating jet fuel-tanks used as oil-coolers. Hmm ... maybe he changed that part of the code a bit too much?

Edited November 11, 2023 by Retnek

[Retnek]

9 hours ago, tkyler said:

a) doesn't fully make sense.   The engines get their fuel from tank 3 yes, but the fuel transfer system pumps fuel from the tip tanks to the main tank as the main tank depletes.....so you would observe no fuel coming out of the center tank #3 until the tips / outers are all empty (or the fuel transfer system is off).     ....so seems fuel transfer is correct for this point (a) you made.

b) Regarding tank 3 being "overloaded"...you're showing 166 gallons in screenshot 2.....and Jet-A at about 6.7 lbs/gal comes out to about 1100 lbs...which is exactly what the main fuel gauge shows....so don't quite understand your point there either.  I don't see tank 3 overloaded at all in those screenshots.

 

Cited just to understand the topic:

a) Looking at the fuel-lines installed the only source of fuel for both engines is main tank #3. So I would expect the output of engine1tank# should be "3" all the time. Maybe it is coded in a way the engines first use a "virtual fuel line" from the tip-tanks, secondly the wing-tank and the main-tank finally. To avoid extra-code virtually pumping the fuel from the wing-tanks into the main tank.

b) According to your handbook the capacity of the main fuel tank is 1040 lbs. The gauge is presenting lbs and 1040 was maximum until 12.07. My pictures show values around and well above 1100 lbs. Flying a bit longer the needle is moving above the zero-value to the left. So that tank is overloaded by the recent code for sure.

No critics intend here, your first-class module just ran into trouble with the 12.08-beta-update.

There's an easy work-around by re-arranging the level of fuel via the "flight" and "edit weight & balance"-options every hour or so. Disabling the "auto"-option in the Mu-2's fuel-pump-section will stop the transfer from wing tanks into the main tank. As long as the wing-tanks have fuel the engines do fine.

[meierzwo]

Jepp, it's broken.
Doing a Flight with max Fuel Capacity in all Tanks.
Starting the Engines with Main Only, then switching to Auto and watching the Fuel Indicators in Flight.
Tip Tanks are draining and Main is raising up.
Tip Tanks reaching the Level from the Outer Tanks and now both Systems are Draining. Main still raising up.
Tip and Outer Tanks running Dry and the Engines are out. Switching Auto Fuel System Off and Restarting the Engines didn't work because Main Tank is not used.

Next Test. Only Fuel in Main. Auto Fuel System Off, Outer and Tip Tanks with no Fuel.

Starting the Engines did work but after a Minute, they Shut Down. Main Tank is not used for Feeding the Engines, only the Wing Tanks, but the Wing Tanks still feed up the Main Tank over the Limit.

Next. Fuel in Main and Outer, but not in Tip. Auto Fuel System Off. Engines Running, feed from Outer, Main is not raising up.
Waiting until the Level is about 100 lbs in the Outer Tanks. Now adding Fuel to the Tips. Auto Fuel System still Off. Fuel Level in the Tips is now Draining but no Feeding to the Outer or the Main. Tip Tank is reaching the Level from the Outer Tank and now the Level off both Systems is draining again.
Filling up the Tip again and now Auto Fuel System to Auto: Main Tank is filled up very quick (was at 600 lbs) until its normal Full Level is reached, then the Filling Rate slows down but the Main is still feeding with Fuel. Tip is loosing Level at the same Rate (First quick than slow), Outer is not filled up. Not with Auto Fuel System ON or OFF. It looses Level when the Tip Tanks are reaching the same Level.

Edited November 11, 2023 by meierzwo

[tkyler]

I completely override X-Plane's fuel transfer, so the transfers you describe are happening "in my plugin"..i.e. "from tank 1 to 3.   

What is SUPPOSED to happen....is "plugins get the last say".  In other words, when X-Plane has its own logic for fuel transfer and then writes to a dataref...then us plugins get the opportunity to write and our values are supposed to be final.  ..but clearly X-Plane is writing to the m_fuel datarefs also.  This is the essence of our challenge with plugin programming, always 'fighting' with X-Plane as to who has the better logic and gets control.   BUT....I did talk to a Laminar rep and we don't believe the base fuel transfer model to have been "redesigned"...maybe tweaked, but not overhauled...so I've filed a bug.

-TK

[Retnek]

Tom, two further problems ahead, sorry. Please let me know if you prefer to handle such reports in an extra-posting per topic.

1) Selecting a 10-nm-away airborne approach results in partly switched-of systems like battery or radio. Switches are off and systems do not work, that's consistent. In contrast the engines are running - but RCS-switches are off, main fuel valves closed. Bringing them into the supposed correct positions it switches off the engines. Looks like the settings are correct, but these switches indicate wrong. Tested it with the 4- and 5-blade-OEM - same results. Starting on ground with engines off or on I couldn't find any problems.

2) The  com-radio-frequency-dials no longer show the freq. automatically set by using the ATC-window. Communication with ATC (within the usual limits) isn't affected, but it's confusing to see the dials differ from those called out.

Edited November 13, 2023 by Retnek

[tkyler]

13 hours ago, Retnek said:

Please let me know if you prefer to handle such reports in an extra-posting per topic.

No need for myself...possibly others for future reference....but I don't think so in this case.  I record these instantly as I read them.    I admit I haven't looked at those default "in-air" starts much....but its on my list and I will.  Starting to turn my attention back to the Moo finally for a bit.  

-TK

[tkyler]

Just an update on the fuel transfer....there has definitely been some "wonkiness" in the latest update with regards to fuel transfers.   The report is in their system so we'll see.  Whether or not a fix "comes up short" or exposes other issues we won't know till it comes out.

One of the things we see with X-Plane is "new systems paradigms" coming online as XP evolves....and the fuel tanks / transfer sequence is one of these things that have evolved when Austin worked on the F4 model.  So in some cases, it may or may not be a 'bug' per se....but an 'evolution' that requires us 3rd party devs to reconfigure our ACF files.

The MU2, for example, doesn't yet integrate the new "weight stations" and so this can cause some funny business in some cases and isn't really a bug, but my needing to research XPs latest features and make sure the MU2 integrates them properly.

So we'll see what comes of this fuel thing....but at the least I have some input with Laminar.

-tk

[rosseloh]

Quote

The MU2, for example, doesn't yet integrate the new "weight stations" and so this can cause some funny business in some cases and isn't really a bug, but my needing to research XPs latest features and make sure the MU2 integrates them properly.

For what it's worth, Tom - both CaptCrash and I have manually added the weight stations and I haven't noticed any issues related to that, yet. But I also haven't been in the sim for a bit.

[tkyler]

@rosseloh Thx for that report.

After quite a bit of investigating...it may be X-Plane didn't 'break' anything.     As the sim evolves, Laminar puts in more detailed models and for older aircraft where those details didn't exist, then Laminar has to toss in some default values.   In some cases, those default values provide behavior counter to the way things used to be...so while it seems X-Plane BROKE something...they really didn't

I think that's the case here.  X-Plane has refined their fuel transfer and 'tank types' a little ways back, but since I wasn't affected, I never bothered to look at their new system and try and leverage it...I just let my old 14 year old fuel transfer code stick around.  I think they might have "tightened up" some code, which closed holes in their own code.

I've been able to manually set up a fuel tank / dataref config that seems to work, but need to tie it into the cockpit controls.   If it works in 12.08, the that will be a good thing and I'll move focus to the Moo for a bit and get out the next round of patches.

TK

[meierzwo]

XP 12.08.03.

Some Changes with Beta 3. Main Tank could be used now. Did a Start only with Main. But Tip Tanks still feed the Main, not the Outer. But I did not see any Overloading of Main anymore. So, Tip Tanks are filling up the Main very Quick until Main is on Full Capacity. If Tip is empty and Main not Full, the Outer Tanks took over and filling up the the Main.

I must say, I did not watch the Behavior before. Fuel is on Auto. Tip filling up the Main quick if it is not Full, Outer take over if Main is still not Full.

Is that the correct Behavior?

Edit. Just studied the Fuel System. Seems to be correct in this way and the "Bug" from Beta2 is solved.
I always fly with full Main Tanks.

Edited November 21, 2023 by meierzwo

[Retnek]

Can confirm report by MeierZwo - started with all fuel-tanks filled up from St. Johns CYYT to Corvo LPCR. Fuel-tanks were emptied as expected again.

Btw: Lady Moo is a bit thirsty - that flight was ca. 1050 nm. Mostly flow at 21.000 to 25.000 ft with an indicated fuel-consumption between 400 and 450 lbs / h. Winds more or less insignificant, pushed a bit in the beginning, headwind at the end. Straight flight from start to touch-down. Made it to Corvo with ca. 300 lbs in the main tank. That way I can't see how to get a range of 1400 nm plus reserve as given in the manual.

[meierzwo]

Hmm, did a Flight around Sint Maarten this Morning at 20.000 Feet.
Torque at 66% with Throttle full forward.
Props at 98%.
Airspeed around 200 knots.
Fuel Flow was at 240 Lbs/Hr.
Realistic Data?

[tkyler]

On 11/21/2023 at 11:16 AM, meierzwo said:

Is that the correct Behavior?

no,  the tank types need to be changed in PM.  I've done this for the next patch.  There is no "fix" coming from Laminar.  If you open up one ACF in Planemaker and set tanks 1, 2,   4 and 5 to type "TRIM",  then it might work.  I say MIGHT because Laminar confirmed that Austin defaulted the fuel tank draw to be "side based" in the first beta 12.08b....instead of 'ALL' and I haven't tested whether or not the latest update b3 fixes that. Tank type TRIM has no fuel transfer algorithm associated with it, hence my plugin handles it.  Any other tank type and X-Plane moves the fuel around per its own algorithms, which is probably what you're seeing.

For myself, I simply initialize that dataref now to what I need...TBH, I didn't expect Austin to change that one.  SO...if they did initialize the fuel tank selector to 'all' in the latest BETA....AND you set the aforementioned fuel tanks to TRIM, then it should work as it did previously.   I've done this already for the next patch.

6 hours ago, meierzwo said:

Realistic Data?

Regarding the fuel flow and torque?  Doubtful.  A performance 'pass' needs to be done again.  I haven't touched it in a long enough time and X-Plane has had quite a bit of tweaks since.   I've started on that process...but flight testing takes quite a long time.  ...the perf charts have performance figures for something like 10 differing temperatures and different altitudes and torque settings....when all permutations are considered, it could add up to multiple dozens if not 100+ test flights......and still you're at the mercy of the X-Plane model.  BUT yea..the perf needs some work.

-tk

Edited November 23, 2023 by tkyler

[N602AC]

Is there going to be an update at some point? I bought this aircraft somewhere around a year ago, and have not flown it most of that time because I've read in this thread there are issues with fuel not feeding correctly, and the performance numbers being off. Is that going to get fixed?

Thanks,

Dan

[meierzwo]

The Fuel Feed Issue was with one of the XP12 Betas and is History. The Fuel System is working as it should. Tip and Outer feed the Main and Engines are feed from Main only. And the Performance? I don't know the real one but it performs very good and is not too far away from the real one I think. XP is still Beta and full of changes. A Update for the Moo is in the Queue as mentioned in a other Thread. Better wait for XP is going less Beta then having a Update for the Moo and the next Update for XP is breaking Things again. Sadly, the Moo is not using a Online Update System like SkunkCrafts Updater. That would make it easier for fixing I think. Would be nice if this is possible for this Plane.
I enjoy the Moo and it's my favorite Plane in XP. Take it out of the Hangar and bring it in the Air. :-)

Heinz-Juergen

[N602AC]

Ah, excellent! I guess I was under the impression that there was still a problem. Thank you! I shall fly it today!

Edited June 23 by N602AC