Ground refueling work around.

[Rubberduck85]

 

With that being said, I can confirm that opening the AAR 'door' or extending the fuel probe (depending on aircraft) while on the ground, prior to rearm/refuel ground crew interaction, does indeed fill the external and internal tanks.
 
Tested with the Hornet, Tomcat, Viper and A10C (the latter was just for inclusion - in the mission, I never actually use externals on the A10C).

It's good to know that it works for other modules too, however I think we need an official statement on this? Is it intended/a workaround to a bug/a w.i.p. feature? (Btw why should I extend the AAR refuel probe to refuel my externals on the ground???)

 

The point I was trying to make above is, ED need to stop trying to be so clever and 'fully modelling the internal workings of the fuel system' when they just end up introducing bugs, which in this case results in the inability to have full drop tanks following a hot refuel (unless your internals are nearly empty, you punch off your old tanks and fit new ones etc etc).
Bottom line I park up and politely ask for a jet full of fuel including full drops - I don't care how,
 

Pretty much this: just refill every fuel tank, internal or external. Want to simulate the internal workings of the fuel tanks/pumps/pressure? Do it internally and release it when it works, avoid breaking basic functionalities without documentation to back it up.

Sent from my MI 10 Lite 5G using Tapatalk

[Creature_1stVFW]

4 hours ago, =Panther= said:

I love when someone taunt their years of working the jets. So since we went there, I have over 20 years on the F-16. It is not possible to over wing the 370 gallon fuel tanks from just the nose cap point. That was the point I was trying to make. The 370 gallon tank is sectioned off in three parts. The spill over tube which allows fuel from the nose to go to the aft section sits above the lowest point of the cap opening. So no matter how gingerly you operate the refueling nozzle, you will not fill the entire external tank via the nose cap. In order to accomplish an over the wing one must use all the points and fill each one individually.
 

 

I love it too @ Panther. I also have over 20 active duty years on Vipers as a Weapons Troop and still work them as a contractor here at Luke. When I OP’d this thread, I thought I would share something that was told to me by a member of my VFS who is also a Viper Crew Chief. I had no idea that was actually how it works IRL. I’ve done thousands of ICTs and didn’t know that they opened the door to Hotpit. How would I, I’m a weapons troop right? Thanks for teaching this old guy something. Knowledge is power!

[Ziptie]

16 hours ago, Rubberduck85 said:

It's good to know that it works for other modules too, however I think we need an official statement on this? Is it intended/a workaround to a bug/a w.i.p. feature? (Btw why should I extend the AAR refuel probe to refuel my externals on the ground???)

 

 

Guessing it makes the tank pressure inert - like opening the AAR door....?  Just guessing.  Not saying that is real world realistic, or isn't.  Just guessing.


Cheers,

 

Ziptie

Edited February 17, 2021 by Ziptie

[=Panther=]

[Frederf]

Are we expecting different behavior out of DCS doing this engine off vs engine on? DCS doesn't seem to get hung up on the minutia for fuel plumbing. It just teleports the dinosaur juice into the can.

[Ziptie]

40 minutes ago, Frederf said:

Are we expecting different behavior out of DCS doing this engine off vs engine on? DCS doesn't seem to get hung up on the minutia for fuel plumbing. It just teleports the dinosaur juice into the can.

 

 

I have not tested ground crew rearm/refuel with the engine off and leaving the AAR door closed (or refueling probe retracted).  Would be great if someone was able to test before I can, as I'm not sure if I am able to fly virtually tomorrow.  If I am able to fly tomorrow, will give that a go and see if it will fill external fuel tanks without opening/extending AAR (inert tanks).

 

 

Cheers,

 

Ziptie

[Frederf]

Test #1: Spawn F-16 with 2x370, 10% fuel. Check rearm menu and says fuel = 79%. Set fuel master off, external power, main power to see fuel gauge. Wing tanks full, internal 10%. This suggests fuel slider is not showing internal fuel and that fuel is only transferred by airplane from external to internal. Fuel master on. Gauge shows rapidly decreasing external tank needles and rapidly increasing internal.

 

Test #2: With 30% internal, 2x370. Fuel slider shows 99%. Main power switch to BATT. Check rearm panel shows fuel 98%. There must be a small amount of fuel being removed from tanks by pump or something, interesting. Didn't get the same from 79% to 78% above. Weird. Tried 20% 15% 11% 9%, no decrease. Weird.

 

Test #3A: From 50%+2x370 state with master fuel off check externals full, internals 50%, slider 100%.

Test #3B: Without checking fuel with electrical, request rearm with no changes. Airplane refueled to 100% (slider was 100%) and all tanks full.

Test #3C: Same as 3B but set slider 50%. No refueling occurs. Results same as 3A.

Test #3D: Apply power for >73s to allow externals to drain internal. Rearm no changes (slider 100%). Rearm does not alter externals.

Test #3E: Rearm with all electrical off. Externals remain partial.

Test #3F: Defuel to 99%. External tank continually dumps into internal during defueling such that it empties completely and then internal reduced to 99%.

 

Test #4: Ground power, master fuel off, all tanks 100% internal, 2x370. Defuel to 50% slider with external isolated with fuel master off. Result is 3650 total fuel, externals empty, reservoirs full, fuselage partial appropriate for normal burn.

 

Test # 5: From state 4, AR door open, fuel master on, fuel slider 100% refuel. Result is 10,800 pounds. Internals all full, externals partial. 10,800-3,650=7,150.

 

Test #6: From state 5, request 50% defuel then 100% refuel. Result 12,100 lbs.

Test #7: From full cycle with master fuel isolate slider 50% and then 100%. Result 12,100 lbs.

Test #8: From full cycle with master fuel isolate on slider 0% and then 100%. Result 7450 lbs.

 

Series 2

Test #4: Request 0% fuel. No fuel in any tank. Externals were drained and not replaced.

Test #5: Request 1% fuel. Internals filled 1%, externals still empty.

Test #6: Electrical off, refuel no change (1%). externals still empty.

Test #7: Remove one external tank. No change in fuel levels.

Test #8: Add back external tank. Tank is added full which quickly drains into internal 35%.

Test #9: From 0% fuel, 1 external missing, set fuel master switch off, eng feed off, with electrical off add external tank back. With elec reapplied only replaced tank has fuel. It does not flow into internal. Eng feed norm, no flow. Fuel master on, flows internal in 73s.

Test #10: From 0% fuel, fuel master off, add two new externals, fuel master on. Flows internal in 73s.

Test #11: Engine running. ~5000 lbs internal, 0lbs external, 2 370 tanks carried, AR door closed. Rearm without change to options. No change on rearm complete.

Test #12: Same as 11 but increase fuel slider 1%. Same result.

Test #13: Same as 11 but add wingtip missile. Same result.

Test #14: Remove and re-add external tank. No fuel change on remove. New external added full, quickly filling internal. Slider shows 100% despite internal not full although total fuel is > internal capacity.

Test #15: Request 99% fuel from state at end of 14. Fuel added internally, total fuel is now > 100% of internal capacity. Slider shows 100%.

Test #16: From 10% internal, two new external tanks are added. Quickly after new tanks are added, 100% refuel is commanded. Total fuel at end of refuel is 8900-9000 lbs.

 

Conclusions: later

[=Panther=]

Fuel MASTER has nothing to do with external fuel tanks. It is the control for the Main Fuel Shutoff Valve, which shuts off fuel flow to the engine. Way down stream of fuel transfer from the externals. 
 

The only things that should prevent the externals from transferring are AIR REFUEL door, AIR SOURCE, and TANK INERTING
 

So if MFSOV is having an affect on the quantity, that should be reported but not ground breaking bug. 

[Frederf]

Well in DCS it prevents fuel flow from externals in internals. I'm guessing it's freezing all flow between all tanks but I'd have to test. It's not having an effect on fuel quantity. I agree that the shutoff appears to only exist at the FFP in the real airplane. Would you expect an engine-off F-16 with empty internal (or otherwise some capacity) to transfer fuel from external when hooked up to external power and MAIN PWR switch? Because if you set up that situation it dumps all 2500 lbs inside in 73s. I'm not seeing a mechanism for that to happen unless ground power includes some air pressure to replicate bleed air.

 

Anyway, conclusions from previous tests:

• An airplane spawned with external tanks (full) and partial internal will not reconfigure its fuel on spawn. However given proper electrical power (ground power/MAIN PWR or engine running/MAIN PWR) it will very quickly move external to internal. Lesson: If this condition exists and it is desired not to have external transfer before adjusting internal fuel then do internal refuel before powering.
• Fuel slider on rearm screen does not represent internal fuel but total fuel owned by the airplane divided by internal capacity capped at 100%. E.g. if internal capacity is 1000 lbs and fuel on board is 500 lbs internal 250 lbs external then fuel slider reads 75%. If 800 lbs internal and 800 lbs external then slider reads 100%. Lesson: Do not treat fuel slider as internal quantity.
• Fuel slider at refuel command is desired internal quantity commanded. E.g. if internal is half full but other half is external the slider reads "100%". If attempting to refuel with slider 100% it will fill internals to full and external quantity will remain in addition. If slider is adjusted to match actual internal (e.g. 50%) then no refueling occurs. Lesson: If refueling or defueling set fuel slider to match desired amount and don't assume not changing the slider will result in no fuel change.
• When defueling the externals will be emptied trying to replace the missing internal fuel as it's removed. E.g. full external, 50% internal, defuel to 49%: result is empty external and 49% internal. This seems to be a simulated "hungry engine" and fuel is removed in the normal order even with fuel flow isolated (master switch off).

Ultimate takeaways:

• Hot refueling, remove externals while doing initial refuel and add externals when refueling complete.
• Hot defueling, if empty externals desired defuel with externals attached. If externals added after defuel they will rapidly replenish internal tanks.
• Cold refueling, exchange external tanks if not full otherwise adjust internal fuel as desired before applying power.
• Cold defueling, will empty externals. If full externals desired exchange for new external tanks after defueling.

[=Panther=]

5 hours ago, Frederf said:

Well in DCS it prevents fuel flow from externals in internals. I'm guessing it's freezing all flow between all tanks but I'd have to test. It's not having an effect on fuel quantity. I agree that the shutoff appears to only exist at the FFP in the real airplane. Would you expect an engine-off F-16 with empty internal (or otherwise some capacity) to transfer fuel from external when hooked up to external power and MAIN PWR switch? Because if you set up that situation it dumps all 2500 lbs inside in 73s. I'm not seeing a mechanism for that to happen unless ground power includes some air pressure to replicate bleed air.

 

 

 

Ground external power shouldn't transfer externals, unless bleed air was applied. Same with just running on A/C Battery, the externals shouldn't transfer until the engine was on. 

 

I'll admit at this point, we are getting into the weeds of the system. The F-16 fuel system is one of the most complex systems on any fighter. To model is 100% accurate would be beyond what we need as flight simmers.

 

The original post was to highlight how to get fuel into the externals during a hotpit scenario by opening AERIAL REFUEL. Which is the same way pilots IRL do it..

[Frederf]

With AR door open there is some "back flow" into external tanks but it is not a reliable technique. It does not fill the external tanks completely in every situation. With DCS you get back flow into external tanks equal to the difference between slider amount and internal fraction. E.g. to get 5000 lbs into externals you need to ask for 5000 lbs by slider which can be impossible since slider maximum is 100%.

 

Total fuel resulting from commanding 100% slider with empty 2x370 and internal at...

10%: 12,110

30% (2153): 12110

31% (2215): 12110

32% (2299): 12026

33% (2369): 11955

35% (2515): 11806

40%: 11,500

50%: 10,800

90%: 7,900

lose 9-10 lbs when closing AR door

 

So if trying to fill empty 370x2 tanks with AR door open technique then fuel must be 31% or less and slider placed at 100% otherwise various tanks including externals will not be filled completely. I don't think it's a coincidence that 7160-2215 = 4945, almost exactly 2x370 tanks capacity.

 

Trying with 300 CL.

35% 2515 9164

40% 2872 9164

43% 3088 9164

44% 3159 9160

48% 3445 9014

50% 3586 8944

lose 8 lbs close door

OK 43% or less.

 

Trying with 370x2, 300 CL. 14100

0% (9): 14116

20% 1425 14115

25% 1799 14115

30% 2156 14115

33% 2373 13956

35% 2514 13811

 

OK looks like the 300 fills up first and the 370 takes more time so triple tank and double tank fill the same, 32% and up.

[Ziptie]

Indeed, you have to be low on internal fuel.  My 50% was simply a "hip shot" from memory.  Works like a charm and haven't had to "swap" my external tanks when rearm/refuel since discovery.  Hope it helps others as well - even if your server doesn't share the same theory on stores.

 

 

 

Cheers,

 

Ziptie

[Machalot]

Sounds like you could request a defuel to 31%, then refuel to 100% with the AR door open. Probably slower than removing and replacing externals, but avoids wasting tanks in resource-limited campaigns. 

[Frederf]

It doesn't waste tanks. If you remove tanks (or any weapon or liquid or airframe) they go back into warehouse.

Edit: Having trouble returning airframes to warehouse in single player, MP works tho.

Edited February 25, 2021 by Frederf

[brindle]

OK - I've read everything here, and it still doesn't add up.

 

I've been flying the F/A-18 for years. Never had issues with refueling until (February 2021).

 

Things I've tried:

 

Purposely jettison all external tanks before landing.

I choose 'empty' for loadout and then fuel slider to 100%

Stops at 92% every time (with AR door open and closed).

 

Flew Saturday with a few other F/A-18 pilots, and I'm the only one who can't refuel to 100%.

Jumped off of mission early because of this bug.

 

None of these 'workarounds' work for me.

 

Bottom line - this is a DCS bug that needs to be fixed, and I hope soon.

[Machalot]

2 minutes ago, brindle said:

OK - I've read everything here, and it still doesn't add up.

 

I've been flying the F/A-18 for years. Never had issues with refueling until (February 2021).

 

Things I've tried:

 

Purposely jettison all external tanks before landing.

I choose 'empty' for loadout and then fuel slider to 100%

Stops at 92% every time (with AR door open and closed).

 

Flew Saturday with a few other F/A-18 pilots, and I'm the only one who can't refuel to 100%.

Jumped off of mission early because of this bug.

 

None of these 'workarounds' work for me.

 

Bottom line - this is a DCS bug that needs to be fixed, and I hope soon.

Have you tried rearming with no tanks and 100% internal fuel, then rearming again to add the tanks? 

[brindle]

[RESOLVED] - It was definitely 'pilot' error on my end.

 

Explained: I use the WinWing HOTAS F/A-18 throttle start-up panel, along with the landing and combat panels.

Unfortunately, having this many 'switches and buttons' at my disposal allows for an increased chance of error.

 

Conclusion: Make sure to have your INTR WING switch on 'norm', not 'inhibit.

I vaguely remember reaching down to put my STROBE to BRT (while in VR), about a month ago.

Must have hit the wrong switch in the process...   

[Terzi]

@Frederf I noticed the same issue. Any idea if this is made intentionally or is this a bug? You cannot refuel externals well, if you aren't really low on internal fuel.

[Nealius]

My math-challenged brain is having trouble with this. Let's say I have 2x370gal tanks, total 11,700lbs. I want a total of 5,850lbs, which is 50% fuel, from a cold start. In the rearm menu I set the slider to 50%. Result is empty 370gal tanks and around 3,500lbs on the totalizer, which does not increase when I turn on electric power, engine power, nor does it increase as I taxi and take off. For some reason that 50% change effectively defueled me 70%. Knowing that internal capacity is around 7,000lbs then it seems that the rearm menu slider only defuels internal tanks....except it also defueld my external tanks?

 

So if I want to defuel from a cold start down to 5,850lbs, what's the easiest method?

[Machalot]

1 hour ago, Nealius said:

My math-challenged brain is having trouble with this. Let's say I have 2x370gal tanks, total 11,700lbs. I want a total of 5,850lbs, which is 50% fuel, from a cold start. In the rearm menu I set the slider to 50%. Result is empty 370gal tanks and around 3,500lbs on the totalizer, which does not increase when I turn on electric power, engine power, nor does it increase as I taxi and take off. For some reason that 50% change effectively defueled me 70%. Knowing that internal capacity is around 7,000lbs then it seems that the rearm menu slider only defuels internal tanks....except it also defueld my external tanks?

 

So if I want to defuel from a cold start down to 5,850lbs, what's the easiest method?

I think you would set the slider to 81% = 5850/7200.

[Frederf]

3 hours ago, Nealius said:

My math-challenged brain is having trouble with this. Let's say I have 2x370gal tanks, total 11,700lbs. I want a total of 5,850lbs, which is 50% fuel, from a cold start. In the rearm menu I set the slider to 50%. Result is empty 370gal tanks and around 3,500lbs on the totalizer, which does not increase when I turn on electric power, engine power, nor does it increase as I taxi and take off. For some reason that 50% change effectively defueled me 70%. Knowing that internal capacity is around 7,000lbs then it seems that the rearm menu slider only defuels internal tanks....except it also defueld my external tanks?

 

So if I want to defuel from a cold start down to 5,850lbs, what's the easiest method?

I'm not sure exactly what fuel you want where but assuming you want the normal distribution of fuel at that total then you simply set as Machalot says.

 

Since external fuel rushes in to replace internal when defueling (power on) it doesn't matter how much external you have, ground services will keep sucking it out of the airplane until it gets to the goal. If you watch the qty gauge monitoring externals you see them empty on defuel.

[Nealius]

11 hours ago, Machalot said:

I think you would set the slider to 81% = 5850/7200.

 

Ah okay, so the bug/issue is with the rearm/refuel emptying the external tanks, with the % slider only affecting the internals?

[Machalot]

2 hours ago, Nealius said:

 

Ah okay, so the bug/issue is with the rearm/refuel emptying the external tanks, with the % slider only affecting the internals?

The % slider only affects the internal fuel.  As @Frederf wrote above, when power is on, the fuel in the externals is fed continuously to fill the internals, even during the refueling/defueling process.  Do you see this also happening with power off?  Maybe that is a bug.

Edited July 6, 2021 by Machalot

[Nealius]

1 hour ago, Machalot said:

The % slider only affects the internal fuel.  As @Frederf wrote above, when power is on, the fuel in the externals is fed continuously to fill the internals, even during the refueling/defueling process.  Do you see this also happening with power off?  Maybe that is a bug.

 

 

Yes, it happens with power off during a rearm/refuel. If I spawn with a 2x370gal A2A payload, rearm/refuel to a 2x370gal A2G payload with the fuel slider at 50% it appears to give me empty 370gal tanks and takes 50% out of my internal tanks. If I do the same rearming but leave the fuel slider at 100%, it gives me full 370gal tanks in addition to full internal tanks.

[Machalot]

19 minutes ago, Nealius said:

 

Yes, it happens with power off during a rearm/refuel. If I spawn with a 2x370gal A2A payload, rearm/refuel to a 2x370gal A2G payload with the fuel slider at 50% it appears to give me empty 370gal tanks and takes 50% out of my internal tanks. If I do the same rearming but leave the fuel slider at 100%, it gives me full 370gal tanks in addition to full internal tanks.

I think anything less than 100% internal fuel will empty your external tanks because it will keep drawing from the externals to refill the internals while the ground crew pulls fuel out of the internals to keep them less than full.  But I don't know why this would happen with the power off.

Edited July 6, 2021 by Machalot