F/A-18 Random Engine Out - Incorrect Fuel sequencing

This THREAD started as a question about Engine’s quitting BEFORE fuel Starvation of all Fuel Tanks and has since become a THREAD to address that issue and re-author the FUEL_SYSTEM Section in the Flight_model.cfg. of the F/A-18.

So, dive in and lend a hand.

Original First Post left for reference.
Had the Left Engine suddenly quit today at about FL260. Not in Afterburner - not thrashing it at all.
Couldn’t re-light with the APU switching off after a couple of seconds repeatedly.
Landed on one Right Engine only.
On ground could crank Let but no re-light (igniters INOP?) possible.
Plenty of fuel.

Anyone else experiencing random engine out with no re-light possible?

It IS an issue - deduced through a process of discussion - so please DO VOTE!

I also confirm that the left engine stalled, the problem is that the plane for some reason does not use fuel from the wing tanks, when both engines stalled, the wing tanks were 100% full.

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Interesting and thanks.
Did you cheat and re-fuel in flight?
Could you start the APU to crank?

My (very early theory) is not only do the donks not register fuel in the main wing tanks below a certain amount - but that they will not acknowledge an in-flight re-fill - so stay starved; precipitating a loss of ability to re-light in flight.

What I know is that the default fuel load is pretty low for the aircraft. So when you spawn at first, there’s only little fuel in the tank. I had to manually refuel the aircraft at the start of the session to full tank otherwise, the aircraft is so underfueled that when you use afterburners, it just drains the fuel tank really quickly. Then you get the left engine out.

When it happened to me, I just open the fuel page, refuel mid-flight. Then proceed with turning on the APU again, then restart engine 1 until it fires up again.

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Ive had the same thing happen here multiple times with unlimited full on and off. About once ever six flights or so…

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The problem was Neo - that even after topping off ALL tanks the APU wouldn’t light.

Huh weird… it worked when I did it…

Yes, it has worked for me before - but yesterday? no dice. Not even back on the ground going from C + D with ALL tanks full.

Going to do some heavy experimenting today.

I started with full tanks from the ground. I noticed such a feature that after the tanks tk1 l fd tk4 reach the value 33, the left engine turns off, the right engine runs until the r fd tank runs out. At the same time, the wing tanks are not used in any way, and remain full.
No toggle switches work on the fuel panel, so I do not know how to activate them.

It seems to me that the F/A 18 still has problems

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model is buggy, main fuel tanks, what in the menu empty, have to stay empty, all another - set to 100%, when you eat all fuel from high set tanks, engines stop to get fuel, whatever main tanks load, so again, before flight “weight and balance” leave empty tanks empty and refill another to full, in other way you will get excess weight

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Had a look at how the fuel system works, I think there´s an error in the plane´s flight_model.cfg, {FUEL_SYSTEM] section:

Trigger.3 = Name:TransferLeft#Condition:TankImbalanceAbove#Threshold:0#Target:LeftWingTank,RightWingTank#EffectTrue:OpenValve.LeftWingTransferValve#EffectFalse:CloseValve.LeftWingTransferValve
Trigger.4 = Name:TransferRight#Condition:TankImbalanceAbove#Threshold:0#Target:RightWingTank,LeftWingTank#EffectTrue:OpenValve.RightWingTransferValve#EffectFalse:CloseValve.RightWingTransferValve

Notice that the trigger “Target” mentions “RightWIngTank, LeftWingTank”, which, to my understanding, means that the transfer is only triggered if there is an imbalance between the wing tanks. It probably should be “RightWingTank, CenterTank1” or any of the other center tanks (I don´t know how the real thing does it).
Not able to test this right now, probably later today.

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Good find.

Time to get the spanners out on the flight_model.cfg

Investigating now. Let’s report findings back here later.

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I was trying to figure this out too - it looks like you may be on to something.

A workaround might be to simply adjust the fuel tank capacity values in flight_model.cfg, removing fuel from the wing tanks, and adding it to the main ones. From the look of it, if you transfer the fuel equally to tanks 3 & 4, it should leave the CG in the same place, and not affect handling significantly. I’ve not actually tried this yet though, as a proper fix for the issue would clearly be preferable.

For the time being I might just fly with 50% fuel and unlimited fuel turned on if I’m going to be flying a long way; just planning the flights as if I had limited fuel. It’s an annoying bug though, I like fuel conservation while I’m flying.

You could always refuel in air via the menus if you start to run low.

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I think it’s the Trigger Events - they must be configured wrong.

My findings today were;

  1. Left Eng Out when Tank 4 to 1%

  2. Had BOTH Wing Tanks at 100% - Left ENG didn’t feed.

  3. Wing Tanks should empty first - so that Transfer Event should be changed to what you say - Center - in fact any of the other Tanks except Tank 4. You can specify to which of the 1,2,3 and 4 the Transfer Event goes.

Will do some flying tomorrow in Dev Mode to be able to make the Trigger Events change on the fly.

BubbaBlitz - Thanks, that’s a good solution if you need it - but we’re trying to fix the problem so you don’t have to do that. The above Pic will give you an idea of what we’re dealing with. We’re under the hood, tinkering with the spanners.

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Yeah I know what your doing , just saying that all ;p

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I did a quick test, pointing both triggers to CenterTank4. Could fly longer, left engine stopped when Main Tank 2 (which is the tank that feeds the left engine) was empty, the right engine continued on, as it´s fed from MT3 (the wing tanks started emptying, but still had plenty of fuel, as had MT3. The total fuel left was down to approx 34%). Thus it´s a bit more involved than I thought, but otherwise no fun, right? :slight_smile:

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Edit: now with MS Paint example

How it works in the sim right now
Tank 1 transfers to tank 2 once the fuel quantity in Tank 1 matches tank 4 (this is why the left engine always starves first in the sim)
Tank 2 feeds the left engine
Tank 3 feeds the right engine
Tank 4 feeds tank 3
Left Main feeds nowhere
Right Main feeds nowhere

How it’s supposed to work

Tank 1 feeds Tank 2 and can transfer to/from Tank 4
Tank 2 feeds left engine with an interconnect to Tank 3 for balancing
Tank 3 feeds right engine with an interconnect to Tank 2 for balancing
Tank 4 feeds Tank 3 and can transfer to/from Tank 1
Left Main feeds Tank 4
Right Main feeds Tank 4

While not an exact diagram, this is a rough visualization of how it all should work (minus fun things like pumps and valves)

Not familiar enough with the .cfg on how to correct this though.

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Fun indeed. :slight_smile:
Looking at what you observed and what Raynen has written below - the main culprit (s) here are

  1. the wing tanks feeding nothing at all.
  2. Tank 2 and Tank 3 need to be fed from all the other tanks to be as full as possible as they are the primary tanks.
    Oh well, it’s raining outside here today so I guess this is today’s project.