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Fuel Qty Low Trigger Issue within FSX

(Original thread started on 11-06-11 by Mark L.)

Don't remember doing this before, but a few times lately if I had flown or let the aircraft idle to the point that the MFD is displaying "L R Fuel Qty Low", I will just go up to the FSX menu under Aircraft - Fuel and reset the fuel levels. The status will reset and all is well, but 10-15 minutes into the flight and I'll get the "L R Fuel Qty Low" status again with over 2500 lbs of fuel on board. Unfortunately I don't have my Master Reset built or wired up yet, so I can't see if that would reset it.


Anyone else seen this or could try it to see if they get the same results?


(Posted by Jason Hite on 11-07-11)

Do you see the low qty warning on the FP EICAS screen also or just the Jet45 EICAS after takeoff?


(Posted by Mark L. on 11-08-11)

Okay, I replicated the scenario. With 50% fuel on board, flew from KSEA TO KPDX. About an hour on the ground idling (high idle) I burned off enough fuel to set off the low fuel warning. I had about 1100 lbs. Bumped it up via the menu/Fuel to 3500lbs. Hit the runway and headed back to KSEA, got about 10-15 minutes into the flight with around 2900 lbs of fuel and got the Fuel Warning again. The warning first pops up on the JET45 EICAS screen.


A few minutes later, FSX EICAS popups and displays the Low Fuel as well. Doesn't make sense why I'm seeing this. Using the FP LearJet45 if that makes any difference. Hitting Master Caution Reset in FP doesn't clear it either by the way.


(Posted by Eric Tomlin on 11-08-11)

Mark, thanks for the details- this helps. The warning should not go off until it reaches 350 lbs, but I documented it in the JET45 manual at 330 lbs, which should be fixed. We'll mark this one up for investigation/fixing for the DU update. Thanks again!


(Posted by Mark L. on 11-08-11)

Hey Eric, I just noticed something and wondering if the following is the reason I'm seeing this, but never though it would cause this to happen. Is it because the wing tanks are low? Less than 300 lbs, yet there is over 2000 lbs in the center tank? If so, that's annoying!


(Posted by Eric Williams on 11-08-11)

Hey Guys, I think I noticed this problem a long time ago and it rest with FSX. You should not be able to have fuel in the fuselage and not have the wings full- it drains into the wings from the fuselage as the system draws from the wings (in the real Lear) Anytime you are below 350 in the wings you should get a warning.


Sorry to jump in, but this just reminded me of scratching my head a few years back. I could be wrong though.


Here's the info from the Lear Manual:


Two, 2 inch transfer lines (one on each side) connect the fuselage fuel tank and the wing tanks (Figure 5-1). Anytime there is fuel in the fuselage tank, it automatically flows into the wing tanks to replenish fuel that has been used."


(Posted by Eric Tomlin on 11-08-11)

Absolutely! Yes, the aircraft is supposed to empty the fuselage tank first then the wings. This is your issue Mark, I'm sure of it. It's annoying because it's a safety issue. What's the first thing that breaks away from the aircraft when it makes a really hard landing? For a hint, go look at the photo of N476AJ- the Learjet that Shane now has interior parts for. It was the WING. It's better to do a gear-up landing with no fuel in the fuselage tank and have the wings shear off than to be skidding down the runway/ground and have that center fuel tank full. At least that's my personal theory anyway.


On a ranting rave- Yet just 1 one reason why I hate FSX. They screwed so much up with that program. I'd rather have lacking visual graphics (ground-wise) and a much better aircraft model than the ground textures being better.


You can mark this fuel draining issue right up there with the Engine Start issue that FSX has. This makes me so upset that it was messed up from FS9 to FSX and makes no sense as to how they got around to breaking the airplane.


(Posted by Mark L. on 11-08-11)

Glad we got this figured out. Haven't paid that much attention before to the fuel draw and then it hit me looking at the EICAS Fuel readout with almost empty wing tanks. Really hard with the build, designing new parts blah blah and keep it straight about the quirks that Flight Sim has with this plane.


Eric and Jason, I'm thinking that you could fix this with a quick and dirty little function in JET45 to background xfer fuel from the center tank to the wings? This would just be called within the loop of the main program:


if left.wing or right.wing < 100% and center > 0

xfer %/.5 to left.wing and xfer %/.5 to right.wing



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