I am running the X-Plane 11 version of Carenado's PA31 Navajo. I have successfully completed sevral shorter flights, so tried a longer flight of just over 4 hours (Oxford, UK, EGTK, to Figari, Sud-Corse, France, LFKF. Note that I use kgs for fuel quantity to accommodate my flight panning app.

I have just lost the right engine due to NO AUTO SWITCH TO  RIGHT WING TANK #4 after the fuel tank 2 ran dry. As the Fuel Control Panel does not appear to have any available functionality this means the fuel in tanks 3 and 4 is unusable.

My current fuel load is:

Total Internal Fuel Weight = 210.5 kgs

Left Side Fuel Total           = 108.2 kgs

Fuel Tank 1                       = 6.0 kgs

Fuel Tank 3                       = 102.2 kgs

Right Side Fuel Total         = 102.2 kgs

Fuel Tank 2                       = 0.0 kgs

Fuel Tank 4                       = 102.2 kgs

The overhead Fuel Gauges both read zero (+/-), confirming that they only show the fuel quantity of the default tanks in use.

If I view the Fuel Control Panel and also activate <Show Instrument Click Regions>, a left-right (shows as  "<--  -->" ) green illumination appears on the Fuel Control Panel right of centre (away from the non-functioning Fuel Tank Selector Switches themselves). However, it does not appear to do anything when pressed.

Does anyone know how to overcome this problem? I have also sent a support request to Carenado (zendesk).

Edited January 12, 20233 yr by roadrabbit149

I have come up with a fairly obvious work around: simply use use the Flight dropdown menu, Edit Weight & Balance as if it was the Fuel Control Panel.

Wait until you have approximately 5 kgs (or equivalent) in the Tanks 1 and 2 (you should monitor this closely, as you don't want a no-fuel engine shut-down!).. Then transfer about 95% of the fuel in Tanks 3 and 4, individually, into Tanks 1 & 2. Next, reduce the fuel to remain in tanks 3 and 4 to approximately 5 kgs in each tank.Your fuel planning for the trip should, of course, take this 5 kgs remaining in each tank as unusable, and thus added to your total fuel required.

The fuel, less the 10 kgs left in tanks  3 and 4, is now in the usable fuel tanks: 1 and 2. The draw-back to this work around is that you finish up with empty (ish) inboard fuel tanks, and fairly full out board tanks - technically far from ideal. [I am assuming, in the absence of any information, that tanks 1 and 2 are the left and right outboard fuel tanks].

2 hours ago, roadrabbit149 said:

tanks 1 and 2 are the left and right outboard fuel tanks].

Interesting... I'd think those are inboard, following the logic that central or inner ( closer to CoG ) tanks should be emptied first, like in most modern airliners?

If the tanks are not wing tanks but 'within' the fuselage, then you are correct.

However, once 'center' tanks are depleted, with wing tanks you usually empty the outer tanks first (see Boeing 777, 787 and also Airbus A320 etc) - so, if fitted, empty tip tanks first, then outer main tanks then inner mains. Of course tip tanks are often fitted to drain into the outer main tanks as those are emptied in use. Also, the inner wing is the stronger part of the wing, so is better suited to carrying the final fuel load as it is used, and so reduces wing stresses.  Aircraft often will have larger inboard tanks than outboard to reduce roll inertia. Again, by reducing outboard tanks first you further reduce the roll inertia of the aircraft (think of it like a dumbell weight - if the outer weight lumps were moved to the centre of the handle, it would easier to twist in your hand)

The Carenado PA31 is basically following this principle by using the outer tanks first. The problem is that it does not then switch to the inner tanks after depletion of tthe outer tanks. My solution to this is to artifically use the fuel loading page as described previously. However this puts all the final fuel load in the outboard tanks, and so acts against the benefits described above. So, although allowing the use of all fuel loaded preflight, it is NOT an optimum solution.

roadrabbit

Edited January 13, 20233 yr by roadrabbit149

Solved! I need to go to an optician.

I have discovered those three icon letters near bottom left of screen. Opening the <C> icon and , yes - you guessed - it gives access to the fuel control panel in the drop-down menu. This means all 4 fuel tanks are now availlable and usable as desired.

It also means my previous fuel tank usage in the Navajo is not needed     😡