Orbx PAC 750 XSTOL

Doesn’t sound like it.

Can you guys elaborate on what needs fixing with the fuel?

The fuel only flows from one tank. I haven’t flown it in ages, can’t remember which one it flows from. The handbook says fuel should flow from all tanks simultaneously

Oh, that’s a bummer. Any crossfeed? I really wanted a STOL turboprop and already have the Kodiak in X-plane so was hoping to get something different.

Nope, no way of selecting tanks or transferring fuel

The fuel can be fixed by adding a set of valves to work around a limitation in Asobo’s fuel flow loop. As-is, when fuel from multiple tanks into a single tank is calculated the flow from the first tank is calculated and that chunk of fuel fills the tank, then the rest of the tanks in the loop are like ‘nah tanks full’. It goes back to the beginning of the loop and keeps doing this. In the time it takes to get back to the beginning, it calculates the engine fuel burn and voila there’s space in the tank again.

To avoid this problem, using triggers and valves the fuel can be set to only flow into the collector when it has enough room to receive fuel from all four tanks.


Line.23=Name:TO_COL_VFL#Title:vflToCol #Source:V_BAL_COL_FL#Destination:TANK_COLLECTOR#GravityBasedFuelFlow:80
Line.24=Name:TO_COL_VFR#Title:vfrToCol #Source:V_BAL_COL_FR#Destination:TANK_COLLECTOR#GravityBasedFuelFlow:80
Line.25=Name:TO_COL_VRL#Title:vrlToCol #Source:V_BAL_COL_RL#Destination:TANK_COLLECTOR#GravityBasedFuelFlow:80
Line.26=Name:TO_COL_VRR#Title:vrrToCol #Source:V_BAL_COL_RR#Destination:TANK_COLLECTOR#GravityBasedFuelFlow:80

; Collector Balancer
Valve.9    =Name:V_BAL_COL_FL    #DestinationLine:TO_COL_VFL   #Circuit:5
Valve.10   =Name:V_BAL_COL_FR    #DestinationLine:TO_COL_VFR   #Circuit:6
Valve.11   =Name:V_BAL_COL_RL    #DestinationLine:TO_COL_VRL   #Circuit:7
Valve.12   =Name:V_BAL_COL_RR    #DestinationLine:TO_COL_VRR   #Circuit:8

Trigger.6 = Target:TANK_COLLECTOR#Threshold:6.69#Condition:TankQuantityBelow#EffectTrue:OpenValve.V_BAL_COL_FL,OpenValve.V_BAL_COL_FR,OpenValve.V_BAL_COL_RL,OpenValve.V_BAL_COL_RR 
Trigger.7 = Target:TANK_COLLECTOR#Threshold:6.70#Condition:TankQuantityAbove#EffectTrue:CloseValve.V_BAL_COL_FL,CloseValve.V_BAL_COL_FR,CloseValve.V_BAL_COL_RL,CloseValve.V_BAL_COL_RR

These new valves need power, over in systems.cfg like so:

just kidding this block was wrong... see next post

Bus.9 is hard-wired to the battery. They have a tiny draw. This isn’t perfect, but it’s a functional proof-of-concept workaround for the Asobo fuel flow bug. Orbx, other modders, whoever, please feel free to take this and improve on it. Would love to see it cleaned up or integrated.

At the moment, I have an issue where the 530 and the ADF are just blinking on and off. Hard to say why, but seems to be related to these triggers. Someone let me know if it’s just me?

Ed: Yeah not just me, maybe don’t define the same circuit twice… I am not smart. See correct block for systems.cfg below.



circuit.55 = Type:CIRCUIT_FUEL_VALVE:5        #Connections:bus.9			#Power:0.1, 0.2, 20.0		#Name:COL_TANK_V_FL ; Col_Tank_Valves
circuit.56 = Type:CIRCUIT_FUEL_VALVE:6        #Connections:bus.9			#Power:0.1, 0.2, 20.0		#Name:COL_TANK_V_FR ; Col_Tank_Valves
circuit.57 = Type:CIRCUIT_FUEL_VALVE:7        #Connections:bus.9			#Power:0.1, 0.2, 20.0		#Name:COL_TANK_V_RL ; Col_Tank_Valves
circuit.58 = Type:CIRCUIT_FUEL_VALVE:8        #Connections:bus.9			#Power:0.1, 0.2, 20.0		#Name:COL_TANK_V_RR ; Col_Tank_Valves

Tagging those above who were interested in this fix (see previous messages) - @flybeast691 @dciskey @TrevKiwi


Hi, thanks for this. Do we need to add all the lines, including the ones on the second post you made?

Edit: ah looks like the first post was edited to remove them. So circuits 55 to 58 only?

The first block replaces the lines in ‘; TANKS => COLLECTOR TANK’ in the flight_model.cfg files. So what is just four Line.# lines becomes eight lines, four valves, and two triggers. (Basically, it takes the four lines that collect each tank to the collector, splits them in half, installs valves in them, and wires those valves to a collector tank level threshold trigger to open and close them. They only open when the collector has at least 0.1 gal space available).

So the behavior you’ll see if you watch the fuel window is when the collector is below 6.7 gal, some flow starts from all four until it’s just over 6.7, then stops, then drops below and starts again. It won’t ever fill to 100%, because if it does it won’t draw equally from all four tanks on that last iteration.

The second block is added to systems.cfg files, four new circuits connected directly to the battery on existing bus.9.

I screwed up the wiring the first time and tried to create new circuits but wrote them on top of existing circuits because I didn’t read the file carefully enough, so the power to the valves was also flipping the power to the pre-existing circuits I overwrote, which is why I broke the GPS. All good when the new four circuits are 55 - 58 as those are unused.

These changes should be written to each of the four variants, cargo, pax, ag, and skydive. The fuel component #s and electrical circuit #s are compatible with all four variants.

We’ll get this packaged up as a drag and drop mod at some point.

Also, ORBX, if you’re reading this, all yours. Feel free to adopt for a future update.


What a shame for Orbx to abandon a product and then have the users fix it for themselves while they completely ignore the problems.
I expected better from a big dev such as Orbx.


Wow, amazing work! Just two days ago I bought the Kodiak in the sale because of this bug, but now I have to have a real think.

Who said that they have abandoned it? They released a patch a few weeks ago but didn’t include the fuel fix.

They just patched the GPSs, they seem to have completely abandoned the project.

That seems like a bad decision to do. Sure, the new sim is 1 year away. Btu this has a crop dusting and skydiving variant. Come a year from now when people are looking for payware planes to fill those roles in the sim’s activities, this seems like it would be sitting in a prime place. Right now, there really isn’t much to do with those variants. To abandon it now would give it a bad rep which will sacrifice its unique position in a year.


ORBX have a history, IMHO, of releasing planes that become orphans. Unlike their scenery which they generally support well the planes just seem to languish, shame really but its not like there is a shortage. Sure the PAC is nice but there’s other stuff just a s fun to fly.

It’s a bit premature to claim they’ve abandoned it, isn’t it? It was released in October and has received a few patches already. A visit to their support forums shows no mention of the issues you guys are discussing here. As this is not the place to get support, maybe head on over there and inform them that not only have you found a problem, you’ve apparently found the solution too.

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Thanks @TheReproCase and hello everyone!

We had intended on releasing the custom sounds for PAC but hit a snag when we arrived to record them and the airplane wasn’t in the same location. We’re working out a new date, and we’re also going to be looking at some fixes in addition to the fuel issue. As @CaptHawkeye50 pointed out, please use the Orbx forums for support.

We’re also keen to get into FS2024 - looks like those new mission features were made for the PAC!


@TheReproCase amazing! Thank you so much, just tried this out and works well. :smiley:

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They really were. I hope once you get your hands on the SDK it will give you a good jump-start to come out with a bang when the next version releases. You have all the ground work for making an addon that has massive potential to be a big hit. I feel it will give this aircraft a second life so I hope your team can pull it off :wink: