Fuel Logic

[FLIGHTO 8]

Does anyone know how the fuel system is supposed to work?

 

I did a flight with the center tank full and 1000lbs in each wing tank. I did not have the aux fuel transfer on. When the wing tanks went dry the engine shut off....so I restarted with the aux transfer lever and the both started (mind you no fuel quantity displayed on the screen - both wings read 0 and the ventral tank was greyed out) -

 

The thing is - with both engines restarted the fuel flow on the proline screen was around 400lbs per engine but the fuel flow in the FMS was around 2500lbs and the fuel remaining was draining very fast... What is going on with this a/c.

 

This has to be the most buggiest product ever to come out of Carenado...

 

PLUS - once airborn the landing light do not function properly - among many many many many many other issues..... This sucks, and I cant get the "ELECT" cas warning to shut off... I tried the STBY INV - No luck...

[WarpD 824]

On the MFD they appear to be showing corrected fuel flow: >(A:TURB ENG CORRECTED FF:1, pph)

[JRBarrett 3,034]

 

When fueling a Hawker, the wings are always completely filled before putting any fuel in the ventral tank.

 

If the ventral has fuel, the aux transfer valve is opened. The engine fuel is supplied only by the wing tanks. The ventral tank can send its fuel only TO the wing tanks. The net result is that the wings remain nearly full while the ventral quantity decreases. The exact rate and timing of the transfer is controlled by the fuel system logic to maintain a relatively constant CG

 

Once the ventral is empty, the aux fuel annunciation illuminates on the warning panel, at which time the pilot can close the aux transfer valve. Apparently in the Carenado Hawker, if the ventral runs dry, and the aux valve is not immediately closed, the engines quit. If so, that is a bug, because in the actual aircraft, the ventral does not directly feed the engines - it only feeds the wing tanks.

 

The electrical warning is due to another bug. The Carenado aircraft has the engine generators linked to the Alternator switches, which are located on the left side of the overhead panel. If you turn the alternator switches on, the warning disappears. By contrast, the generator switches, which SHOULD cause the electrical warning when switched off, do nothing at all.

 

The actual purpose of the alternators is to supply 115 volt AC voltage solely for heating the cockpit windows. They have nothing to do with supplying any of the aircraft's main electrical power.

 

There is also a bug in the logic of the inverter switches. The inverters supply 115 and 26 volts AC used by some of the aircraft instruments, such as the attitude and heading system. There are two primary and one standby inverter. The standby inverter is intended to come online only if the main inverters fail, but in the sim, when the standby inverter switch is placed to "arm" mode, it comes online immediately and lights an annunciator on the master warning panel.

 

In any case, the inverter system appears to be only for "show". Even if you turn all three inverters off, the AC voltmeter on the overhead panel still shows an indication. It should read zero with all inverters off.

[autogyro 18]

I've tested the aux fuel transfer before, it is basically a toggle for which fuel tank to use rather than to transfer fuel to the wing tanks.

[JRBarrett 3,034]

I've tested the aux fuel transfer before, it is basically a toggle for which fuel tank to use rather than to transfer fuel to the wing tanks.

Yes, they apparently simply created 3 tanks, each of which feed the engines directly, with the ventral having priority. I guess the only work around is to keep a close eye on ventral quantity, and turn off the aux transfer before it runs completely dry...

[autogyro 18]

Yes, they apparently simply created 3 tanks, each of which feed the engines directly, with the ventral having priority. I guess the only work around is to keep a close eye on ventral quantity, and turn off the aux transfer before it runs completely dry...

 

I'll write up a gauge update to autoswitch the ventral tank off when it's <1 gallon of fuel as a workaround for now.

[JRBarrett 3,034]

I'll write up a gauge update to autoswitch the ventral tank off when it's <1 gallon of fuel as a workaround for now.

Excellent! I have a reasonable amount of C and C++ experience, but have never tried my hand at gauge programming. Perhaps this would be a good time to crack open the SDK documentation and start learning more about it. This aircraft has potential, but seeing careless errors like the mis-assigned Alternator vs. Generator switches is a bit aggravating.

[autogyro 18]

Okay guys, in your FSX/gauges or Prepar3d v2/gauges folder, there should be a GAUGE850XP.cab file.

 

Extract it into a folder (keep the name GAUGE850XP so that you now have a FSX/gauges/GAUGE850XP or Prepar3D v2/gauges/GAUGE850XP folder.

 

Within the folder, there is a file called Gauge_UPDATE_DIG.XML

 

Open the file using a word editor, notepad etc. I prefer Notepad++

 

Go to line 936, and insert the following:

 

<!-- Toggle AUX Transfer lever off when under 2% of fuel --!>

(A:FUEL TANK CENTER QUANTITY, gallons) 4 <
if{ 
	(L:ASD_LEVER_FUEL_CENTER_850XP, number) 0 != if{ 0 (>L:ASD_LEVER_FUEL_CENTER_850XP, number) }
	}

Then save the file.

 

This will automatically switch off your AUX transfer when it is under 4 gallons of fuel remaining (2%, whereby the empty comes on the copilot PFD for the ventral tank.

 

That'll have to do until Carenado sorts out the fuel transfer issue.

 

 

Alternatively, if you want for all 3 tanks to be used (ventral and wing tanks when you have AUX transfer on), change lines 933 and 934 to:

		(A:FUEL TANK SELECTOR:1,enum) 1 != if{ 1 (>K:FUEL_SELECTOR_SET)   }
		(A:FUEL TANK SELECTOR:2,enum) 1 != if{ 1 (>K:FUEL_SELECTOR_2_SET) }

This means, use all tanks. You'll still get fuel use on the wing tanks but once the ventral tank runs out it won't automatically shut down the engines and you can switch the AUX Fuel Transfer lever off at your discretion.

[piperarrow41 4]

Quick question, how do you find line 936?  I'm using just regular notepad.

 

Thanks,

 

John

[autogyro 18]

You can basically insert it most places, but I've just put it after the other fuel tank selector coding, you could just search for what is in the second code box above, i.e. search for (A:FUEL TANK SELECTOR:2,enum) in the document.

 

Just need to put it past the lone } bracket that closes off the previous argument.

 

Or in other words, before the line:

(A:AIRSPEED SELECT INDICATED OR TRUE, knots) (L:AIRSPEED_VS_850XP,knots) / 100 * 100 - 0 max 50 min (>L:NEEDLE_VDIVVS_850XP,number)	 

[piperarrow41 4]

Your fix works great!  Thank you!

 

It is pulling fuel from all 3 tanks.  Is there a way to have it only pull fuel from the ventral tank until its empty then start pulling fuel from the wing tanks?

 

John

[piperarrow41 4]

After applying this mod I wasn't able to start the APU.  The annunciator on the panel said APU ON however the gauges on the APU did not respond. Any ideas?

[autogyro 18]

Are you starting from cold and dark? I've found if you use Ready to Taxi it'll pull from 3 tanks.

 

It shouldn't affect APU behaviour. If you read the coding it's quite a simple mod. It basically says if the ventral tank has under 4 gallons of fuel, and if the AUX fuel transfer switch is on, shut the fuel transfer switch off. So that's all it should change.

[piperarrow41 4]

I was able to get it to work, just formatting issue on my end. 

 

Thank you!

[deltamike172 2]

I got the Aux switch to auto close via this code.  Thanks!

 

But, I too have no APU anymore.  Regardless of how load the plane or if I hit Cold and Dark or not.  What kind of "formatting" fixed it?