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Engines die when wing tanks empty and wing tank fuel pumps on


SirGosht

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Hi, when flying the DHC-6-100 Wheels Cargo in MSFS, I fill in the wing tanks. During cruise, I switch the wing tank pumps on (bottom of the pedestal). The plane begins to use the wing tanks fuel as expected.

 

I believe the correct behaviour when the wing tanks are depleted is for the plane to continue using the regular tanks but instead the engines die. There is still fuel in the regular tanks, and the fuel setting is NORM.

 

The current behaviour however is that the engines die as if cut off from fuel. Am I doing something wrong?

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Lol this just happen to me.

There I was cruising along fat, dumb and happy and both engines quit. FWD and AFT about 600 lbs and Tip tanks fuel pumps to wing. Never did get the low level light. If that is normal behavior there should be a big .. warning label
 
Easy to reproduce, sitting on the ground,engines running  tip tanks empty, Place the tip tanks switch to Wing and instant shutdown.
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tommyh454 then you're another fine aviator taken down by this bug. ;)

 

I say bug because it feels wrong but also I saw this mentioned years ago on this very forum in regards to a different simulator; the person said the main tanks should be used upon exhaustion of the wing ones.

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23 minutes ago, SirGosht said:

tommyh454 then you're another fine aviator taken down by this bug. ;)

 

I say bug because it feels wrong but also I saw this mentioned years ago on this very forum in regards to a different simulator; the person said the main tanks should be used upon exhaustion of the wing ones.

After saying a few  "Oh my, whatever could be wrong"  and " Whatever could have happened"

I was able to get them re-started.  

(Come to think about it, I probably use my ex-AF  version of the above) :)

I agree, I think this is a bug because the main fuel pump should be still pushing fuel.

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31 minutes ago, tommyh454 said:

I agree, I think this is a bug because the main fuel pump should be still pushing fuel.

Are you sure? I am not familiar with that particular plane but most planes I have flown would simply stall the engine if the selected tank runs dry, no matter if the main pump, boost pump or whatever other pump is running. Especially some older planes are quite challenging in that respect and there were not too few fatal accidents because of wrong tank selection...

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  • Aerosoft

I now have confirmation the Twin Otter does NOT automatically switch sources. So when the tank runs dry, the engine will stop.

 

As EDNR said, it is a real issue with some older aircraft because even when you still have 10% fuel left in a tank you can still suck air with some turbulence.  My instructor always said that the last 15% of fuel in a tank was for when you calculated wrong. He believed that a good pilot would switch between tanks every 20 minutes. When I asked him why he told me he flew from France to the UK and found out over the channel that the fuel selector lever was loose. 

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21 minutes ago, SirGosht said:

Thanks for your insight, guys - just to be sure, since the main pumps are on, should it not continue to pump from the main two tanks?

No, it cannot if the selector is set to the wrong tank, it will only pump dry air and that could destroy the fuel pump if you are unlucky and don't react quickly... - most tank selectors are directly connected to the respective tank only and there is no connection between the individual tanks.
A pilot has to know the fuel selection process by heart and some old planes can be particularly tricky and demanding... - in a Cessna 340 you are only allowed to land with empty tip tanks but you are at the same time not allowed to take off with the tip tanks selected. So you always have to be aware of when and how you have to select which tanks in some aircraft. If you fail to do so you can quickly become a line in a statistic...
Changing tanks too late often meant the engine would quit and some engines are a real challenge to restart in cruise and require special procedures to avoid internal explosions or overspeeds. Therefore some later aircraft implemented connections between tanks and special pumps for fuel transfer from external tanks to the main tanks to avoid such situations but that could be tricky too in some cases...  😉

...and Matthijs is right, it is good practice to switch tanks every 20 to 30 minutes in flight to avoid situations as described but there are other reasons as well. Only if you were flying extreme long distance to the max range of your aircraft experienced pilots ran their tanks dry on purpose to see whether the fuel consumption was as calculated. With todays's modern engine monitors and fuel transducers this is no longer required...

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