use of the external tank only

here is the situation.

putting one under fuselage extra tank.

went to the target about one hour away...

"fus" swith on

then go to the target thenI got chased by MIG 21, so I drop the externl thank then I had only 7000 pds og full left

so it is like I took full from external and internal or only intervnal

My question:

How to use external only

The engines always use the internal fuel. The external tanks only supply the internal tanks. In normal operation from the fully fueled state at the moment external tanks are exhausted the internal tanks will be full.

The situation you describe may happen if external fuel is applied to a partial internal fuel state. For example if there are 5,000 lbs. internal fuel and a 3,700 lbs. of external fuel is added for 8,700 lbs. total. After 1,000 lbs. are used there will be approximately 5,000 lbs. internal and 2,700 lbs. external. It won't be the case that there are 7,700 lbs. internal and 0 lbs. external.

The fuel system does slightly better than 1:1 replacement of internal fuel. If there is less than full internal fuel and some external fuel the internal fuel quantity will raise very slowly. If for example there is 3,000 lbs. of external fuel and 8,000 lbs. of internal fuel it will be impossible to have 11,000 lbs. of internal fuel during the flight.

The situation you describe may happen if external fuel is applied to a partial internal fuel state. For example if there are 5,000 lbs. internal fuel and a 3,700 lbs. of external fuel is added for 8,700 lbs. total. After 1,000 lbs. are used there will be approximately 5,000 lbs. internal and 2,700 lbs. external. It won't be the case that there are 7,700 lbs. internal and 0 lbs. external.

 

The fuel system does slightly better than 1:1 replacement of internal fuel. If there is less than full internal fuel and some external fuel the internal fuel quantity will raise very slowly. If for example there is 3,000 lbs. of external fuel and 8,000 lbs. of internal fuel it will be impossible to have 11,000 lbs. of internal fuel during the flight.

That’s not really how the majority or tank transfers work on fighters man, at least not USAF ones.

That’s not really how the majority or tank transfers work on fighters man, at least not USAF ones.

That is how the externals on the A-10 work. I’m not at home so i cant quote the exact text but external fuel tanks on the A-10 feed the wing tanks which feed the mains which feed the engines.

That is how the externals on the A-10 work. I’m not at home so i cant quote the exact text but external fuel tanks on the A-10 feed the wing tanks which feed the mains which feed the engines.

Don’t argue that, and it would coincide with what all the others do...but xfer rates into voided spaces aren’t going to roll that slow. You’d be waiting a day to transfer enough gas to do a leak and sqeak for example. The standpipes in the tanks aren’t that small.

As far the first post, I would either think it’s a bug or something swithology wise at fault...otherwise internals should be full until tank runs dry...unless you have some weird auto-trans stuff like the -15 has for CFT transfer which will keep fuel from transferrig from those tanks until main tanks drop to a certain level...in which case...cool...but not something I would think would be sound operation and a bit silly in this case.

so what I understand :

"The engines always use the internal fuel. The external tanks only supply the internal tanks."

so nomaly, external should fill up the internal.

ether it is a bug or I did somthing or did not do something...

Thanks

I will check it out in a solo none agressiv environement.

Raab

so what I understand :

"The engines always use the internal fuel. The external tanks only supply the internal tanks."

 

so nomaly, external should fill up the internal.

 

ether it is a bug or I did somthing or did not do something...

 

Thanks

I will check it out in a solo none agressiv environement.

 

Raab

Yes to the above. Perhaps air source turned off or something on your fuel control panel not in the right place?

Yes to the above. Perhaps air source turned off or something on your fuel control panel not in the right place?

I will give it a retry.

Thanks for your time

Don’t argue that, and it would coincide with what all the others do...but xfer rates into voided spaces aren’t going to roll that slow. You’d be waiting a day to transfer enough gas to do a leak and sqeak for example. The standpipes in the tanks aren’t that small.

In my particular test I was running at the maximum fuel rate I could (300' 100% throttle) to shorten the test. Perhaps at lower engine consumption rates the overfeed transfer from external to internal would be faster. Real airplane behavior or not, that's what is seen in DCS.

Am I the only one amazed that people use external tanks on a hog?

As far as I know, tanks are used only for ferry and NEVER in combat.

Come on, even going full throttle the hog can stay for hours in the air.

missions with wp an hour away would need an extra tank to be on the "safe" side

Am I the only one amazed that people use external tanks on a hog?

 

As far as I know, tanks are used only for ferry and NEVER in combat.

 

Come on, even going full throttle the hog can stay for hours in the air.

I’ve seen info out there to suggest that the hog has been cleared to carry the tank in combat, the question becomes would they. Obviously they have decent loiter time already, but there could always be a time and a place.

Am I the only one amazed that people use external tanks on a hog?

Nope, same here. ;)

Not saying it's never done, but I can't say I ever heard about it.

The Hog's loiter time and the omnipresence of USAF tankers in theater mean it would probably be a rather special case where they bring a bag to combat, and then they'd probably drop it before anything serious might start to happen.

My 0.02€ anyway.

I’ve seen info out there to suggest that the hog has been cleared to carry the tank in combat, the question becomes would they. Obviously they have decent loiter time already, but there could always be a time and a place.

They have but in all my deployments we have never carried an external with combat loads.