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External fuel tanks not working??


Ala12Rv-watermanpc
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Hi guys!, after messing a few hours with the external fuel tanks I cant manage to find a way to make em work :huh:...tried in the ground and in flight, nothing...every time I set the ext fuel switch to CL/pilon the only thing that happens is that the emergency panel lits with the "ext tank empty" which is not possible as I have just started the mission.

 

The fuel amount gauge just indicates the amount of the internal tanks and as sson as they get empty the engines stop. Also, I can confirm ext tanks are full because I can clearly feel the weight they provoke when controlling the plane so...wth is going on??is it a bug???am I missing something here??

 

Also, another thing I dont understan in the manual is that at some point it says that you must use the inboard tanks FIRST, then CL tank and lastly the internal fuel tanks...OK.

 

The problem is that when talking about jettison, the manual says that the logic secuence you must follow is first eject the CL, then inboard :huh:...that has no sense to me, whats the logic in use the inboard pilon tanks first if then I will have to eject the CL tank which may be totally FULL?¿?¿?¿?:huh: ...also, 2 tanks should weight more than 1 so not only they weith more but also they may be empty by the time I need to drop CL tank, which would be totally full...

 

 

thanks!!

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No one has problems with that?...tested a bit more and another thing I have noticed is that if I start the mission already in the air, then ONLY the pilon tanks work correctly but not the CL one. Starting in ramp never make them to work right. As soon as I eneble them using the EXT switch the "ext tank empty" light goes on inmediately.


Edited by watermanpc

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The requirement to use internal tanks first is that there is an inbalance when they are full, and the first step is to balance them, then you can switch to external fuel tanks.

 

I can't help with the functionality as I haven't used them much myself. However, as you also seem to be having issues with other systems, it might be worthwhile uninstalling, and re-installing the F-5E to see if there has been a corruption somewhere?

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Many thanks for your help...yes, I was thinking about reinstalling/repairing hte game as Im having several weird issues...about the balancing, not sure if you need to use it with the tanks totally full, and even then that wouldnt explain the problem with the CL tank right??..is there any way to repair only one module btw??

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...about the balancing, not sure if you need to use it with the tanks totally full

The Right (Aft) tank holds more than the Left (Forward) tank, so the first action after takeoff is to balance the aircraft. It isn't done during take off as drawing fuel from both tanks gives redundancy in the event of a pump failure.

 

... and even then that wouldnt explain the problem with the CL tank right?

I don't own the module yet, so can't help with the CL tank function.

 

IIRC the RL manual has lots of limitations on jettisoning stores, for external fuel tanks, some are due to the risk of fire (if part full), others due to risk of striking the aircraft/other stores or just to keep the aircraft well balanced. Because of these limitations, the jettison order can look awkward/illogical unless the underlying reasons are taken into account.

 

External Fuel Sequencing

 

When external tanks are carried, use inboard tanks first, centerline tank next, and internal fuel last.

 

During ground operation, delay or stop transfer of external fuel when either the left system indicates 1700 pounds or more, or right system indicates 2300 pounds or more.

 

When inboard tanks are empty (indicated when EXT TANKS EMPTY caution light comes on), check fuel quantity indicator for a decrease in quantity to assure that inboard tanks are empty.

 

To transfer centerline tank fuel, turn off PYLONS fuel transfer switch and turn on CL fuel transfer switch.

 

Failure to turn off the fuel transfer switch when inboard tanks are empty prevents EXT TANKS EMPTY light from indicating when the centerline tank is empty. The light remains on until the switch is turned off.

 

NOTE

Fuel balancing should be delayed until external fuel transfer is complete.

Source: T.O. 1F-5E-1-1984_OCR.pdf, page 61

http://www.476vfightergroup.com/downloads.php?do=file&id=445


Edited by Ramsay
Add note on Exturnal Fuel Sequencing

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The requirement to use internal tanks first is that there is an inbalance when they are full, and the first step is to balance them, then you can switch to external fuel tanks.

This doesn't sound right, as external tanks add fuel faster than the jet uses it, so activating the external tanks will just re-fill the internal tanks.

 

Page 96 says: When external tanks are carried, use inboard tanks first, centerline tank next, and internal fuel last. (emphasis mine)

 

i.e. use the wing pylon tanks first, followed by the centreline external tank, and then internal tanks.

 

I think the reason for not using external tanks during takeoff is probably due to safety or reliability. This could be as simple as having fewer things to potentially go wrong, or might be for specific issues. e.g. a rejected take-off with full external tanks currently feeding fuel might be dangerous, or some other possible scenario.

 

There's also a note in the manual which might offer some kind of clue to someone who understands how these fuel systems work:

 

NOTE: During ground operation, it is not recommended to transfer fuel from external tanks when fuel quantity in the left fuel system is 1700 pounds or more, or in the right system is 2300 pounds or more.

 

For the OP, are you setting only one of the CL or Pylon external fuel switches on at a time? I've not tried it and I don't know if that'd result in the behaviour you describe, but I don't think the system will work properly if you enable both at the same time.

 

Also you can't repair a specific module, but you can repair DCS World using the shortcut in the start menu, and it will replace any altered or missing files for all installed modules.

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The problem is that when talking about jettison, the manual says that the logic secuence you must follow is first eject the CL, then inboard :huh:...that has no sense to me, whats the logic in use the inboard pilon tanks first if then I will have to eject the CL tank which may be totally FULL?¿?¿?¿?:huh:

I think you're referring to page 121, and it's not saying what you have to do, only what the internal logic does if you have multiple stations selected.

 

Sequencing logic provides the following store release priority:

  1. centreline;
  2. inboard;
  3. outboard;
  4. wingtip missiles emergency launch.

NOTE: For example, in order to jettison the outboard stores, the armament position selector switches of the centerline and inboard stores must be set in OFF position.

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You can uninstall and reinstall a specific module - therefore effectively carrying out a repair by going to the module manager, and removing it. Then re-start DCS World, and you'll be prompted to re-install it.

 

It should give you a clean install of the module, and hopefully eliminate your issues.

 

It may also help to rename the module's inputs file in your saved games directory, which will force DCS World to create a new one. If everything appears normal, replace the new inputs with the old, and see if the issue returns, in which case, you'll need to re-map the inputs after doing the re-name again.

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I read on one of these forum threads that you have to use the outboard tanks first because the CL tank will, and I can't remember the reason why, keep the "tanks empty" light on all the time, so you would never know when your outboard tanks are actually empty.

 

Not sure if this is right, but here's how I run it, and I have no issues:

 

1) Normal light off. Skip step two if your mission is set up with the jet spawned armed as desired

 

2) Rearm with desired external tanks

 

3) Turn off the port and stbd wing tank boosters, turn on the crossfeed. You will get caution lights for this.

 

4) Select the CL tank, OR if you have outboards select ONLY them

 

This has worked for me. I haven't run pylon tanks out of fuel yet, but I have carried a CL in the above config until it was dry, and the light does come up on the caution panel. I close the crossfeed, turn my wing tank pumps on, turn off the CL tank feed, then drop it!! Oh yes, and balance tanks once you drop the others....

 

Again, I did some reading, not sure if it's 100% correct, but it appears to be working for me.

 

~S

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Ok, I think I have solved the "mystery" :D

 

This is how ext tanks work:

 

When the plane is using ext tanks, their fuel is NOT spent directly into the engines but stored in the plane's INTERNAL tanks first. So, if you start a mission (WITH AN INTERNAL FUEL AMOUNT REDUCED IN THE SAME AMOUNT THAT THE EXTERNAL TANKS CAN PROVIDE), the sim (very cleverly) suppose that the external tanks would had drained their fuel to the internal ones!!...that explain why I got the "ext tanks empty" emergency panel light inmediately after starting the mission.

 

My "error" was, that I was always configuring an internal fuel amount lower that 50% systematically (just to not overload the plane in my tests :doh:) and thus, as the total amount the F5 can load is like 4500lb (so 50% is 2250lb aprox), every time I used 1 or even 2 275gal ext tanks which add up to 2200lb more or less, they were totally drained by the time the mission start because there is actually that capacity available into the internal tanks...so, external tanks are already empty!!.(note that, the "empty ext tanks" warning has also ist own 400lb aprox margin of aware before the tanks get really depleted, so expect the warning alarm to be displayed a bit before the exact moment in which the tanks get depleted)

 

 

Also, this explain the behaviour of the fuel gauge...it just reads the INTERNAL tanks quantity and so, if the internal tanks are totally filled, you wont see any movement in the needles.

 

Another thing maybe useful for many is that the external tanks seem to be perfectly balanced during the draining proccess as I cant feel any roll trim changes during prolonged flight BUT, as the fuel is being drained into the internal tanks there is still the need to balance the L and R tanks either manually or automatically.

 

Everything seems to be good now :thumbup: and working as expected (no more "empty ext tanks" warning at start when using an internal fuel amount big enough to cant completally drain ext tanks)...even made an "assurement" test :D to check all this:

 

When fliying with the ext tanks (2 in this case) depleted at the start, if I drop one of them I can see how much the plane gets disbalanced in roll (very little in this case as the tanks are depleted)...when flying with a 100% (for example) of internal fuel amount plus ext tanks, when I drop one of them the plane gets extremely disbalanced so, obviously the dropped tank was full.

 

So you should never subtract in the editor an internal fuel amount equal to the ext tanks capacity if you want to actually use them :doh:

 

So...I guess all this is solved right?:)


Edited by watermanpc

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