Forum: F-16 Procedures

can the internal fuel system cause the external tanks to over fill. Lets say one of the internal Shutoff valves are stuck open. OR some other problem internal cause it.

F-16.net Sponsor

I think bealio is right. The valves are presurized and bring additional fuel into the existing fuel system. I dont think that the fuel would spill back into the external tanks.

B.T.W. The fuel system is prisision monitered. They can load fuel into the plane measured down to the liter, i think they can pretty much avoid those kinda things. But it would be interesting to just keep filling one through the planes fuel system to see what would happen. *cough* POP!

Active Member Joined: Apr 08, 2004 - 10:40 PM Posts: 203

The external tanks can over fill if the R&D valve in the tank is bad which would cause the unwanted fuel to be vented overboard onto the ground

Tankrat is correct. But there is no way the intenal system could cause the externals to overfill, the jet would vent before that would happen. Tankrat, how are the t-birds treating you?

Hi guys,

The F-16 fuel system is a syphon system so it will go from tank to tank.
When the F-16 is full it will stop refueling .
The only time that you can overfill the airplane is when you have a bad vent valve and the fuel will vent overboard from the left wing.
Had this happen a time or 3 and it's a big mess.

If you fill the F-16 the external fuel tanks will fill up first and then after they are full the internal tanks will fill up.

If the pilot wants to do some BFM he will ask for a intenal plus.
That means internal all the way full with fuel and a little bit in the tanks.
This is so when they fly to the range he will take fuel from the tanks first and when he gets there he doesn't have to worry about over G the airplane because of the weight in the tanks who are mostly empty anyway.

In order to do that internal plus thing you need a key to close out the external tanks so the internal tanks will fill up first . After internal is full the fuel truck will stop and then all you have to do is open the externals and keep on going to the right amount of fuel they want in the external tanks.

When the external fuel tank is full don't mess with the negative pressure relieve falve on the side DO NOT try to push it in you will have fun cleaning up fuel.
When the tanks are empty it's ok to check them to see if they stick or not but otherwise don't mess with them.

what it comes down to is that you can't over fill the airplane it will stop fueling on it's own the fuel truck will not be able to push more fuel in to the jet so there for you can't really overfill it.

sometimes when you open the valves in the external tanks you do hear the fuel run in to the tank but I have no idea how much that would be.

Have fun,

Henk

henkster, there are many things that can cause the jet to over fill, and the vent valve is not one of them. And by vent valve, i assume your talking about the intenal and external vent and pressurization valve. Bad float valve, bad shuttoff valve, foreign objects getting stuck in the shutoff valves, cracks in sense lines, leaking manifolds are the most likely. The vent valve will vent the fuel after the vent box is full of fuel cause by another problem, not the vent valve. Have a great day!

Bealio,

I did mean the internal and external vent and pressurization valve. If the valve gets bad due to anycause it will throw fuel overboard when the tanks are almost full but if you keep a eye on the vent you will see some indication that the valve is going bad because it will start leaking fuel may be a few drops here and there.

I have never seen a F-16 overfill, the fuel truck will stop before that normally.
unless the fuel truck operator uses toomuch pressure to pump it in the jet.

Other than that I have never seen anything like that.

greetz henk

henkster, the v&p valve is designed to dump fuel overboard, so if fuel is venting, the v&p valve is doing it's job, the valve is not bad, if the valve is bad, it won't pressurize the jet correctly or it won't depressurize the jet correctly. That is the only purpose to the valve. When fuel overfills the jet and fuel gets to where the air is supposed to be, it will dump fuel intead of air. Am i making sense?

Active Member Joined: Apr 08, 2004 - 10:40 PM Posts: 203

Bealio is correct

@ Bealio T_Birds are going great

henkster, sorry to pop your circuit breaker but bealio is correct. The V&P's (2) will not actually cause a venting problem. The job of the valves are to CONTROL venting. The high level shutoff in the internal wings will stop the truck unless you have unwanted fuel from somewhere (cracked line, bad shutoff valve in RES, bad tank), not the V&P.

Can't mess with the fuel shop boys! Hey Tankrat, can you put in a good word for me?

for the fellow fuel shoppers out there.........................

Ok guys,

Thanks for the refreshing of my memory.

I know it has been a little while since I got out of tech school and not working fuels alot.
I thought I was on the right way, but that got terminated pritty fast.

Thanks anyway guys,

Henk

Forum: F-16 Procedures

External fuel tank over filling