External Fuel Tanks on Tactical Jets...How they fill 'dem things?

[82Whitey51]

I spent 20+ years around Naval aviation...zero of it in fighters or "tac-air" (E-2s, CODS, E-6A/Bs, P-3s). So, my question is for external fuel tanks, how are they filled? Are they filled from the single point refueling panel, by selecting the station the tank is mounted on? With my limited knowledge of aircraft I imagine this is how it is done...I did spend some time on carriers and never noticed the "Grapes" hooking fuel hoses up to external tanks. Or is the hose in fact hooked to the tank and filled?

 

Just one of those details I guess I've never given much thought to.

Edited February 15, 2017 by 82Whitey51

[Chris L]

 

 All the USAF fighters of modern area were single point refueled up to 1994 . I can't think of a reason they would go backwards now.

 

 Cheers, Christian 

[Scooby]

On the Hornet we fueled from the single point refueling panel, we had a valve that we flipped to fill the external tanks. Once they were full we filled the mains.

 

We listen to the fuel flow and watched the hose to determine when to switch over. It isn't like the Hercules where we had fuel gauges and we could distribute the fuel.

 

We did fuel calculations later to verify the added value matched the fuel gauge in the cockpit.

 

On the T-33 we dragged a hose to the tip tanks, no SPR on that technology. Same for the CF-104.

Edited February 15, 2017 by Scooby

[Ol Crew Dog]

On the F-15, F-16 and F-4 we had single point refuelling power off all tanks would gravity feed, the only time we would do over the wing refuelling was when we had just installed the external tank and had to do a leak and transfer check?

[Andrew Maverick Taylor]

Also on that note, do the external tanks have their own drain points to check for water in them like on the aircraft?

[martin_sam_2000]

11 hours ago, Andrew Maverick Taylor said:

Also on that note, do the external tanks have their own drain points to check for water in them like on the aircraft?

I am sure they do,  but I have never seen a pilot check for water in the fuel on a jet aircraft. We do water tests a number of times a day on the actual fuel truck. Not to mention jet aircraft are not as susceptible to water in the fuel system. In reality, the combustion chamber is open to the environment and can, and will, ingest water any time there is precipitation. A small amount of water in the fuel will make no difference to the engine operation. The big issue with water is it freezing at high altitudes blocking fuel lines, and to counter that either the fuel line itself is heated, or there is FSII  (Fuel System Icing Inhibitor [usually and alcohol based chemical]) added to the fuel that bonds to the water and lowers its freezing point to an acceptable level/.

[Ol Crew Dog]

18 hours ago, Andrew Maverick Taylor said:

Also on that note, do the external tanks have their own drain points to check for water in them like on the aircraft?

 Yes there is a sump drain on the all fuel tanks including external, this was used most to  " depuddle" the tanks for maintenance or weight and balance. 

[Andrew Maverick Taylor]

8 hours ago, martin_sam_2000 said:

I am sure they do,  but I have never seen a pilot check for water in the fuel on a jet aircraft. We do water tests a number of times a day on the actual fuel truck. Not to mention jet aircraft are not as susceptible to water in the fuel system. In reality, the combustion chamber is open to the environment and can, and will, ingest water any time there is precipitation. A small amount of water in the fuel will make no difference to the engine operation. The big issue with water is it freezing at high altitudes blocking fuel lines, and to counter that either the fuel line itself is heated, or there is FSII  (Fuel System Icing Inhibitor [usually and alcohol based chemical]) added to the fuel that bonds to the water and lowers its freezing point to an acceptable level/.

I've never worked on military jets, only commercial and light turbo prop.  Never really did much with the drains on the larger Boeing's but certainly on the light GA stuff and mainly the Beechcraft 1900D which I spent most time on.  They only flew at medium to low altitudes and for short hops so wasn't an issue to make the fuel lines heated.  Fighter jets fly at all altitudes and in all manouvers so makes sense to heat the lines.  Nice explanaition, thanks.