MIflyer
1st Lieutenant
When I was stationed at Tinker AFB, Oklahoma City Air Logistics Center, a dispute developed between the engineering offices at OC-ALC and Sacramento Air Logistics Center in California. The T-33 has a large 230 gallon fuel tank on each wingtip. The fuel is forced out of those tanks and into the aircraft's internal tanks by regulating air pressure from the engine compressor bleed air, regulated at a pressure of about 11-13 PSI. When the tip tanks are selected by the pilot the pressure is applied to the tip tanks and forces the fuel out.
Each tip tank has what is called a "sniffle valve" which works rather similar to the spring loaded valve built into radiator caps. When the pressure exceeds the amount the sniffle valves are set, it opens and bleeds off some of the pressure. Presumably, it is called a sniffle valve because in releasing some pressure it also lets go a little bit of fluid - the fuel.
If one tip tank does not empty that means the T-33A has up to 1300lb out on one wingtip, and you can't really land with that condition. The F-80A flight manual says "It has been landed with one tank full but it is tough." The SA-ALC people said that the problem could be fixed by tightening the allowable output pressure range of the regulator, which would be a OC-ALC problem. OC-ALC replied that the pressure in the tank and therefore the amount of fuel, was ultimately controlled by the sniffle valves, so the answer was for SM-ALC to make sure that the two sniffle valves in the tip tanks were hand selected to be as close as possible. If one sniffle valve was set to the upper limit, about 14 PSI, and the other to the lower limit, about 11 PSI, then that would determine if the tanks fed at an equal rate.
In the story below, a pilot figured out a way to fix the problem on his F-80.
By LtCol. A.J. D'Amario USAF Ret. From the pages of the American Rifleman, November 2013.
On my first solo flight at K-13, Suwan, Korea, in June 1952, I took off in an F-80 Shooting Star. It was not a combat mission. All I had to do was go up and have fun boring holes in the sky for about an hour and a half.
Immediately after takeoff, I felt the left wing was heavy and determined that the left tip fuel tank was not feeding properly or not at all. Afraid it might fall off and rupture during landing, potentially melting asphalt on the runway, the tower would not let me land with the full tank. I was instructed to make a bomb run and drop the whole tank.
Arriving at the bomb range, I set up my bomb-release switches to release the tank. Flying over the impact area, I pushed the button but nothing happened. I tried a second time and again there was no response. On my next pass, I tried the manual release handle but to no avail. Making one final run, I used the button we called the "panic button" because it allegedly released everything hanging on the airplane. It worked as advertised and dumped everything, save my errant left tip tank.
The tower control officer advised me that if I couldn't get rid of the tank or its contents, I should give them my location, eject and await pickup.
Well, pilots really hate to punch out of a perfectly flyable airplane and I figured I still had one option worth trying.
The canopy of an F-80 can be opened in flight up to about 220 MPH. So I opened the canopy and unholstered my G.I. issue Colt M1911 .45 automatic.
Now, liquid fuel will not burn, at least not like vapors, so I aimed for the part of the tank I was sure would be full of liquid. Firing my first shot, I had no idea where the bullet went--perhaps airborne, high-speed physics were at work, or maybe just my nerves. But my next three shots punctured the tank, passing through the fuel and exiting cleanly out the far side of the 24" wide tank.
For the next thirty minutes, I flew with the left wing down in a series of circles to drain the fuel and slowly return to base. By the time I got to the airstrip the tank was empty. I made a routine landing. As far as I know, I am the only pilot in the Air Force who ever shot his own plane to correct a malfunction.
Thank goodness for my .45.
Each tip tank has what is called a "sniffle valve" which works rather similar to the spring loaded valve built into radiator caps. When the pressure exceeds the amount the sniffle valves are set, it opens and bleeds off some of the pressure. Presumably, it is called a sniffle valve because in releasing some pressure it also lets go a little bit of fluid - the fuel.
If one tip tank does not empty that means the T-33A has up to 1300lb out on one wingtip, and you can't really land with that condition. The F-80A flight manual says "It has been landed with one tank full but it is tough." The SA-ALC people said that the problem could be fixed by tightening the allowable output pressure range of the regulator, which would be a OC-ALC problem. OC-ALC replied that the pressure in the tank and therefore the amount of fuel, was ultimately controlled by the sniffle valves, so the answer was for SM-ALC to make sure that the two sniffle valves in the tip tanks were hand selected to be as close as possible. If one sniffle valve was set to the upper limit, about 14 PSI, and the other to the lower limit, about 11 PSI, then that would determine if the tanks fed at an equal rate.
In the story below, a pilot figured out a way to fix the problem on his F-80.
By LtCol. A.J. D'Amario USAF Ret. From the pages of the American Rifleman, November 2013.
On my first solo flight at K-13, Suwan, Korea, in June 1952, I took off in an F-80 Shooting Star. It was not a combat mission. All I had to do was go up and have fun boring holes in the sky for about an hour and a half.
Immediately after takeoff, I felt the left wing was heavy and determined that the left tip fuel tank was not feeding properly or not at all. Afraid it might fall off and rupture during landing, potentially melting asphalt on the runway, the tower would not let me land with the full tank. I was instructed to make a bomb run and drop the whole tank.
Arriving at the bomb range, I set up my bomb-release switches to release the tank. Flying over the impact area, I pushed the button but nothing happened. I tried a second time and again there was no response. On my next pass, I tried the manual release handle but to no avail. Making one final run, I used the button we called the "panic button" because it allegedly released everything hanging on the airplane. It worked as advertised and dumped everything, save my errant left tip tank.
The tower control officer advised me that if I couldn't get rid of the tank or its contents, I should give them my location, eject and await pickup.
Well, pilots really hate to punch out of a perfectly flyable airplane and I figured I still had one option worth trying.
The canopy of an F-80 can be opened in flight up to about 220 MPH. So I opened the canopy and unholstered my G.I. issue Colt M1911 .45 automatic.
Now, liquid fuel will not burn, at least not like vapors, so I aimed for the part of the tank I was sure would be full of liquid. Firing my first shot, I had no idea where the bullet went--perhaps airborne, high-speed physics were at work, or maybe just my nerves. But my next three shots punctured the tank, passing through the fuel and exiting cleanly out the far side of the 24" wide tank.
For the next thirty minutes, I flew with the left wing down in a series of circles to drain the fuel and slowly return to base. By the time I got to the airstrip the tank was empty. I made a routine landing. As far as I know, I am the only pilot in the Air Force who ever shot his own plane to correct a malfunction.
Thank goodness for my .45.