I am installing a Wren Mk54 mk4 into a FEJ rafale. Now, this is the first time I have installed a turbine in an airframe. Bench tested the turbine plenty of times and all is good to go. I am using the small tygon to do most of the plumbing. I was told to use 1/8 tygon, but it is too big and does not fit snugly enough over brass tubing from main tank or nipples on FlightWorks fuel pump. I am tying off all lines at connections with wire as well. I am using small tygon from main tank to Tamjets UAT, as well as from UAT to fuel pump. I have encountered 2 problems. Number one is the main fuel line for the turbine is like 3mm festo line. The nipple coming off the pressure side of the fuel pump is for tygon. What I have been doing is using a short piece of tygon connected on the nipple of pressure side of pump and then plugging the 3mm main fuel turbine line into the tygon. I have pushed the festo line as far as I can into the tygon and tried tying it tight with wire. Just does not seem all to secure. Seems like under pressure festo line might blow out of tygon. I would think there is a much better way of doing this, I just do not have the experience to know. I have seen some Hausl pumps that have a festo fitting screwed directly into the pressure side of pump instead of the tygon nipple. This seems like a much better setup. Any suggestions would be appreciated. Problem number 2. Plumbed as such, I ran the turbine in the aircraft for the first time yesterday in the airframe. My Tams UAT is secured to the top of the main tank with velcro straps. I filled the system and was getting some good size air bubbles in my air trap. I tried tapping the tank as it was filling. got rid of most air, but still have a little in UAT. My UAT is also secured pointing very slightly down towards the nipples of tank, not level. When running the engine, any time I moved the aircraft it would create air bubbles which would almost cause turbine to flame out. I could see the air bubbles in the line. When plane was not moving with turbine running, I did not have problems. I removed tanks and checked for leaks using underwater method. Everything seems to be good. Not sure where to go from here. Any suggestions for the newbee would be greatly appreciated. Thanks Jon

I am not sure that I totally understand the problem but if a festo fitting is involved using tygon fuel line won't work. It is just way too flexible to make a good seal.

jon,
you can always get a 4mm to 3mm festo reducer and use 4mm festo fuel line from the pump to the reducer to the turbine. Also, most of the time if the air is accumulating in the UAT, you have an air leak somewhere further down the system. this could be from a small pinhole in the lines or a "crimped" connection where the safety wire is on the tygon line. What i typically do when safety wiring the tygon onto the brass tubes is to make on complete 360* round and then another w/ the wires coming off at the same sides. That way the tygon is clamped onto the tube a full 360* and doesn't "crimp" an edge allowing an air bubble. I can't get a good visual of how the UAT is mounted, so pictures might be a good idea.

thomas

Jon

I would re-pipe the tanks to use bigger brass tube and 1/8 tygon and make sure the tube to the clunk and the clunk is also of a good size bore. Use the same for the vents. T the tanks togeather with some T pieces of atleast 1/8 bore and use equal length pipes for both sides. For the pipe between the pump and UAT use a 1/2 inch long piece of 4m pushed on the pump nipple and then push the supplied 6mm tube over that, you will find it is a very good fit but also wire it on. For the pipe between the pump and engine, use a length of 4mm pushed on to the pump nipple (there is enough room with the 6mm on the other nipple) and use a Festo 3-4 reducer to take it to the 3mm engine tube and although your engine has a filter under the cover, another in this line would be good. Don't forget to purge the UAT properly by holding it vertical or you will get bubbles and it may flame out.

Jason

Hey fellas,
thanks for all the help so far. Could someone please explain to me the proper UAT air purging technique??? Also, does the orientation of my UAT matter? My UAT currently is strapped on the top of my main tank backwards. The main tank how it sits in the fuselage is anged back slightly. So that means that my UAT is angled slightly forward. Visible air bubbles are collecting at the front by the 2 top nipples. Maybe it would be better to flip the UAT around so the any small bit of air will collect at the back of the tank. Any ideas? Thanks Jon

the best way to purge the uat is to hook 1.5 volts to your fuel pump after filling everything, and let it run. Just use a AA battery and a couple of wires. take the output of the pump and dump it into the same can you are drawing the fuel into the UAT from through tygon or 6mm. Let it run and shake the uat, and tap it and eventually all the bubbles will quit. then let it sit and soak for a bit, and repeat. It took me about 30 min to get rid of the bubbles AFTER I had a flameout. I suspect I got a bubble, but not really sure. Take the time to get the air out, its time well invested. Once saturated, it will give years of pleasure.

The Wren pump, both the Hasl and Flight works has a 4mm input and a 3mm output. Its really tight but the 3mm will go on it on the pressure side. You will need to get a reducer to go from 6mm to 4mm. I would strongly suggest a simple brass 6 to 4 barb available from dreamworks.

The output of the pump to the motor should never be tygon. it has to be hardside tubing. it will go. safety wire it when done.

I use 6mm tubing for my feed line, but alot of guys use tygon successfully. If you want your shutoff on the pressure side, you can put a 3mm festo cutoff or barbed cutoff somewhere after the pump.

Generally speaking festo is designed for pressure not suction, but alot of guys use it on suction side with hardside tubing.