Shok

My Feedback: (28)

Should I put a festo rotary valve between the UAT and pump or between the pump and turbine?

Terry Holston

My Feedback: (1)

Between the UAT and the pump.

Shok

My Feedback: (28)

thanks Terry

Gordon Mc

My Feedback: (11)

Yup - this way, any minor air leak from the shutoff valve has a chance of being dealt with by the UAT.

Other than that, the most important thing about the location of the shutoff valve, is ease of access in an emergency.

Gordon

Harley Condra

My Feedback: (4)

Gordon hit the nail right on the head again.
Any bubble in the fuel system is better on the suction side than on the pressure side, and it can come from the UAT fill line. Make sure that you have a tight seal at the UAT fill line, or you will burn the fuel from the UAT and get e a flame out. I use .020 safety wire on all of the fuel system connections. If you lose the plug that comes with the UAT, you can substitute a 6mm ball valve or a 6mm one-way check valve in it's place. I saw an airplane flame out after takeoff when the owner substituted an allen bolt for the plug that he left on the workbench. The air leaked past the threads, and allowed the UAT to get run dry. Fortunately, good piloting skills got the bird back on the runway without a scratch. It had an empty UAT, but full mains and header. 4 ounces won't get you very far.

Make sure that the line to the ball valve is straight if possible. The Festo type connectors don't like tightly bent bent tubing at the fitting.

Harley Condra
BVM REP
Team JetCat

MDEE

I hate to disagree but I have always put festo taps on the pressure side of the pump circuit ie between the pump and the turbine, they are designed to work under pressure not suction. Festos will leak air under suction if the pipe is not cut exactly right

Mark Diggle

grbaker

My Feedback: (29)

If you have the valve between the pump and the turbine and have an emergency that requires you to close the valve to shut down the turbine. Then if the tubing or festo fitting develop a leak, you have raw fuel under pressure going all over the place.

If on the other hand the valve is installed on suction side of the pump (between the UAT and the pump) a failure in the tubing or festo fitting will result in little or no fuel spillage.

just a thought

Kelly W

My Feedback: (2)

Wouldn't this actually mean the valve is downstream of the UAT, where it wouldn't be able to absorb a bubble? In that case the seal is critical. Regardless, I've always put the valve on the pressure side for the same reason Mark mentioned. Festos are designed to seal with positive internal pressure. On my Stingray its bundled in the wiring harness right beside the engine. On my Hotspot its buried inside the speed brake opening. Both are located immediately before the engine in the fuel circuits.

The downside of putting a valve after the pump is the sudden load on the pump motor in an emergency shutoff. The current draw would be rather high, but most (likely all) of the ECU's out there will detect the drop in RPM and/or EGT and start the shut down sequence anyway. Any current spike would be short lived and infrequent so the chance of damaging anything is very low. As Gordon also said, the most important thing is access so if the pressure side is unavailable, the suction side is a good alternative so long as the seal is good. Last, when cutting the tubing, don't just use a pair of scissors. Use a SHARP exacto and make sure the end is square with no burrs. There is a proper hose cutting tool available, but a sharp knife will do. Its hard to go wrong if you're careful.

My $.02 Canadian

Kelly W

PST Jets
North American Tech Support