UAT Purge
 

Hi Guys,


Yesterday I made my 7th flight on my Eurosport, I´m using a rinho and I live at 8000 ft. I made an emergency landing and it seems that the turbine took some air, giving me a scary flame out. [X(] This is not the first time that I land like this, but today we know that it was air. So my question is for help about how to make a perfect purge of UAT . Can someone help ?

THX

Leon G.


PD
I´m Building a new F18 and don´t want to loose it to an air bubble. ;)

RE: UAT Purge
 

Reading from other posts and from The JPO site at this link: http://www.jetpilots.org/PDF%20files...M_500_Tips.pdf

You need to disconnect the line that coming from the UAT prior to it going to your fuel pump and pump it back-wards through your system. I followed this procedure and after 40 flights have yet to experience a flame out. Other more experienced than I might have some better suggestions. But for me it has worked perfectly. Other info:

http://www.bvmjets.com/tips/uat.jpg

It is important that the U.A.T. (Ultimate Air Trap) BVM #6044 is mounted in the model such that it is visible during the engine start and runup. Position the U.A.T. as per sketch if possible. It can face forward in the model or aft with good results.



After startup, run the engine at full power for about 15-20 seconds and observe that the fuel level in the U.A.T. does not decrease.

If it does decrease, their is a minute air leak in the fittings (tubing) from the tank that is feeding the U.A.T. This minute leak may not be obvious at less than full power demands on the system.

HOT REFUELING
If you choose to hot refuel, the time interval between disconnecting the fueling line from the U.A.T. and replacing the line plug is critical. The fuel level in the U.A.T. will decrease, therefore it is best to pinch the line from the U.A.T. with forceps during this disconnect period of time.

Multiple Tanks - check for even fuel consumption
During the initial engine and fuel system check of a new installation, observe that the tanks that are plumbed in parallel burn off equally. If they don't, there is restriction in the slower tank's plumbing or an air leak in the connections to it.

Click to enlarge
FUEL SYSTEM ADDENDUM FOR AUTOSTART
The JetCat people highly recommend using one of their filters between the output side of the pump and the fuel solenoid valve.

This will prevent any microscopic metal parts (that may result from pump use) from fouling the fuel valve. See also www.jetcatusa.com

The JetCat filter is a high quality machined aluminum piece with an effective o-ring seal.

YEARLY MAINTENANCE
We have observed that the fuel line tubing in and outside the tanks can deteriorate from extended use (about 2 years in our models).

It would be a good practice to replace all of it every 12-18 months. Check that the replacement tubing is fresh and that the urethane variety has a round cross section, not oval. The oval shaped tubing may not seal correctly in Festo type fittings.

Replace rubber stoppers and "O" rings in the tank caps and check for leaks before re-installing.

Turbine jet airplanes do not require a lot of maintainance that was formerly associated with ducted fan models. However, time invested in keeping the fuel system in proper working order and keeping a close eye on the battery systems will be well spent.

IT'S CALLED EXPERIENCE
This article was prompted by an engine-out occurence on my Blue Angel F-4 Phantom at Florida Jets. Head's up piloting skills and a lot of luck got the model on the ground with only a few scratches. I thought the lessons learned here might help you avoid a similar problem.

Bob Violett



Hope this helps...

Cheers,

RE: UAT Purge
 

Thank you very much, I think I had an air leak because the uat drop its level a lot and the thanks were half full. I´ll check all of this again.

Thank you.

Leon G:D

RE: UAT Purge
 

all good teaching

RE: UAT Purge
 

After 7 flights there should not be any air trapped in the UAT. Make sure you are leaking from the filler line on the uat.

V..