Hello.

Recently bought an airplane from a friend that has not been flown for 4 years. Its an Avonds F15. Builts very nicely and in pristine condtion. Its got 8 doors with 6 being main doors. These are operated with UP 2 and UP 4 valves in tandem. The UP 4 being the secondary valve to keep one set of main door open when the gears are down. The other doors will close. I find that the UP 4 valve won't keep these main doors OPEN. The moment I pressurise the system, these doors will close even when the mains are down and touch the struts. I have gone through the entire plumbing and everything is connected correctly with no leaks. Basically the UP 4 is not sending a signal to EVER open the door. The UP 4 manual is only a schematic and it doesn't show how to adjust anything. That being said, this airplane was functioning perfectly when it was flown last (4 years ago). Could the UP 4 valve be jammed? I thought it was a static secondary valve with no moving parts. The UP 2 that is feeding the signal pressure is functioning perfectly. Any suggestions?

Thanks
Anurag