I bought Dantley, ex Raffy Chippy Ho. I did re-maiden the plane today and I'm pretty happy, except for a weird problem with the retract valve, which is an Ultra Precision UP-3 valve. Here are the symptoms along with all the relevant information.
- the plane has Tam's gear in it and 9 gear door cylinders.
- when the retract system is empty (no pressure) and after filling it to 100psi, the front gear won't go all the way up. It starts moving until about half way. At that point, I can feel a lot of air coming out the UP-3 valve itself. It sometimes bleeds all the air. After a few attempts, the gear goes up normally. Once it works, it keeps working until the air runs out completely.
- Sometimes, closing one door manually or forcing the gear up helps the system get out of this mode. Not sure.
- Each outlet (gear up, gear down, door up, door down) are T'ed together into one line. I wonder if maybe using one outlet for say the front gear and the other for the rear gear would help.
It appears there is some kind of abnormal pressure balance in the valve causing the air to escape instead of being applied to the retract cylinder. This appears to be caused by an empty (no pressure system) on the door cylinder side. I tried to change the needle setting for the main gear but that did not help.
Can an UP-3 valve drive 9 gear doors? Can you guys think of a fix?
Thanks for any suggestion.
Arnaud
Had the same issue with a 1/5th Skymaster F-86. You definitely have a bleed thru on one or more cylinders. Start by pinching off lines at the gear one at a time to isolate the culprit. Pinch off each airline for the gear up at each cylinder one at a time. You have to fix the bleed thru or the UP valve will not work correctlly
Joe Lewis
Kingtech
K-80, K-140, K-180
Owner