I'm trying to figure out what is going on with a JT Dual Valve. It's on my landing gear and is giving me the biggest headache! I've been searching the forums here and all over the web trying to see if anyone has had a similar issue and no luck. So here we go:

Setup: DX-18QQ with Powerbox Mercury SRS and Jet Tronics Dual Valve hooked through the internal sequencer to Door 1. 100% travel both ways on TX. Done multiple resets of the valve and gone through the sequencer setup in the Powerbox multiple times.

Problem: Power up the airplane trough the Powerbox after filling the air tanks. Go to cycle the gear up, and they make it half way up and hang there as air is being released from the air exhaust on the JT Valve and if I don't do anything, it just bleeds the air tank empty and the gear will just fall back down. Gear will only go up with me gently assisting by pushing the nose and mains up a little and then they retract. Then, I cycle them down and they go down great. Next, I'll cycle the gear up once more and they retract like nothing's wrong. It's just the first try to cycle them up after airplane power up that there is a problem. If I keep flipping the switch to put it down and back up without helping it go up, the gear with just continue to hang halfway like described above.

Also, is it normal the valve bleeds some pressure out when you power down the airplane?

I hope I'm just missing something easy that someone encountered before and can take care of it without having to remove the valve completely and send it in.

Check to see that you don't have a leaky retract cylinder. Sometimes when it appears that the valve isn't functioning correctly it's not the valve but the retract itself. I would pinch each of the retract lines in turn (with hemostats or similar) to isolate each unit one by one and see if there is any improvement.

Just went out to the shop and tried your suggestion. I pinched each line both up and down for each gear with a pair of hemostats, while trying to cycle and no change. I'm not going to have any hair left to pull out shortly!

Is there anything else you can think of or suggest I try?

What happens if you operate the valve in manual mode using the buttons on the valve?

Presumably the lights on the valve are showing correct operation whilst the air is leaking?

Edit: what is the model and what retracts are you using?

I'll go try manual again. I think it did the same thing, but let me make sure before answering.

The model is a 2.5m FB Viper with stock retracts. I put BVM thin lube in and bench cycled them before putting new/good air line on and re-installing into the model. The retracts seemed to work fine and held pressure (pumped to ~70psi) then, but maybe something changed in the cylinders when more volume and pressure hit them now?? I dunno.

I operated in manual again and the same result. A new thing I did find out was that if I only helped the Left Main go up, the rest went up. Before, I was lifting the nose gear and then going to the mains to help them and they would go up and lock. Now, if I just grab the Left Main and help it up, the rest go too.

Perhaps a leak in the left main?? Does that sound like a likely scenario with what I'm seeing?

Ok, I had the same happen to me but only on one of my valves. In the Powerbox setting, I had to increase the setting on both sides of the valve. 50 was not enough power to operate the valve correctly. It wouldn't cycle it properly. I hope you understand what I am talking about.

Paul

Hi
Similar thing happened to me once. Changed the valve, no deal. An the end it was a tiny scratch inside the cylinder that made it leak to the other side when it was retracting. When you helped it go up with the hand, it passed the scratch and it sealed again and worked. Changed the cylinder and no more problem.

Regards
Eduardo

Thanks guys! I'll try increasing the Powerbox value first, and then I'll pull the Left Main gear if I don't get any different results from doing that.

If it is the gear, the isolation check should have found that. ??

I think you guys are right about the cylinder. I went out and double clamped both up and down lines on the Left Main and the other gear went up just fine. I guess when I did one line and then the other before, I didn't get them totally clamped off. Looks like that Left gear is coming out today. FB included replacement O-rings in the hardware bag, so it looks like I'll try and replace the O-rings and hope for the best.

Thanks for all your help guys!

I have a different problem when I put that retracts up they stay for about 20 seconds and then the valve just powers off . I already tried 50% 100 and 125 I am also using a second generation spectrum radio buddy only happens in this valve not on my other airplanes why do I lose both in the getting lights green and red thank you any suggestions Nick.

It's either the switching point or failsafe that could cause that on the valve. Make sure there isn't a delay on the sequencer programming on your TX. That's all I can think of.

Just changed the O-ring on the Left Main piston, and everything works perfectly! Thanks again guys!

The Jettronics valves have a mode where they switch off the air after 15 seconds so that sounds like proper operation for that mode. I personally like this mode since my gear is already locked up or down air pressure is no longer needed and a slightly leaky gear cylinder won't continually leak air in flight. If you dont want this behavior simply perform the valve reset sequence which as I recall is press and hold both buttons for 5 second while powering up the unit. Double check the instruction sheet to be sure I've got the reset sequence correct.

My valve is connected directly to the receiver I only have gear up and get down no doors and which piston do you mean! on the valve itself and how can I get these o-ring . Thank you

What retracts are you using? Are they retracting and lowering correctly?

It sounds like the valve is working as it should.

I have the regular retracts just that after 15 to 22 seconds the valve goes completely off both lights on the valve and it releases the air by it self. This is a double action valve which I have six of them in different other airplanes and they all were OK I know how to program it in just this one doesn't want to keep the program thank you .

What do you mean it doesn't keep the program ? Are you saying that you've reset the vale to stay permanently on but it keeps falling back to the mode where it shuts the valve off after 15 seconds and releases the air ? I'm not understanding the problem from what you describe but it simply sounds like the air-failsafe function is enabled.

from the manual:
Air-Failsafe-Function About 90% of air leaks occur between valve and cylinders because this is where the highest error sources exist. (Junctions, connections between fuselage to wing and cylinders). In units that lock mechanically, there is no need to keep the system pressurized. This reduces the chance of lost pressure, so full pressure is available for delivering the gear IN or OUT again. If this option is chosen the valve shuts off the pressure after 15sec, which is enough time for most units to operate.

What I'm saying is that the lights go off the red and the green where is usually one light green stays on on my other valves throughout the whole flight it seems like it's going into timeout and then when I have to retract or extend the gears again it will not take the command from the assigned switch

The switching points were not set if the lights go out. Do a complete reset of the valve and make sure you program the switching points again. I skipped that step (pressing whichever coresponding button for longer than 0.5sec with light on AFTER actuation) when I initially set up the Dual Valves for my gear and gear doors, and the exact thing happened that you are experiencing.

The only valve I have which the lights go out is the the Jet Tronics Brake Valve.

Hope this fixes your issue.

What do you mean by switching points I did a complete reset and I followed the instructions from the manufacture but it still doesn't work properly . it will work for the first time but after that it will not go through the cycle again I can only . I only get one cycle after the programming .

could anyone tell me on the Jet tronics double valve how to adjust the air speed/flow?

My retracts are slamming both up and down pretty hard and I would like to slow them down just a bit.

Fly it first...air flow and G forces slow it/dampen it quite a bit. Stick your arm out the car window at 40mph and try and wave it up and down...
If it really is too fast, you restrict the breather nipple airflow.