I am working on a scaled research airplane for my university, and it is equipped with Robart air brakes on the main gear. The problem is that it uses this valve:

https://robart.com/collections/air-s...trol-valve-red

which depending on the valve position either puts out air on one side or the other since it is designed for retracts. I need to plug one of the outlets and closing the needle all the way does not accomplish this. Is there a good way to do this? The air tubing being used is the pink 1/8" OD 1/16" ID stuff. I would rather not do a permanent mod to the valve nipple if at all possible and just close off the end of the air tube some how. It needs to hold 110 psi. Thanks.

A couple of options for this. First is to take a piece of short tubing, heat one end, flatten and fold it over. You can even wrap it with thin wire to ensure it holds the pressure.

Another is to insert something solid of that diameter such as rod or wire, then do the wire wrap technique.

Even on stock setups my friend uses this wire wrapping. Most of his jets are expensive and heavy so gear failure is more critical.

And that brings up the second part of your question.

Simply plugging one of the two outlets likely will not work. That valve is designed to allow for rate adjustment in either direction, mostly to more mimic a full scale setup in cycle speed, NOT block the port. The stock system needs to allow one side to vent while the other applies pressure.

NOTE: The two adjustments only control flow, not pressure, so all they do is adjust the amount of time it takes to add air into each side.

Unfortunately brakes really need pressure control, not rate. If you add this to your brake system the adjusters will only alter the time it takes to fill the system.

You may be able to feather the valve to try and control how much pressure reaches the brakes, but it would likely not work well as the valve was specifically designed to ensure reliable operation in either direction. It would also likely be extremely wasteful of air.

wooden toothpicks and super glue...insert into a short air line tube from nipple