aaflyer

My Feedback: (121)

Ok, I have a simple air up/air down system. BV Retract Valve. Air up to 100 psi Gear Down very slow leak. Gear Up leak is much faster. I have checked all T's and connections I can get to. Should I suspect the air cylinders? I swapped out retract valves same story.

Ron S

My Feedback: (2)

You could easily just plug air directly into one side of each cylinder, and watch for a leak. Thats what I usually do before I install them. There should be zero leakage. Keep the items in the hookup down to a minimum. I have a small Robart hand pump that works great for this - its a small volume of air, and it will let you know very quickly if there is a leak or not.

fw190pilot

I would suspect one of the retract units myself. Easy way to check the retract unit is pull it out of the plane air it up and dunk it in a pan of water. Have you tried putting some oil in the system sometimes that will fix minor leaks.

pilott28

My Feedback: (27)

One quick way to find it is to put a forceps or clamp on each line in turn until the leak goes away. That is the easiest way to isolate the problem without starting to take things apart. I usually start with the lines up by the valve and localize it to gear up, gear down, nose gear, mains, and then when it is debugged to this point, I check each cylinder individually. If you have doors, work those lines up by the valves too and then back to the cylinders.

You might find a quiet place and air the system up to around 120 psi and maybe you will get lucky and hear the leak too. This occasionally works if the leak is fast. Wiggle the struts ... some times the leak is only evident when they are moved a certain way.

It is a good suggestion to check all the cylinders before installation and the robart hand pump is one of the most used tools in my shop.

aaflyer

My Feedback: (121)

Found the problem(s) Up line had leak at one of the mains and down line had small leak at the nose cylinder. Thanks to all

AndyAndrews

Good info guys. I too will use it.

Andy

dbarrym

My Feedback: (47)

A couple of locking forceps, soapy water, a pressure gauge, and liquid Teflon are your friends...

I've gone through this pain a few times, I always test my air system - up and down - before closing everything up. If I lose more than 10 psi in 8 hours or so, I start chasing leaks. No plastic T's, wire wrap (not tie wraps) on airline/nipple joints, add thin lube to all air cylinders and excercise them a bit, and use liquid Teflon to seal all the screw-in air fittings before mounting the retracts and air cylinders...no leaks (knock wood) in the last 4-5 years since doing this.

Barry

petera38

Hi Barry,

Could you please inform me about: "liquid teflon"?
I´m going to install missing nipples on the retracts of my SM L-39 Albatros, and was looking for some stuff to smear on before screwing them in, to secure tightness.

Pete

CraigG

My Feedback: (40)

Anybody know how to get air lines off brass nipples (connections to cylinders/tee's/restrictors) without sliting them and creating a scratch on the nipple? The newer type air lines like BV sells are very robust and I have a heck of a time getting them off without cutting them. The resulting scratch will frequently leak air when I reconnect the line. The problem is compounded when the connection is difficult to reach inside the plane.

I mention this because sometimes when I am trouble shooting leaks, I create additional problems by disconnecting and reconnecting air lines.

Craig

pilott28

My Feedback: (27)

Use a soldering iron to melt the tubing. Just melt about 1/3 of the tube that sits on the nipple, and it should pop right off with no damage. You don't have to melt it down to bare brass, as you don't want to heat up the nipple.

I have a small butane fired iron from Weller that heats up in less than a minute and I use it a ton. it also converts into a small pencil torch. One of those great little tools I use all the time.

RCISFUN

My Feedback: (44)

A Monokote heat gun works well also

CraigG

My Feedback: (40)

Thanks Keith and RCISFUN. Great solution I had not heard of before.

Craig

dbarrym

My Feedback: (47)

It's also called liquid pipe sealant, I use Loctite "PST", which is available at good hardware and DIY stores. Look in the plumbing section. It's a thick, viscous, white teflon sealant used for threaded applications where teflon tape is too difficult or awkward to use.

Apply sparingly with a toothpick and make sure you apply all around the threaded area of the nipple, re-install and lightly tighten (it's easy to strip out the threads on thin aluminum cylinders). I've had Skymaster, Robart, Jet Legend, and some unknown aiy cylinders leak until doing this.

As Keith S mentioned earlier, if the nipples don't want to come out, I apply heat with a soldering iron, it will loosen the epoxy or other (usually none) sealant used during manufacture. Ditto with removing old/hardened air line from nipples - just heat them up or melt off.

I have a set of very small ignition and jeweler's wrenches to remove and tighten fittings, but on really small ones, I uses some small, flat/wide nose pliers, being careful not to grab or mar the nipple part of the fitting.

Barry

JetCatJimmy

May I ask why you prefer not to use plastic T's?

dbarrym

My Feedback: (47)

Sure...they usually leak along the mold parting lines...as the air lines age/harden up, the very slight ridge at the seam causes them to start leaking.

Barry