Tip: Easy way to bleed aircraft brakes

[IowaRV9Dreamer]

Yesterday I had to bleed the brakes on my Skipper... they are standard 6" Cleveland brakes that are (I think) very similar to RV brakes. The setup is plumbed identically, with a single reservoir feeding the copilot master cylinders and then the pilot master cylinders.

My A&P gave me this tip: go to your local aviation / farm supply store and buy three things:

• An old fashioned pump oiler - big with a heavy base that won't tip over
• Some clear tubing that tightly fits both the end of the bleeder screw and the pump oiler
• The biggest horse syringe they have (no needle)

Total cost was under $25.

Cut a length of tubing and safety wire it on the end of the oiler. Make this tight... it will be under some pressure.

Put some more tubing on the end of the syringe.

Fill the oiler with fluid.... pump the air out of the clear tubing.

Hook it to the bleeder screw - open the screw and start pumping.


As you are pumping, have somone tap/vibrate the master cylinders.. first the one closest to the wheel and then the opposite side. For example, if you are working on the left wheel, have your helper tap the pilot left brake and then the copilot left brake. The tapping helps unstuck any air bubbles in the master cylinders.

Pump about 30 or 40 strokes while your assisant taps each cylinder. You will be forcing new fluid up from the bottom and the old fluid and air bubbles will be pumped into the reservoir. Use the horse syringe to remove excess fluid from the reservoir before it overflows. When you are tired of pumping, tighten the bleeder screw, remove the clear tubing, and install the bleeder cover. Done! Move on to the other wheel.

This procedure worked for me - rock solid brakes on the first try with no spilled fluid. It was very easy.

Hope this helps someone.

[petehowell]

Hi Dave,

We gotta get together for a -9A ride before the snow flies. Maybe a picnic at Rushford? We could bring the daughters.

[Geico266]

It works everytime! I use an airpressure setup to force brake fluid up. Takes all of 10 mins to bleed one side.

[TSwezey]

I was taught that trick a couple of weeks ago!

[Kahuna]

Is there some other way to bleed the brakes? Ive always seen it done this way and have never seen it done any other.

[osxuser]

Originally Posted by Kahuna

Is there some other way to bleed the brakes? Ive always seen it done this way and have never seen it done any other.

Yep, like a car, you can fill up the reservoir and then with two people, pump pump pump, hold the pedal down, and open the bleeder, close the bleeder, pump pump pump, hold, open, close.... you get the picture.

Bleeding up is the quick/easy way to go, and works on about 80% of airplanes. I've got both an oiler and a pressure pot <--- (Which is even more awesome).

Also when using this method to re-bleed brakes, it's usually easiest to completely drain out the line on the side you are bleeding, otherwise you could easily overfill the reservoir and make a mess on the firewall

[Geico266]

Originally Posted by Kahuna

Is there some other way to bleed the brakes? Ive always seen it done this way and have never seen it done any other.

I can't tell you the number of hours I spent trying to bleed brakes like a car.

[cguarino]

Bleeding the brakes like a car will never result in a perfect bleed because unlike a car the bleeder valve is on the bottom of the brake cylinder. Air rises to the top of the brake cylinder and you can't get it out by opening a valve on the bottom. Go look at your car. The bleeder valve will be on top unless it requires a pressure bleed like your airplane. I learned that from race cars.

[allbee]

That way worked great for me as well. I used a smaller oil can and didn't safety wire the ends of the hose. I used the same hose I used on the static lines. I had one little bubble come out of the oil can, I just opened the line at the wheel and let it out. Make sure you pump oil through the line before hooking to the brake. I had a person watch my lines in the plane, vans original, until the air was all gone. Took all of 5 minutes and had great brakes when done.

[kentb]

But never have anyone around to watch for reservoir overflow.
I pump for a while and then look at the reservoir .
Pump for a while more and then it always overflows.

I always end up cleaning the firewall.

By the way I use a spare West system resin pump to remove excess fluid from the reservoir, before I start.

Kent