Aluminum brake lines

dongor2 · #1 06-15-2013, 09:08 PM

Ok guys what I want to know is do the assembly drawings show how to connect the brake lines to the caliper? I developed a leak under the left main on an RV6 and traced it it where the 1/4" aluminum tubing connects to the 90deg AN fitting and discovered no flare on the tubing. Is it supposed to have a ferrule fitting or an AN?

Rick_A · #2 06-16-2013, 08:32 AM

AN fittings require a B-nut, a ferrule and a flared tube end.

I would think that if you were missing either the ferrule or the flare the fluid would be pouring out at a rapid rate.

hydroguy2 · #3 06-16-2013, 08:59 AM

Or is the flare and ferrule there but snapped off the end and stuck in the nut

dongor2 · #4 06-16-2013, 09:35 AM

The fluid was running out while sitting in the hanger. I have owned the plane since April and never had a leak before. The builder is a well known craftsman in Or and has a great reputation. I suspect someone else was not careful when assembling the brake line and overlooked the flare. I was looking in the Vans book section 5P and it clearly calls out for a 37 deg flare on the end of the al tubing so I gues I'll check a few more fittings and make sure they didn't forget to flare elsewhere.

Gary 40274 · #5 06-16-2013, 09:57 AM

Quote:

Originally Posted by dongor2

The fluid was running out while sitting in the hanger. I have owned the plane since April and never had a leak before. The builder is a well known craftsman in Or and has a great reputation. I suspect someone else was not careful when assembling the brake line and overlooked the flare. I was looking in the Vans book section 5P and it clearly calls out for a 37 deg flare on the end of the al tubing so I gues I'll check a few more fittings and make sure they didn't forget to flare elsewhere.

I think you are missing something here. A flared fitting will not hold a nonflared tube in it, it will just fall out. Some folks used a nut and Ferrell fitting and if the nut is not tightened sufficiently the tube can work out, or as suggested the tube has completely broken off and the Ferrell is still in the nut. You may want to get a homebuilder to look at it with you to determine what is amiss.

Gary Specketer
Tech counselor, flight advisor

aerhed · #6 06-16-2013, 10:07 AM

Nobody forgets a flare. I have seen a really high number of bad flares on RV's though. Quite a few are so lame it appears the builder just waved the flaring tool over the tubing. Take the blue nut off, push out the little blue ferrule and see if the flare end is snapped off inside there. If it's not broken off cleanly, you better inspect some more flares. Starting with the other brake. Have fun.

Mike S · #7 06-16-2013, 10:21 AM

Quote:

Originally Posted by dongor2

The fluid was running out while sitting in the hanger. I have owned the plane since April and never had a leak before.

This sure sounds like the flair has broken loose at the end of the tube. May not be completely broken all the way around, but cracked part way.

Quote:

Originally Posted by dongor2

Is it supposed to have a ferrule fitting or an AN?

Dont get confused by the term ferrule, by the above I suspect you are thinking of the household compression bead type of unit.

The AN ferrule we use is not the same thing.

The term ferrule also applies to the metal ring holding the eraser on a pencil----and many other items.

Remove the B nut, and inspect the end of the alum tube.

dongor2 · #8 06-16-2013, 01:19 PM

Mike thanks for the pictures, now I understand the term ferrule as it applies here. I have a buddy that is the AI for the local 141 that took the line apart and found the lack of a flare but now I will go back and look for the original flare that may be in the end of the female AN. The ferrule is on the tubing because you can see it sticking out of the shoulder next to the tubing. The tubing itself had a clean cut that looked like a normal prep for a flare but may have broken off clean. The AI costs nothing and is instructing me how to do all the cool stuff like pulling the mags checking the L R rotation and timing, spark gap (football shape and when to replace), brake linings ect..Thanks to all who responded here, we have the best suppot system anywhere.

Mike S · #9 06-16-2013, 01:56 PM

Quote:

Originally Posted by dongor2

Mike thanks for the pictures, now I understand the term ferrule as it applies here.

You are welcome, glad I could help.

dlomheim · #10 06-16-2013, 04:02 PM

Over the years I have heard about this type of failure with regularity. Some of my local RV buddies have encouraged me to terminate my brakeline near the bottom of the gear leg, and then buy a pre-built up brake line to go from there to the brake caliper. From what I've seen of this installation over the years, it seems to be quite a bit less prone to a catestrophic failure, than spiraling the brake line around the gear leg bottom before hooking it up to the caliper.

An RV-6A buddie had his flared fitting fail and it created a massive fireball that went over the leading edge of the wing, and got his immediate attention! It had failed upon application, the brake pedal immedately went to the bottom, and fluid sprayed all over the hot brake assembly and ignited. His "fix" for the future was to switch to a different hydraulic fluid (higher flash point), and he also went with built up brake lines on the ends.

Doug Lomheim
RV-3 Restoration
RV-9A / 13B on hold