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Square Feet 12-27-2019 08:01 AM

On Fire
The last time I was in the RV-6, it was on fire. *That was 12/26/2019 about seven hours and three beers ago.

I headed out west to the Lake Michigan coastal airport of Frankfort to fly the RV a couple weeks ago. *There was a small, dried puddle of something around the right wheel pant and the right brake pedal was mush. *The right line from the master was visibly white, and empty to the reservoir. *I removed the right pant and inspected the caliper and brakes in place. *Line and fitting were dry - the caliper had fresh 5606 drops dangling, the pads were wet and there was 5606 mud in the bottom of the wheel pant. *But no real culprit at this point. *I clipped the safety wire and plucked the caliper thinking the piston o-ring must be misbehaving.

Incidentally, the return from annual inspection was the last flight, and more than a month ago, where we had installed new tires, tubes, etc., and packed wheel bearings. *At the time, the left brake pads looked new, with the right showing slight wear, but definitely serviceable.

Back to the shop a week ago, an inspection of the cleaned brake assembly showed absolutely no signs of wear on the piston, nor the bore of the caliper. *The original o-ring had no visible defects, or stiffness, but it was likely 20 years old. *While I was at it with a new o-ring, just for good measure, I installed new brake pads at the shop then took the clean, fresh package out to install in today's 50+ degree balmy weather. *With the hangar door open, the bright sun lighted my workspace and warmed the recently-frigid wrenches and pliers to the bone. *The classical music station (keeping the mice out, because mice have no class) still played Holiday music; even the day after. *Bing, and Nat. *I was loving life.

We know that our phones will answer any question on the spot. *This would be a good time to take a micrometer to the brake disc, and compare to minimum thickness from Cleveland's specs. *The mic in the box was metric, but translated to .175-ish on a couple spot checks with min. spec for the 500x5 in the .160's. *Installed, the pad-to-disc clearances looked like a new installation.

I gas-ragged the 5606 mud (dirt and hydraulic fluid) from the belly of the right pant, pumped new brake fluid into the right bleeder, tested the right pedal until rock-firm while letting the volatile blue 100LL flash off before final installation of the pant. *Many brake cycles, no leaks, so on went the pant.

Now, back to the phone for a reminder of the Cleveland brake lining conditioning sequence... Oh yes, taxi 1500 feet with engine at 1700 rpm and brake(s) applied. *Stop. *Let cool 3 minutes, then test the brake-hold at a full power run-up. *If it holds, go fly. *If not, repeat process.

So that I did. *Sort of. *The frisky wind on the 15-33 runway was 200-240 at 12G22, so I thought maybe I'd just break-in the brake today instead of fly. *AWOS was showing an enticing downward trend of wind however, and I was being tempted to fly as I taxied in the stiff-ish left crosswind. *Dragging the right brake for the prescribed 1500 feet I couldn't hold 1700 rpm. *That's nearly take-off power in an RV-6 with a 160hp Lycoming 320. *Sub-1400 rpm *was getting me there just fine. *And largely because I was only breaking one brake in, (the right) as the left pads were fine, remember? *Everything was splendid. *The right brake was holding my taxi straight in the stiff left crosswind. *And braking was firm and effective. *I probably *ran an extra 500 feet to the run-up area with the break in procedure to generate glazing heat because of the cold.

When I finally slowed, then stopped at the runway end I could, not surprisingly, smell a little heat from the right brake side. *Then maybe a glimpse of smoke? *Or was that my imagination? *Nah, couldn't be that hot. *Then, at this stopped position the right brake pedal suddenly went limp. *#*!$$@. *Now what's going on? *And I'm 3000 feet down the runway from the barn. *Well, the now-right crosswind was a blessing having no right brake, I was able to idle very slowly, cautiously and carefully back to the hangar-ish. *All left turns, and all very slowly, and deliberately, because once the tailwheel unlocks, any asymmetrical braking situation, as in this case, makes this plane spin about aimlessly like a dazed housefly. *I was actually wondering about my insurance coverage as I straddled this delicate situation.

I did seem to get an occasional whiff of heat on the way back, but certainly no additional heat could be generated by the now-dead right brake.

I taxied to within 50 feet of the hangar before I ran out of directional wind benefit, and it's maneuvering luck. *I stopped, and now saw another puff of smoke. *Or not? *Could it be? Fuel off! mixture lean! electrical off! *key off! I hopped out and rounded the beak only to see the right wheel pant of my favorite airplane burning like yesterday's Christmas hardwood in great-nephew Kenny's home-heating fireplace. *I mean really burning, and right under the wing tank. *Yes, very momentarily, but there was again denial on my part. *Then an immediate *sprint to the hangar looking for something wet - yet not frozen. *Nothing in the wash bucket... Windex won't be adequate... WD40? *McGuiars won't ever put a shine on this again... the 5 gallon can of 100LL avgas sure ain't gonna help this situation!

"You idiot. *You have a fire extinguisher in here somewhere." And there it was., by the door, where it's supposed to be. *Dated, but there. *I grabbed the extinguisher, pulling the pin as I sprinted to the burning airplane. *You know, an extinguisher about 4" in diameter and 18" tall isn't quite adequate to put out a wheel pant, and now, tire-fire. *In retrospect, I wish I had choreographed this moment ahead of time to include time for a quick photo, or video, or selfie of this persistent, olympic torch. So a sprint back to the hangar for the bucket hoping the frost-faucet at the terminal building is working. Then a sprint back to the rekindled campfire with five gallons of water. *Boom! went the new $350.00 tire and tube combo with the five-gallon surgical douse of cold water. *And it wasn't out yet. *So, another sprint to the terminal building and another wet five, which got things under control. *Then one more, walking this time in disbelief of what just happened, and what nearly happened.

Well, with a little neighborly help, Richard, the Airport Manager, and another neighbor were able to help get the right gear on a dolly and back into my hangar before dark. *I still have a plane, but also a boatload of redundant, needless work.

The way that fire-retardant 5606 hydraulic fluid and fiberglass combo burned has me re-thinking the aluminum vs. composite construction world. *My wheel pant was very difficult to extinguish, and turned into a literal dishrag that I simply ripped from the mounts before dollying.

What a day. *Now, I need to think about *the root cause of this event. The quick answer may be that there are times "to go the extra mile" but riding the brakes on break-in, or ever, ain't one of 'em. *Funny, it could even happen in a fiberglass sailplane with no fuel aboard. *Some have disc brakes, and of course, that flame-retardant 5606. Dang, I always felt safer with no gas aboard. Does that even make sense?

Parachutes, Baby!
Happy New Year.


jcarne 12-27-2019 09:16 AM

Wow, sorry to hear of your misfortune there. Glad you still have a plane in the end!

elev666 12-27-2019 09:30 AM

Royco 782
Mike two things come to mind after reading your story , ( I also have a RV6 100 miles east of you ) I?ve read of this happening before with the 5606 and the risk associated having a leaking Caliper or ruptured brake line onto the hot brake disc drove me to going with a set of manufactured brake lines & using Royco?s synthetic fire resistant 782 Hydraulic fluid On my build 4 years ago,
So far after 200 hours in three years I?ve had no issues with leaks at the calipers or anywhere in my system so I?m going to endorse its use here and It?s now available at Aircraft Spruce!!!

Papa 12-27-2019 10:31 AM

I had a similar experience a few years ago. In my case I suspect it was due to damage (probably a knick and subsequent leak) to the aluminum brake line; I regularly land on a gravel strip. I replaced the aluminum brake lines with braided steel lines and use the 782 hydraulic fluid now. I had exactly the same experience with the brake pedal going limp, and then smoke from my left wheel pant.


mfleming 12-27-2019 10:44 AM

This is not the first time I've read about a brake fire in a RV.

I believe this break in procedure. is dangerous (obviously)

Over the years I've always used the taxi fast and stop method for breaking in new pads. I think the drag the brake for 1500 feet is bad advice from the manufacturer.

Sorry for your misery but at least the plane is saved.

PS: By the way, where was your cockpit fire extinguisher?
PSS: This is a very good lesson that when one has a malfunction of this sort, STOP and inspect, Before going on.

gasman 12-27-2019 11:42 AM

"Now, back to the phone for a reminder of the Cleveland brake lining conditioning sequence... Oh yes, taxi 1500 feet with engine at 1700 rpm and brake(s) applied. *Stop. *Let cool 3 minutes, then test the brake-hold at a full power run-up. *If it holds, go fly. *If not, repeat process."

This procedure works fine for a Piper Warrior because they were designed with brakes powerful enough to dissipate the heat. It takes 1500 rpm to taxi a Piper with the brakes dragging. It takes less than 1000 rpm to drag the brakes on an RV. The thin discs used on 2 seat RV's are too thin to drag for that long.

You will find when you dig into the VAF search box that many have done this same thing. You can install thicker discs as I did. My disc bell has not changed color and there is no rust on it...... so it looks like it is running a LOT cooler.

With new pads, just go fly it if you have solid pedals. Or break them in by doing three hard stops from 25 mph with power to idle.

RV8JD 12-27-2019 12:03 PM


Originally Posted by Square Feet (Post 1395514)
I hopped out and rounded the beak only to see the right wheel pant of my favorite airplane burning like yesterday's Christmas hardwood in great-nephew Kenny's home-heating fireplace.

Glad you are OK.

It's a good idea to do the break-in with the wheel pants off to help with cooling, and don't over do it. The tight wheel pants on the RVs allows heat to build up quickly. There have been some brake fires in RVs when pilots have dragged the brakes during a long taxi. Some folks don't bother with the recommended break-in procedure at all.

snopercod 12-27-2019 12:09 PM

What kind of brake lines, please?

rapid_ascent 12-27-2019 01:26 PM

Wow that is a great learning experience for me and those others who still have new yet to be used brakes. I?m glad the outcome isn?t any worse than it is. It does make me think that an on board fire extinguisher is a requirement though.

I had a similar but slightly different experience. I have a small Kubota tractor. It had been sitting for a while and I decided I better go trim a little area where some weeds had grown. I climbed aboard half expecting the battery to be dead but it cranked right up. Unknown to me a squirrel or field mouse had decided the engine area was a nice place to build a nest. It took about 15 or 20 minutes and I began to smell smoke. I had to run a get a fire extinguisher so I know that feeling of panic. I was lucky to get the fire put out. It did take some of the wiring with it. Like they say experience is from making mistakes. I?m very experienced BTW.

I was planning on using Royco?s 782. This seems like a cheap way to buy a little safety factory.

Thanks for sharing.

Finley Atherton 12-27-2019 01:41 PM


Originally Posted by gasman (Post 1395583)
You can install thicker discs as I did. My disc bell has not changed color and there is no rust on it...... so it looks like it is running a LOT cooler.

I just installed new pads and the new thicker discs two days ago. Bedded them in with a couple of hard, higher speed runs. Initial impressions are little or no brake fade after hard braking.

I used the Rapco thick discs RA164-09900 which are less than half the price of the equivalent Cleveland discs and longer calliper bolts, AN4H-16A all available from Aircraft Spruce. I made 1/8 shims for each calliper to accommodate the thicker discs.


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