Brakes and the "A" Models

I previously noted that one of the advantages of the tail draggers was they could still taxi if they lost their brakes. We flew our RV-6A to St. Augustine and Panama City, Florida this past week and we had a few problems. One was I wore the brakes down on the right main gear to the extent that the piston (puck) came out of the housing enough to leak the fluid out of that side. When I got in the plane to leave Panama City yesterday I saw fluid on the ground but attributed it to fuel venting. I got in to start up and the right pedal flopped forward with no resistance. I pumped it and it seemed like I got some pressure so I started the engine. With over 4,500 hours of flight time I thought I could handle with pumping finese. I had to give it some power to overcome inertia and move the plane then I had to turn left coming out of the spot. Well, it turned to the left alright, all the way around like a pinwheel. My friend J that lives there thought I was demonstrating how maneuverable the plane is. DON'T DO WHAT I DID - THE PLANE IS TOTALLY UNCONTROLABLE ON THE GROUND WITHOUT BOTH BRAKES! I know, anybody that can think ought to know that but it is amazing what you can make yourself think you can do in spite of the physics involved. When that nose gear pivots into a turn there is no way to stop the turn except to shut down, get out and put it where you want it or worse (heaven forbid) hit something.

Bob Axsom

You think thats bad? I had ONE wheel on a Tiger lock up when I was trying to taxi it. That made me look like an idiot, fortunitly there were no airplanes parked nearby. I agree, there are some SERIOUS issues with the use of a free-castoring nosewheel if you brakes go wacko.

Steerable nosewheel for 'A' models?

osxuser said:

I agree, there are some SERIOUS issues with the use of a free-castoring nosewheel if you brakes go wacko.

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So has anybody designed a steerable nosewheel for the A's at all?

Bob Axsom said:

Well, it turned to the left alright, all the way around like a pinwheel.

Bob Axsom

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Neat. 2 years ago I had the same thing happen when I taxied out of the RV corrall at the Arlington airshow. Neat project to lay in the grass and repair a broken brake line at 5pm on Sunday while everyone is tearing down the airshow! You are right, with no brakes you only go quickly in one direction!

I have felt your pain....

....And I am sure there are MANY other former Grumman drivers here in the RV world who do as well! You get very protective of your braking systems when you own a Grumman - can you say "Primary ground control system?!"

Paul
(ex - AA1B-160 owner)

Bob Axsom said:

One was I wore the brakes down on the right main gear to the extent that the piston (puck) came out of the housing enough to leak the fluid out of that side.

Bob Axsom

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Not to sound unkind, but don't you do 100 hour checks on the brakes? At my current level of pad wear, I'm looking at over 400 hours before I have to replace mine. (6A)

Caliper assembled wrong?

Sorry if you're already aware of this:
A while back there was a notice(SB maybe?) about some of the Cleveland calipers having been assembled incorrectly by reversing the piston and having the "O" ring groove closer to the puck when in fact it needs to be inserted first into the bore. I met an RV-er at our local airport(he had borrowed the plane) and during his taxi in, he lost some brake fluid from one side. I informed him of this occurance with several other pilots, he found a local A&P to help him out and turned out that that's what happened to his. Replacing the "O" ring, reinstalling the piston ring groove inwards(towards the bleed valve) and reassembly got him on his way.

Hawkeye7A said:

Sorry if you're already aware of this:
A while back there was a notice(SB maybe?) about some of the Cleveland calipers having been assembled incorrectly by reversing the piston and having the "O" ring groove closer to the puck when in fact it needs to be inserted first into the bore. I met an RV-er at our local airport(he had borrowed the plane) and during his taxi in, he lost some brake fluid from one side. I informed him of this occurance with several other pilots, he found a local A&P to help him out and turned out that that's what happened to his. Replacing the "O" ring, reinstalling the piston ring groove inwards(towards the bleed valve) and reassembly got him on his way.

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A thousand word's worth...


you can easily visualized how it's possible to turn the piston around backwards.

That is why

That is why T/G's are better. No brake riding, longer brake life and positive gnd steering with the rudder (pedals). George

Mine was correct

Mine was correctly assembled I just stretched it too long before replacing the pads. I had them at home - I know, I know - but moving into a new home has been very time consuming. Anyway, the message is don't think you are Superpilot and can move one of these birds under power with questionable brakes - if they are bad it can't be done! One other caution - I probably have worn the right brake pads on takeoff. I conciously try to avoid it but I suspect when I'm standing on the right rudder peddle, I'm getting some brake as well. You can do better I'm sure.
Bob Axsom

It's kinda weird, without having the discs under dimension, it shouldn't wear enough to pop out. Maybe switching to a thicker disc might help

It will leak if you wear the pads thin enough

I had the problem once before on another airplane that was maintained by a friendly A&P (a good guy really). In order to get back we took some two hole pads that fit the outboard holes in the calipers and installed them. We had to grind the pad thickness down a lot to get the assembly completed and allow the wheel to rotate (not clamp it in place) and the inner arc of the outer pad had to be ground down to clear the cylindrical section of the disc. Once that was done and the system was filled and bled everything was OK for a temporary application. Basically the dimension across the caliper opening and the width of the disc dictate using the correct linings. I would not normally do what we did and I will replace them with the correct linings during the current inspection before any more operations.

Bob Axsom

All is good

osxuser said:

It's kinda weird, without having the discs under dimension, it shouldn't wear enough to pop out. Maybe switching to a thicker disc might help

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This is common and it happened on a Piper I had long a go. Brake to the floor and puddle of brake fluid on the ground. This plane had nose wheel steering so it was no big deal.

On my RV-4 when the pads got thin the puck would get cocked in the bore and the brakes would drag real heavy, almost lock. After the cooled the puck would retract. Try taking off with the bakes on.

My comment is if you check the pads and you go, "You know they don't look that bad I think I can go another......" replace them. Thin pads are a double whammy.

Why are they designed this way? I guess to make is small, light and compact brake calliper setup, they had to cut the puck/bore O-ring overlap to the min.

Just replace the pads more and all is good. George

With a few hours in both sissy wheel and t/w rv's, I can tell you that the t/w can be flown with a brake failure. I recently returned from a trip out west with a complete right brake failure(fluid loss from leaky fitting on the grove gear). Didnt bother me at all. Left brake and use of rudder and its easy to control in any direction.
Brakes are highly over rated.
Id of been toast with the sissy wheel rv.

I am burning up pads at twice the rate on the t/w Super 8 than the sissy wheel -6A though. I developed the technique of keeping the tail up using the brakes and I cooked em in 100 hours. The heavier weight of the super 8 and my wanting to see over the long nose with the tail up has cut my brake life in half. Oh Well.

Best

Kahuna, please don't hold back.

Tell us how you really feel about nosedraggers!

Pat

I can turn my sissy wheel 6A with rudder only and a bit of throttle. Not tight but I can make it back to the hangar if careful. Is this something only Subie powered 6As can do or am I just an exceptional pilot?

You are exceptional

There is little doubt that you are exceptional but if you apply a brake into a turn and it is the only one you have it will go into a turn that you can neither control or get out of. If you start with a straight nose wheel, never touch the brakes, and never get the nose gear far off of dead center it seems like your power and rudder only approach could get you back to a hangar after landing. I have filed that away in my mind because I'm sure the opportunity to use that technique will present itself somewhere down the road. However, there is no way one should consider such movement from standing start or worse begin a flight with a failed brake.

Thanks for the very good technique input.

Bob Axsom

rv6ejguy said:

I can turn my sissy wheel 6A with rudder only and a bit of throttle. Not tight but I can make it back to the hangar if careful. Is this something only Subie powered 6As can do or am I just an exceptional pilot?

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Sounds like your sissy wheel break out force is not up to spec. There is little chance that you could maintain control at taxi speed no brakes and the proper break out force.

Best

Kahuna said:

Sounds like your sissy wheel break out force is not up to spec. There is little chance that you could maintain control at taxi speed no brakes and the proper break out force.

Best

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I run breakout force at 22-25 lbs. If I don't it shimmies on landing bad. Agreed if you get the nosewheel fork turned too much, rudder and slipstream will take a LOT of room to get it straightened out. If you keep it pretty straight however, I can negotiate all the 90 degree turns on my taxiways without brakes. Done it quite a few times. Would I take off with a U/S brake? Nope.

My comment about being exceptional was definetely tongue in cheek. I have no doubt that Bob is better than me!

no-brake turns

just remember --

two wrongs don't make a right.

but three lefts do.

john

(pa28r -- one brake out, no problem)
(p210n -- one brake out, don't even think about it.)