I had an interesting excursion last Saturday that I attribute to the one piece brake line form the fuselage down to the Cleveland brake wheel cylinder on my 170A. I was landing at Arlington AWO as a flight of two. I was in trail to the left at my friends 6;30. I landed slow at about 60 and in a three point attitude. My friend in his 172 TD was slowing for the intersection turn off as was I. I started to correct for a little drift to the right while taxiing when I suddenly realized I had no left brake. I had full left rudder in and could not raise the RPM for fear of gaining on my friend’s airplane. I could not ground loop the airplane to the right to stop the progress for fear of turning into the other plane. I kept it as straight as I could until Steve cleared the runway. I cleared to his rear and on to the grass between the taxi way and runway. Then I hard braked to the right and ground looped the plane to stop the forward movement. All worked out OK. No broken airplanes. Ultimately I attribute the brake failure to the Hard one piece brake line pulling the wheel cylinder away from the disc and causing to much gap Between the Disc and pads. I was able to duplicate this in the hanger later by playing with the caliper, master cylinder and a jack manipulating the gear up and down..
What I have done to fix it is install a section of flexible brake line between the caliper and about 8 “ up the gear leg to allow the caliper to float more freely. I know a lot of Cleveland brake STC’s include this flexible line in the kit. The airplane has operated 100 hours of time for me without issue. But I do not want to experience that again.
A&P, IA, New owner C170A N1208D, Have rebuilt some 50 aircraft. So many airplanes, So little time!
I think you hit the nail on the head regarding the brake line. of course you need some flex as the caliper has to float, I'm amazed you didn't have a flexible line segment to begin with.
I don't need to tell you to watch out when flaring the old line for the new fitting further up, as it is probably pretty old and work-hardened and could easily crack. so I won't, I'll just mention it for someone else who hasn't run into it yet
'56 "C170 and change"
'52 Packard 200
'68 Arctic Cat P12 Panther
"He's a menace to everything in the air. Yes, birds too." - Airplane
I have not seen any Cleveland installation instructions that did not call for the flex line. I did have a friend in Bellingham that put together a 170 with all solid lines and after I clued him in he promptly corrected it. You experienced a good example of what can happen when someone ignores the proper documentation as to how to put each part of the airplane together
I can't believe that the cause of your problem was a hard line to the caliper. How long had the hard line been operating without the problem? Brake lining wear is relatively slow and I can't immagine sudden wear great enough to precipitate the described failure.
I believe that some Cessna models were delivered new with hard lines all the way to the calipers, especially those with wheel fairings. (pants)
There is normally only a very small gap between the linings and the rotor and the outer lining will not allow the caliper body to retract very far when the brake is released. This is the basis of the self adjusting feature of this brake system.
I would be very cautious with that brake until I was very sure that was the problem.
It well may be low brake fluid or air in the system. My guess, however, would be a failed, or failing, "Lock-o-seal " in the master cylinder.
When the brake is applied, there is a lot of pressure on the caliper piston, and unless that brake line was very solidly anchored, I think it would move.
My 170B has the solid lines all the way to the wheel brake (I believe they are original) The previous owner had the airplane for 30 years. I have had it for nearly ywo - neither of us have ever experienced any difficulty attributable to the solid lines.
I have the Instructions for the original STC for the Cleveland wheel & brakes with the aircraft records there is no flex line mentioned in the kit. But I have seen kits that come with them. The lines were only a year old I duplicated what was there when I got the airplane. I thought that it needed the fl I have the Instruction for the original STC for the Cleveland wheel & brakes with the aircraft records there is no flex line mentioned in the kit. But I have seen kits that come with them. The lines were only a year old I duplicated what was there when I got the airplane. I thought that it needed the flex section in it and had already purchased the fittings & Line. The brakes have been operating that way for a year and quite nicely I might add. The master cylinders have new lock-O-Seals in them installed when I rebuilt the airplane.
I was able to duplicate the issue simply by jacking up and down on the gear though not quite to the extent that landing or flying the plane seemed to. The loc-O-Seal is designed so that when brake pedal pressure is released the fluid is allowed to flow back to the master cylinder. The same loc-O-seal will allow the brake caliper to open wider than the dimension needed to allow the pads to stay in contact with the Disc. This can be demonstrated by simply using a large screw driver to spread the brake caliper open. (which is of no practical purpose) And the caliper will not close by itself with out steeping on the pedal. If the loc-0-seal is working properly the brake pedal will return once released and not retract the piston at the wheel. It was real obvious that the solid line basically makes a fixed point that can pull the caliper open and make it impossible to close the gap when the caliper has been pulled away from the disc without stepping on the brake.
Yesterday I was looking at my Partners 140A and he has one wheel with the flex line and one without. We are going to change that. The brake would probably have worked if I had had time or thought to pump it a couple of times. These things can happen pretty fast.
And yes many Cessna’s have a solid line all the way from the fuselage to the caliper the original 180’s & 185’s with McCauley Brakes do except for having double Puck brakes? . Which are essentially the same as what the Cleveland Wheel & disc arrangement is. Later Cessna 172 & 182 RG’s run the Brake line down the center of the tubular gear leg and then goes through several bends to come to the wheel cylinder. The brake line can get flexed and come in to contact with the inside of the disc and start wearing a notch in it. Then when least suspecting it the pilots looses a brake when hard braking on both at the same time and exits the Run way stage left or right with some times tragic results.
I feel Blessed to have survived this with no more than having to put the flex line in. You only need one brake failure to ruin you whole flying experience for a long time.
A&P, IA, New owner C170A N1208D, Have rebuilt some 50 aircraft. So many airplanes, So little time!
Something doesn't compute. Might double check wether the calipers match the disc thickness. I had that problem when I bought my current magic carpet, 1/4" disc and 3/8" calipers, had to pump the brakes to get any brake.
I have had problems with Cleavland's and solid brake lines, but in a different manner. My brakes would lock, but it only happed when I parked the plane (fortunately). I would have to pry the caliper apart with a screwdriver and then they would work fine. I described the problem to my IA and he asked first thing if I had solid brake lines. We put on flex lines about 12" above the brake and the problem was solved.
I have a theory as to why this happens, but it is just a guess. When the pins and holes start to wear the pins can get cockeyed with the holes and cause the caliper to bind. With the flex lines the parts can float and line up better. This may be why you can go for years with no problems. I still have solid brake lines on my 170, and after this discussion I will be shopping for flexible brake lines tomorrow.
John
N2865C
"The only stupid question is one that wasn't asked"
I re- read the STC today what it says regarding the flexible brake line is, " If necessary cut the original brake line and install flex line between the caliper and the old brake line," or something to that affect.
They are the correct caliper.
A&P, IA, New owner C170A N1208D, Have rebuilt some 50 aircraft. So many airplanes, So little time!
The 2007 Galveston Convention maintenance seminar will address flexible hydraulic and/or fuel lines. (It's part of this summer's subject.)
Last edited by GAHorn on Wed Feb 21, 2007 8:49 am, edited 1 time in total.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention. An originality nut (mostly) for the right reasons.
I'm getting ready to take my own advice and put flex lines on the lower part of the brake line.... I was thinking about 10 inches long, but what is working well for everyone else?
John
N2865C
"The only stupid question is one that wasn't asked"
I flew a Great Lakes Biplane for five + years with Cleveland single caliper brakes and solid aluminum brake lines. Howsomeever, the brake lines did have a generous loop near the caliper apparently to allow the caliper to move slightly for brake pad wear. The year of Manufacture was 1976 and I am confident the brake lines are original. I have installed solid brake lines on my 170B and have had no problems. Just one more observation.
chuck
N2865C wrote:I'm getting ready to take my own advice and put flex lines on the lower part of the brake line.... I was thinking about 10 inches long, but what is working well for everyone else?
Well I finally got my flexible brake lines. I dropped them off at the hanger and left with a friend to Harris Ranch for lunch (about an hours flight) planning to put them on when I returned. After lunch on preflight there was a puddle of brake fluid by the tire . The line had cracked just above the fitting. . 30' wide runway with a brisk crosswind. No way I was going to chance it. I spent the rest of the day begging airplane and car rides to get home.... Moral of the story, I'll let you draw your own conclusions.
I had a friend fly me down the next day and I fabricated a new brake line on the ramp. Flex lines now installed.
John
N2865C
"The only stupid question is one that wasn't asked"
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Ultimately I attribute the brake failure to the Hard one piece brake line pulling the wheel cylinder away from the disc and causing to much gap Between the Disc and pads. I was able to duplicate this in the hanger later by playing with the caliper, master cylinder and a jack manipulating the gear up and down..
