Cleveland brakes

[jongibson]

We have a Cessna 170B with a 180 gear, and Cleveland brakes. The aircraft is kept hangered. Recently during the 5th landing of the day the left brake locked up. after the tire skidded down the runway the brake finally released. Anyone else had this problem? If so what is the fix? Thanks Jon Gibson

[n2582d]

Jon,
That’s a well know issue on the 170. Assuming your plane still has the parking brake locking plates (fig. 59-7 in the IPC) attached, it’s likely the one on your left brake engaged. See this thread.

Fig. 59, Click to Enlarge

[GAHorn]

Jon, I called and talked to you about this only yesterday, and you and I ended the conversation with the conclusion that I would send you a “link” to a discussion in which this subject was addressed. Gary, has done that in his post immediately preceding this one. I hope that will prove sufficient.
(here again, is that link: viewtopic.php?t=5714&hilit ) There are many many others where we have cussed and discussed the parking brake problem.

Folks, Jon is a very experienced pilot and has owned many airplanes, and recently has suffered a locked brake upon landing which resulted in severe damage and Jon informed me that somehow the NTSB has become interested in this and is investigating his incident. FYI

[n2582d]

So sorry to hear this issue has resulted in another bent aircraft. George it appears removing the parking brake tabs on the master cylinders is missing on the C-170 Special Attention Areas list. I’d also suggest replacing the serrated shaft style master cylinders be added to that list.

[GAHorn]

So sorry to hear this issue has resulted in another bent aircraft. George it appears removing the parking brake tabs on the master cylinders is missing on the C-170 Special Attention Areas list. I’d also suggest replacing the serrated shaft style master cylinders be added to that list.

Agreed! I thought I’d edited the Special Attention List to include that…. I’ll recheck it. One of the few really good recommendations found in the out-of-print SRAM addresses the serrated brake shafts on the Master Cyls. I’ll add it to the list. Thanks.

[Bruce Fenstermacher]

I'd thought I'd posted this just after Jon created the post. Must have not hit the submit button. Jon had PM'd me on this subject prior to and at my suggestion, creating the post. I'm not sure if Jon had talked to George first but think not. I was not aware of the damage to Jons plane.

I'm including it here because I included things I'd check after the parking brake connections and tabs being installed or removed.

Here is what I told Jon:

• Now first, sounds like you were very lucky not to ground the loop. You need to get to the bottom of this quick.
  
  The first thing I have to ask is, is your parking brake system still hooked up to the brake master cylinders? If not are the tabs on the top of the master cylinders still in place?
  
  If the answer is yes to either question, I wonder if the parking brake got set for the left brake. This can happen without your knowledge with the brake cable still hooked up to the tabs or just having the tabs in place if anything causes the tab to be pulled or pushed up. Could happen with normal rudder deflection but most often probably happens with more extreme movement. And if your rudder cables are misadjusted placing your rudder pedals closer to the firewall, this can happen even easier.
  
  We have always recommended the parking brake system be disabled and removed to include the tabs. Or at least the tabs be wired down so they can not be lifted which causes them to jam the shaft of the master cylinder. If the parking brake cable has been disconnected from the tap on the top of each master cylinder and each tab removed, this can not happen.
  
  Assuming no parking brake, next I'd have to remove your inside (closest to the tire) brake puck(s) and confirm the wheel cylinder and the inside brake can freely slide in and out thus releasing any brake pressure if it is applied. If your wheel cylinder can not slide on freely on the pins as intended, any brake pressure applied can not release and the brake will lock.
  
  If the wheel cylinder slides freely, I'd then go to the master cylinder. I'd remove it and carefully disassemble it looking closely at the action of the Lock-o-seal. The Lock-o-seal is the magic seal that under normal circumstance, allows pressure to be built when you apply the brake, but releases that pressure and allows brake fluid to flow back into the master cylinder which then allows the wheel cylinder to slick loose and release the brake disc.

I want to put emphasis on two points. When I discuss removal of the parking brake system, that also includes the tabs on the top of the master cylinders the brake cable attach too. It is not only the cable but the tabs that can tangle with the firewall environment and get jammed on depending on their orientation to the firewall. I have had owners ask me to inspect their parking brake removal only to find they didn't remove the tabs. Removing the tabs requires partial disassembly of the master cylinder to slide the tab of the master cylinder shaft.

The second point I became aware later in 170 ownership. Your rudder cable length/adjustment dictates how close your pedals and master cylinder come to the firewall at extreme limits. The rudder cables must be the correct length and adjusted properly so the pedal is set far enough from the firewall in neutral position. But much harder to realize is if pedal travel is allowed to move to far in the forward direction, the geometry of the pedal and it's linkage to the master cylinder, starts tio push in on the master cylinder shaft, which can start to apply break pressure at the wheel cylinder and braking action at the wheel. Rudder cable length including having the correct turnbuckle parts and attachment tabs in the back is important. My own 170 was flown for many many years with wrong turnbuckle parts and owner produced parts made to compensate but didn't actually compensate enough.