Need Brake Bleeding Education

[alaskabearhawk]

FWIW, I have Parker valve installed and will leave it in. There have been so many times I have parked on a slope near fuel pumps wishing I had one. That alone is worth it to me. Read under “Full Description” https://ph.parker.com/us/en/park-brake-valves

[Sir Newton]

Piper park brake adds an extra master cylinder into the system that has mechanical locking system similar to your flaps handles.

[gregc]

I cursory review of the NTSB database seems to indicate that the mechanical approach with tabs or latches is no better than the hydraulic lock approach.

[noema]

I definitely want to install a parking brake. There are too many occasions where I fly that involved parking the plane at an incline. So just getting some choke in first requires some parking brake.

That being said, not only can you flip the plane on landing. These guys managed to wreck it on takeoff because the brake was halfway on. https://youtu.be/mMG2HwIFfgU

The more I think about this the more I like the Husky parking brake. You get your fingers full of grease and occasionally scratch them up on a sharp edge but seem otherwise fool-proof. It has two latches on the pax master cylinders that hold the cylinders in a compressed position. They are designed in a way to release as soon as you hit the brakes.

[robcaldwell]

Removing the Park Brake could be removing one risk, and replacing it with another.

I'll take that risk. This experience has scared the shit out of me! Pumping the brakes on final, unwittingly ensuring that you have just locked the parking brake valve? No thanks.

My lesson and take away from this experience is this, I will NEVER install anything that goes in the middle and interrupts the brake fluid system. However, if I can incorporate an external pressure force that manipulates the brake system, possibly I will consider that. I understand the old Cessna 140's had something similar to that.

[Nev]

Mark, do you know what the issue was with the parking brake ? Was it inadvertently let ON ? Or a mechanical issue with it ?

[Mark Goldberg]

I do know of one ground loop in a BH that was attributed to a parking brake issue. Mark

[Nev]

It’s commonly taught to check for brake pressure before landing, so if the brake valve was in the ON position, checking for pressure would lock the brakes on. But I agree, there are a lot of holes to line up in the Swiss cheese.

[gregc]

It's always good to think ahead but this seems like a pretty low risk given how the Matco and Grove devices work. To land with the brakes locked up, I think you would have to take-off with a working system, apply the brakes firmly while in the air and, at the same time, have the cable fail in a manner that changed the position of the actuating lever.

It is possible I guess that if the parking brake cable failed and the lever somehow moved to the on position but you had not applied any pedal pressure, the first time you did so, the brakes might not release (I never tried this) but that isn't likely going to lead to nosing over.

Anyway, if all this transpired, in order to fix it you would have to notice that the brake lever was in the wrong position and correct it manually and that seems pretty unlikely.

[Nev]

Tailwheels flip all the time because of faulty or wrongly set parking breaks.

You certainly got me thinking. I googled and found a couple of accidents due to landing with the Park Brake set. One after the pilot had locked the wheels to skim across a lake....... Another when the valve arm wedged against a brake line.

Definitely the manoeuvre has a greater downside on a taildragger, but the accident reports I found seemed to be isolated occurrences. Perhaps some are going unreported.

Removing the Park Brake could be removing one risk, and replacing it with another.

On my installation, the Park Brake valve is under the floor. So if something went mechanically wrong in the air, (and I was able to detect it) I wouldn’t necessarily be able to do anything about it. I’m thinking a cable going over center, or the cable sheath moving through an Adel clamp etc. Those that have valves mounted on the firewall could easily reach and sort out this condition.

Has anyone ever needed to physically access their Park Brake valve in anger valve while airborne ?

One idea is to install a pressure transducer in the hydraulic lines, downstream of the valve. This would indicate anytime the brakes are actually on, and would be an indication in the air if the Park Brake is somehow set. Is this overkill ? How would I go about installing such a transducer? Any other ideas?

[Utah-Jay]

Go fly that thing!

[Bcone1381]

Good to know it common to go without. I removed my PB valve in order to simplify and because I did not like my install....I was wondering if I was an outlier not having one.

[zkelley2]

PROBLEM SOLVED.

I eliminated the Matco Parking Brake and I can now watch the calipers compress and decompress as I work the toe brakes.

Good Lord!!!

I cannot say that I endorse the Matco PB. Pretty scary to think about pressure in the brake lines on short final. I'll be buying a nice set of wheel chocks...

Tailwheels flip all the time because of faulty or wrongly set parking breaks. I'm not a fan personally.

[Nev]

Glad you resolved this Rob. I’ll be keeping the parking brake on mine, but I do think the valve arm needs to be adjusted to be in the correct position, with the cable then locked in position so it can’t move.

We’re all standing by a first flight video All the best with it !

[quadra]

I don't know how I missed that last image Rob, but glad you found the problem!