Need Brake Bleeding Education

[svyolo]

I have just about talked myself out of a parking brake. In addition to not adding weight or failing, without it there, I can't screw it up.

[JimParker256]

Good point on releasing the parking brakes after chocks are in place or the airplane is tied down. That's my practice as well, since increasing temps can cause the fluid to expand, making it harder to unlock the brakes later.

[Nev]

......but it needs a name, "Plop a Chock", "Stop and Chock" etc. Somewhere a farmer with a J-3 has figured this out.

Too funny! How about: “Park n Brake”

[BravoGolf]

Somewhere a farmer with a J-3 has figured this out.
Gerry
Patrol #30

Absolutely. My wife asked me what I was laughing about.

[geraldmorrissey]

I wonder if you could design a chock placement device that could be portable, extendable and would allow you to place and retrieve a aluminum angle chock from the cockpit. In a Patrol your sitting pretty close to the main gear. Seems doable. Sort of like the pistol grip can grabber devices Harbor Freight sells. Cracks me up just to think about it, but it needs a name, "Plop a Chock", "Stop and Chock" etc. Somewhere a farmer with a J-3 has figured this out.
Gerry
Patrol #30

[Pbruce]

Hmm. I find that where I often fly, ramps are seldom level. Winds are very strong from the wrong direction. There’s another plane nearby. My RV9 (without park brake) was always rolling away on me. I’ll never voluntarily do without a park brake again. I’ll still have to exercise good airmanship and not depend too much on it though. Also, I’ll release the park brake after chocks-in. It’s not a substitute for tie downs and chocks; it’s safety on top. Granted, a high-wing strut braced bush plane is much easier to jump out of and chock than my tiny low-wing cantilever job. I think it’s worth it in terms of cost and effort.

[zkelley2]

It's the same with little airplanes, only tied down instead of chocks if it's outside.

Obviously whatever choice a person makes is the correct one since it's their airplane. I'm just scratching my head on how people need them to keep the plane from rolling while they get out. Ramps are almost always quite level and off airport is even less an issue due to the divots and such unless you're on a crazy hill.

[svyolo]

This thread did make me move my parking brake to the floor. I originally had it on the firewall, but when I decided to use the caliper mounted brake reservous that probably wasn't going to work.
Zkelley2 has me wondering why I need one, probably just convenience.

On big airplanes, the plane is not parked until the chocks are in place. The parking brake is for pilot convenience.

[BravoGolf]

On one twin that I flew there was a brake hydraulic pressure gauge. One step of the before landing check was step of the brakes and verify a pressure increase AND decrease. A fluid pressure transducer / gauge could be added to the brake hydraulic system of our aircraft.

[gregc]

I think this is an interesting topic not so much for the specifics but rather as a approach to making a build decision.

1) Does something add weight and/or complexity? Complexity has to include operational issues as well. Chocks are clearly mechanically simpler but using them on a slope in the wind may not be simple.

2) Do I understand how the particular solution/system works? In this case there are engineering diagrams that support JimParkers explanation of how hydraulic parking brake locks function. Rob’s problem can be explained if the parking brake lever was in the transition zone and fluid flow was restricted enough to cause a slow pad release. The heat generated during taxi soon overcame the entire system.

3) Is there data available on failure and/or risk? How common is the solution or system? Nev didn’t find much on-line and there is little data in the NTSB database to indicate a significant problem. Parking brakes are very common. Still we have to be careful here - there may not be enough data to give an accurate picture.

4) My behavior. Would I be as diligent as zkelley and use an alternative every time or might I personally be better overall with an easier option (even a perfect system is no good if you don’t use it) .

5) Finally, how do I prioritize risk. Like Battson, I am generally more worried about damaging someone else’s person or property than my own so I have to factor this in.

For me, this adds up to having a parking brake but for you it may not.

[zkelley2]

In fact, you only need a few degrees slope or a strong wind to require a brake. Without brakes it would be a nightmare, chocks - no way.... Honestly.

Anyone parking near me without a brake gets because it's my plane, not theirs, which is at risk.

Something like 3000 hours SEL. I've never used a parking brake. There's always an option. Littererally never have been in a position to need one. No plane I own will ever have one because of the exact issue in this thread. It's not remotely rare.

They're great on the jet but that's a wildly different environment, but it's not because of slopes.

[Battson]

Are you guys parking on 30 degree inclines or something? Turn the plane sideways to the hill. No parking break needed.

In fact, you only need a few degrees slope or a strong wind to require a brake. Without brakes it would be a nightmare, chocks - no way.... Honestly.

Anyone parking near me without a brake gets because it's my plane, not theirs, which is at risk.

[Battson]

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...

The Grove parking brake gets my full recommendation. I have never had a problem with any Grove gear.

[JimParker256]

Turning sideways to the hill is not always an option. I went to a fly-in in a Commander 114, and when I got there, there was only one tie-down spot available. It was on about a 10º slope, between two other airplane, and pointing at another row of airplanes in front. With no parking brake, and no one around to assist me, I wound up having to carefully choreograph my exit from the airplane (with wheel chocks in hand) so that a hit the ground rolling under the wing to drop the wheel chock in front of one gear, then quickly roll to the other side and get it under the other gear. I managed to acquire a few bruises along the way, and of course there was a small oily puddle I rolled through... It would have been a little easier with a Bearhawk, but still...

I think if the Beringer parking brake valve is properly installed, it is pretty reliable. I cannot imagine any scenario other than pilot error that would allow the parking brake to be set inadvertently. That valve is not a "one-way" valve, it is functionally like a pair of fuel shutoff valves in parallel. To engage the parking brake, you have to pressurize the brake lines by holding the brakes, then turn the parking brake arm to shut those valves. The result is that the pressure you just created becomes trapped in the brake lines, keeping the brakes engaged.

Applying the brakes with the parking brake already engaged does nothing - fluid cannot flow through, so the brakes are not activated. Likewise, applying the parking brake without first building pressure in the brake lines (pressing the brakes) merely locks in the "atmospheric" pressure to the brake lines – which should NOT result in any braking action.

Of course, pilot error is still a possibility, but it would take a significant screw-up (IMHO) to inadvertently engage the parking brake by pressing the brakes, then pulling the parking brake lever, all without the pilot noticing...

[zkelley2]

Are you guys parking on 30 degree inclines or something? Turn the plane sideways to the hill. No parking break needed.