Parking Brake Locked Up in Flight??

[nels]

Was your wife with you? If so, will she ever fly with you again?

on subject: the vent hole plugged sure sounds plausible.

Edited November 26, 2018 by nels

[Skates97]

1 hour ago, cbarry said:

I realize you mentioned that the last time you touched the brakes was just prior to takeoff.  Is it possible that you still touched the brakes just prior to retracting the gear and that brake application somehow set the parking brakes?

 

I would like to say yes or no definitively as I "try to remember to tap the brakes before retracting the gear but I probably only do it about 75% of the time. When I do tap them that is all it is, not exactly pushing hard on the brakes while climbing out, which I wouldn't think would be enough to accomplish anything. 

51 minutes ago, Yetti said:

Should be fine.   The master cylinders are pretty small and the movement of fluid is not much to operate the calipers.   It is possible that you did not get the parking brake off during takeoff, but the brakes were not locked due to cold weather.  The heat caused the expansion of fluid due to heat and thus locked brakes.   It's only about an inch of movement to make the parking brake valve work.  My parking brakes were last used a year ago at the annual check.

I don't think so, the brakes were locked when fueling and when I push it in I can feel it stop at the panel and feel a little pop as they release. Eye witness accounts are terrible and I'm sure I'm no exception. Although I don't recall anything feeling different when I released the brake than any other time. 

My parking brake knob only moves about an inch as well. After the landing it was not fully out, just a little bit. 

[Skates97]

22 minutes ago, nels said:

Was your wife with you? If so, will she ever fly with you again?

on subject: the vent hole plugged sure sounds plausible.

Nope, she and my oldest son stayed up in UT for a few extra days so she can have more time with grand kids and he could see friends from his time as a missionary.

My youngest son didn't think much of the landing, he was sitting in the backseat and after said he knew something must have gone wrong because he heard me swear (something I rarely do). In hindsight I'm not sure if it means it wasn't that bad, or flying with me has made him numb to bad landings... 

[Yetti]

could be as simple as a bent control cable

[Shadrach]

17 hours ago, Skates97 said:

I use the parking brake, but still hold the toe brakes when doing a run-up because I just don't trust it either.

It is odd, the last time I touched the brakes was prior to take-off roll three hours earlier. When the parking brake is on pushing on it always releases it, just not this time. Pushing the knob in results in it coming back out. One of the guys had said "Just start it back up, it will take some power but you should be able to roll clear." I told him no good, the parking brake is stuck.

There was another guy in the pattern behind me, he was about a mile out from the field when I landed. I quickly made a "Corona traffic, Mooney 878 is stuck in the middle of 25, don't land" which got an immediate "You're what?!" He circled overhead while the others helped me get clear. One of the guys there had a handheld and gave the guy in the air updates, it only took about five minutes from coming to a stop to them showing up with dollies and getting clear, great to be based at a friendly little airport.

The brake valve is rated for 1500psi. They typically leak down over time.  Seems silly to use both your feet and the brake valve during run up. Probably best to use your feet. Not a bad idea to occasionally check how the parking brake holds under power.   

You do understand that the valve merely locks in what ever pressure you have applied to the system.  Pulling the brake without depressing the pedals does nothing, zero, nada. Somehow, someway, pressure was applied to the system.  The return line from the flaps is above the brakes.  Even if the reservoir vent was blocked (unlikely),  I find it hard to believe that would create enough pressure to even be noticeable.   The parking brake not being flush against the panel is not really a big deal. The Scott type park brake valve in your plane is binary as in it's either on or it's off. It can't be "a little bit" seated (see illustration) 

Any chance you stretched in flight and depressed both brakes?  I do this on long XCs sometimes when stretching (I'll not be doing it anymore after reading this).  The fact that both brakes were locked leads me to believe the parking brake was on. Easy to grab it instead of the vent or heater in flight.

 

 

Edited November 26, 2018 by Shadrach

[Skates97]

1 hour ago, Shadrach said:

The brake valve is rated for 1500psi. They typically leak down over time.  Seems silly to use both your feet and the brake valve during run up. Probably best to use your feet. Not a bad idea to occasionally check how the parking brake holds under power.   

You do understand that the valve merely locks in what ever pressure you have applied to the system.  Pulling the brake without depressing the pedals does nothing, zero, nada. Somehow, someway, pressure was applied to the system.  The return line from the flaps is above the brakes.  Even if the reservoir vent was blocked (unlikely),  I find it hard to believe that would create enough pressure to even be noticeable.   The parking brake not being flush against the panel is not really a big deal. The Scott type park brake valve in your plane is a binary as in it's either on or it's off. It can't be "a little bit" seated (see illustration) 

Any chance you stretched in flight and depressed both brakes?  I do this on long XCs sometimes when stretching (I'll not be doing it anymore after reading this).  The fact that both brakes were locked leads me to believe the parking brake was on. Easy to grab it instead of the vent or heater in flight.

 

Yes, I know that is how the brake works, learned that early on when I first got the plane, I set the parking brake, got out, leaned against the wing and the plane rolled a few inches. I also understand it is either on or off, but it is not out as far as normal when I engage it and it is not flush against the panel as it normally is. I wouldn't think anything of the brake not being flush against the panel if it weren't for the fact that it has always sat flush against the panel, at least for the 250 hours that I have put on the plane. One of the nice things about always flying the same plane and flying it often is that when something is different you usually notice. The fact that it is not flush and also not fully out where it has been when engaged, the brakes were locked up, and that it will not release is why I think there is something else going on.

I'm not saying it couldn't happen, but I doubt that I stretched out and depressed both brakes in flight and simultaneously pulled on the parking brake knob to set it instead of the heater knob next to it. Even so, if that were the case I should have been able to release it after coming to a stop but it will not release.

[Skates97]

11 hours ago, larryb said:

A Mooney owner in the hanger right next to me told me a similar story. His parking brake jammed and the aircraft could not be moved. Now, I don’t remember the exact fix, but it involved removing a panel somewhere. This guy called his buddy Mark Rouch at Top Gun in Stockton and Mark knew exactly the problem. So I suggest calling Mark.

Nice conversation with Mark this morning. He said is sounds like an issue with the cable, he has seen them break, rust up, bind up, etc... If it won't release he said that it's pretty easy to get up under there and disengage the cable and then release the brake. If it releases then you know it's an issue with the cable and the valve is fine. If it doesn't then you have a problem with the valve. I'll report back after I hear from my AP and what they find. They're going to replace tires/tubes today and take a look at the system.

[Shadrach]

31 minutes ago, Skates97 said:

Yes, I know that is how the brake works, learned that early on when I first got the plane, I set the parking brake, got out, leaned against the wing and the plane rolled a few inches. I also understand it is either on or off, but it is not out as far as normal when I engage it and it is not flush against the panel as it normally is. I wouldn't think anything of the brake not being flush against the panel if it weren't for the fact that it has always sat flush against the panel, at least for the 250 hours that I have put on the plane. One of the nice things about always flying the same plane and flying it often is that when something is different you usually notice. The fact that it is not flush and also not fully out where it has been when engaged, the brakes were locked up, and that it will not release is why I think there is something else going on.

I'm not saying it couldn't happen, but I doubt that I stretched out and depressed both brakes in flight and simultaneously pulled on the parking brake knob to set it instead of the heater knob next to it. Even so, if that were the case I should have been able to release it after coming to a stop but it will not release.

Yeah I get it. I'm just baffled by the fact it happened in flight. I don't know of any other way for both calipers to get pressurized.  Both pedals would need to be depressed to put enough pressure on the system to lock both wheels. You blew two tires... That doesn't happen from a little extra brake drag. Your tires flat spotted all the way to the tube on both sides, so almost no rotation. I can see why you're perplexed.

[Shadrach]

6 minutes ago, Skates97 said:

Nice conversation with Mark this morning. He said is sounds like an issue with the cable, he has seen them break, rust up, bind up, etc... If it won't release he said that it's pretty easy to get up under there and disengage the cable and then release the brake. If it releases then you know it's an issue with the cable and the valve is fine. If it doesn't then you have a problem with the valve. I'll report back after I hear from my AP and what they find. They're going to replace tires/tubes today and take a look at the system.

It's like a bike cable. it's no big deal. This still does not explain how the brakes locked in flight.

Edited November 26, 2018 by Shadrach

[bob865]

Maybe this is a silly question, are you sure it was the brakes that locked up and not the wheel bearings?

[Marauder]

The brake valve is rated for 1500psi. They typically leak down over time.  Seems silly to use both your feet and the brake valve during run up. Probably best to use your feet. Not a bad idea to occasionally check how the parking brake holds under power.   
You do understand that the valve merely locks in what ever pressure you have applied to the system.  Pulling the brake without depressing the pedals does nothing, zero, nada. Somehow, someway, pressure was applied to the system.  The return line from the flaps is above the brakes.  Even if the reservoir vent was blocked (unlikely),  I find it hard to believe that would create enough pressure to even be noticeable.   The parking brake not being flush against the panel is not really a big deal. The Scott type park brake valve in your plane is a binary as in it's either on or it's off. It can't be "a little bit" seated (see illustration) 
Any chance you stretched in flight and depressed both brakes?  I do this on long XCs sometimes when stretching (I'll not be doing it anymore after reading this).  The fact that both brakes were locked leads me to believe the parking brake was on. Easy to grab it instead of the vent or heater in flight.

 
 

Thanks for posting this. I am about to rebuild mine and this will come in handy. My parking brake has never, ever held the plane during run up. I had always just used the toe brakes. Since there is a slight leak there, I will rebuild it as I replace all of the hose and O rings in the system.


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[Shadrach]

9 minutes ago, bob865 said:

Maybe this is a silly question, are you sure it was the brakes that locked up and not the wheel bearings?

Both bearings at the same time? If they did, then he should play the lottery... think the odds are better he'd hit the mega million than have a double, independent. bearing failure at the exact same moment! 

[bob865]

Just now, Shadrach said:

Both bearings at the same time? If they did, then he should play the lottery... think the odds are better he'd hit the mega million than have a double, independent. bearing failure at the exact same moment! 

I don't disagree, but wouldn't brakes locking up in flight have similar odds? I feel like that is just as unlikely.  If I'm seeing above and remembering right, the parking brake is just a valve.  It will not apply brakes, only hold what has been applied.  For the parking brake theory to hold, at some point he would have had to depress the brakes AFTER he actuated the valve.  Correct? 

[Shadrach]

5 minutes ago, Marauder said:

 

Thanks for posting this. I am about to rebuild mine and this will come in handy. My parking brake has never, ever held the plane during run up. I had always just used the toe brakes. Since there is a slight leak there, I will rebuild it as I replace all of the hose and O rings in the system.


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Yours is likely a 4500. It matters not though because the differences are minimal (I think the 4500 is just a newer version of the 4200). The internals and the mechanism should be the same.  Good luck on your rebuild!

[Shadrach]

Just now, bob865 said:

I don't disagree, but wouldn't brakes locking up in flight have similar odds? I feel like that is just as unlikely.  If I'm seeing above and remembering right, the parking brake is just a valve.  It will not apply brakes, only hold what has been applied.  For the parking brake theory to hold, at some point he would have had to depress the brakes AFTER he actuated the valve.  Correct? 

You're correct about the brake application.  Odds of a double brake self activation are probably about the same as a double bearing failure. This is why I believe there is more to the story...

[Skates97]

8 minutes ago, bob865 said:

I don't disagree, but wouldn't brakes locking up in flight have similar odds? I feel like that is just as unlikely.  If I'm seeing above and remembering right, the parking brake is just a valve.  It will not apply brakes, only hold what has been applied.  For the parking brake theory to hold, at some point he would have had to depress the brakes AFTER he actuated the valve.  Correct? 

 

5 minutes ago, Shadrach said:

You're correct about the brake application.  Odds of a double brake self activation are probably about the same as a double bearing failure. This is why I believe there is more to the story...

I thought the parking brake only worked if you pressed the brakes and then pulled the parking brake knob to hold that pressure. If you actuated the valve and then pushed on the brakes would it allow the pressure applied to then remain, like pumping the brakes and every time you pushed it increased the pressure?

If that is the case and something went wrong with the cable/valve (can't release the parking brake so there is something wrong there) it would be possible that throughout the flight and on final which was a little squirrley (variable winds that had me back and forth with the rudder pedals) that I touched the brakes enough creating enough pressure built up where they were locked up when I touched down.

[Marauder]

I thought the parking brake only worked if you pressed the brakes and then pulled the parking brake knob to hold that pressure. If you actuated the valve and then pushed on the brakes would it allow the pressure applied to then remain, like pumping the brakes and every time you pushed it increased the pressure?
If that is the case and something went wrong with the cable/valve (can't release the parking brake so there is something wrong there) it would be possible that throughout the flight and on final which was a little squirrley (variable winds that had me back and forth with the rudder pedals) that I touched the brakes enough creating enough pressure built up where they were locked up when I touched down.

Based on what I am seeing looking at my system, you have a true mystery on your hands. The only thing that makes sense in the scenario you described is that if the valve failed internally and allowed hydraulic fluid to flow out to the brakes and not return. If something like that happened, it would be an interesting piece of FOD that restricted flow in one direction.


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[gsxrpilot]

We're all curious as hell about this one. Be sure to get pictures!

[mike_elliott]

Probably running LOP.....

[Shadrach]

46 minutes ago, Skates97 said:

 

I thought the parking brake only worked if you pressed the brakes and then pulled the parking brake knob to hold that pressure. If you actuated the valve and then pushed on the brakes would it allow the pressure applied to then remain, like pumping the brakes and every time you pushed it increased the pressure?

If that is the case and something went wrong with the cable/valve (can't release the parking brake so there is something wrong there) it would be possible that throughout the flight and on final which was a little squirrley (variable winds that had me back and forth with the rudder pedals) that I touched the brakes enough creating enough pressure built up where they were locked up when I touched down.

 Indeed, the parking break only works if you pressurize the system with your feet and then lock the system closed with the parking brake. If you were to walk the system first and then apply pressure with your feet I don’t think it would set.   That’s a tight tolerance plunger type seal. I don’t think that ambient pressure would be enough to push fluid past the seal, especially given that vacuum on the master cylinder side and pressure on the reservoir side would be working with to hold the seal in the closed position. The reason I think that there’s more to this story (and we may never know what that is) is my belief that there is no possible way to pressurize your brake calipers without depressing the brake cylinders. 

We also have the parking brake cable issue. Which in reading your description appears to of happened on its own sometime between the last time you used it and the blow out. Am I correct in assuming that you did not notice a parking brake cable issue until after the blowout?

So if I understand correctly, you took off with free spinning wheels and landed with a tire screeching double blowout without depressing the brakes or touching the P-brake during flight?

[EricJ]

12 minutes ago, mike_elliott said:

Probably running LOP.....

...or doing touch-and-goes.

 

[Rookie]

......AOA?

[Marauder]

...or doing touch-and-goes.
 

I blame it all on Aspen. The resolution isn’t good enough.


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[Skates97]

1 hour ago, Shadrach said:

 Indeed, the parking break only works if you pressurize the system with your feet and then lock the system closed with the parking brake. If you were to walk the system first and then apply pressure with your feet I don’t think it would set.   That’s a tight tolerance plunger type seal. I don’t think that ambient pressure would be enough to push fluid past the seal, especially given that vacuum on the master cylinder side and pressure on the reservoir side would be working with to hold the seal in the closed position. The reason I think that there’s more to this story (and we may never know what that is) is my belief that there is no possible way to pressurize your brake calipers without depressing the brake cylinders. 

We also have the parking brake cable issue. Which in reading your description appears to of happened on its own sometime between the last time you used it and the blow out. Am I correct in assuming that you did not notice a parking brake cable issue until after the blowout?

So if I understand correctly, you took off with free spinning wheels and landed with a tire screeching double blowout without depressing the brakes or touching the P-brake during flight?

Yes, released the parking brake after fueling and took off without any issue. I was using the cabin heat and adjusting it here and there but don't think I pulled the parking brake by accident. To reach the parking brake knob requires reaching around the yoke so fairly certain I didn't do it on accident. Even if I did I would have had to be pressing the brakes while in the air at the same time, even more unlikely.

As I touched down to the sound of screeching and sliding back a forth a little the first thing that came to my mind was "Did I forget the gear?!" Seriously felt sick to my stomach for a second thinking I joined the club of those that have landed gear up. Came to a stop, realized that I hadn't forgotten the gear because the prop was still turning and the engine was running. I tried giving it some power to limp out of the way of the next guy but wouldn't budge. That was when I noticed the parking brake knob and tried to push it in to disengage but it wouldn't. At that point I shut down and got out seeking assistance from the guys sitting in front of the hangar just to my left.

When we got it over to their hangar the mechanics put it on jacks and tried releasing the brake and moving the wheels but no luck, locked up tight. They were just about to leave for the day so didn't put any more time into it than that. I'm just thankful there were folks there to help out.

1 hour ago, mike_elliott said:

Probably running LOP.....

If only my carburetor would let me...

1 hour ago, EricJ said:

...or doing touch-and-goes.

Nope, this one was a touch-and-no-go 

1 hour ago, gsxrpilot said:

We're all curious as hell about this one. Be sure to get pictures!

Won't have more answers until Wednesday/Thursday. I talked to the AP, they are buried in the shop right now so I told him no rush, I wasn't planning on flying until Saturday. He said they would replace the tires Wednesday or Thursday and take a look at the brakes. If fixing the parking brake requires more time/parts (Aircraft Spruce is a mile away) than they have available at that point he said they would just disconnect it until he could get it back in the shop so I could at least go fly. His comment was "Nobody uses the parking brake anyway..."

After this, depending on the findings, I may just leave it disconnected...

[DualRatedFlyer]

13 minutes ago, Marauder said:

 

I blame it all on Aspen. The resolution isn’t good enough.


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I vote using the trim to flare