Parking Brake Locked Up in Flight??

[Skates97]

I finished a nice flight from Salt Lake back home to SoCal only to come to a screeching, skidding stop on the runway. The parking brake worked fine at run-up at South Valley Regional. It worked fine when I stopped for fuel at Fillmore KFOM (cheaper fuel than U42). It obviously released fine when I departed Fillmore. Three hours later I touched down at KAJO and blew both tires coming to a stop. Temp was 2 degrees Celsius at KFOM and 24 degrees Celsius at KAJO when I landed.

After landing I found the knob for the parking brake was out maybe a half inch and pushing it in just results in it popping back out to the same spot, it will not release. Fortunately because a couple of the mechanics at my AP's shop took Thur-Fri off they were there at the field. They got a couple dolleys and with the help of a couple others we got under the wing along the spar and lifted each side up to put the dolleys underneath and wheeled it over to the front of their shop. Also fortunately there was no damage to the wheels or the gear doors. They put it up on jacks and there is no way to move the wheels, the brakes are locked up and still no way to release the parking brake. They'll replace the tires/tubes tomorrow and take a look at the parking brake.

So, what could cause the brakes to lock up in flight? There's no way I pushed on the toe brakes and engaged the parking brake in flight. I have made my share of mistakes while flying but that would require a specific effort, not really a "forgot the check list" type thing.

I'm glad it happened at my home base instead of my fuel stop at a sleepy little airport in the middle of nowhere.

[Yetti]

Was there ice in the calipers?

[Skates97]

11 minutes ago, Yetti said:

Was there ice in the calipers?

No, it had rained and snowed in Salt Lake on Thursday, Friday, and Saturday but I had them put it in a heated hangar for the 3 1/2 hours before we departed. The plane was clean and dry when we left and taxiways/runways were all clean and dry today.

[Yetti]

How high did you fly?   If you had air in the lines, it could have expanded.

[DXB]

Am no expert on hydraulic brakes but here's my "stayed at at Holiday Inn Last Night" stab at it:  The hydraulic reservoir was recently topped off and the vent at the top got plugged somehow.  With the huge increase in temp during the flight, the fluid and any air in the system expanded and had no pressure relief, thus actuating the calipers?  When you take the top off the reservoir, the fluid should come gushing out.  Answer from people who actually know something to follow...

That is a horrifying story by the way - luckily both locked up equally or you could have had an uncontrollable  swerve off the runway.

It also made me look in my service manual regarding filling the hydraulic reservoir, which says leave 2 inches airspace at the top.  I don't do that 

 

[Skates97]

2 minutes ago, Yetti said:

How high did you fly?   If you had air in the lines, it could have expanded.

10,500'

[Skates97]

4 minutes ago, DXB said:

Am no expert on hydraulic brakes but here's my "stayed at at Holiday Inn Last Night" stab at it:  The hydraulic reservoir was recently topped off and the vent at the top got plugged somehow.  With the huge increase in temp during the flight, the fluid in the system expanded and had no pressure relief, thus actuating the calipers?  When you take the top off the reservoir, the fluid should come gushing out.  Answer from people who actually know something to follow...

That is a horrifying story by the way - luckily both locked up equally or you could have had an uncontrollable  swerve off the runway.

It also made me look in my service manual regarding filling the hydraulic reservoir, which says leave 2 inches airspace at the top.  I don't do that 

 

I stayed at my sister's last night, not a Holiday Inn... but...

The reservoir has not been topped off recently. The last time it was opened was about 4-5 months ago when I took a look and while it wasn't to the top it I didn't add to it. I have flown a lot since that time with no issues.

Yes, glad they were both locked up. As it was it still swerved back and forth a bit while I was trying to keep it somewhat in the center of the 60' wide runway. While I believe it would have been survivable it could have resulted in a lot of bent metal. As is, it just needs two main tubes/tires (which I was going to replace in probably another 6 months) and whatever it turns out caused the problem. Could have definitely been a lot worse.

[carusoam]

Great report Richard!

interesting thought, Dev!

Anyone know how the brake system vents?

There might be a small hole in the reservoir cap?

I wouldn’t expect much related to system venting... because the flight went to altitude and returned back, expanding and contracting...

Anything is possible so far...

 

The situation requires two odd things to happen...

1) Brake pressure to be applied, both L&R, supplying pressure to the system...?

2) Locking That pressure in place using the parking brake valve...?

3) The obvious question is... what would make the parking brake valve to continue to want to actuate?

 

I very much don’t use my parking brake.  Due to lack of trust... and lots of even paved surfaces...

Best regards,

-a-

[Skates97]

2 minutes ago, carusoam said:

Great report Richard!

interesting thought, Dev!

Anyone know how brake system vents?

There might be a small hole in the reservoir cap?

I wouldn’t expect much related to system venting... because the flight went to altitude and returned back, expanding and contracting...

Anything is possible so far...

 

The situation requires two odd things to happen...

1) Brake pressure to be applied...?

2) Locking That pressure in place using the parking brake valve...?

3) The obvious question is... what would make the parking brake valve to continue to want to actuate?

 

I very much don’t use my parking brake.  Due to lack of trust... and lots of flat surfaces...

Best regards,

-a-

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.

[Marauder]

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.

Your brakes may be similar to the one on my 75 F. I’m in the process of collecting parts to rebuild mine. The theory presented above about the system being pressurized might be something to look at. When I pulled the cap on my reservoir, I noticed it had a hole in it. I wonder if that hole got plugged would it pressurize the system. If that happened, you would think it would release that pressure when you descend.

I would look at the cable. If it popped out, something doesn’t sound right.

This is the parking brake in my plane.




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[takair]

Do you recall when you retracted flaps?  Prior to lock up or after?  Wonder if your vent got plugged and retracting the flap created slight positive pressure in the reservoir.  Wonder what pumping the flaps down would do?

[Skates97]

26 minutes ago, Marauder said:

 

Your brakes may be similar to the one on my 75 F. I’m in the process of collecting parts to rebuild mine. The theory presented above about the system being pressurized might be something to look at. When I pulled the cap on my reservoir, I noticed it had a hole in it. I wonder if that hole got plugged would it pressurize the system. If that happened, you would think it would release that pressure when you descend.

I would look at the cable. If it popped out, something doesn’t sound right.

This is the parking brake in my plane.



Sent from my iPhone using Tapatalk Pro

 

The cable is one of the things they are going to look at. They were getting ready to leave when I landed. In fact if I had arrived about 30 minutes later I would have been out of luck looking for some help.

16 minutes ago, takair said:

Do you recall when you retracted flaps?  Prior to lock up or after?  Wonder if your vent got plugged and retracting the flap created slight positive pressure in the reservoir.  Wonder what pumping the flaps down would do?

Flaps were retracted after coming to a stop. Normally as I am rolling out I raise flaps and open cowl flaps, but as soon as the mains touched I had my hands full staying on the runway and didn't touch anything. I'm wondering if pumping the flaps down somehow also pressurized the brakes? I don't know enough about how the two systems tie together. Maybe @M20Doc or @N201MKTurbo could shed some light on it.

[Shadrach]

It’s not mechanically possible for the parking brake to actuate itself. Something else is going on.

Edited November 26, 2018 by Shadrach

[Skates97]

14 minutes ago, Shadrach said:

It’s not mechanically possible for the parking break to actuate itself. Something else is going on.

Hence my confusion... Something occurred which resulted in the brakes being locked up and the knob for the parking brake not flush against the panel and unable to disengage it by pushing it in. I will know more tomorrow after they get into it but thought I would see if the collective wisdom here had any ideas.

[Andy95W]

I just removed "Repair Parking Brake Valve" from my to-do list.

[Ragsf15e]

Dang, scary.  Especially since I just finished annual and had my parking brake valve seals changed!  Had a slow leak (drip on my left foot once in a while) for like 2 years.  Fixed with kit from lasar, $10 for parts, 1 hr labor.  

You can bet I’m taking the wide runway for the next few flights!

[Yetti]

How old is your brake fluid?  could have gummed up the valve?

[larryb]

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.

[Skates97]

32 minutes ago, Yetti said:

How old is your brake fluid?  could have gummed up the valve?

Not sure how long the fluid is supposed to last but from what I can find it looks like it is almost 4 years old. The only recent entry I can find is when the previous owner replaced the brake lines to the calipers and bled the brakes at that time. I have never had any problems with the brakes, until today...

[Skates97]

Just now, 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.

Thanks, I will give him a call in the morning.

[DXB]

Does someone have a good diagram of the hydraulic system in the pre-69 vintage Mooneys?  I think  I've  seen one before but can't find right now in the parts or maintenance manual.  Since both brakes locked up, clearly the problem is somewhere between the hydraulic reservoir and the split to the left and right brakes, and the system being excessively pressurized is likely to be part of it.  Looking forward to knowing the answer, so this nasty problem never happens to me .

[Jim Peace]

When was the last time a touch and go was performed?

What did you have for dinner the night prior?

 

[Shadrach]

5 hours ago, DXB said:

Does someone have a good diagram of the hydraulic system in the pre-69 vintage Mooneys?  I think  I've  seen one before but can't find right now in the parts or maintenance manual.  Since both brakes locked up, clearly the problem is somewhere between the hydraulic reservoir and the split to the left and right brakes, and the system being excessively pressurized is likely to be part of it.  Looking forward to knowing the answer, so this nasty problem never happens to me .

Enjoy!

[cbarry]

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?

 

[Yetti]

7 hours ago, Skates97 said:

Not sure how long the fluid is supposed to last but from what I can find it looks like it is almost 4 years old. The only recent entry I can find is when the previous owner replaced the brake lines to the calipers and bled the brakes at that time. I have never had any problems with the brakes, until today...

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.