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Parking Brake Locked Up in Flight??


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The brakes will be released and there will be no evidence of the problem when the mechanics finally get to looking at it.

The ice (flight at 10,500') in the brake line will have melted and all will be fine until it feezes again.

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45 minutes ago, Skates97 said:

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 I talked to the AP . . . His comment was "Nobody uses the parking brake anyway..."

I've had my C for 11-1/2 years. I have no idea if the parking brake works or not.

But I have looked, and there's a knob at the bottom of the panel labeled "Parking Brake." It's by the left yoke, Cabin Heat is by the right yoke.

Hope you get this figured out!

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5 minutes ago, Hank said:

I've had my C for 11-1/2 years. I have no idea if the parking brake works or not.

But I have looked, and there's a knob at the bottom of the panel labeled "Parking Brake." It's by the left yoke, Cabin Heat is by the right yoke.

Hope you get this figured out!

I'm not sure how skates is plane is configured but my 67F 4 cable controls to the right of the yoke (5 if you count the CFs but the control is slightly below the rest) In order they are Parking Brake, Cabin Heat, Cabin Vent, Ram Air.  The Heater and the Ram Air have lock buttons in the middle. The  Parking Brake and Cabin Vent look and feel identical.

 

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1 hour ago, Skates97 said:

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.

I believe your story but it comes with a dose of cognitive dissonance.

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I vote for bringing a PP to help the owner to take a cable off the parking break... to operate the valve... and independently test the cable operation...

still expecting this to be a two part problem...

Draining and refilling the hydraulic fluid would be high on the list...

All work to be done under the eyes of a real mechanic when available... for return to service...

Be on the look out for a proper cap for the fluid reservoir... and possibly a vent there...

Thanks to Ross for posting drawings of the prints with the O-rings that have a tendency to wear... and may have a high probability of a broken one blocking something it shouldn’t have...

Lots O wonder regarding the two step malfunction, three including the brake not releasing afterwords...

Wish this was closer to N.J. or Toronto...  :)

Best regards,

-a-

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18 minutes ago, Shadrach said:

I'm not sure how skates is plane is configured but my 67F 4 cable controls to the right of the yoke (5 if you count the CFs but the control is slightly below the rest) In order they are Parking Brake, Cabin Heat, Cabin Vent, Ram Air.  The Heater and the Ram Air have lock buttons in the middle. The  Parking Brake and Cabin Vent look and feel identical.

 

I suspect his is like yours, based on his comments. Apparently more than the instruments were reconfigured when Mooney got rid of the shotgun panel (68? 69?).

Here's mine. Heat and Vent are close together, but far from the parking brake, with the whole throttle quadrant and left yoke separating them. I just stand on the brakes for runup, even at WOT when checking my dynamic prop balance (still .01 after 14 years).

20181126_181136.jpg

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+1 for holding the brakes...

It may be too late to get on them after they let go...

if you recognize them letting go...?

But this would be somebody else’s challenge, not Richard’s...

The O has mixed the knobs together again as a set of identical and labeled push/pull handles...?

PP thoughts only,

-a-

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17 minutes ago, Shadrach said:

I'm not sure how skates is plane is configured but my 67F 4 cable controls to the right of the yoke (5 if you count the CFs but the control is slightly below the rest) In order they are Parking Brake, Cabin Heat, Cabin Vent, Ram Air.  The Heater and the Ram Air have lock buttons in the middle. The  Parking Brake and Cabin Vent look and feel identical.

 

Four to the right of the yoke, Parking Brake, Cabin Heat, Cabin Vent, Carb Heat. First three look identical but to get to the Parking Brake knob you either reach around the yoke or from under as it is behind the yoke. The heat and vent I can reach easily. The Parking Brake is also stiff to pull while the heat and vent knobs are not, very different feel. It will also only come out a little while the heat and vent  knobs pull out about twice as far.

Old picture from a different flight four months ago.

20180726_104845.thumb.jpg.35ce184310c8cec56f982c6f4226e4f5.jpg

Parking Brake is circled in red. Because of the tablet mounted on the yoke the only way to reach it is around from the right or up under from below. It is enough of a pain to get to that I usually turn the yoke all the way to the left to reach it when I am setting it. Again, would be hard to do it on accident. Even more so to apply the brakes and then set it while flying.

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48 minutes ago, Hank said:

I suspect his is like yours, based on his comments. Apparently more than the instruments were reconfigured when Mooney got rid of the shotgun panel (68? 69?).

Here's mine. Heat and Vent are close together, but far from the parking brake, with the whole throttle quadrant and left yoke separating them. I just stand on the brakes for runup, even at WOT when checking my dynamic prop balance (still .01 after 14 years).

20181126_181136.jpg

 That is indeed a different configuration. Are the cowl flaps on the quadrant?

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3 minutes ago, Shadrach said:

 That is indeed a different configuration. Are the cowl flaps on the quadrant?

Negative cowl flaps, they are fixed on my C. Not sure about Richard's converted D. Neither of us have Ram Air, either.

The 75 F I have 10 or so hours in, the Cowl Flaps are on the right side of the quadrant. 

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40 minutes ago, Skates97 said:

Four to the right of the yoke, Parking Brake, Cabin Heat, Cabin Vent, Carb Heat. First three look identical but to get to the Parking Brake knob you either reach around the yoke or from under as it is behind the yoke. The heat and vent I can reach easily. The Parking Brake is also stiff to pull while the heat and vent knobs are not, very different feel. It will also only come out a little while the heat and vent  knobs pull out about twice as far.

Old picture from a different flight four months ago.

20180726_104845.thumb.jpg.35ce184310c8cec56f982c6f4226e4f5.jpg

Parking Brake is circled in red. Because of the tablet mounted on the yoke the only way to reach it is around from the right or up under from below. It is enough of a pain to get to that I usually turn the yoke all the way to the left to reach it when I am setting it. Again, would be hard to do it on accident. Even more so to apply the brakes and then set it while flying.

Interesting, the heat knob has a lock on my bird which I just assumed was there to ensure a secure shutoff in the event of a CO leak.

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2 minutes ago, Hank said:

Negative cowl flaps, they are fixed on my C. Not sure about Richard's converted D. Neither of us have Ram Air, either.

The 75 F I have 10 or so hours in, the Cowl Flaps are on the right side of the quadrant. 

He has cowl flaps. They are controlled by the under panel knob just left of the throttle. While we’re talking peculiarities, my power knobs from left to right are throttle, mixture and prop...

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40 minutes ago, Shadrach said:

While we’re talking peculiarities, my power knobs from left to right are throttle, mixture and prop...

Definitely old school, prop goes in the middle . . . Colors are black, black, red.  ;)

In addition to higher gear speed (120 mph), the electric flaps also deploy faster (125 mph). So I fly approaches at 105-120 mph with Takeoff flaps, and drop gear to begin descent.

None of which affects the parking brake . . . . Although it may all be tangential to the root cause of Richard's prematurely flat tires (ouch!). 

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6 minutes ago, Hank said:

Definitely old school, prop goes in the middle . . . Colors are black, black, red.  ;)

In addition to higher gear speed (120 mph), the electric flaps also deploy faster (125 mph). So I fly approaches at 105-120 mph with Takeoff flaps, and drop gear to begin descent.

None of which affects the parking brake . . . . Although it may all be tangential to the root cause of Richard's prematurely flat tires (ouch!). 

Gear speed is the same.

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1 hour ago, Shadrach said:

Interesting, the heat knob has a lock on my bird which I just assumed was there to ensure a secure shutoff in the event of a CO leak.

The carb heat was identical to the other three when I got the plane, it was replaced with the one you see there after it broke. I like it better with the lock button. I want it to stay either on or off, not wander about somewhere in between. 

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6 hours ago, Mooneymite said:

The brakes will be released and there will be no evidence of the problem when the mechanics finally get to looking at it.

The ice (flight at 10,500') in the brake line will have melted and all will be fine until it feezes again.

Unlikely there was any ice in the line. It was much colder on the leg from U42 to KFOM. The last two hours of the leg from KFOM to KAJO the OAT was above freezing according to the mechanical gage as well as the one the EDM gets its data from, and it was a balmy 24 degrees Celsius when I landed. 

 

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On 11/26/2018 at 6:37 AM, 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 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.

1468627274_ScottParkingBrakecutaway.thumb.jpg.4b6a63d0fb281f644de5d51ec95f5fd2.jpg

 

 

I went out to the airport tonight to take another look at things and take a few pictures before the mechanics start on it. The parking brake is still stuck and with it sitting on the jacks I tried turning the wheels and they are still locked. The diagram above shows the plunger either all the way in or out. If you look at the way my valve is stuck, it doesn't look open or closed. As I said earlier the knob is not all the way out where it is when normally engaged, nor is it against the panel where it is when disengaged. The knob is just a little way out and the lever on the valve is about halfway in between, but that must be far enough to be closed as the brakes are locked. 

Reading your post again, you said the return line for the flaps is above the brakes. All speculation at this point, but those of you with more knowledge than I have about the braking systems (I think that is just about everyone) see if you can follow my thinking and tell me if it's plausible or plain crazy.

 If the parking brake is set and you push on the brakes I am assuming they still work? Once a tire has started skidding it doesn't take as much pressure to keep skidding. I wonder if the parking brake was in this position when I retracted the take off flaps if that would put enough pressure in the system where light pressure on the brakes upon landing would be enough to lock them up and stay locked up although no extra pressure continued to be applied. Although I try to have my toes on the bottom of the pedals I am sure I am not above having my toes too far up on the pedals, especially on a landing like this one where I was back and forth on the pedals on short final and while bleeding off the last bit of speed in ground effect.

20181127_194619.thumb.jpg.60fe38b37b75f0bb1e25363d1643994b.jpg

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R,

were you able to...

  • move that arm?
  • open the vent on the reservoir... (we are discusssing brake reservoirs in another thread, you are invited to visit...)

From here forward...

I would be cautious based on principle...

Hydraulic power can unleash some real powerful surprises...

Not knowing how much pressure might be stored in there, it would be good to know that the pressure has been let out.

It might be nothing, but it might be enough to power a bullet... it would require something odd to do this...

But a pair of flat tires is odd enough... and the brakes still locked up a day later, is pretty intriguing...

PP thoughts only, not a mechanic...

Best regards,

-a-

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The parking brake valve simply traps fluid and pressure.  Once the parking brake is set, fluid and pressure below it are trapped and physically separated from the fluid reservoir above it.

Is it possible that in flight you pulled on the parking brake knob instead of the heater knob?  And when it didn't pull out as far as you were expecting, you pulled hard enough for the plunger with the 6227-1 o-ring to be jammed into the seat?

My bet is that if you stick one arm into your pilot window and push on the knob at the same time you're pushing the plunger arm away from the valve it'll unstick itself and everything will be back to normal (except your tires, of course.)

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Andy,

That would explain how the valve could get stuck fully closed...

Any thought on what situation could cause the pressure in the brake lines? While the valve was closed... or before the valve was closed..?

Anything possible beyond stepping on the brakes and accidently jamming the valve?

Best regards,

-a-

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26 minutes ago, Andy95W said:

The parking brake valve simply traps fluid and pressure.  Once the parking brake is set, fluid and pressure below it are trapped and physically separated from the fluid reservoir above it.

Is it possible that in flight you pulled on the parking brake knob instead of the heater knob?  And when it didn't pull out as far as you were expecting, you pulled hard enough for the plunger with the 6227-1 o-ring to be jammed into the seat?

My bet is that if you stick one arm into your pilot window and push on the knob at the same time you're pushing the plunger arm away from the valve it'll unstick itself and everything will be back to normal (except your tires, of course.)

Possible, but unlikely. It's a reach to get to the parking brake knob as I have explained before. 

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35 minutes ago, carusoam said:

 

Any thought on what situation could cause the pressure in the brake lines? While the valve was closed... or before the valve was closed..?

 

Just spit balling here, but if there was unconscious pressure on one brake pedal by a lazy foot, and then the parking brake was engaged, pressure would be trapped below the park brake valve.  The master cylinders are connected with a Tee fitting, which could theoretically allow pressure to equalize between both master cylinders. And as Richard pointed out, it would take very little hydraulic pressure to lock a brake before rotation.

At this point we're all just guessing, right?  It sure would be nice to know the real answer.

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