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Parking Brake Locked Up in Flight??


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Thanks Andy.

That is helpful for me...

This reminded me of some checklist items that might get mentioned, but don’t quite make it to the GUMPs level...

in preparation for landing, I always make sure my feet aren’t on the brakes...

It is difficult for me to even feel the brakes... 

Making sure I am on both rudder pedals, and not on the brakes...

Brakes only below 50kias....

I have learned how little pressure it takes to flat spot tires at landing speeds...

How this applies to Richard’s situation... still to be determined....?

Best regards,

-a-

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20 hours ago, Skates97 said:

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

Fluid from flap retraction would take path of least resistance which is back to the vented reservoir. I can wrap my head around the parking brake malfunction but not around it’s spontaneous in flight self destruction. I believe that it had to have happened while being actuated, it just was not recognized until after the incident. Perhaps the valve has failed in such a way as to allow fluid into the system but not out. 

Edited by Shadrach
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17 minutes ago, Shadrach said:

Fluid from flap retraction would take path of least resistance which is back to the vented reservoir. I can wrap my head around the parking brake malfunction but not around it’s spontaneous in flight self destruction. I believe that it had to have happened while being actuated, it just was recognized until after the incident. Perhaps the valve has failed in such a way as to allow fluid into the system but not out. 

This is the only failure mode that makes sense to me as well (I have been noodling on this since the thread started).  It would have had to fail right as he released the parking brake after run up (as he said he uses the parking brake for that) and when he tapped the brakes prior to gear retraction, they forever locked.

This assumes he didn't touch the brakes after releasing the parking braking and lining up for TO.  I usually stop once lined up to do a final short checklist prior to applying power but I have also done that check prior to rolling onto the runway and not touch the brakes.  

I'm also watching this thread very closely. 

-Steve

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3 hours ago, Steve_B said:

This is the only failure mode that makes sense to me as well (I have been noodling on this since the thread started).  It would have had to fail right as he released the parking brake after run up (as he said he uses the parking brake for that) and when he tapped the brakes prior to gear retraction, they forever locked.

This assumes he didn't touch the brakes after releasing the parking braking and lining up for TO.  I usually stop once lined up to do a final short checklist prior to applying power but I have also done that check prior to rolling onto the runway and not touch the brakes.  

I'm also watching this thread very closely. 

-Steve

I missed where he said he tapped the brakes prior to gear retraction. Not everyone does that.  I too was taught to stop the wheels before gear retraction (due to bearings being subjected to the torque caused by the angular momentum of the spinning wheel).  However, my sense is that that load pales in comparison to those imposed on the wheel during taxi, take off and landing.  

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1 minute ago, larryb said:

That valve looks closed to me. I would remove the wire and try to move the lever and hopefully free the brakes. With the wire separated from the lever you can figure out if one or the other does not move freely.

I think Richard is treating it like a crime scene in hopes that a bright mechanic can give him a forensic analysis of the failure.

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4 minutes ago, larryb said:

That valve looks closed to me. I would remove the wire and try to move the lever and hopefully free the brakes. With the wire separated from the lever you can figure out if one or the other does not move freely.

Here is a picture of mine in the open state. I agree, the valve appears to be closed.

IMG_3172.thumb.jpg.1fa732dcc87562fee044cca376641211.jpg

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Looks closed and also looks like it has been replaced or taken out and cleaned/rebuilt.   The fittings are dirty, but the valve is not.  So now we have a slipped push pull cable attachment point.  Could be at either end of the cable.   The valve is just doing what it is told to do by the cable.

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5 hours ago, Shadrach said:

I missed where he said he tapped the brakes prior to gear retraction. Not everyone does that.  I too was taught to stop the wheels before gear retraction (due to bearings being subjected to the torque caused by the angular momentum of the spinning wheel).  However, my sense is that that load pales in comparison to those imposed on the wheel during taxi, take off and landing.  

I was always concerned about a spinning wheel catching a brake line or gear wiring that decided to flex the wrong way and getting caught by a spinning wheel. If memory serves correctly, the F-18 landing gear applies the brakes to stop the wheel as part of gear retract sequence.

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That last comment makes me think, what about a brake line that got out of place and kinked/pinched in the landing gear during extension?  Shot in the dark, but I'm trying to come up with something that could happen between gear up and gear down.

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7 minutes ago, bob865 said:

That last comment makes me think, what about a brake line that got out of place and kinked/pinched in the landing gear during extension?  Shot in the dark, but I'm trying to come up with something that could happen between gear up and gear down.

Those odds are only slightly better than the double, simultaneous bearing failure!  Say something were to have interfered with the line(s).  Moving it is one thing but compressing the system seems highly unlikely.

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16 minutes ago, larryb said:

Not only does the cable clamp appear to be missing, the valve is not bolted to it's mount. The bolts are present in Maurader's pic but not in Skates pic. 

It's hard attached to the brake reservoir.   Mauraders has a flexible line to attach.    Not saying it should not have bolts in it.   I am wondering about the loose white wire that changes gauge mid stream and is wrapped with tape.   Crimp butt splice or solder and heat shrink.   That is an awfully big gauge change.   Wonder what the circuit breaker is rated for.

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It does appear that neither the valve nor the outer cable sheath are attached to anything.   This suggests that when the cable is actuated the torque is applied to the line fittings into and out of the valve rather than just the valve actuator arm, which is not desirable.  

There may be several problems with this installation.

 

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Lots of observations and great questions. I have no idea what the white wire goes to but will have to trace it and see. Will also have to go back through the logs and see if I can find where the valve was either replaced or rebuilt, assuming it is in the logs and was not just done by a previous owner. As far as the valve mounted to something, I would be interested to see how it is mounted on someone with a C/D that has the same round reservoir.

The cable not attached could be part of the problem if pushing on it just flexes the whole thing instead of moving the inner cable. I had something similar happen with my prop cable shortly after purchasing the plane, there's a thread around here somewhere about it. I wasn't getting full RPM and it turned out that the cable had slipped in the clamps not allowing the inner cable to push the arm all the way.

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I do notice you have a rigid pipe going to the reservoir and what looks like a soft line going to the pressure side and not even a hose clamp. I would think that side sees all the brake pressure and would be rigid or at least a flexible brake hose? Maybe Im seeing the wrong thing and what appears to be a rubber hose is just a covered pipe? If it’s a hose made of fuel or vacuum line it can’t be right and brake fluid may have collapsed that hose locking the brakes by not allowing fluid to return to the reservoir? If it’s a fuel line or vacuum line it isnt compatible with brake fluid. If it is an old flexible brake line it also may have swelled up and closed off not allowing fluid to return? Are you using the proper brake fluid?

And, one more possibility, residual pressure from the system may be holding the valve in place not allowing fluid to escape back to the reservoir. This would probably be caused by a  lose cable casing at the clamp..

 

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2 minutes ago, nels said:

I do notice you have a rigid pipe going to the reservoir and what looks like a soft line going to the pressure side and not even a hose clamp. I would think that side sees all the brake pressure and would be rigid or at least a flexible brake hose? Maybe Im seeing the wrong thing and what appears to be a rubber hose is just a covered pipe? If it’s a hose made of fuel or vacuum line it can’t be right and brake fluid may have collapsed that hose locking the brakes by not allowing fluid to return to the reservoir? If it’s a fuel line or vacuum line it isnt compatible with brake fluid. If it is an old flexible brake line it also may have swelled up and closed off not allowing fluid to return? Are you using the proper brake fluid?

And, one more possibility, residual pressure from the system may be holding the valve in place not allowing fluid to escape back to the reservoir. This would probably be caused by a  lose cable casing at the clamp..

 

It looks to me like a hard line with black anti chaffing plastic around it. 

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I shared this thread on my trip with a very seasoned captain who is also a gear head and A&P.  

He thinks the the park brake was inadvertently pulled instead of a vent or carb heat and not returned to its normal flight/off position.  Its the simplest reason and there is a physics theory to this (Occam's razor.)

This has happened many times in corporate jets and it is always a crew messing around with the park brake in flight.

 

My thoughts are I think it was from a touch and go that may have been performed months or even years ago.....

either way good luck with the repair, it should only take a few bucks and some downtime and you get brand new tires and tubes out of the deal.  I just did new Air stop tubes and Michelins.

 

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More than likely you were trying to fly lean of peak and the reduced manifold pressure suck the excess brake fluid through the reverbulating framulator.   Once the suction was applied to the brake fluid, the extra velocity from flying LOP via adverse momentum cause the PB Knob to retract to the rear of the plane.  After you exited the black hole. Really there was no way to prevent this from happening.

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2 hours ago, Jim Peace said:

I shared this thread on my trip with a very seasoned captain who is also a gear head and A&P.  

He thinks the the park brake was inadvertently pulled instead of a vent or carb heat and not returned to its normal flight/off position.  Its the simplest reason and there is a physics theory to this (Occam's razor.)

This has happened many times in corporate jets and it is always a crew messing around with the park brake in flight.

 

My thoughts are I think it was from a touch and go that may have been performed months or even years ago.....

either way good luck with the repair, it should only take a few bucks and some downtime and you get brand new tires and tubes out of the deal.  I just did new Air stop tubes and Michelins.

 

I was actually thinking about Occam's razor yesterday, and that would point to exactly what you are saying. I am not above stupid mistakes, and I'm sure I will make others in the future. It's a constant learning process and as I have said at other times you just hope that you learn from the mistakes you make and that thy are small enough that there are no serious consequences from any of them. If that is what happened it is a bit disconcerting that I have no recollection of it... I would sure feel a lot better if I could run it back in my mind and say "yep, I think I remember doing that."

Of course if it was from a touch and go years ago I could blame it on a previous owner as I have only had the plane for two years. ;)

New tubes and tires should be on it, my wife picked them up at AS this morning and dropped them off at the shop and they already had the wheels off and were waiting on the new ones. Wanted to put the Michelin Airstops in but the only tubes that AS carried that had the bend in the valve stem were some expensive Goodyear tubes. Did not hear back from the shop today but it wouldn't be the first time they finished something on my plane and put it back in my hangar without a call to let me know it was done. They aren't there Friday so I will just head out there Saturday morning to see if it is done. Still want to know why I couldn't get the cable to release no matter how hard I pushed on it. It is probably the original cable and may just have bound up, again hoping to hear something from the mechanic about it.

1 hour ago, Yetti said:

More than likely you were trying to fly lean of peak and the reduced manifold pressure suck the excess brake fluid through the reverbulating framulator.   Once the suction was applied to the brake fluid, the extra velocity from flying LOP via adverse momentum cause the PB Knob to retract to the rear of the plane.  After you exited the black hole. Really there was no way to prevent this from happening.

That's funny stuff. Always get a chuckle out of some of the creativity here on MS.

53 minutes ago, carusoam said:

https://en.m.wikipedia.org/wiki/Occam's_razor

Simple life lessons, the MS way...  :)

Filing a flight plan keeps goofy stories from being printed about you in the newspaper... every goofy accident story ever printed includes a phrase regarding a flight plan not being filed...

-a-

Doesn't prevent the goofy stories, just changes the opening line of the article from "He did not file a flight plan" to "Despite filing a flight plan..."

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