Brakes Locked Up

[1980Mooney]

22 minutes ago, gevertex said:

What does everyone think about the brakes being hard compared to a 172?  Is that Mooney normal or a sign something else is going on? 

The pic on your post shows that you have serial number 24-3275.  See parts diagram below.  It shows the 4 cylinders better.  You can download this M20J parts manual for free.  See page 482.  I assume your A&P has the parts manual and Service manual.  

I don't understand how the copilot brakes could be "INOP" unless the mechanical linkages are disconnected.  Everything is in series as @M20Doc says.  

The fact that the Copilot brakes don't work and that the Pilot brakes stick (or are harder than a C172) sounds serious. If it were my plane I would not fly it until a competent mechanic troubleshoots it.  You started this because you are worried about the brakes sticking - we may read an accident report when they "don't stick".  

Mooney M20J Illustrated Parts Catalog.pdf (free.fr)

Mooney Service Manuel M20J Vol. 1 of 2.pdf (free.fr)

 

 

[gevertex]

2 hours ago, 1980Mooney said:

The pic on your post shows that you have serial number 24-3275.  See parts diagram below.  It shows the 4 cylinders better.  You can download this M20J parts manual for free.  See page 482.  I assume your A&P has the parts manual and Service manual.  

I don't understand how the copilot brakes could be "INOP" unless the mechanical linkages are disconnected.  Everything is in series as @M20Doc says.  

The fact that the Copilot brakes don't work and that the Pilot brakes stick (or are harder than a C172) sounds serious. If it were my plane I would not fly it until a competent mechanic troubleshoots it.  You started this because you are worried about the brakes sticking - we may read an accident report when they "don't stick".  

Mooney M20J Illustrated Parts Catalog.pdf (free.fr)

Mooney Service Manuel M20J Vol. 1 of 2.pdf (free.fr)

 

 

Really appreciate the advice. This is exactly why I am asking more experienced minds. I am going to ground the airplane until it gets looked at. 

[carusoam]

Let’s review for a moment…

1) Breaks are hard… meaning not squishy…

2) Holding the breaks to keep the plane from moving during a run-up….

3) Up to this point… everything is normal…

4) Brakes didn’t release….  (Oops…. This is not normal….)

5) Lots of force is applied when the breaks are pressed….

6) start at the brakes shoes to see what is sticking…

7) guide pins are a great source for causing a sticking situation… (I’ve never seen it actually happen in real life)

8) hydraulic pressure staying applied is less likely, hydraulic systems give better feedback prior to failure…

9) How hard did you step on the brakes?

10) it doesn’t take a whole lot of pressure to lock the tires in place… but, if you supply full body weight to the brakes, they will try to apply all of the extra force into bending something….

11) It is possible that a blob of old hydraulic fluid escaped the flushing… but it would need to have solidified in place to completely block the flow trying to escape the calipers…

PP thoughts only, not a mechanic… pulling the guide pins out of the brakes of a Firebird is really easy… straight and smooth, they go back in… bent and scratched, they get tossed out….   

Best regards,

-a-

[skykrawler]

23 hours ago, gevertex said:

Good info. I’ll ask for it to be inspected. 

The way the parking brake works is you pressurize the brakes with the pedal (master cylinders) then close a valve by pulling the knob.  This retains the pressure in the system (the wheel cylinders) until released by pushing the knob in which releases the pressure and allows the fluid to return to the master cylinder.

If the knob is out (valve closed) or partially out it will make the brakes seem ineffective.  Your initial post sounded exactly like the parking brake had not been released.  There have been quite a few aircraft accidents over the decades (jets in particular) attempting to take-off with the parking brake on.

https://www.nbcconnecticut.com/news/local/ntsb-releases-preliminary-report-on-fatal-plane-crash-in-farmington/2591922/

Recommend a thorough read of the airplane operating manual.

 

[1980Mooney]

7 hours ago, carusoam said:

Let’s review for a moment…

1) Breaks are hard… meaning not squishy…

2) Holding the breaks to keep the plane from moving during a run-up….

3) Up to this point… everything is normal…

4) Brakes didn’t release….  (Oops…. This is not normal….)

5) Lots of force is applied when the breaks are pressed….

6) start at the brakes shoes to see what is sticking…

7) guide pins are a great source for causing a sticking situation… (I’ve never seen it actually happen in real life)

8) hydraulic pressure staying applied is less likely, hydraulic systems give better feedback prior to failure…

9) How hard did you step on the brakes?

10) it doesn’t take a whole lot of pressure to lock the tires in place… but, if you supply full body weight to the brakes, they will try to apply all of the extra force into bending something….

11) It is possible that a blob of old hydraulic fluid escaped the flushing… but it would need to have solidified in place to completely block the flow trying to escape the calipers…

PP thoughts only, not a mechanic… pulling the guide pins out of the brakes of a Firebird is really easy… straight and smooth, they go back in… bent and scratched, they get tossed out….   

Best regards,

And let's not forget that @gevertex thinks he has Dual (Copilot) Brakes that don't work "Copilot rudder pedals looks exactly like pilot’s, but don’t have any effect on the brakes. Is this normal?"....That is Definitely Not Normal. 

Has anyone ever seen that before?

[gevertex]

10 hours ago, carusoam said:

Let’s review for a moment…

1) Breaks are hard… meaning not squishy…

2) Holding the breaks to keep the plane from moving during a run-up….

3) Up to this point… everything is normal…

4) Brakes didn’t release….  (Oops…. This is not normal….)

5) Lots of force is applied when the breaks are pressed….

6) start at the brakes shoes to see what is sticking…

7) guide pins are a great source for causing a sticking situation… (I’ve never seen it actually happen in real life)

8) hydraulic pressure staying applied is less likely, hydraulic systems give better feedback prior to failure…

9) How hard did you step on the brakes?

10) it doesn’t take a whole lot of pressure to lock the tires in place… but, if you supply full body weight to the brakes, they will try to apply all of the extra force into bending something….

11) It is possible that a blob of old hydraulic fluid escaped the flushing… but it would need to have solidified in place to completely block the flow trying to escape the calipers…

PP thoughts only, not a mechanic… pulling the guide pins out of the brakes of a Firebird is really easy… straight and smooth, they go back in… bent and scratched, they get tossed out….   

Best regards,

-a-

I wasn’t standing on the brakes, but was applying a lot of pressure just before they got stuck. I went back out to the airplane today and tried the copilot brakes for myself while still. They feel exactly like the pilot brakes. Hard. Plane moved freely today. But it is also a lot warmer today. 47 degrees. 

[carusoam]

gever,

Can you review if you were using the parking brake?

Airplane parking brake systems are a simple valve that holds the hydraulic pressure in place, until allowed out…

If you forget to let the pressure out…

or the cable (?) doesn’t move the valve properly… the pressure is held in place until the valve gets moved…

Verify the valve, and it’s controls are working properly…

It would be cool to find the cable isn’t healthy… a nice low cost explanation… 

Brakes are really good in low temps… since we fly in the altitudes where -40° is common….

Can’t afford to have them be locked up during landing… after a long cold flight….

Fortunately, the systems are simple… troubleshooting should be straight forward… the culprit will reveal itself…

 

PP thoughts only, not a mechanic…

Best regards,

-a-

[gevertex]

8 minutes ago, carusoam said:

gever,

Can you review if you were using the parking brake?

Airplane parking brake systems are a simple valve that holds the hydraulic pressure in place, until allowed out…

If you forget to let the pressure out…

or the cable (?) doesn’t move the valve properly… the pressure is held in place until the valve gets moved…

Verify the valve, and it’s controls are working properly…

It would be cool to find the cable isn’t healthy… a nice low cost explanation… 

Brakes are really good in low temps… since we fly in the altitudes where -40° is common….

Can’t afford to have them be locked up during landing… after a long cold flight….

Fortunately, the systems are simple… troubleshooting should be straight forward… the culprit will reveal itself…

 

PP thoughts only, not a mechanic…

Best regards,

-a-

I have someone coming Thursday to take a look. I was not using the parking brake that day when brakes got stuck. Though it wouldn’t surprise me to find out that the valve is stuck closed. I do have to press really hard relative to the braking force I get. 
 

[philiplane]

brakes with old fluid will feel hard. Bleed the system with fresh fluid. Fluid older than 5 years will cause problems, it turns gummy, and yellow. Fresh fluid will flow easily and be red in color. Aeroshell Fluid 41 is recommended over the old 5606 formula. 

The caliper pins need cleaning and greasing at each annual. Rusty/sticky calipers will not retract the pistons properly and they can also jam if the pins/guides are worn and dry. 

[gevertex]

1 hour ago, philiplane said:

brakes with old fluid will feel hard. Bleed the system with fresh fluid. Fluid older than 5 years will cause problems, it turns gummy, and yellow. Fresh fluid will flow easily and be red in color. Aeroshell Fluid 41 is recommended over the old 5606 formula. 

The caliper pins need cleaning and greasing at each annual. Rusty/sticky calipers will not retract the pistons properly and they can also jam if the pins/guides are worn and dry. 

Good point. However the fluid was just flushed. I have a working theory. I think the parking brake valve is partially stuck closed. This explains why the brakes are slow to apply when pressed, why they got “stuck” for a few seconds after I was pressing hard on them (the fluid slowly moved away from calipers due to restriction from the parking brake valve), why the brakes are hard (fluid has to squeeze through a small opening to get to the calipers), and why the symptoms affect both left/right pilot/copilot sides equally. 

[A64Pilot]

18 hours ago, gevertex said:

Good point. However the fluid was just flushed. I have a working theory. I think the parking brake valve is partially stuck closed. This explains why the brakes are slow to apply when pressed, why they got “stuck” for a few seconds after I was pressing hard on them (the fluid slowly moved away from calipers due to restriction from the parking brake valve), why the brakes are hard (fluid has to squeeze through a small opening to get to the calipers), and why the symptoms affect both left/right pilot/copilot sides equally. 

In other aircraft the parking brake valve is also or contains the shuttle valve, if everything is hooked up it could also explain why your CP brakes are inop. if it has a shuttle valve

If the CP side are disconnected then they should be way forward at the tops and be sloppy loose with lots of brake pedal play.

[Fly Boomer]

3 minutes ago, A64Pilot said:

In other aircraft the parking brake valve is also or contains the shuttle valve, if everything is hooked up it could also explain why your CP brakes are inop. if it has a shuttle valve

If the CP side are disconnected then they should be way forward at the tops and be sloppy loose with lots of brake pedal play.

Last post he clarified that co-pilot brakes are not INOP:

" the brakes are hard (fluid has to squeeze through a small opening to get to the calipers), and why the symptoms affect both left/right pilot/copilot sides equally."

[A64Pilot]

Aeroshell 41 is still 5606, what you want is 83282, synthetic, fire resistant and does not turn to goo, it’s also fully compatible with 5606.

There are many sources of it, but if you like Aeroshell it’s Aeroshell 31 I believe.

https://www.aircraftspruce.com/catalog/lgpages/aeroshell08-14635.php

[A64Pilot]

7 minutes ago, Fly Boomer said:

Last post he clarified that co-pilot brakes are not INOP:

" the brakes are hard (fluid has to squeeze through a small opening to get to the calipers), and why the symptoms affect both left/right pilot/copilot sides equally."

A stuck shuttle valve could still explain that as it normally shuttles from one side to the other opening one system and closing the other, stuck in the middle neither side is fully open.

Not saying it’s shuttle valve is in the parking brake, but one aircraft that I have a lot of experience with had its shuttle valve as part of the parking brake.

[gevertex]

8 hours ago, Fly Boomer said:

Last post he clarified that co-pilot brakes are not INOP:

" the brakes are hard (fluid has to squeeze through a small opening to get to the calipers), and why the symptoms affect both left/right pilot/copilot sides equally."

Yes, I should have been more clear. When I tested copilot brakes yesterday they were symmetrical with pilot brakes. But apparently that’s bad enough for my CFI to call them inop. 

[gevertex]

8 hours ago, A64Pilot said:

Aeroshell 41 is still 5606, what you want is 83282, synthetic, fire resistant and does not turn to goo, it’s also fully compatible with 5606.

There are many sources of it, but if you like Aeroshell it’s Aeroshell 31 I believe.

https://www.aircraftspruce.com/catalog/lgpages/aeroshell08-14635.php

I’ll have to check the logs, but I believe brake fluid was replaced with aero shell. 

[Guest]

9 hours ago, A64Pilot said:

A stuck shuttle valve could still explain that as it normally shuttles from one side to the other opening one system and closing the other, stuck in the middle neither side is fully open.

Not saying it’s shuttle valve is in the parking brake, but one aircraft that I have a lot of experience with had its shuttle valve as part of the parking brake.

No shuttle valves installed, just a simple hydraulic line lock operated by an eccentric.

[A64Pilot]

There are two lines in and two lines out? Or two parking valves or valve only locks one brake?

There is only one poppet valve

[A64Pilot]

1 hour ago, gevertex said:

I’ll have to check the logs, but I believe brake fluid was replaced with aero shell. 

Aeroshell is the brand name, they make both 5606 and 83282.

83282 was adopted by the military and many commercial aircraft decades ago as it’s much superior, but for some reason GA has stuck with 5606.

If it was good enough for pops, it’s good enough for me I guess is the theory, like straight weight oil, or maybe it’s cheaper?

If you stick with 5606 flush it anytime you do brake work like pad changes and likely it will never give you any trouble

[gevertex]

10 minutes ago, M20Doc said:

No shuttle valves installed, just a simple hydraulic line lock operated by an eccentric.

Amazing. Thanks for the reference. Do you know where this is located or where I can easily access the linkage / cable to push this into the off position?

[A64Pilot]

You really should be working at least under the supervision of an A&P for this.

[gevertex]

Just now, A64Pilot said:

You really should be working at least under the supervision of an A&P for this.

Agree, I don't intend to make it airworthy by fixing it myself, or even take the airplane apart at all.  Just thinking there might be another mechanism for releasing the parking brake than the control in the cockpit to confirm the hypothesis.  Then A&P can come and fix it for real. It's obviously broken, I am not qualified to fix it by myself. I have someone coming in a couple days, but perhaps I can save them some time (and me some money) by having the answer in hand.

[Guest]

42 minutes ago, A64Pilot said:

You really should be working at least under the supervision of an A&P for this.

He is, remotely by all of us!

[Guest]

46 minutes ago, gevertex said:

Amazing. Thanks for the reference. Do you know where this is located or where I can easily access the linkage / cable to push this into the off position?

It should be under the floor on the pilot’s side.  You’ll have to remove the belly panel to access it.  Send me your logs and a picture for an entry when you get it working!!

[A64Pilot]

It’s got me stumped, both pedals are difficult to push which I don’t understand unless both brake calipers are stuck on their slide pins.

‘I think that’s where I’d start, and I think a pilot can change brake pads? Which means brake caliper removal. It’s really easy I’m sure there is either a You tube tutorial or step by step instruction on the internet, it doesn’t have to be Mooney brakes, just cleveland brakes on any small airplane will show you.