Brakes Locked Up

[gevertex]

I tried a short field takeoff last week. After applying full power, I released the brakes and nothing happened. The plane just sat there. After a couple seconds it started lightly hopping to the right. I was able to get it unstuck by reducing power and trying a normal takeoff, and brakes worked as usual for the next landing. I am brining it back to AGL Tuesday. 
 

After getting stuck, I did notice one of the brakes was dragging when pushing it back into its tie down. Also, I have always thought the brakes were hard compared to the 172 I came from (about 2x the amount of force for the same stopping power).  Brakes also take a second or so to actually actuate, not immediate like the 172 I am coming from. Brake fluid was just flushed by AGL which improved it from after purchase, but still hard imo.
 

Copilot rudder pedals looks exactly like pilot’s, but don’t have any effect on the brakes. Is this normal?

Anyone have any ideas as to the problem?

[1980Mooney]

3 hours ago, gevertex said:

I tried a short field takeoff last week. After applying full power, I released the brakes and nothing happened. The plane just sat there. After a couple seconds it started lightly hopping to the right. I was able to get it unstuck by reducing power and trying a normal takeoff, and brakes worked as usual for the next landing. I am brining it back to AGL Tuesday. 
 

After getting stuck, I did notice one of the brakes was dragging when pushing it back into its tie down. Also, I have always thought the brakes were a hard compared to the 172 I came from (about 2x the amount of force for the same stopping power).  Brakes also take a second or so to actually actuate, not immediate like the 172 I am coming from. Brake fluid was just flushed by AGL which improved it from after purchase, but still hard imo.
 

Copilot rudder pedals looks exactly like pilot’s, but don’t have any effect on the brakes. Is this normal?

Anyone have any ideas as to the problem?

Copilot brakes are an option. The standard Mooney has copilot rudder pedals (just a bar) without the toe/heel brake pedal  (see pic). If you have toe/heel pedals on the copilot side that look like the pilot side then they should be functional. 

[gevertex]

5 hours ago, 1980Mooney said:

Copilot brakes are an option. The standard Mooney has copilot rudder pedals (just a bar) without the toe/heel brake pedal  (see pic). If you have toe/heel pedals on the copilot side that look like the pilot side then they should be functional. 

Yes. I have toe heel pedals on the copilot side. CFI reported they were inop. I’ll have to try them. Thanks!

[skykrawler]

You mention nothing about the parking brake valve.   

[goodyFAB]

Sounds like you need a rebuild of the calipers. 
pull calipers and take the piston out, inspect, clean, replace oring. Bleed brakes

[gevertex]

28 minutes ago, skykrawler said:

You mention nothing about the parking brake valve.   

So far I haven’t engaged the parking brake. What is the significance of the parking brake valve?

[gevertex]

10 minutes ago, goodyFAB said:

Sounds like you need a rebuild of the calipers. 
pull calipers and take the piston out, inspect, clean, replace oring. Bleed brakes

Left caliper (according to invoice) was already rebuilt as it was leaking and both were bled. Maybe it’s time to rebuild right caliper?

[goodyFAB]

1 minute ago, gevertex said:

Left caliper (according to invoice) was already rebuilt as it was leaking and both were bled. Maybe it’s time to rebuild right caliper?

I dont like giving advice without seeing it for myself. It seems logical that the right is getting stuck as you mentioned the plane turned right. It’s worth having it looked at I can’t think of a more embarrassing way to have an incident. 

[cferr59]

Make sure the brake line hoses aren't getting pinched by the landing gear when it is lowered.

[gevertex]

3 minutes ago, goodyFAB said:

I dont like giving advice without seeing it for myself. It seems logical that the right is getting stuck as you mentioned the plane turned right. It’s worth having it looked at I can’t think of a more embarrassing way to have an incident. 

Agree. I’m having it looked at tomorrow. Just trying to get ahead of the curve on info. Thanks!  Merry Christmas!

[gevertex]

1 minute ago, cferr59 said:

Make sure the brake line hoses aren't getting pinched by the landing gear when it is lowered.

Where on the airplane does that typically occur?

[cferr59]

Just now, gevertex said:

Where on the airplane does that typically occur?

On the hose from the airframe to the caliper. It can be seen without taking anything apart.

[A64Pilot]

While I haven’t worked on a Mooney with dual brakes, it’s not uncommon for an aircraft to have a shuttle valve that isolates which brake is being used, that valve can stick, if it has one, I don’t know if it does. Inop CP brakes has me thinking you have a problem that may be related to a shuttle valve, and you may have three more master cylinders that need rebuilding

For a single brake aircraft the most likely suspect for sticking or dragging brakes is a caliper dragging on its pins where it normally slides, often it’s corrosion and easily cleaned up, but as a caliper rebuild is really just changing an O-ring and they need it every so often, I’d go ahead and do it, even if it didn’t need it it’s not much money and should buy you a few years before they need it again. It’s possible you have corrosion inside of the cylinder and you have to pop the piston out to inspect, may ad well put a new O-ring in.

I just got through rebuilding both my master cylinders, the hardest thing is accessing them and getting them out, yes in my opinion if your doing one, both should have been done as it’s not a whole lot more work and your there, mine were leaking obviously due to age of the O-rings, they were hard and broke on removal, they just weren’t pliable anymore, but they lasted 40 years so I’m not complaining.

My bet is either the shuttle valve or a caliper sticking on its pins, I lean towards the pins as they are easier to eliminate as a possibility, no parts to buy etc. May not be a bad idea to put a little bit of anti seize on them, but just a little you don’t want anti seize on your brakes.

I would not fly it until it’s fixed, if you have to fly it be sure they are free before takeoff and don’t touch them in flight or on landing until your real slow, stuck brakes have caused more than a few accidents

[Shadrach]

47 minutes ago, gevertex said:

So far I haven’t engaged the parking brake. What is the significance of the parking brake valve?

It’s  purpose is to prevent the flow of fluid back to the reservoir. If your passenger brakes are  not working, the system should be fully inspected. 

[gevertex]

20 minutes ago, A64Pilot said:

While I haven’t worked on a Mooney with dual brakes, it’s not uncommon for an aircraft to have a shuttle valve that isolates which brake is being used, that valve can stick, if it has one, I don’t know if it does. Inop CP brakes has me thinking you have a problem that may be related to a shuttle valve, and you may have four master cylinders that need rebuilding

For a single brake aircraft the most likely suspect for sticking or dragging brakes is a caliper dragging on its pins where it normally slides, often it’s corrosion and easily cleaned up, but as a caliper rebuild is really just changing an O-ring and they need it every so often, I’d go ahead and do it, even if it didn’t need it it’s not much money and should buy you a few years before they need it again. It’s possible you have corrosion inside of the cylinder and you have to pop the piston out to inspect, may ad well put a new O-ring in.

I just got through rebuilding both my master cylinders, the hardest thing is accessing them and getting them out, yes in my opinion if your doing one, both should have been done as it’s not a whole lot more work and your there, mine were leaking obviously due to age of the O-rings, they were hard and broke on removal, they just weren’t pliable anymore, but they lasted 40 years so I’m not complaining.

My bet is either the shuttle valve or a caliper sticking on its pins, I lean towards the pins as they are easier to eliminate as a possibility, no parts to buy etc. May not be a bad idea to put a little bit of anti seize on them, but just a little you don’t want anti seize on your brakes.

I would not fly it until it’s fixed, if you have to fly it be sure they are free before takeoff and don’t touch them in flight or on landing until your real slow, stuck brakes have caused more than a few accidents

Hopefully it’s just the remaining caliper needing to be rebuilt. I’ll take it easy on the brakes until it’s fixed. Planning on flying directly to AGL tomorrow. I won’t takeoff if they are stuck at all. 

[gevertex]

1 minute ago, Shadrach said:

It’s  purpose is to prevent the flow of fluid back to the reservoir. If your passenger brakes are  not working, the system should be fully inspected. 

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

[A64Pilot]

I’d still try to find out why the right side brakes don’t work, they should.

On edit, I personally never use a parking brake, I removed them from my C-140 as they have caused ground loops in those, but it’s a different type of system.

I don’t use them because if you set the brakes when they are hot you lock the fluid in the system to maintain pressure of course, but from the brakes being hot, the pressure increases. Besides I don’t trust them, I trust chocks and tie downs more.

Another edit, sometimes the shuttle valve can be a part of or built into the parking brake valve

 

[Guest]

From the IPC, it appears the master cylinders are plumbed in series, no isolating valve appears in the system, unlike earlier F models.

[Fly Boomer]

1 hour ago, A64Pilot said:

Inop CP brakes has me thinking you have a problem that may be related to a shuttle valve, and you may have three more master cylinders that need rebuilding

I know nothing about Mooney brakes.  Why three master cylinders?

[1980Mooney]

1 hour ago, Fly Boomer said:

I know nothing about Mooney brakes.  Why three master cylinders?

 

There are 2 master cylinders with standard brakes and 4 with dual (copilot) brakes

[Fly Boomer]

2 minutes ago, 1980Mooney said:

 

There are 2 master cylinders with standard brakes and 4 with dual (copilot) brakes

I see.  I guess it was implied that one had already been rebuilt.  Thanks.

[Shadrach]

1 hour ago, Fly Boomer said:

I know nothing about Mooney brakes.  Why three master cylinders?

Most small GA aircraft have manual brake systems systems. That means every peddle actuates its own brake cylinder. Master cylinder is kind of a misnomer in that there is no “slave cylinder” other than the caliper. 

[Fly Boomer]

1 minute ago, Shadrach said:

Most small GA aircraft have manual brake systems systems. That means every peddle actuates its own brake cylinder. Master cylinder is kind of a misnomer in that there is no “slave cylinder” other than the caliper. 

I just got fixated on "three" vs "four".  Thanks.

[gevertex]

34 minutes ago, Fly Boomer said:

I see.  I guess it was implied that one had already been rebuilt.  Thanks.

Ah, the master cylinders have not been rebuilt.  Only one of the calipers. 

[gevertex]

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?