Joe Larussa

How good do your brakes work?

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Rebuilt my brakes from top to bottom. Rotors, pads, brake lines, master cylinders and shiny new brake fluid. I got to say this does not stop as well as my 172 on a bad day. Ideas ?

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Is it at all speeds? Do they lock?  If everything has been properly reassembled during the rebuild, It's likely not the condition or capability of the brakes that's an issue. It's more likely the speed at which they are being applied. 172s are less affected by ground effect and far more tolerant of airspeed variations at touchdown. The next time you land, pull the yoke back before braking. If the plane still wants to fly, you're too fast. I don't know how long you've had your Mooney, but it's not uncommon for transitioning pilots to "fly it on" smoothly and then apply the brakes to wheels that have very little weight on them. 

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Did you follow the pad conditioning procedure in the Cleveland manual?  In my experience Cleveland brake pads and discs are better than the others.

Clarence

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Should be able to lock up and flat spot the tires.  If the pedals go all the way to the floor, then you probably still have some air in the line.   If the pedals are tight but plane won't stop then there may be glaze on the discs.

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Joe, 

Have you tried a  static full power run-up? 

Guide AWBTSG0001-12/USA

A. Conditioning Procedures

When new linings have been installed, it is important to condition them properly to obtain the service life designed into them. The metallic and organic linings have different operating characteristics. Separate conditioning procedures are given for metallic and organic linings.

ORGANIC LININGS

METALLIC LININGS

  1. Taxi aircraft for 1500 feet with engine at 1700 rpm applying brake pedal force as needed to develop a 5-10 mph taxi speed.

  2. Allow the brakes to cool for 10 to 15 minutes.

  3. Apply the brakes and check for restraint at high static throttle. If brakes hold, conditioning is complete.

  4. If brakes cannot hold aircraft during static run-up, allow brakes to completely cool and repeat steps 1 through 3.

  1. Perform two (2) consecutive full stop braking applications from 30 to 35 knots. Do not allow the brake discs to cool substantially between the stops.

  2. Allow the brakes to cool for 10 to 15 minutes.

  3. Apply the brakes and check for restraintat high static throttle. If brakes hold, conditioning is complete.

  4. If brakes cannot hold aircraft during static run-up, allow brakes to cool completely and repeat steps 1 through 3.

CAUTION: DUE TO THE EFFICIENCY OF THESE BRAKES, EXTREMELY HARD BRAKING ON AIRCRAFT WITH TAIL WHEELS COULD RESULT IN LIFTING THE TAIL FROM THE GROUND.

These conditioning procedures will wear off high spots and generate sufficient heat to create a thin layer of glazed material at the lining friction surface. Normal brake usage should generate enough heat to maintain the glaze throughout the life of the lining.

Properly conditioned linings will provide many hours of maintenance free service. A visual inspection of the brake disc will indicate the lining condition. A smooth surface, one without grooves, indicates the linings are properly glazed. If the disc is rough (grooved), the linings must be reglazed. The conditioning procedure should be performed whenever the rough disc condition is observed. Light use, such as in taxiing, will cause the glaze to be worn rapidly and reduce the designed service life of the linings and discs. 

 

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Large oil can with brake fluid at the wheel.  Pump oil can vigorously while someone removes fluid from the reservoir will get most of the air out

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Best I can remember the J weighs as much empty as the older 172 models at max gross weight. 

And there are numerous threads on this and other websites discussing how difficult it is to bleed the brakes on a Mooney.

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If I were a betting man, I would bet that the OP's brakes are fine. The way I read this he didn't like the braking action on the aircraft as it was purchased and then had the brakes rebuilt only to be disappointed the braking action didn't improve. My thoughts are this is more than likely a landing technique issue. Any brake work beyond changing pads needed to be done by qualified A&P.

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Yeah, I've found braking action in other planes to be much stronger. The Arrow I used to rent would stop very short. The Mooney braking is weaker and the apeeds involved are higher. You have to really really control your landing approach, speed, and have an early touchdown point. The brakes aren't going to salvage a long/fast landing for you like they might in other planes. I don't really feel this to be an issue now, but definitely an observation I made while switching to Mooney. New tires and brake work hasn't changed my mind.

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Don't use them very much, but when I do they tend to perform very well. First time I had the opportunity to use them after I got the plane, I just about locked them up. They are as good or better than the ones on my prior 172.

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Yeah, I've found braking action in other planes to be much stronger. The Arrow I used to rent would stop very short. The Mooney braking is weaker and the apeeds involved are higher. You have to really really control your landing approach, speed, and have an early touchdown point. The brakes aren't going to salvage a long/fast landing for you like they might in other planes. I don't really feel this to be an issue now, but definitely an observation I made while switching to Mooney. New tires and brake work hasn't changed my mind.

Owning the same plane for the past 24 years, I have done my fair share of landings with brakes & tires in various conditions. It's all about the same.

I found by trying to use as much aerodynamic braking as I can muster, it helps a bit. In extreme cases, heaven forbid (I know I am going to the Mooney penalty box for saying this), I do retract the flaps to get more weight on the wheels on the roll out.

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One other comment on the brakes. There is a break-in procedure for them. If you don't break them in correctly, you will notice it. Ask me how I know

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6 hours ago, Shadrach said:

Is it at all speeds? Do they lock?  If everything has been properly reassembled during the rebuild, It's likely not the condition or capability of the brakes that's an issue. It's more likely the speed at which they are being applied. 172s are less affected by ground effect and far more tolerant of airspeed variations at touchdown. The next time you land, pull the yoke back before braking. If the plane still wants to fly, you're too fast. I don't know how long you've had your Mooney, but it's not uncommon for transitioning pilots to "fly it on" smoothly and then apply the brakes to wheels that have very little weight on them. 

I have about 100 hours on this Mooney in the last three months. Coming in at 75-80 MPH depending on runway length. The A&P that I was working

with did the break in process. Just seems like I can stand on the brakes and couldn't lock them up if I tried. 

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Hmmh.

I have to watch how hard I hit the brakes.  I somehow manage to flat spot one or two tires a year getting too enthusiastic about turning off early.

There is a difference in braking when you land at 80-85 vs. the Skyhawk's 60 something. 

I didn't like the breaking on the 172's I flew.  "Cessna shimmy."  You had to be sure to hold back pressure on the yoke because the nose gear would start to shake.

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My K has been with me for 75 hours worth and a few months and I was initially surprised at the braking power as compared to the old Arrow and 172's I flew previously.... I had them looked at and was told they were fine. Guess they just don't have the stopping power I have felt before. I fly in at 75-80 knots on short final and easily get off runway quick but braking power is not as strong as I was used to.... You'll get used to it though. I haven't had any issues thus far just a characteristic of the plane.

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1 hour ago, Joe Larussa said:

I have about 100 hours on this Mooney in the last three months. Coming in at 75-80 MPH depending on runway length. The A&P that I was working

with did the break in process. Just seems like I can stand on the brakes and couldn't lock them up if I tried. 

Something is wrong then. You should always be able to lock your brakes (though there is almost no good reason to do so). Do they feel spongy? Have you tried a static run-up? 

Also, 75-80mph over the numbers is a little on the fast side unless you're at typical max gross (2740lbs.)

 

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Summary of the good ideas provided here...

1) Air bubbles in the line give the spongy feeling and poor braking.

2) Bubbles are a challenge to get out. Yetti gave a nice rendition of a procedure that works.

3) Break in of discs and pads is important to avoid glazing. Ross gave an excellent copy of a procedure for testing how well the system is working.

4) Increased braking effect is best achieved using aerodynamic braking of the elevator at higher speeds.

5) Braking while the wings are still providing lift may lock the brakes and flat spot the tires. If you lock the brakes, it is possible to let up and reapply.  As PIC, you get to decide your tire's and your ship's fate.

6) Marauder has pointed out a good way to end a 24year long winning streak. :)  Raising the flaps and using speed brakes can increase the load on the tires by removing the lift from the wings.  It can also prove that an ordinary person under an elevated cognitive load can make a rushed action that does not match his intention.  This is where the pilot hits the gear lever instead of the flap lever. They call this error a 'distraction'.

7) Slow before landing. You know you have done well when the stall warning has gone off as the tire's hit the ground. No stall warning, is probably flying onto he runway. Or the stall warning is not working properly (I've had both).

8) Other planes may at least seem to be different.

9) Light Mooneys will stop much better than heavy Mooneys.

10) Personal performance can be measured by how much braking is needed at your home drome. There is nothing like landing softly at the right speed, the stall warning chirped briefly, the elevator helps slow the plane and the halfway point is still aways out...

I'm just jealous of Marauder's and most other people's cognitive skills. :)

Let me know if I missed or messed something.

Best regards,

-a-

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I've had my K for a few months now and the brakes suck in comparison to my old C. I had the master cylinders rebuilt and bled and it's better but not a ton. I've just attributed it to the weight difference.

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9 hours ago, OR75 said:

Mooney brakes are a pain to bleed, particularly if you have dual breaks. Affects breaking strength 

It panes me to no that your breaks aren't breaking well!

Clarence

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8 hours ago, Zwaustin said:

My K has been with me for 75 hours worth and a few months and I was initially surprised at the braking power as compared to the old Arrow and 172's I flew previously.... I had them looked at and was told they were fine. Guess they just don't have the stopping power I have felt before. I fly in at 75-80 knots on short final and easily get off runway quick but braking power is not as strong as I was used to.... You'll get used to it though. I haven't had any issues thus far just a characteristic of the plane.

Hey Zach, It's the same with my 231.  I really don't know how folks flat spot tires unless they are landing with the breaks already locked up.  That said,  I have been able to lock the breaks up, but it's not easy.    I have also found is one quick pump of the breaks helps with stopping power.

Oh, and if you think it doesn't stop well now, wait till you put new pads on it.  The first stop or two will be not be sudden!

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