I want better/more brakes

[aviatoreb]

The brakes on my M20K are barely sufficient I feel.  I wish I could have more kick-ass brakes.  This is not a chronic problem - just something I wish.

I remember once talking with Bennet (who sadly has left us), that he once had a M20k where he had Lasar install a second set of brakes on field approval so that he had double brakes.  I wish I had that!

Has anyone done anything to improve brakes like double brakes like Bennet, or otherwise some kind of more beefy brake set?  Field approval?  Or is there some kind of STC out there I am unaware of?

[KSMooniac]

Upgrading a 252 to the Encore config requires upgraded brakes due to the higher gross weight. It seems like that would be a reasonable path for a minor mod or a field approval since it would be using all Mooney parts.

Sent from my LM-V600 using Tapatalk

[Aerodon]

24 minutes ago, aviatoreb said:

The brakes on my M20K are barely sufficient I feel.  I wish I could have more kick-ass brakes.  This is not a chronic problem - just something I wish.

I remember once talking with Bennet (who sadly has left us), that he once had a M20k where he had Lasar install a second set of brakes on field approval so that he had double brakes.  I wish I had that!

Has anyone done anything to improve brakes like double brakes like Bennet, or otherwise some kind of more beefy brake set?  Field approval?  Or is there some kind of STC out there I am unaware of?

The ‘Encore’ mod to a 252 installs ‘Bravo’ double cylinder calipers to replace the single cylinder calipers and that probably comes close to doubling the braking friction. 

there are quite a few changes - new master cylinders, new lower gear legs and new doors.  New disks, new calipers. Probably $10k in parts now, but used ones are available from time to time.

No STC that I am aware of, but you may persuade someone to get field approval?

Aerodon

 

 

 

[EricJ]

I keep hearing that there's a difference between the Rapco and Cleveland pads, with the Cleveland being superior.    I've only ever run the Cleveland pads, so I don't know personally.    That said, the stock brakes with the cleveland pads aren't anything to write home about, either.     I'd like better brakes as well, but I think the significant re-engineering effort is probably not worth it.

 

[N201MKTurbo]

I try not to use brakes on the runway and rarely need to, but I do know that with my 2700 Lb. airplane, I can skid the tires any time I want. Without more weight on the tires, I'm not sure what more brakes will get you.

[Pinecone]

THIS ^^^^^

The limiting factor is the friction between the tire and the runway.  If you can skid the tire, more brakes will not do a thing.

If you can't skid the tire, there is something wrong with your brakes, probably some air in the system.

[EricJ]

7 minutes ago, N201MKTurbo said:

I try not to use brakes on the runway and rarely need to, but I do know that with my 2700 Lb. airplane, I can skid the tires any time I want. Without more weight on the tires, I'm not sure what more brakes will get you.

That's a common misconception about the function of brakes.   People say this when trying to turn a street car into a race car, too, "It'll lock the wheels, what more do I need?"

Many crappy brake sets will lock the wheels, but what they really need to be able to do is efficiently convert kinetic energy into heat very quickly.   That's a good brake, and it takes a lot of attention into materials and heat management to do it.    Many GA airplane brakes are small, so that they're light, but it also means there's not much mass to sink and dissipate heat.   They're often also small diameter, which means less opportunity for braking torque, which means you need better pad and rotor friction.   GA brakes tend to be steel rather than iron, which helps longevity and weight, but detracts from braking capability.

So we start out with the deck stacked against us, but that said most other small airplanes have much better braking capability than Mooneys.   I've not looked closely enough to know what the actual differences are that matter, but I'm curious about it.

[Schllc]

While the technology could be better, I agree with some of the later posts. 
I’ve never run out of brake in my plane, but it is easy to skid a tire if you aren’t conscious. 
I have put a full gross acclaim down on a 2400’ runway, zero displaced threshold and water on both ends of the runway, without having to crush my brakes. 
if you’re needing that much brake power, you way want to look at your approach speed?

in the event that sounds critical, please know that was NOT my intention!

 

[N201MKTurbo]

20 minutes ago, EricJ said:

That's a common misconception about the function of brakes.   People say this when trying to turn a street car into a race car, too, "It'll lock the wheels, what more do I need?"

Many crappy brake sets will lock the wheels, but what they really need to be able to do is efficiently convert kinetic energy into heat very quickly.   That's a good brake, and it takes a lot of attention into materials and heat management to do it.    Many GA airplane brakes are small, so that they're light, but it also means there's not much mass to sink and dissipate heat.   They're often also small diameter, which means less opportunity for braking torque, which means you need better pad and rotor friction.   GA brakes tend to be steel rather than iron, which helps longevity and weight, but detracts from braking capability.

So we start out with the deck stacked against us, but that said most other small airplanes have much better braking capability than Mooneys.   I've not looked closely enough to know what the actual differences are that matter, but I'm curious about it.

Well, OK. but a race car needs to brake continuously over the whole race. most brakes will overheat very quickly doing that. The pads won't bite very hard on white hot disks. Not sure exactly what that mechanism is, but I understand it is true. The airplane has a single braking event that doesn't last all that long. I don't recall ever having an airplane brake fade from overheating.

[N201MKTurbo]

I wonder if y'all with weak brakes have conditioned them properly? It makes a big diference.

 

liningconditioningprocess.pdf

[KSMooniac]

CIrrus and other similar planes without nosewheel steering have had some brake issues (and fires!) in the wild, but that shouldn't be an issue for Mooneys.  

[PT20J]

If you don’t like your brakes, fly a twin Beech for a while. Your brakes will seem much better afterwards 

[N201MKTurbo]

1 hour ago, KSMooniac said:

CIrrus and other similar planes without nosewheel steering have had some brake issues (and fires!) in the wild, but that shouldn't be an issue for Mooneys.  

If the Cirrus is going too fast, can't you just pull the parachute to slow it down? 

[EricJ]

4 hours ago, N201MKTurbo said:

Well, OK. but a race car needs to brake continuously over the whole race. most brakes will overheat very quickly doing that. The pads won't bite very hard on white hot disks. Not sure exactly what that mechanism is, but I understand it is true. The airplane has a single braking event that doesn't last all that long. I don't recall ever having an airplane brake fade from overheating.

It's just material tradeoffs and picking materials and mechanical bits that do what you need.   Ideally aircraft brakes get more time to cool between braking events and are expected to work well when cold, so the heat management tradeoffs can be made with different assumptions, but their purpose is still to convert kinetic energy to heat.   If they're not efficient at that, they don't slow the airplane down very well.   I think that's what we're up against.    So many other small airplanes brake so much better, it's appears to just have been suboptimal design tradeoffs as far as braking performance goes.

Race brakes work better as they get hot.    At the beginning of a lap/session/race you have to be careful about diminished performance due to insufficient heat in the brakes (and tires).   You can overheat them as well, but that's actually a little easier to engineer around.   Street car brakes need to work well cold, and the same is true with GA airplane brakes and most do.   Not so much on a Mooney, though.   How to do the engineering is pretty well known, we just didn't get a very good system.   It's not really too surprising to me.

[aviatoreb]

Thanks for all the information.

Yes - yes - just fly the approach more on speed and I will never need brakes.  Yada yada - 

Yes I have landed on sheer ice so slick I didn't use any brakes at all - and the most dangerous part of that flight was the walk from the airplane to the FBO without falling down.

But a plane should not have crappy brakes.

Good brakes would require discipline to apply successively more pressure on landing roll out so as not to skid the wheels before the weight is on the wheels.  But that is not an excuse to just have crappy brakes.

I just go the plane out of annual with new pads and brakes bled funny - so the braking action was poor - which got me thinking - but even in top form my brakes are not excellent.  They should be excellent. Why aren't they excellent.

Do I really need to do the whole Encore mod thing to get the Bravo style better brakes - or can I just do part of that mod for just the brakes?

Or surely there is some other brake set out there and a friendly field approval.... :-/

[Hank]

20 minutes ago, aviatoreb said:

Yes - yes - just fly the approach more on speed and I will never need brakes.  Yada yada - 

. . . .

Good brakes would require discipline to apply successively more pressure on landing roll out so as not to skid the wheels before the weight is on the wheels.

Once the nose wheel comes down, I reach out a finger and raise the flaps without letting go of the throttle. This puts more weight on the wheels right away. Then I wait and don't brake until below 50 on rollout. This worked well the seven years I was based at an obstructed 3000' field, and I rarely go anywhere shorter except for the occasional grass field (which slows the plane much faster than asphalt or concrete).

[N201MKTurbo]

I’ve never thought my brakes were lacking.

[Pinecone]

15 hours ago, EricJ said:

That's a common misconception about the function of brakes.   People say this when trying to turn a street car into a race car, too, "It'll lock the wheels, what more do I need?"

Many crappy brake sets will lock the wheels, but what they really need to be able to do is efficiently convert kinetic energy into heat very quickly.   That's a good brake, and it takes a lot of attention into materials and heat management to do it.    Many GA airplane brakes are small, so that they're light, but it also means there's not much mass to sink and dissipate heat.   They're often also small diameter, which means less opportunity for braking torque, which means you need better pad and rotor friction.   GA brakes tend to be steel rather than iron, which helps longevity and weight, but detracts from braking capability.

So we start out with the deck stacked against us, but that said most other small airplanes have much better braking capability than Mooneys.   I've not looked closely enough to know what the actual differences are that matter, but I'm curious about it.

Car, especially for track is a different situation.  You need to brake several times a lap, lap after lap.   So you need to dissipate the heat.  The car I track weight 3400 pounds empty, so about 3700 pounds on the track.  At the local track, I am doing 145 at the end of the front straight.  A LOT of energy.  The heat buildup causes the pads to lose their friction, in some cases even melting the pad compound.  It can also boil the fluid.  My car, driven hard on the track, can boil 600 degree fluid.

There are two fairly heavy braking zones, one medium and one light.  All in less that 90 seconds.  Repeat every 90 seconds for 20 minutes.

And I still stand by, if you can lock the wheels, you have all the brakes you need.

Funny story.  Back in the 60s, Hertz had a run of Shelby GT-350s for rental cars.  In DC, the deal they had was that one of each model car would be inspected, and then all the cars of that same model would get an inspection sticker.  They took a GT-350 in, the guy inspected it, then did a test drive.  He came back and told Hertz the car failed due to the brakes.  They didn't work well.  After some head scratching, they figured out, that the high performance pads did not have good friction when cold and also required more pedal pressure.  So they arranged to use a local drag strip and took the inspector out there.  A race driver took the inspector on about 5 drag strips passes with heavy braking at the end.  No bid deal.  They they took a regular street car.  The first pass, the car stopped fine.  The second pass, it took a LOT longer to stop.  The third pass, the brakes faded to nothing and they ended up in the catch fence.  The inspector got out, and said, that they all passed, but he even wanted to ever see one of those f***n cars again in his life.

 

The issue with Mooney brakes, IMO, is the same reason they require you to be precise on speed to land.  The wing is closer to the ground, so there is more ground effect lift at touchdown, leading to less weight on the tires and less traction.

The problem is not that our brakes are weak, but they if you try to brake too hard, you will flat spot the tires.

[wombat]

All the discussion of if you *need* more brakes is interesting and may have some value, but @aviatoreb gets to decide what he does with his own plane and if he wants brakes that have generate more friction than his current ones, then I'm all for helping him accomplish his goal.

 

There are really only a few ways to increase the brake force for the same pedal force, assuming there is not any sort of mechanical failure or problem right now.

• Decrease the size of the master cylinder. 
• Increase the size of the slave cylinder.
• Increase the distance from the axle to the brake pads.
• Change the brake rotor and/or pad material to one that has more friction.

All four options are possible, although a lot of research might be needed to figure out what other parts are either already certified for install on his aircraft, or which ones might make for an easy install and either doable as a minor mod or would be an easy 337.

[Echo]

Yada yada to you too sir.

[Echo]

And blah, blah, blah...

[Echo]

I prefer to NOT spend money and add weight where it is NOT needed.  

[EricJ]

3 hours ago, Pinecone said:

And I still stand by, if you can lock the wheels, you have all the brakes you need.

It won't be close to what is available from the tire.   The static friction of a locked wheel, and the torque it presents to the brake, is far less than the torque presented by a tire near the limit of rolling friction.   The better the brake can sustain that increased torque of the higher rolling friction, the more efficient the braking will be.    Locking the brake only requires momentary application of lock-up torque to get locked, and will take much further to stop.   

I think some Mooneys won't even lock a wheel once the weight is on the wheels, which means they're giving up a lot of potential braking capability.

How much brake one "needs" depends entirely on the situation.   If the runway is wet you don't need much, because you can't use it.     If an animal or other airplane enters the runway while you're moving down it, you may need a lot more.    If what you could have isn't there, you'll miss it.

[Aerodon]

13 hours ago, aviatoreb said:

 

Do I really need to do the whole Encore mod thing to get the Bravo style better brakes - or can I just do part of that mod for just the brakes?

 

Erik,

The double puck caliber is mounted on the back of the wheel, so the mounting ring is 'mirrored' on the lower gear leg (spindle).  These are expensive, but can be found used.

Then the middle and inner gear doors don't fit. You might not have the inner door?

And I guess they change the master cylinder to change the stroke or pressure to the calibers.  

 

Don

 

 

 

 

 

[wombat]

1 hour ago, Echo said:

I prefer to NOT spend money and add weight where it is NOT needed.  

'need' is relative.  None of us 'need' an airplane to begin with.

 

Would you add a cabin speaker?