I want better/more brakes

[1980Mooney]

2 hours ago, aviatoreb said:

When I was at Oshkosh a number of years ago - Beringer was promising an STC for Mooney - the more modern looking red anodized stuff - but now browsing Beringer's website I see no such STC.  I think there was a discussion on this forum on it at some point.

Not surprised. There is no profit if designing, STCing and tooling up for a shrinking fleet/market. WYSIWYG. Be happy with what you have….

Edited June 10, 2023 by 1980Mooney

[Aerodon]

7 hours ago, Niko182 said:

I think so. I took @Aerodon 's comment on the first page. I believe @Aerodon, @gsxrpilot and @Parker_Woodruff have all done encore conversion. Paul isn't on here anymore but the other 2 are so they might be able to give you more solid details.

  

 

 

The Encore brakes are the Bravo and on brakes, spindles, master's.  My Encore mod parts came from a M20M, part numbers matched the Encore parts list.

Rumour has it that when Mooney produced the Encore in 1996, they just took the then current brake system, aileron, rudder, elevator balance weights and used it on the Encore.  The brakes were probably necessary for the higher gross weight, but I don't think the balance weights are?  No change in V speeds.

There is also a SB that applies to the inner gear doors to add a door stop to the M20M's and on.  Mooney didn't apply this mod to the Encore, but given the problems that some have had with the inner gear doors links, it seems like a smart idea.

The 252 is still an M20K, so it is less of a major modification than say asking someone to sign out installing M20M into M20K parts.  Also, there is a drawing package available, so there is some solid data to use in a 337.

But don't underestimate the cost of doing all of this.  There is a lot of labor and expensive parts.

Yes BAS have a set of gear legs, I tried asking if they would take the spindles off and they declined.  But the whole gear legs are less than factory spindles.

Aerodon

 

 

 

 

 

 

 

 

[Aerodon]

3 hours ago, 1980Mooney said:

Long body spindle assemblies won’t work

520002-501

Not true, they are the same except for the location of the mounting holes for the brakes.  I have heard the suggestion that you can just re-drill the mounting holes to accommodate the aft mounted calipers, but that is below my standard.  

And the lower gear legs are heat treated, so a well known welding shop declined to modify my standard gear legs.

I think it is a worthwhile mod for Erik to do to his 3200lb Rocket.  

Aerodon

[1980Mooney]

54 minutes ago, Aerodon said:

Not true, they are the same except for the location of the mounting holes for the brakes.  I have heard the suggestion that you can just re-drill the mounting holes to accommodate the aft mounted calipers, but that is below my standard.  

And the lower gear legs are heat treated, so a well known welding shop declined to modify my standard gear legs.

I think it is a worthwhile mod for Erik to do to his 3200lb Rocket.  

Aerodon

Thanks for the insight and correcting my assumptions. You have obviously been investigating and at this for a long time. Did you successfully make the switch to the dual cylinder brakes?  I wasn’t sure when you said that, you asked BAS if they would sell you the spindles separate from the entire gear and they declined and you said the welding shop would not work on the spindles. Also you talk about the inner gear door but if someone just wants improved brakes is the inner gear door required?
 

 

[kortopates]

Thanks for the insight and correcting my assumptions. You have obviously been investigating and at this for a long time. Did you successfully make the switch to the dual cylinder brakes?  I wasn’t sure when you said that, you asked BAS if they would sell you the spindles separate from the entire gear and they declined and you said the welding shop would not work on the spindles. Also you talk about the inner gear door but if someone just wants improved brakes is the inner gear door required?
 
 

Yes, two inner doors are required on both sides to clear the bigger calipers.


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[1980Mooney]

13 hours ago, 1980Mooney said:

No. You can’t “just put Bravo brakes on a M20K”. Because the dual puck assembly has different geometry and mounting points, the Encore uses a different spindle assembly (lower gear leg) than the M20K. And the Bravo has a different spindle  than the Encore because long bodies sit differently than mid bodies. So some of the parts are the same and some of the parts are different. Look at your parts manuals. I think those spindles are chrome, Molly heat treated so that you cannot make any modifications – you need to find the correct part.

@aviatoreb well based on the last post by @Aerodon maybe the Bravo parts do work. I don’t have a m20m parts manual to check. However I still don’t understand why inner doors are needed. The current doors leave a small gap and portion of the tire exposed. 

[donkaye]

The original Bravo brakes thru serial number 27-106 were 2 puck just like the 201.  My serial number is the 27-106 so I had the 2 puck system.  The plane at gross weighs 623 pounds more than the 201.  The 2 puck system was really inadequate.  In the beginning of ownership, even treating the brakes gently, I had to replace the pucks every 73 hours.  I still thought it was cheaper than buying the 4 puck brake kit at about $4,500.  By 2016 labor rates and fuel prices had gone up so much that I revisited doing the brake update.  The kit cost had increased to $8,000.  I decided to do it anyway.  Lead time from Mooney at the time was 6 weeks and they required upfront payment at time of shipping.  Included in the kit were new axels and gear doors that needed to be fit.  Labor was 20 hours.  Total cost in May of 2016 was $10,353.81 and that include a 10% discount on the parts.  The new brake pucks now need to be replaced about once a year.

One other VERY IMPORTANT thing; you need the gear door stops discussed above.  Failure to have them installed will result in multiple broken costly rods over time.  They were NOT included in the kit and I spent an untold amount of money replacing rods over the next couple of years.  My maintenance facility tried their best to figure out why the rods kept breaking.  Finally with their approval last year, I flew down to Kerville and had Mike Knesse look at it.  They found the problem in a couple of minutes because they still had a mechanic working there from 30 years before.  The issue arose when Mooney went to the 4 puck system on the Ovation and were having many broken rods.  The fix was adding the door stops to prevent the inner gear door from extending past vertical and thereby being exposed to excessive loads on retraction.  They even had a Service Bulletin about it, but being 30 years old, it wasn't obvious to my service center that it existed.  Luckily, Mooney still had a couple of them, and since being installed I've never had an issue with broken rods.

[A64Pilot]

No disrespect, but I can’t imagine what your doing to chew up brakes every 73 hours.

For me brakes last as long as tires, If I had to guess at least 200 hours or so and almost all my flights are less than an hour. I really don’t know, but years.

But then I rarely use them and when I do it’s usually less than 20 kts or so.

I did the first flight on a few hundred aircraft, so I know if you don’t properly “season” pads your braking is poor and you chew through pads, in seasoning as strange as it sounds what your doing is depositing a layer of pad material on the rotors, this apparently greatly increases friction and therefore braking effectiveness.

https://www.univair.com/content/cblcp.pdf

But judging on the number of flat spotted tires my guess is we have more than enough brakes. What we could use I think is an anti-lock system, but I wouldn’t pay for one myself.

Brake up grades usually to double puck from single puck are common, usually for running Bush Wheels. The STC to put 29” tires on my Maule required double pucks, because of course the big ole tires travel probably five times as far per revolution than little tires, so much more brake is needed. 

[donkaye]

38 minutes ago, A64Pilot said:

No disrespect, but I can’t imagine what your doing to chew up brakes every 73 hours.

For me brakes last as long as tires, If I had to guess at least 200 hours or so and almost all my flights are less than an hour. I really don’t know, but years.

But then I rarely use them and when I do it’s usually less than 20 kts or so.

I did the first flight on a few hundred aircraft, so I know if you don’t properly “season” pads your braking is poor and you chew through pads, in seasoning as strange as it sounds what your doing is depositing a layer of pad material on the rotors, this apparently greatly increases friction and therefore braking effectiveness.

https://www.univair.com/content/cblcp.pdf

But judging on the number of flat spotted tires my guess is we have more than enough brakes. What we could use I think is an anti-lock system, but I wouldn’t pay for one myself.

Brake up grades usually to double puck from single puck are common, usually for running Bush Wheels. The STC to put 29” tires on my Maule required double pucks, because of course the big ole tires travel probably five times as far per revolution than little tires, so much more brake is needed. 

I always "condition" new brakes.  73 hours also surprised me, but that's what it was.  Remember, with nearly 25% more mass than the J model a lot more energy needs to be dissipated in the Bravo as opposed to the J.  J brakes on a Bravo didn't work so the brake system was improved from 27-107 onward.  The new braking system was worth it to me.  I should have done it sooner.

[Aerodon]

7 hours ago, 1980Mooney said:

@aviatoreb well based on the last post by @Aerodon maybe the Bravo parts do work. I don’t have a m20m parts manual to check. However I still don’t understand why inner doors are needed. The current doors leave a small gap and portion of the tire exposed. 

I think there is confusion around the definition of inner doors.  An older M20K has 2 gear doors on each side, outboard on the wing and one on the gear leg.  So on an older M20K terms, the lower door is the inner door.

The 252 and Encore have an inboard gear door attached to the wing to close the remaining gap when the gear is retracted.  This needs to be replace if doing the Encore mod, but if its not there in the first place.....

Attached is an image of all 3 doors - showing the bulge that covers the double puck brakes.

Also a picture of the inner door open - I think the earlier M20K's have a fixed panel that mostly closes the hole.

Aerodon

 

 

 

[Aerodon]

13 hours ago, 1980Mooney said:

Thanks for the insight and correcting my assumptions. You have obviously been investigating and at this for a long time. Did you successfully make the switch to the dual cylinder brakes?  I wasn’t sure when you said that, you asked BAS if they would sell you the spindles separate from the entire gear and they declined and you said the welding shop would not work on the spindles. Also you talk about the inner gear door but if someone just wants improved brakes is the inner gear door required?
 

 

Yes I did, I found the parts of a M20R.  Had to buy more than I wanted, but have successfully sold most of the remaining components.

Aerodon

 

 

[1980Mooney]

On 6/10/2023 at 12:50 PM, Niko182 said:

If you are looking for changing brakes, BAS has a totaled Bravo that they parted out. might want to check if they still have the calipers, and the full brake system.

Yes BAS have a Bravo - S/N: 27-0043.  As @LANCECASPER pointed out anything with serial number 27-0107 or below has the single cylinder brakes (2 puck same as typical M20K - excluding Encore).  520022-504 is the same as what @aviatoreb already has on his plane.

520022-504 Mooney M20M Main Gear Assy RH (baspartsales.com)

[Pinecone]

On 6/10/2023 at 11:34 AM, EricJ said:

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.

Difference is about 30% in stopping distance.

You still need to generate enough brake torque to get over the point of maximum friction to get them to lock.

But, if a Mooney cannot lock the brakes one weight is fully on the tires, then yes, there is room for improvement.

[Pinecone]

On 6/10/2023 at 11:56 AM, Aerodon said:

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

 

As I understand the Encore upgrade to a 252 (the drawing is available online) there is a change in the master cylinders with the brake upgrade.

[kortopates]

 
As I understand the Encore upgrade to a 252 (the drawing is available online) there is a change in the master cylinders with the brake upgrade.

Yes, larger capacity for the larger capacity calipers. The entire brake system is replaced except for the parking brake.


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[EricJ]

32 minutes ago, Pinecone said:

Difference is about 30% in stopping distance.

Depends highly on the tire compound, the pavement surface, and the pad compound, and some other things. 

32 minutes ago, Pinecone said:

You still need to generate enough brake torque to get over the point of maximum friction to get them to lock.

You only need to do it momentarily, just enough to lock the wheel, which means you only need good initial cold bite (attack) of the pad compound and hardly any thermal capacity or performance at high temperature.   After that the wheel is locked and all it has to do it hold static friction at the rotor sufficient to overcome the torque from the sliding friction of the tire on the surface.   The brake itself won't get hot at all, because it's not dissipating any of the energy.   In other words, it can be a really, really crappy brake system, but as long as it has reasonable initial cold bite it can lock a wheel.   If you settle for that, you may be settling for a really, really crappy brake system. 

[Aerodon]

1 hour ago, 1980Mooney said:

Yes BAS have a Bravo - S/N: 27-0043.  As @LANCECASPER pointed out anything with serial number 27-0107 or below has the single cylinder brakes (2 puck same as typical M20K - excluding Encore).  520022-504 is the same as what @aviatoreb already has on his plane.

520022-504 Mooney M20M Main Gear Assy RH (baspartsales.com)

Good catch, that is probably not the correct lower spindle.  Slight chance they may have upgraded.  I have my old spindles handy will take a picture.

Aerodon

 

 

[A64Pilot]

2 hours ago, EricJ said:

Depends highly on the tire compound, the pavement surface, and the pad compound, and some other things. 

You only need to do it momentarily, just enough to lock the wheel, which means you only need good initial cold bite (attack) of the pad compound and hardly any thermal capacity or performance at high temperature.   After that the wheel is locked and all it has to do it hold static friction at the rotor sufficient to overcome the torque from the sliding friction of the tire on the surface.   The brake itself won't get hot at all, because it's not dissipating any of the energy.   In other words, it can be a really, really crappy brake system, but as long as it has reasonable initial cold bite it can lock a wheel.   If you settle for that, you may be settling for a really, really crappy brake system. 

Yes, but, there is always a but. Aircraft brakes are pretty much one use from a thermal perspective. If you’re really heating up your brakes, you might should evaluate your brake use. I maintain that except for rare circumstances there is very little need to use the brakes anything but very lightly, and again except for a rare circumstance they should never get very hot. It’s not like we are doing multiple maximum braking repeatedly, if we were then we would have car sized brakes, or at least ventilated disks.

The actual limit on braking is actually how much energy the disk can absorb, it’s not swept area of the pads, more pad swept area could reduce the amount of force required on the pedal and increase holding power at zero speed, but again based on how often I’ve seen flat spots on Mooney tires I suspect that power brakes aren’t needed.

From an automotive perspective airplanes have exceedingly crappy brakes, you shouldn’t expect auto brake performance from an airplane.

Yes I know brakes can be burnt up, I’ve seen very close to a brake fire on a crop duster, from a DER that didn’t know what they were doing. But that was not normal use.

The only brake requirement, or at least the only flight test check point for FAA on brakes is if they can hold the aircraft at T/O power, there is no have to do multiple stops from high speed etc.

Just curious for those that do, why are you using the brakes hard?

 

[EricJ]

6 minutes ago, bluehighwayflyer said:

It’s too bad no one has a drag chute STC for Mooneys.  It sounds like some of you guys could really use it, and how cool would that look when you are taxiing in?  Especially Erik with that four blade prop and checkerboard paint job.  

My Dad was a KC-135 pilot and I remember as a kid having family picnics on base when he was on alert.  It was a joint SAC/TAC base and the F-4s popping their chutes after landing was bad ass!   

We were stationed at Bergstrom AFB in Austin (now Austin International) when I was in 6-7th grade, which at the time was a TAC base with F-4s.   There was a spot at the end of the runway that we could get to on our bikes to watch the F-4s and everything else take off and land.   The chutes were cool.

[Pinecone]

16 hours ago, EricJ said:

Depends highly on the tire compound, the pavement surface, and the pad compound, and some other things. 

You only need to do it momentarily, just enough to lock the wheel, which means you only need good initial cold bite (attack) of the pad compound and hardly any thermal capacity or performance at high temperature.   After that the wheel is locked and all it has to do it hold static friction at the rotor sufficient to overcome the torque from the sliding friction of the tire on the surface.   The brake itself won't get hot at all, because it's not dissipating any of the energy.   In other words, it can be a really, really crappy brake system, but as long as it has reasonable initial cold bite it can lock a wheel.   If you settle for that, you may be settling for a really, really crappy brake system. 

Actually not.  It is close to 30% difference in stopping distance between sliding tires and maximum braking with the tires turning about 15% slower than the travel speed.

I was teaching a safe driving class and made this statement.  3 guys got in a MASSIVE argument (in Ukrainian, so I could not follow).  All of a sudden, then stopped arguing and sat down.  I asked the guy translating (a PhD physicist) what the argument was about and what was the resolution.  So he asks.  One guy stands up and said something and sits down.  The guy translating is almost laughing.  He say, not to worry, the 3 guy arguing were also PhD physicists.  And they decided that while the 30% number was not precisely correct, it was close enough for the class to illustrate why ABS or modulating the brakes is better.

Again, we do not have multiple stops, so heat is not a huge issue.  Unless you taxi dragging the brakes then abort the takeoff.  Most any pad will give you enough bit to maintain braking for one stop from speed.  And with out airplanes, we are talking about 3000 or so pounds from maybe 80 knots.  Even cheap street car OEM pads will handle a 4000 car at 1.5x that speed for one stop.

[EricJ]

2 hours ago, Pinecone said:

Actually not.  It is close to 30% difference in stopping distance between sliding tires and maximum braking with the tires turning about 15% slower than the travel speed.

Non-skidding minimum stopping distance can vary a lot based on the pad compound and brake configuration, so the difference between sliding friction (locked) and rolling friction braking varies a lot based on the equipment, assuming the tire compound and surface condition is the same.

Some cases of sliding friction turn into hydroplaning if the tire compound liquifies due to the sliding friction (called reverted rubber hydroplaning).    This depends on the tire compound and the road surface.    So even the sliding friction braking distance can change a lot just due to conditions, since the reverted rubber hydroplaning takes longer to stop than just sliding friction.

So, it does depend on a lot of different things.   

 

2 hours ago, Pinecone said:

Again, we do not have multiple stops, so heat is not a huge issue.  Unless you taxi dragging the brakes then abort the takeoff.  Most any pad will give you enough bit to maintain braking for one stop from speed.  And with out airplanes, we are talking about 3000 or so pounds from maybe 80 knots.  Even cheap street car OEM pads will handle a 4000 car at 1.5x that speed for one stop.

Yes, but the complaint is that for some there is not even good performance for one stop.

[Pinecone]

26 minutes ago, EricJ said:

Non-skidding minimum stopping distance can vary a lot based on the pad compound and brake configuration, so the difference between sliding friction (locked) and rolling friction braking varies a lot based on the equipment, assuming the tire compound and surface condition is the same.

Nope  It based on the tire to road juncture.  The pads and brakes have little to do with it if meets the minimum to hold the tire at 15% slower rotation that the speed.

It DOES depend on the tire compound, tire size, and pavement.   

But for the same car, with the same tires, on the same pavement, the difference between maximum effective braking and sliding is about 30%.

My M3 with 265 Max Performance tires will stop a LOT shorted than the family minivan.  But both will add about 30% of the ABS fails and the tires lock.

[EricJ]

21 minutes ago, Pinecone said:

Nope  It based on the tire to road juncture.  The pads and brakes have little to do with it if meets the minimum to hold the tire at 15% slower rotation that the speed.

i.e., Rolling friction, or grip, which is temperature dependent for tire compounds.   The interaction between being able to maintain maximum braking torque between the road interface and the pad/rotor interface is a bit complex.    They both generate heat and both react to heat.   If the tire is the limiting factor then, yes, it will be the limiting factor.   It sometimes isn't, which is to the case in point.

21 minutes ago, Pinecone said:

It DOES depend on the tire compound, tire size, and pavement.   

Which doesn't change during a braking event.

21 minutes ago, Pinecone said:

But for the same car, with the same tires, on the same pavement, the difference between maximum effective braking and sliding is about 30%.

Very roughly.    The arguing PhDs in your story realized that there are many factors that affect it, widely.    It is demonstrable.

21 minutes ago, Pinecone said:

My M3 with 265 Max Performance tires will stop a LOT shorted than the family minivan.  But both will add about 30% of the ABS fails and the tires lock.

Roughly.   I've done brake swaps on several race/track cars to improve performance when the existing brakes were limiting and the performance differences can be very, very big.   Even with the same tire/wheel combos, brakes can make a huge difference, even in one cold initial braking event.   The ability to quickly get to and maintain maximum braking effort across the temperature profiles generated at the tire surface and the rotor surface during the braking event can make a significant difference.  An insufficient brake system may not be able to generate sufficient heat, or continue to generate optimal torque as the heat increases, or a number of things that may not be optimal.   The difference between a more optimal system and a suboptimal system, on the same tires and wheels and surface, can be significant.   It is demonstrable, and it is why vehicles that need high braking performance have brakes that differ significantly from more plebian applications.

In the case in point it is also demonstrable that some GA airplanes with similar, but different, braking systems have significantly different braking capability even with similar landing speeds and weights.  Matching pads/rotors/caliper pistons/and master cylinders is not always done optimally, and given the limited variations in the field for GA airplanes, I think the parts bin combination selected for Mooneys, at least the J and K models, was not nearly as good as it could have been.   It has been opined, and I think a realistic possibility, that a master cylinder change would make a positive difference, but I haven't looked into details.    There are very limited pad and rotor options for small GA airplanes, so properly matching the master cylinder and caliper pistons becomes more important.   I think for some Mooney models the engineering tradeoffs didn't favor optimizing performance.

[A64Pilot]

There is one really huge difference between Auto’s and Mooney’s.

An Auto at 70 MPH will have about the same braking effectiveness as it does st 30 MPH.

A Mooney will have very little effective braking at 70 MPH and its braking effectiveness increases rapidly with decreasing speed due of course to loss of lift. 

So I maintain that braking especially at high speed is very difficult in an airplane, it’s really tough to modulate the brakes to be just before the lock up point, so it’s very common to flat spot a tire if you brake hard, not wanting to flat spot tires, I don’t brake hard.

As I fly so much off of grass where there isn’t nearly as much braking force as pavement it’s just become second nature to not rely on brakes, but also you don’t flat spot on grass either. Dew wet grass has about as much friction as ice.

[Pinecone]

Track/race cars have to deal with multiple hard braking events.   Airplanes don't.   

The reason you need to upgrade brakes on track/race cars is that stock car braking systems are not designed to deal with multiple hard braking events.  Which builds up heat, LOTS of heat.   As I stated before, my car with a pretty stock brake system (but a good one) I could boil 600 degree boiling point fluid.  But that occurred after getting off the track.  The easy fix was to drive around slowly for about 5 minutes to dissipate the extra heat

The initial cold bit is based on the brake pad compound, but good cold bite tends to loose performance when hot.