Hi Dennis,

It seems there's more to the story after further inspection. It looks like the overheating/brake melting may have also led to hydraulic failure. At first I though that the state in which the right brake assembly was left was due to the right wheel collapsing and dragging the assembly through the impact on the ground down the embankment (assembly is on the front of the wheel - towards the nose of the aircraft). But the more I think about it, the more likely it seems that hydraulic failure followed brake melting before impact.

Attached is a picture of the right brake assembly. I drew a few colored lines on it including one long pink horizontal that shows how much the inner brake mounting plate bent. As I've mentioned before, this is the part that is fixed to the leg and it seems that it gave way in the direction of the piston (which is why i think it bent while braking instead of at impact). You can see that the rear side of the piston and o-ring is completely inside the cylinder but the o-ring on the front side has popped out resulting in a leak.

From what I can tell, it seems that those springs on the bolts, which are compressed fully in the picture, are too long to allow for brake wear. It seems that it lost hydraulic pressure after the piston travelled further than designed to by pushing and bending the mounting plate in the center. The length of that piston doesn't have enough margin of safety to take into account a mounting plate failure in the center. As the brakes melted and wore through, the plate collapsed with the pressure of the piston.

So in addition to the improvements mentioned in the previous email...
1) the springs need to be shorter to allow full brake wear
2) the piston needs to be longer (like on my hangarmate's grumman where it seems to be 2-3 times as long)
3) the mounting plate needs to be thick enough and be designed in a way that doesn't collapse in the center (and in my opinion shouldn't be fixed on the leg as mentioned in my previous email)...
4) since the plate flexes on the leg, the piston failed on the outside (radially) as expected... a non-squared piston in a cylinder is dangerous in my opinion even if the piston were long enough... so in my opinion, i'd change the design and get rid of the flexing plate concept altogether to keep everything square

Anyway, my revised conclusion is:
Brake pads/rotors overheated which led to pads melting.... melted pads resulted in significantly diminished/lost(?) braking and excessive (full) pad wear... then because of the pressures on the design, the mounting plate collapsed (right wheel only) which gave way to the overextending piston and rupturing the o-ring... with the o-ring ruptured, hydraulic pressure was lost on both brakes.

Roger
N522RJ