Gary,

 

While I agree whole heartedly with your conclusion that the combination of holes and slots in a rotor is redundant and that neither is probably needed on an aircraft, your assertion that race cars generally use organic pads is at odds with my experience. Perhaps things have changed in the past few years, but back when I was driving fast and turning left (yes, terrible lizards still ruled the earth then) full metalic pads ruled the day in long races on road coarses and short oval  tracks. In shorter events like the local Saturday night stock car race, semi-metalic pads were typical as the races didn't last long enough between caution for the brakes to get really hot.

 

Once the brakes heated up in a longer race, organic and even semimetalic pads would lose a great deal of their effectiveness. Slots or holes greatly helped, but full metalic pads were the only thing that really worked well once hot. The big drawback with full metalic pads is that they hardly worked at all when cool. If you didn't scrub them a little before the race started, the first corner entry could be a little hairy to say the least.

 

You are right that the heat transfer through full metalic pads is much higher and needs to be addressed to prevent the brake fluid from boiling. This could also make life interesting midway in the race when you applied brake entering a corner and locked up the wheels. Things got even more interesting after you lifted your foot from the pedal and the boiling fluid just expanded, keeping the brakes locked. At that point, it was time introduce yourself to the retaining wall.

 

I have heard a lot about carbon brake pads the past few years and have heard they are being used in racing aplications these days, as well as carbon rotors. I have used carbon pads on my street cars for some time now, but have no experience with them on the track.

 

Another thing to keep in mind with drilled rotors (and to a lesser degree slotted rotors as well) is that the holes lower the thermal mass of the rotor. This causes the rotor to heat up faster under the same heat input. Yes, the rotor will work better once it is heated, but it will heat up more quickly. Also, unless the brakes are over heating, adding holes and/or slotts will not make them any more effective.

 

Just my two cent worth,

 

Rob