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At Bendix many years ago we built some of the first carbon-carbon brakes for aircraft. Being a car nut, of course I asked why not use them for cars. There turns out to be a good reason and it would also apply to our aircraft. On large aircraft the requirement is to make one stop and then it's allowed to wait at least 30 minutes for the brakes to cool before another takeoff is attempted. Consequently the brakes are "full-diameter" alternating stationary and rotating disks. There is very little air contact and therefore little oxidation. A car or our planes need to have significant heat transfer capability to the air so that the brakes can cool more quickly after a stop. Or in our case allow taxiing with more brake application. The rotor, being carbon, will oxidize (burn), gradually eroding itself away. Race cars don't have that problem because the owners are willing to replace the rotors often. commercial airliners also get rotors replaced fairly often, but their rotors are protected from exposure to air. I'm afraid carbon rotors aren't in the cards. And yes, while they are very strong are probably very brittle. Aluminum, on the other hand, could be used, but that's another story.
Gary
On Apr 14, 2008, at 3:01 AM, Lancair Mailing List wrote:
Posted for "Dan Schaefer" <dfs155@roadrunner.com>:
Fred,
Question here regarding a carbon brake disk.
Would a carbon disk be brittle or easily damaged by impact on the edge? The
reason I ask is that, on my older 235 (original brakes), when experiencing a
flat tire during roll-out, the edge of the disk sustained damage around the
entire outside diameter from contact with the runway surface. Obviously, the
steel can take it without shattering - but, in your opinion, how might a
carbon disk fare?
Dan Schaefer
Early LNC2 N235SP
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