How exactly does air racing work? What's the challenge? To know the planes turn-speed/radius or what? I'm convinced there's a lot to it, but I've never had the chance to see it explained.
Frank
Fly low, fly fast, turn left!
Ok, you can't fly BELOW a pylon, but there is also a height restriction...1500 AGL I believe (Tundra, you remember?). As stated by Baradium, the idea is to have the fastest course time without breaking the altitude rules or "cutting a pylon". There are several classes of racrers:
Forumula 1: Got to use an O-200, mostly stock and have a miniumum wing area
Biplane: Gotta have two wings...sometimes called the "Pitts" class

Sport: Gotta be a homebuilt with no more then 600 Cid engine and has to be a produced kit, not a scratch build
T-6: Only T-6/SNJ/Harvard allowed, virtually no speed mods. Fun class to watch as it really comes down to pilot skill
Unlimited: Long as it's piston engine it's allowed. This is where you see the P-51s, F8Fs, Sea Furys, Yaks, Lightnings, F7F and what have you. One year a B-25 qualified for Bronze

OK, after the classes you have the races. Depending on how you qualify you either race for the Bronze, silver or Gold. Gold Unlimited is THE draw at Reno. Last Gold unlimited race is the last race on Sunday. That's when everybody tosses the sandbags out of the tail and shows what their plane can REALLY do.
There are of course time penalties for cutting a pylon (that happened to Dago in '04) or violating the altitude restrictions.
It's a fun thing to watch. Awesome to hear those big Rolls Royce merlins (tuned to about double their original HP) and P&Ws (I'd rather twist and crank then blow and suck

) scream around the course. And what a thrill to watch them come out of the turn and drop in to the valley of speed and unload the aircraft.....