Actually every "chopper" you see on TV or on the streets is a radial engine, just two cylinders.

I'll never forget the opportunity I had to fly a T-6. The airport manager at Sidney Airport where we have a fun-fly ever year always gets his out and plays with it. I was lucky enough to get some stick time in his T-6, which was delivered to the USAAC in April of 1940. It actually went to somewhere in the Pacific at some point I can't remember to help in training. Wish I could be more vague...

I went up first about an hour before sunrise, then my dad went up. It was almost dark when they did a low pass at full throttle about 75 feet from where I was standing, about 50 feet up. Now THAT was awesome! Oh and he passed from left to right, so I could see the cool blue flames coming out the exhaust to. Man I wish I had a camera..