Strykaas...there are a number of different categories such as outright speed, team racing, stunt, combat, scale and most of these have their own sub-categories as well. I'll try to give a quick run down but not being an expert in most of them the details might be off a little.

Speed is obvious...go as fast as possible within the rules for a particular engine size. The current fastest speed for a piston engine was set with a 2.5cc (.15) at 208mph. Only a pulse jet has gone faster than that. I can't remember if this link has been posted here but if you want to see that 208mph being set then check out the video at http://www.flyrc.btinternet.co.uk/re...ntrol_line.htm

Team racing....3 or 4 models all flying at once with limited fuel tanks so pit stops need to be made. Can be raced over a distance or number of laps over a fixed time. Fuel economy, speed and pit work are essential for a good result.

Scale....pretty obvious

Stunt (called Precision Aerobatics in America)...a set pattern of intricate manoeuvres that have to be flown as precisely as possible. Manoeuvres include such things as loops, figure eights, square versions of them, triangles, 4 leaf clover etc. It can be quite frightening to an RC flier seeing it for the first time

Combat...not for the faint hearted!!! The basic idea is to take cuts off a streamer being towed behind the opponent's model. Easy? Well think 2 models at up to 120 mph both trying to attack and evade at the same time. These have the tightest turning ability of any model for the speed they fly at. As a spectator sport they rank #1 by a long margin. Pylon racing is a distant second.

Accidents are rare. The only bad one I know of in Australia was during a practise for a Rat Race (similar to team race but more relaxed rules). There was a problem with one model and the pilot (stupidly) walked out to see what was wrong without saying what he was going to do. The other pilot didn't notice and his model collected the other guy in the head. It was nearly fatal.