[Verriasana]

WTF is a helicopter chunder? Are you saying they stopped it because one of you had a monstrous erection? (See, God knows what I'll read into things...)

Hahaha, and I thought I had a grubby mind [thumbup]

To "chunder" is to vomit, throw up, techni-colour yawn, puke, heave, chuck, etc - get the image/
The helicopter bit is local slang for when, instead of doing so in a limited area, it is spread out. In the case of the chair - it was spinning when the kid chundered - a bit like a circular vomit.