Too skinny to fly

The tail end of the winter weather has grounded me for a while, so in lieu of a flying update I have a quick "strange but true". In one of the huts near our flying group is a helicopter flying school, offering training in the Robinson R22 and R44. The R22 is a tiny and lightweight helicopter, mainly used as a trainer, while the R44 is a bit bigger and can carry a couple of passengers and some luggage. Helicopters are incredibly cool beasts but they're very expensive to learn on (and to fly in general). However, that might not be the only reason you can't learn to fly an R22.

"Robinson R22 Helicopter hovering" by Jitze Couperus. Licensed under CC BY 2.0 via Wikimedia Commons

Because of its modest engine capacity, the max weight limits for the R22 are not huge: 109 kg in either seat, plus 23 kg of luggage. That's less than my bike can carry. But there's also a minimum weight.
The tail rotor on a helicopter provides a turning force to counteract the torque from the main rotor. But as well as turning the helicopter, the tail rotor also applies a sideways force on it. This tends to push the helicopter to the right, if the main rotor spins anticlockwise. To hover or fly straight, the helicopter has to be tilted (rolled) slightly to the left to balance this force. That means it needs more weight on the right-hand side to keep it stable when it's tilted like that. If there were too much weight on the left side, the cyclic control wouldn't be able to generate enough force to roll the helicopter back to the right.
For this reason, if you're flying an R22 solo, you have to sit in the right seat, to keep it balanced, and you have to weigh at least 59 kg. If it's carrying auxiliary fuel, that increases to 61 kg. I'm not that much of a lightweight, but it's close enough that I would probably need to take on some ballast if I were flying with a heavy person in the left seat, or the max weight of cargo, in order to keep the aircraft centre of gravity within its limits.

"Robinson R44 Raven G-RAVN arp" by Adrian Pingstone. Licensed under Public Domain via Wikimedia Commons.

The larger R44 doesn't have a minimum solo pilot weight, but its operating handbook does have the following note:

With all doors installed, a solo pilot weight of 150 lb (68 kg) or greater will ensure CG within limits. For lower pilot weight, compute weight and balance; removable ballast may be required to obtain CG at or forward of aft limit

So if I want to learn to fly a helicopter, I should start working on my ballast now. A bacon butty for breakfast and a couple of pork pies before lunch should set me on the right path.