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There was a concern about starting fires when they came down. I heard the rocket club at my school had to notify the fire department beforehand.

I just remembered I also had a gas engine helicopter. Much more fun since it was free-flying. It would go pretty much straight up then rotor down when it ran out of gas. Couldn't do it on a windy day.

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Those helicopters were very difficult to fly, or so I've been told, as they were unstable. The modern electric copters cheat because they use a computer to stabilize them.

I was going to say. Helicopters are difficult to fly, period! It's not just those -- also the big ones.

Large helicopters are not as difficult to fly as small ones, simply because the time constant of their instability is longer. This is similar to how it is easier to balance a broom on the tip of your finger than a pencil, and a pencil is in turn easier than a toothpick.

I keep trying to explain this to my friends in the aquarium and terrarium hobbies.

"I want to build a tiny one. It'll be so cute."

"It's going to crash in 30 seconds if you so much as look at it funny."

It's possible to build a passively stabilized helicopter and a lot of modern model helicopters use that method. You can even get away with two axis control!

Does anyone have more info on this?

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