Something not mentioned is that these things were pretty messy. At least mine was. It burned a mixture of oil and gasoline, and the plane got coated with a film of oil.
I only used mine a few times. I found it rather tedious just spinning around in place. Much more exiting were the model rockets that used solid fuel engines.
Back in the day, you were allowed to bring ESTES toy rockets in hand luggage... I'd guess today they'll put you into prison just for bringing them to the airport.
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.
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.
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.
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!
I only used mine a few times. I found it rather tedious just spinning around in place. Much more exiting were the model rockets that used solid fuel engines.