Customer Reviews

Scale Model Helicopters (Modeller's World)

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After much pondering, the explanation is simplistic!

To cause the helicopter to move upward, in relation to the helicopter, the leading edge of the blades must be at an angle of > +5.5 degrees. Air is forced down through the blades, and this "pushes" the helicopter upward.

Correspondingly, air is "pulled down" from above the helicopter, and then pushed down below it. If a helicopter is about to fly under a backyard canopy, the aircraft will be pulled immediately and uncontrollably up into the frame, due to the sucking of air down through the blades, with disastrous results.

The larger the positive angle, the faster the rate of climbout upward. Descent is caused when the angle is less than +5.5 degrees.

When the pilot "flips" the aircraft so it is upside down, either by performing a fast roll or loop, we need to have a thought experiment from the helicopter's perspective.

If the blades continued to be > +5.5 degrees with respect to the helicopter, this will cause the aircraft to move upward. Unfortunately this will not last long, as being inverted it will smash into the ground. :<>

Thus to maintain inverted status for any period of time, the blades must now be < -5.5 degrees. In this case the air is pushed above the helicopter, and pushes it away from the ground. The less the angle, for example -10 degrees, the more air is pushed above the helicopter (or taken away from under it) and the bird moves away from the earth even faster.

Unfortunately flying inverted is something that is to be avoided with scale helicopters. As the book correctly points out, it takes considerable time to create a scale helicopter, and the brief moment of satisfaction may be followed by a extended period of ennui.

I don't agree with the other reviews here - this book is seminal in its field. I use it regularly as a most authoritative source of guidance in guidance, control, airfoils, reverse pitch, and flying upside down (in particular). As a good friend told me recently, the helicopter doesn't care if it's flying upside down or right side up. It's possible that this book was read upside down, though, explaining the other reviews shown here.

I was disappointed with this book. I felt that it could have contained so much more about the advantages of joystick control versus roto-noto motion.

But then, perhaps it's too controversial.