## Wednesday, March 11, 2009

### Helicopter Offers Practical Lessons in Physics

This sounds like fun. A bunch of kids got to learn about helicopter physics and got to see it in person.

After the students checked out the lightweight whirlybird, Hall followed them back to school where the theory behind the practical application they just observed would be examined.

Jones said the plan was to have a lesson on aerodynamics that day with a special emphasis on helicopter physics.

I wish they get more explicit in what exactly the principles they are being introduced or being demonstrated using the helicopter. "Lesson on aerodynamics" is rather vague. Besides, and someone can correct me here, what exactly is the lesson from aerodynamics as far as a helicopter is concerned? I would think that it is more to do with straightforward classical mechanics of angular momentum, Newton's 3rd Law, etc. It would have been a lot more jaw-dropping if, while in flight, the tail propeller falls off and the students could see the helicopter spinning out of control - conservation of angular momentum in action! But then again, that could end up in an utter disaster (that's why I called it "jaw-dropping" demonstration).

Zz.

#### 1 comment:

Anonymous said...

I believe the more pertinent question here is, what aerodynamic principle is NOT demonstrated in a helicopter? Of course there is the aviation standard, Bernoulli's priciple as it applies to the airfoil of the rotor blade, but there are many more that are unique to helicopters. The idea of essentially infinite dissymetry of lift is something I doubt applies to a Cessna 172. But of course what makes a helicopter shine are the mechanics invoved, gyroscopic procession, rigidity in space, coriolis effect, ect. Also, loss of the tail rotor can be countered by closing the throttle to remove torque effect and removing all pitch from the main rotor blades allowing the main rotor to conserve angular momentum (maintaining rpm) without causing the helicopter to spin out of control. Raising the nose of the helicopter would allow the upflow of air from the high rate of descent (power is off) through the rotor disc to further maintain rpm entering a standard autorotation.
- Helicopter pilot and mechanic