On Wednesday 20 April 2005 22:30, Jerry Feldman wrote:
On Wednesday 20 April 2005 5:42 am, Colin Carter wrote:
This is interesting. I know about gyroscopes, but hadn't thought about it in the sense of controlling helicopters. To move forward I imagine that the rotor plane would have to lower itself at the front (true?), in which case the force (as you mentioned at 9o deg) would have to cause a little roll of the fuselage, albeit very slight. Is this true?
Not really. The rotor blades are hinged at the rotor mast. A downward force is exerted aerodynamically to the rotor blades 90 degrees in advance of the rotor plane. This causes the rotor blades to tilt forward. Try this with toy gyroscope.
I hadn't thought about that; I guess it would be much like one racing yacht "stealing" the breeze from another.
I don't think I'd be very good in a helicopter: I get sea sick; not at all if the vessel is ploughing through very rough water at speed - rather when the boat has a very gentle sway/roll in almost calm waters.
There are 5 controls in a helicopter that a pilot must operate simultaneously: 1. The cyclic - This is the stick and controls the tilt of the rotor blades and the helicopter. Similar to the stick in a fixed wing, and in forward flight nearly identical.
2. The collective. This makes the helicopter go up or down.
3. The throttle (on the collective). When you pull pitch, you need to simultaneously give it more throttle.
4, 5. The anti-torque rotor pedals. Anytime a change is made with the throttle, you need to compensate for the additional or reduced torque caused by the throttle changes. Additionally, the pedals themself require more or less throttle. Much like a feedback loop.
There are generally 3 kinds of rotor systems: 1. Rigid - not used very much. This was a goal that was finally achieved by Lockheed in the 1970s.
2. semi-rigid - Mainly Bell Helicopters - 2 blades that teeter on the rotor mast. Each blade can feather - increase of decrease its angle of attack independently of the other).
3. Fully articulated. Most helicopters use this. Each blade is hinged to the rotor mast where it can feather, float up or down, and even move forward or backward independently of the others. (The angle between the blades can vary). One interesting anomaly is that if the system is not tuned correctly, the rotor system can cause vibration when in contact wit the ground and self destruct.
Very interesting (and new). The blade independence surprises me.
In any case, the mission of all helicopters is self destruction. This reminds me of Ozymandias. And also of the most important law of physics/universe: "There is a tendency toward maximum entropy."
-- Jerry Feldman
Boston Linux and Unix user group http://www.blu.org PGP key id:C5061EA9 PGP Key fingerprint:053C 73EC 3AC1 5C44 3E14 9245 FB00 3ED5 C506 1EA9