Collective and Pitch?

Question

What is the significance of either? What affect does RPM have? How does the main rotor RPM translate to tail rotor? Is the tail rotor affected by rpm or pitch? Which control is this?

John B since you are an army pilot with thousands of hours this should be real easy for you!

Answer 1

not sure

Answer 2

Yep this ones a walk in the park and ol bio hazard got it wrong. Collective controls rotor blade pitch. Pull it up increases pitch, push it down......ah you know. A grip throttle like on a motorcycle is used to maintain rotor rpm during these pitch changes. So when you "pull some pitch" with collective you "roll on" some throttle to keep the rotor "Rs" in the green.

Of course all this twisting and pulling with your left hand increases torque as you say correctly so now your feet go to work. In most helicopters, depends on which way the rotor spins, that means you push left pedal. Unlike bio hazard said, increasing tail rotor speed, depressing left pedal increases tail rotor pitch providing more anti torque thrust and keeping the chin bubble pointed where you want it. Of course it all has to happen at the same time. But the main and tail rotors always turn at a constant rpm. Neither the tail rotor or main rotor ever slows down or speeds up. Better not anyway.

Us army rotor heads have tons more fun helispeak. During combat assaults in Vietnam if you were listening on Fox Mike, FM radio, you'd hear the flight lead tell the flight, "OK flight, lead's gettin' light." Guess what he's beginning to yank on in the cockpit? If you're behind lead in chaulk two you better start pullin' an armpit full of collective because chaulk three is already nosin' over on the skids right behind you. He and the rest of the flight want out of this hot LZ right now and you're in the way.

Answer 3

The main rotor and tail rotor have a constant RPM (well, that's what you want for the most part.  Changing the RPM a little can get you further if you're low on fuel, and some other situations)  Both main and tail rotors use a reduction gear system so that they're rotating more slowly than the engines.  It's not the same reduction though.  For example, on the models huey I flew, the tail rotor rotates 2.6 times for every time the main rotor goes around.  

As far as RPM, there isn't anything more important.  Rotor is life.  Overspeed it much and you can damage something.  Going low can be even worse, especially in something with a real reactive rotor system.  An N model huey, with much power applied can (in the event an autorotation is needed) lose enough rotor speed that it can never be built back up and you're riding it to the ground.

Answer 4

the collective changes the pitch of all rotors at the same time, usually tied to the throttle, in order to increase lift. the tail rotor will also speed up to counteract the higher torque. the helicopter's pitch is controlled by the cyclic control (the stick) which only changes the pitch of blades as the pass a certain point in the rotation, after which the blade pitch returns to normal. this creates a imbalance in the lift from the main rotor, causing the copter to tilt, and allowing the rotor to pull it in that direction. the rudder pedals vary the speed of tail rotor, allowing the copter to pivot, which is important because the cyclic alone could only move the copter directly to the side, rather than turning it