Originally posted by: otispunkmeyer
Originally posted by: ScottSwingleComputers
Originally posted by: ThePresence
Originally posted by: ScottSwingleComputers
Originally posted by: Specop 007
I believe it would. The rotors would have no net speed in relation to the body of the helicopter, but they would have a net speed in relation to the ground and as such to the air around the helicopter. As long as you have air passing over the rotor blades you have lift, regardless of the body of the helicopter.
You got that a bit backwards.
No, I think he got it right. Air passing over the blades of the rotor provide lift, regardless of what's powering the rotation, be it the turntable or the engines.
But the blades would NOT be moving in relation to the air or ground. The turntable would negate the movement of the blades.
if the table is moving with the blades, then the blades have a net speed of their original speed plus that of the table. if the blades spin at 1000rpm, they will always spin at 1000rpm relative to the table
if the table also moves at 1000rpm, then the blades net speed will be 2000rpm in relation to the stationary ground, and still 1000rpm in relation to the turtable
if the air is also stationary then you are effectively producing more lift than when using the turntable (if rotating in the same direction as the blades)
if the table rotated opposite to the blades well thats a different story
if the blades are going 1000rpm CW and the table 1000rpm CCW, then the blades have a net speed of 2000rpm relative to the table and zero in relation to the ground/air? (lol not sure!)
First lets say when saying 'table' that we could also say 'aircraft body' since the aircraft body and table are fixed and rotate together as one unit.
The blades will *always* be 1000 RPM relative to the table when the engine is running, and is only a function of the engines power output, regardless of pre-existing motion of the aircraft. Don't forget that without power, the rotor-table speed is 0 RPM even if the table is 1000 RPM CCW (the blade is moving 1000 CCW with the table assuming no free-wheeling of the shaft). Thus powering on the engines at 1000 RPM CW will not result in 2000 RPM rotor-table speed, but rather 1000 RPM rotor-table speed and 0 RPM rotor-ground speed.
Before engine power:
rotor-table speed: 0 RPM
rotor-ground speed: 1000 RPM CCW
table-ground speed: 1000 RPM CCW
after engine power:
rotor-table speed: 1000 RPM CW
rotor-ground speed: 0 RPM
table-ground speed: 1000 RPM CCW
You are correct about the zero RPM relative to the ground, but the rotor will *never* be 2000 RPM relative to the body/table. I think what you forgot is that the rotor will turn 'backwards' (relative to ground) along with the aircraft body so that it remains stationary with respect to the aircraft as it rotates CCW, provided there is no engine power.
It appears you assumed that the rotor would freely spin and thus stay fixed relative to the ground and thus be at 1000 RPM CW as the table went 1000 RPM CCW, but if this was the case, the engine would already be at its 1000 RPM limit anway and couldn't spin any faster under power. Here's a car analogy: put a car on a dyno that is able to move the wheels at 150 mph while the car is in gear and peg the red line using only the dyno and the drivetrain to turn the engine. When you turn on the key you will already be at your red line and topped out in engine speed, you won't be able to go 300 mph. The engine is already at speed regardless of burning fuel or not and can't go any faster.
An observer inside the aircraft will read 1000 RPM on the tach gauge observe the rotors spinning 1000 RPM while sitting in his/her seat.
From the ground, an observer would note that the blades are stationary and only the helicopter and turntable are spinning at 1000 RPM CCW in between the rotor and the ground.
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