Supreme Allied Gyro CFI
- Oct 21, 2006
- Colorado front range
- Bell 47G-3B-1 / A&S 18A / Phoebus C, etc.
- Total Flight Time
- stopped caring at 1000
They don't flap up, either. In prerotation at low rpm the blades are not yet flying (essentially stalled with inadequate airspeed) and they're not flapping at all, neither up nor down. Airspeed (with pitch) is what makes everything happen.Cannot agree with this. How do you explain that in an articulated rotor system, during pre-rotation when rpm is low, the blades do not flap down.
When you get significant rpm going in prerotation, you have darn little dysmmetry because you're sitting still (only the prevailing wind to make any difference in airspeed) for the spin-up with no pitch.
Most articulated systems use symmetrical airfoils held at essentially zero collective pitch, so they make very little lift during spin-up. Add some pitch, you get some lift, and the blades cone up. Move forward in that condition and you need flapping for compensation of the airspeed difference across the disc.