Ah, I see. I bow to your superior experience. I recently acquired my private rotorcraft, and we DID have to study all those aerodynamics. I had nightmares about dissemtry of lift there for a while >
Interesting article, I stand corrected. I was originally told that by a military pilot. Having never flown or trained in one, I took his word for it. However, the rest is correct. How did you come across that article?
(PS) The nice fat blades also have nice fat inertia, I've seen one practicing full down autos, made me jealous.
Actually, it isn't so much the design of the hub, it's actually how the blades themselves flex. The advancing blade will have a lower angle of attack, (as a result of it's airspeed, or relative wind), and the retreating blade flexes to have an increased angle of attack. The limiting speed factor for rotorcraft is called "Retreating Blade Stall". The retreating blade stalls (not stops, the relative airspeed is no longer sufficient to produce lift), and 3 things happen. First, when approaching VNe, (Velocity Never Exceed), the ship will begin to shudder. Second, due to gyroscopic precession, the ship will "balloon", the nose will pitch up. Third, the ship will roll to the left. The stall speed of the retreating blade varies by design, however, it is never close to a zero airspeed.
Actually, the tip speeds on the advancing blades of the UH-1's do break the sound barrier, hence the "whop whop" sound is actually a small sonic boom, and as far as the quote...
"Any idiot can fly forwards, try flying backwards"
--any Rotor Head
Slashdot Mirror
Ah, I see. I bow to your superior experience. I recently acquired my private rotorcraft, and we DID have to study all those aerodynamics. I had nightmares about dissemtry of lift there for a while >
Interesting article, I stand corrected. I was originally told that by a military pilot. Having never flown or trained in one, I took his word for it. However, the rest is correct. How did you come across that article? (PS) The nice fat blades also have nice fat inertia, I've seen one practicing full down autos, made me jealous.
Actually, it isn't so much the design of the hub, it's actually how the blades themselves flex. The advancing blade will have a lower angle of attack, (as a result of it's airspeed, or relative wind), and the retreating blade flexes to have an increased angle of attack. The limiting speed factor for rotorcraft is called "Retreating Blade Stall". The retreating blade stalls (not stops, the relative airspeed is no longer sufficient to produce lift), and 3 things happen. First, when approaching VNe, (Velocity Never Exceed), the ship will begin to shudder. Second, due to gyroscopic precession, the ship will "balloon", the nose will pitch up. Third, the ship will roll to the left. The stall speed of the retreating blade varies by design, however, it is never close to a zero airspeed.
Actually, the tip speeds on the advancing blades of the UH-1's do break the sound barrier, hence the "whop whop" sound is actually a small sonic boom, and as far as the quote... "Any idiot can fly forwards, try flying backwards" --any Rotor Head