Originally Posted by
India Four Two
Ah, the Rotodyne. Its main drawback was the noise. I lived near White Waltham. You could hear it coming for miles! Not much good for a stealthy special forces insertion.
A few comments:
1. No, the SB>1 is not a rotodyne. The main rotor is directly coupled to the engines and the rotors are a contra rotating coaxial system. Completely different mechanically and aerodynamically than rotodyne.
2. The rotodyne was loud because it's rotor system was literally jet powered with jets at the tip of each rotor blade. No such jets in the SB>1.
3. The SB>1 uses an advancing blade concept. Simplified, this means the rotor blades (at speed) only generate lift while they are advancing forward into the airstream. The retreating blades go flat and do not generate lift. This gives the system a much higher top speed because the retreating blades do not stall as airspeed increases.
4. The rotor system is rigid and does not tilt forward to generate forward thrust. It only generates lift. The tail propeller provides forward thrust. This has the advantage that the fuselage stays level and the nose and weapons systems do not point downwards as the aircraft accelerates. Even the tiltrotor tends to drop its nose when accelerating. This level acceleration is a huge benefit in an armed helicopter.