Having recently had a go at R22 flying, i realise that the biggest impediment to wider helicopter appeal is the cost
. The hardest skill to master is the hover, so why burn good cash trying to learn a skill that is (from an engineering perspective) a design defect. Some of you high hour folks will disagree, since it's so long since you hovered toddled that you just see it as part of the machine quirks - most will have progressed on to fully augmented machines anyway, so won't see the point of this thread.
I was always impressed with the story of the Lockheed CL475, where a fixed wing pilot jumped in and flew the heli with NO additional training! Although unable to find any e-refs on the mechanics system, i have found a write up on the AH56A which (after development of the 186) the CL475 led to:
http://www.internetage.com/cartercopters/pics9.htm
This is quite a read, but the basics are: The pilot flies the gyro, the gyro flies the heli. This is fundamentally different from the Bell system, in that the gyro has full control of the heli and the pilot is not fighting the gyro. It is similar in design to the Hiller system, but is fully mechanical, without aerodynamic interaction outside of the blades.
Although mechanically simple, the dynamics take more understanding. Basically the gyro is connected to the pitch links and physically flies the rotor cyclic input (ie conventional rotor dynamics apply). The pilot is connected to the gyro via a swash plate, but with a 90 degree lead due to gyro precession. Since the gyro wants to "stay put", any uncommanded input (eg gust) that moves heli results in a stabilising rotor cyclic input. The practical upshot is the gyro will stay in the same relative orientation in the helicopter (or otherway round). When the pilot puts in a commanded cyclic input, the gyro moves (precesses) in the way the pilot wants the heli to go, and the heli just follows the gyro.
The clever bit, which always confuses folks, is the system details. Since the gyro is always at the same relative position to the heli, there are springs in the control links. These do nothing more than allow a reasonable movement, for the desired rate of pitch or roll. The really subtle bit is the flap pitch couple in the blade, which allows the rotor system to aply force into the gyro. This just produces an effective rotor dihedral (similar to flapback), only in this case the entire heli will gently pitch/roll in opposition to any movement. This just means the pilot has to maintain stick displacement for a given longitudinal (or lateral) velocity - just like a fixed wing.
I read/skimmed with interest similar trends developing in RC helis:
http://www.w3mh.co.uk/articles/html/csm9-11.htm
The main benefit for full size machines would be hands-off stability, without ANY reduction in controlability. Basically it is bringing full flight control systems to private helis. This opens up even more applications to helis, and reduces accident rates - no reverting to basic reflexes due to say IMC disorientation.
So how 'bout it? Is it time for the Lockheed system to make a return, but this time to private helis?
Mart