Agreed that Coanda effect design will not be mechanically simpler, Nick. My thought is that the primary modes of failure affecting conventional tail rotor could be designed out. Not suggesting the MD design is an example of this!
Son-of-Notar would have an embedded fan with collective pitch, as per conventional tail rotor. Modes of failure eliminated are TR strike and driveshaft breakage, along with reduced risk to TR pitch control. This provides full anti-torque and left yaw. There would need to be a single control going to the coanda mixer which would switch jet directions for right yaw (spring or pressure default to left). Embedded fan would vary from 0 pitch to full pitch with left or right pedal, direction switcher activated with right pedal.
Considering the mode of failure where the direction switcher breaks, then the engine fails. Initially pilot does not realise loss of powered right yaw, due to need to balance torque. Donk quits, leading to autorotation. Pilot retains full left yaw control, but realises there is a problem achieving powered right yaw. Although forced to make left turns only lands safely and walks away to post on PPRUNE (probably with some good test pilot advise for lesser mortals like myself).
Another interesting possibility would be two embedded rotors for twin engine helicopters, maybe using low bypass turbines. This means that pilot would only ever loose half yaw effectiveness with single embedded rotor failure. Looking at my 1:72 Commanche model suggests that if the aerodynamics could be developed, mixer would offer a good area for air flow.
Not suggesting the idea is a golden panacea, but maybe it has sufficient merit to warrent further design/simulation study.
Mart
Last edited by Graviman; 25th Mar 2007 at 19:23.