Included in the equation has to be the price, i.e. bang per buck or knot, in this particular case. Sikorsky didn't come up with a viable answer to the problem, nor has anyone else.
It seems there is a "hole" in the overall performance / versatility / cost equation, somewhere between the top end performance of helis and the highly manouvreable STOL fixed wing aircraft with a reasonable cruise speed, if such an aircraft exists....
The tilt rotor is another way of getting better cruise speed at the expense of true helicopter low speed performance and manoeuvreability. Of course, it has proved to be massively expensive and with it's own set of problems. Looking forward to the day I'll see one in Battersea Heliport - but I'm not holding my breath... especially since they have introduced that 1400 ft restricted area to the north, resulting in the requirement for an even steeper approach and climbout
Something that has intrigued me about the old noisy tip jets that the Rotodyne had. In a similar way that modern high bypass ratio turbofans have quietened down the airliner, it might be possible to design an efficient high flow / low speed outlet propulsion burner integral to a modern rotor blade. Such a blade could possibly have the benefit of both low drag & noise while being "self powered".
I visualise something like a length of trailing edge burner, moving a high volume of gas more slowly, rather than a pure tip jet which, like a turbo-jet moves a little gas very quickly and in the process generating a lot of unwelcome noise. The reverse flow problem might be a problem for high speed cruise if reducing the gas velocity but NOT for a blade that is only powered in the low speed regime, such as the approach, hover and climb.
I'll still be flying ancient technology until I retire though, I'm certain.
