feasibility check: Vtol with with retractable Roto ?

[Michel Van]

The Sikorsky / North American CARA design

Sikorsky S-57

So do work a VTOL based on retractable Rotor ?
or are to much problem with unfold/refold rotorblades,
during transition vertical to horizontal flight.

 

[Archibald]

I've asked that question before, can't remember where.

EDIT again
There !
http://www.secretprojects.co.uk/forum/index.php?topic=431.msg2929

Back in 1969 when Lockheed was convinced their Cheyenne compound helicopter was the best thing ever happened to aviation, they designed zillions of derivatives.
One of them had foldable rotors. And was tested in wind tunnel around 1970.

Edit checked my source (Le Fana de l'aviation, July 2000). Was called the "composite aircraft".

 

[AeroFranz]

you could probably make it work, but it would be so complicated/heavy that you would have little payload fraction left to have a useful vehicle. I think that more than anything prevented the idea from being explored more in the first place. I don't want to downplay the technical challenges, but why bother if it doesn't make commercial/military sense?

 

[Michel Van]

so complex system were the Rotorblades to have unfold and refold is no good,

and to extend rigid (tip-jet-powered) rotor like in this picture.
would that work ?

 

[AeroFranz]

having an internally-driven rotor (like with tip jets) probably helps, but there are other issues, more thorny ones, like the dynamics of slowing down and then stopping the blades.

 

[Hammer Birchgrove]

Wow, I thought only I and makers of Saturday morning cartoons doodled with such crazy ideas...

 

[The Artist]

so complex system were the Rotorblades to have unfold and refold is no good,

and to extend rigid (tip-jet-powered) rotor like in this picture.
would that work ?

I'll not comment on the technical challenges but it seems to me that the design you've posted here would be impractical for anything but research. The retractable hub, the retraction/extension machinery and associated systems would take up quite a chunk of the cabin space. Would enough usable space be left to produce revenue?

 

[Jemiba]

Actually, both shown methods, the telescopic rotor and the stoppable, retractable rotor
were much en vogue during the '60s/'70s, as can be seen by these two projects from
Sud Aviation from 1969. The compound features a telescopic rotor, that is foldable into the
stoppable hub (!), which then would form kind of a wing, turning the aircraft into a bi-wing.
The Rotojet has a stoppable rotor, which would have to be lowered for stowage after stopping,
similar to the Marchetti project, and here, too, the usable cabin space probably would have
been decreased.
As so many companies thought of such concepts, there probably were at least some wind tunnel
test rigs to elaborate such mechanisms ? Any development programs about such rotors done by
NASA or ONERA ? Haven't found anything still yet, but maybe someone else ?

 

[Stargazer]

There have been many such projects. Here are a couple more... one being apparently Lockheed's competitor to Sikorsky/NAA's project at the top of this page...