Originally Posted by
Dave_Jackson
Mart, Not so fast.
You recover from a stall in an airplane by lowering the pitch of the wings.
You recover from a stall in a helicopter by lowering the pitch of the blades.
Remember, the blades are 'Absolutely' rigid. They will not 'fold up'.
Dave, you recover from blade stall in a helicopter by crashing into the ground, and becoming another statistic in not letting Nr drop too low during a throttle chop or inoperative donk. Why do you think autogyros spin up their blades before flying? The collective pitch varies between roughly 0' to 20', since autorotation requires some AOA to maintain lift. This way the Lift vector is vertical so the induced drag is not slowing Nr.
Originally Posted by
Dave_Jackson
Another possibility would be to install a rotor-governor and not let the rotors stall.
Yes, this is the crux of my discussion with BugDevHeli. I have not yet heard from him via PM (if you're out there Bug), but won't discuss concepts further.
Originally Posted by
Dave_Jackson
...all four configurations (Side-by-side, Interleaving, Intermeshing and Coaxial) have their pros and cons vis vie each other.
Yes, but you have not come up with a single technical justification for SBS or interleaving. A single teetering rotor has dihedral as a result of the aero-gyroscopic forces, and "rigid" rotors are not so far removed in behaviour (but feel less stable). The only problem is rotor dynamic response, and the fact that the cyclic does not auto centre. The Honeywell SPZ7600 system Nick sited takes care of that.
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Originally Posted by IFMU
No way. They are flying the hummingbird, at least in hover. Individual blade control is still a couple of decades behind phasers and transporters. I'll believe in Santa Claus before I believe they are using IBC on that thing. Those wires are more likely instrumentation. With a prototype aircraft you are going to want to know the forces on this new rotor system.
HeHeHe - point received and understood! Thanks for the explanation - it does make much more sense now.
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From earlier post - too much Xmas spirit.
Originally Posted by Ian Corrigible
...As if the OPOC design, the converted 4cyl & 6cyl Subaru boxer engines and Pratt’s PW207 turbine weren’t enough engines for one program, there is a fourth manufacturer developing a 6-cyl diesel for the Hummingbird: Nivek R&D.
I'll watch that space Ian. I suspect 2-stroke will survive in aero for a while after 4-stroke is standard everywhere else, just for that
possible x1.5 weight advantage. Ultimately Extreme boost turbo charging is the way for smaller aero engines to go, and poppet valves are the only way to reduce oil loss. The auto industry flirted with 2-strokes in the 90's, but tier 4 emissions clamped that pipedream to reality....
Merry Xmas all!
Mart