Originally Posted by
GipsyMagpie
You want to go high altitude? You want less engines. Just look at the Lama and B3 Squirrel (altitude record for helis I think).
This should give best power to weight you can get (with sufficiently powerful engine obviously - efficient because you only have single gas generator to drive). Clearly you need to strip out any excess weight too (no redundancy like twin hyds for example).
I would also design the rotor for efficiency at high altitude (it'll fly like a pig at low level though). You would have to design control phasing for the altitude (Lock number effects) - you see this going wrong when flying a "sea level" helicopter at 20000ft - forwards back left and right all get skewed around. I would also increase control gearing/control power as everything gets a little sloppy on the controls.
I think a lower rotor speed would also be a good idea. The speed of sound is lower at altitude (ie lower temperature) so tip effects would kick in earlier. Longer blades might cause problems with tip effects so I think broader chord is the way to go.
Just some thoughts
Well, one of the Testpilots at Airbus said, that the 145T2 would be able to perform nicely at high altitude but they werenˋt allowed to extend the graphs to what is possible by Airbus France....
And thatˋs a twin and I ˋm willing to belive the guy beeing TQ limited all the time with both engines working with bleed valves open at MCP.....