On Tue, 18 Nov 2003 00:10:26 +0000 (UTC), David Lesher
wrote:

"Simon Robbins" writes:


Rather than lack of oxygen, I imagine it would be that the lower air
pressure simply means the rotor is unable to achieve lift without an
unacceptable increase in rotor speed, which would likely overstress the
engines and gearbox.

I've wondered what keeps you from building a high-altitude version.

I envison big fat blades and an engine design for thin air. Or is there
some other issue I'm not seeing?

Density altitude is a crucial factor in high-altitude helicopter
operations.

In a helicopter, the higher you go the more power is needed. But due
to density altitude, the rotor system and engine(s) are less efficient
at higher elevations, and the engines develop less power. A
helicopter may be able to fly at high altitude but may not be able to
hover, and even in level flight might need to use full throttle, and
if it lands it may not be able to take off.

Also, most helicopters don't routinely carry oxygen systems.

The current altitude record for a small helicopter is:

FAI Class E1b - Altitude Without Payload - takeoff weight 500-1000 Kg
International: 40,820 ft; 12,442 m.
Jean Boulet (France)
Alouette SA 315-001 Lama
Artouste IIIB 735 KW engine
Istres, France June 21, 1972

John Hairell )