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Is there a reason why people can't just take the helicopter to mount Everest? Why is it that helicopters can't reach that high?

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Apparently helicopters could reach mount Everest:

http://en.wikipedia.org/wiki/Mount_Everest#2005:_Helicopter_landing

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Helicopters create lift by their rotor blades pushing an equal mass of air downwards.

The air pressure at the top of Mt Everest (29,000ft) is only about 1/3 as much as at sealevel so your helicopter can only generate 1/3 of the lift. In addition it's cold so you risk ice forming on the rotors, fuel and hydraulics freezing and finally the weather isn't always very nice.

The altitude record for a helicopter is 40,000ft. It was set in 1972 with a very light version of a simple helicopter. There isn't much reason to fly helicopters at the height of a jet airliner so there aren't many helicopters developed to fly this high.

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Is the oxygen needed by the engine an issue? – Bernhard May 28 '12 at 17:31
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Other than tuning for a particular role - no. Helicopters use the same type of jet turbine as other aircraft which fly at these heights. – Martin Beckett May 28 '12 at 17:49
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Yes. Helicopters require a certain amount of air for lift. The lack of air near the peak of Mount Everest makes it impossible for most helicopters to get the required lift and therefore fly.

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A rotor is nothing more than a rotating wing, so if the air pressure was the only determining factor, aircraft would have trouble at that altitude, too. I suppose you should add that helicopter blades need to be much smaller than wings, and hence need more air, as rotating them faster is not a real option: the tips soon start going faster than sound. – hdhondt May 29 '12 at 3:50

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