(B2431) wrote in message ...
From: "Simon Robbins"
Date: 11/17/2003 12:46 PM Central Standard Time
Message-id:

"Allen" wrote in message
. ..
I am curious about use of a chopper in the higher altitudes of
Afghanistan. The Canadians are in Kabul and the word is our Griffin, a
Bell 412 helicopter, can't work in the mountains. Anyone now why.....
lack of power at altitude, lack of oxygen ?

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.

Have a look at:

http://www.bellhelicopter.textron.co...z412EP_spec_de
tail.htm
and you'll see the service ceilings. Not much room there to take mountains
into account, less so with a full load.

Si

There was an example of that which made the rounds last year. There was a high
altitude rescue involving an H-60. The helicopter simply dropped out of the
sky, hit the mountain and rolled down the slope.
If anyone has a clip of that please post a link.

Dan, U.S. Air Force, retired

The French built a High Altitide Helicopter called the Aerospatiale
SA-315B Lama. Hovered at 17000 ft. It was for the Indian Airforce.
http://www.evergreenaviation.com/EHI...eets/lama.html

It involved installing the Rotor and Mechanicals of the Allouette III
into the body of the Allouette II.

The Russian Helocopters (eg Mi 24 Hind) becuase of their 5 blade
rotors have better high altitude performance than their 4 bladed US
equivalents.

Some Russian sounding guy posted stuff from a Russian AF General with
Grudging but usefull Advice on this just before the Afghanistan
invasion.