High altitude Helicopter work

"David Lesher" wrote in message
...
"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?

Lack of demand most likely.
Not a lot of places to land on mountains that tall.

Don't know the helicopter type, but it belonged to the Nepalese army
and was piloted by a gent named Madan, who twice flew to above 21,000
feet to rescue two Everest climbers in the spring of 1996. See John
Krakauer's Into Thin Air, a very fine book.

all the best -- Dan Ford
email: (put CUB in subject line)

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

"Dick Snyder" wrote in message
...
On Mon, 17 Nov 2003 20:19:57 -0500, "Allen"
wrote:

Thanks for the info guys. I checked out a web site with articles by
the
crews of the CH-47Ds that worked the mountain ranges in Afghanistan.
They frequently did landings at 17000 - 20000 ft. All very
interesting
and informative.

Allen, RCAF/Canadian Air Force, retired

Mind posting the link. As an ex-hook driver from during the
Vietnam era I'd be very interested. Our A-models had a service
ceiling of 12,500 due to hydraulic cavation. Hooks, at least the A,
B, & C models (all of which I flew), are hydraulic dependent (an
understatement to say the least). Can't even spool up the engines
without pressurizing the systems with the APU. A lot of changes were
made on the D model however.

Thanks,

Snyder, US Army, retired.

Here's a couple:

http://www.globalsecurity.org/milita...aft/mh-47e.htm

http://www.nationaldefensemagazine.o...cle.cfm?Id=850

Afraid I couldn't find the exact site I found last night. Shame on me
for not providing references for my sited info.

Allen

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 )

It was either a AS350 Ecureuil or a AS355 TwinStar. Examining the
photos, I couldn't tell. There was a great account in Aviation Week &
Space Technology of the rescue. They pointed out that the pilot was
operating above the helicopter's published service ceiling.

In article ,
"Larry" wrote:

The footage clearly
showed the machine hovering, attempting to get in close, then things got
bad. It was on Mt Hood or Mt Rainier.
Right down the street at Mount Rainier.



Nope, it was on Mt. Hood.


Among many other links....

http://www.traditionalmountaineering..._HeliCrash.htm




--Mike

I just found this:
http://www.au.af.mil/au/goe/eaglebio...s/khatri98.htm

It was a AS350 B2 Ecureuil. I remember reading that he did the rescue
after stripping the interior and he only had a partial fuel load.

Hmmm...impressive, considering that Ecureuil has ceiling of 4400m.


David Lednicer wrote:

I just found this:
http://www.au.af.mil/au/goe/eaglebio...s/khatri98.htm

It was a AS350 B2 Ecureuil. I remember reading that he did the rescue
after stripping the interior and he only had a partial fuel load.

Hmmm...impressive, considering that Ecureuil has ceiling of 4400m.

It is indeed impressive. Note, h owever, that "service ceiling" is
usually defined as the height at which an aircraft can no longer gain
100 feet per minute. The B-36 seems to have exceeded its service
ceilding by 10,000 feet on occasion.

all the best -- Dan Ford
email: (put CUB in subject line)

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

(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.