AS350 Astar/Squirrel
Join Date: Apr 2003
Location: USA
Age: 75
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devil 49,
The reason for the jack stall is that the blades are stalling, and when they do, they progressively add more and more force to the swashplate. This is due to the pitching moment of the airfoil shifting with the stall. When the swashplate gets heavily loaded, it pushes the servos backwards despite the hydraulic pressure in them. this is called "transparency" or "stall" of the servo.
here is a web site that talks about the dynamic stall of rotor blades. Scroll down to where they talk about the pitching moment (the Cm plot) to see how the moment of the blade takes a big turn at stall. This is the reason why the nose drops on an airplane when the wing stalls - the wings pitching moment shifts sharply downward.
http://aerodyn.org/Dstall/dstall.html
The reason for the jack stall is that the blades are stalling, and when they do, they progressively add more and more force to the swashplate. This is due to the pitching moment of the airfoil shifting with the stall. When the swashplate gets heavily loaded, it pushes the servos backwards despite the hydraulic pressure in them. this is called "transparency" or "stall" of the servo.
here is a web site that talks about the dynamic stall of rotor blades. Scroll down to where they talk about the pitching moment (the Cm plot) to see how the moment of the blade takes a big turn at stall. This is the reason why the nose drops on an airplane when the wing stalls - the wings pitching moment shifts sharply downward.
http://aerodyn.org/Dstall/dstall.html
I am glad there was a very simple answer to my original question. I would hate to think I raised a complicated issue like why some places in the world still use the QFE altimeter setting vice the World-wide accepted QNH method.
Join Date: Jun 1999
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Dear all,
A search for "jack stall" shows the amount of previous discussion. I, like 'scrubba',
http://www.pprune.org/forums/showthr...ght=jack+stall
did all sorts of things in the AS350 that deliberately generated jack stall. I found it to be predictable, progressive and at the far edges of the envelope compared to normal operations.
While I note Nick's view in 2001 and now, I never felt frightened by the phenomena because I knew it existed and I knew the extremes to which I had to go to induce it. The other "mid-envelope" experiences reported just did not gel with my experience.
Stay Alive,
A search for "jack stall" shows the amount of previous discussion. I, like 'scrubba',
http://www.pprune.org/forums/showthr...ght=jack+stall
did all sorts of things in the AS350 that deliberately generated jack stall. I found it to be predictable, progressive and at the far edges of the envelope compared to normal operations.
While I note Nick's view in 2001 and now, I never felt frightened by the phenomena because I knew it existed and I knew the extremes to which I had to go to induce it. The other "mid-envelope" experiences reported just did not gel with my experience.
Stay Alive,
Join Date: Apr 2003
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4dogs,
Thanks for the link to the past! It is interesting to see that old topics don't just go away!
I have to note one issue with your comment,"did all sorts of things in the AS350 that deliberately generated jack stall. I found it to be predictable, progressive and at the far edges of the envelope compared to normal operations"
Could I ask you to add the note, "so far" to the end of your comment? One thing I have found in testing is that when a problem surfaces, it is not likely to just fix itself. When other pilots have loss of control events, and lose their aircraft in an accident, your evaluation has just been trumped by theirs. We all lose if we decide that something which hurt a buddy is really his fault, so that we apologize for the aircraft, blame the pilot and march on to the next accident.
I coined an aphorism to describe the loop we get into when we are trying to decide if a problem we have found really needs to be fixed. I would write this on the chalk board before we started the meetings to decide if it was a "feature" or a problem:
The size of your problem is proportional to the efforts needed to convince yourself that it is not a problem.
IMHO, Jack Stall is like LTE, a sign of a marginal helicopter that has bitten some of us, but others want to simply blame the pilot. Safety of helicopter flight operations will only be achieved when I, and my counterparts at the other manufacturers, face a raft of indignant pilots constantly trying to make their aircraft better, not a group of apologists who want to blame each other when an aircraft fails them.
Regardless of our collective opinion about how much out of control we will accept, the authorities should not let us debate it. In good military aircraft, there is no debate, and I can promise you, it would be a cold day in Hell before the FAA pilots I fly with would accept jack stall at 1.5 g.
Thanks for the link to the past! It is interesting to see that old topics don't just go away!
I have to note one issue with your comment,"did all sorts of things in the AS350 that deliberately generated jack stall. I found it to be predictable, progressive and at the far edges of the envelope compared to normal operations"
Could I ask you to add the note, "so far" to the end of your comment? One thing I have found in testing is that when a problem surfaces, it is not likely to just fix itself. When other pilots have loss of control events, and lose their aircraft in an accident, your evaluation has just been trumped by theirs. We all lose if we decide that something which hurt a buddy is really his fault, so that we apologize for the aircraft, blame the pilot and march on to the next accident.
I coined an aphorism to describe the loop we get into when we are trying to decide if a problem we have found really needs to be fixed. I would write this on the chalk board before we started the meetings to decide if it was a "feature" or a problem:
The size of your problem is proportional to the efforts needed to convince yourself that it is not a problem.
IMHO, Jack Stall is like LTE, a sign of a marginal helicopter that has bitten some of us, but others want to simply blame the pilot. Safety of helicopter flight operations will only be achieved when I, and my counterparts at the other manufacturers, face a raft of indignant pilots constantly trying to make their aircraft better, not a group of apologists who want to blame each other when an aircraft fails them.
Regardless of our collective opinion about how much out of control we will accept, the authorities should not let us debate it. In good military aircraft, there is no debate, and I can promise you, it would be a cold day in Hell before the FAA pilots I fly with would accept jack stall at 1.5 g.
Join Date: Jan 2001
Location: Chilliwack, BC Canada
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4Dogs,
My personal experiences have shown a complete disagreement to your post. I have unknowingly entered the "servo transparency" in a flight condition I feel was very routine and quite gentle.
I say to you, be careful of this situation, don't approach it with such casual disregard.
Given a higher gross weight ( Did you practice this with a full load ? ) a different flight altitude, a different 350 model, a different Outside air temperature, and most importantly, a flight situation where you MUST turn to aviod terrain, you may find that the aircraft may surprise you in how quick it bites.
You end your last post with "Stay Alive", good advice, I say ...practice it !
Fly the type smoothly....
Always leave yourself an "out".....
Anticipate that the control transparency may occur at the worst possible time.....
My personal experiences have shown a complete disagreement to your post. I have unknowingly entered the "servo transparency" in a flight condition I feel was very routine and quite gentle.
I say to you, be careful of this situation, don't approach it with such casual disregard.
Given a higher gross weight ( Did you practice this with a full load ? ) a different flight altitude, a different 350 model, a different Outside air temperature, and most importantly, a flight situation where you MUST turn to aviod terrain, you may find that the aircraft may surprise you in how quick it bites.
You end your last post with "Stay Alive", good advice, I say ...practice it !
Fly the type smoothly....
Always leave yourself an "out".....
Anticipate that the control transparency may occur at the worst possible time.....
Again Nick hits the nail squarely upon the head!
i believe that would be because the manufacturer originally called it the "ecureil" which i believe is french for squirrel...
AStar was a north american name attached to it...
AStar was a north american name attached to it...
Aerospecial called it Ecureuil - Squirrel - cause it was supposed to be a money saver for the operators just like the animal is provident and thrifty.
That was changed to A Star for North America since the name does not mean the same there.
Cheers
ATN
That was changed to A Star for North America since the name does not mean the same there.
Cheers
ATN
Join Date: Feb 2002
Location: Just over there....no there.
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Try ringing +49 2382 82082. they have just bought a B3 with good hours and I KNOW he always likes to sell his helicopters, nearly got a 212 rating until he sold them all from under me...drat!
Don't buy it too quick though, I might still get to fly it
Sorry, slip of the keyboard it\'s a B2 NOT a B3
Rick
Don't buy it too quick though, I might still get to fly it
Sorry, slip of the keyboard it\'s a B2 NOT a B3
Rick
AS 350 engines
Does anyone have any information about the Arriel 1b engines in the AS350 BA. Apparrently a small piece of metal has fallen off the shroud on module 2 and has gone through the whole engine causing total destruction......engine write off 240,000Euros !!
To make it better , this probably happened 2 years ago and it has been flying around on public transport all this time....like a time bomb. Turbomeca deny there is a design problem but how many engines have had this happen and how many crashes ??? Any info really appreciated.
To make it better , this probably happened 2 years ago and it has been flying around on public transport all this time....like a time bomb. Turbomeca deny there is a design problem but how many engines have had this happen and how many crashes ??? Any info really appreciated.
Join Date: Dec 2003
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Arriel 1B huh? Now that seems to be one damned fine engine if it has tolerated FOD some two years back that has apparently taken out the interior of the engine, yet no-one has noticed it.
No vibes? No power loss? Just kept on haulin' a*s.
Doesn't seem that there's any design problem if the chain of events are as written.
I saw a copy of the IFSR for the Arriel a few years back and it was impressive for its reliability. If I recall correctly I could expect an in-flight shut down from all causes (fuel exhaustion, false indications, minor fault precautionary included) each 100,000 or so hours and a catastrophic type engine event each 500,000 or so flight hours.
Going on the data I saw it seemed that I could expect the thing to go BANG once each couple of thousand years at the rate of effort I was doing. Then again, it could be tomorrow, couldn't it?
I still feel real comfortable with them though.
(O.K you guys, I know it's French)
STL
No vibes? No power loss? Just kept on haulin' a*s.
Doesn't seem that there's any design problem if the chain of events are as written.
I saw a copy of the IFSR for the Arriel a few years back and it was impressive for its reliability. If I recall correctly I could expect an in-flight shut down from all causes (fuel exhaustion, false indications, minor fault precautionary included) each 100,000 or so hours and a catastrophic type engine event each 500,000 or so flight hours.
Going on the data I saw it seemed that I could expect the thing to go BANG once each couple of thousand years at the rate of effort I was doing. Then again, it could be tomorrow, couldn't it?
I still feel real comfortable with them though.
(O.K you guys, I know it's French)
STL
Join Date: Jan 2005
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Advice on AS-350 Airconditioning
Does anyone have experience on a good replacement unit for the AS350 airconditioner? Specifically, the electric blower motors are hideously expensive for what they represent and they seem to only have a short life.
Is there a modification that can be made to a Squirrel to make the air vents as good as the Bell air vents (on the 206/407 models).
Many thanks.
Is there a modification that can be made to a Squirrel to make the air vents as good as the Bell air vents (on the 206/407 models).
Many thanks.
Join Date: Mar 2003
Location: the hills of halton
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What system is fitted ? Aero AIre , or Integated ( jack keen version).
http://www.maverickhelicopter.com/
If you talk to these guys I think they have had experience with both versions.
http://www.platinumaviation.com/
now sell the integrated flight system.
http://www.aeroaire.com/ is now run by enviro systems.
I think the french factory installed system was based on Aero aire .
http://www.maverickhelicopter.com/
If you talk to these guys I think they have had experience with both versions.
http://www.platinumaviation.com/
now sell the integrated flight system.
http://www.aeroaire.com/ is now run by enviro systems.
I think the french factory installed system was based on Aero aire .
Join Date: Oct 2004
Location: Where Men Are Men And Sheep Run Scared
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Integrated Flight Systems, owned by Platinum Aviation are the best in the business for air con systems for the AS350. Give them a call and talk to owner Leroy Aday.
www.integratedflightsys.com
and
www.platinumaviation.com
Cheers
Ned
www.integratedflightsys.com
and
www.platinumaviation.com
Cheers
Ned
