AS350 Astar / AS355 Twinstar [Archive Copy]
Rumour network, indeed!
Shawn, what's this about the Australian military finding significant problems with the hydraulics off handling?
AS350Bs and BAs were operated for years with few dramas and lots of practice hydraulics off landings. Very predictable and easy to handle, once the 'fault' was detected and the hydraulic isolate switch operated.
'Jack stall' was a discussed and demonstrated phenomenon in training courses, but I never experienced it or heard of it being a problem in normal aircraft use, and they got a bit of a caning manoeuvre-wise, much more so than the teetering-head types that were also used by the Aussie forces, because they could take it!
To paint this phenomenon (which certainly does exist but is only in my experience a problem if you like to throw the controls around like a gorilla, although to be fair, I don't know much about how they respond in extremely cold conditions) seems to be hysterical over-reaction based on a lot of hearsay.
Over...
Shawn, what's this about the Australian military finding significant problems with the hydraulics off handling?
AS350Bs and BAs were operated for years with few dramas and lots of practice hydraulics off landings. Very predictable and easy to handle, once the 'fault' was detected and the hydraulic isolate switch operated.
'Jack stall' was a discussed and demonstrated phenomenon in training courses, but I never experienced it or heard of it being a problem in normal aircraft use, and they got a bit of a caning manoeuvre-wise, much more so than the teetering-head types that were also used by the Aussie forces, because they could take it!
To paint this phenomenon (which certainly does exist but is only in my experience a problem if you like to throw the controls around like a gorilla, although to be fair, I don't know much about how they respond in extremely cold conditions) seems to be hysterical over-reaction based on a lot of hearsay.
Over...
"Just a pilot"
Collective Bias:
The present aircraft I'm in is the only one I've ever flown any significant time in that has SAMM servoes. There's no apparent difference as to jack stall.
The SAMMs have other bad habits unique to the type- they "kick" when the pressure comes up. It's in the RFM....
The present aircraft I'm in is the only one I've ever flown any significant time in that has SAMM servoes. There's no apparent difference as to jack stall.
The SAMMs have other bad habits unique to the type- they "kick" when the pressure comes up. It's in the RFM....
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First of all we need a EC tech rep on the line who actually knows what is going on - anyone, anyone?? Ken where are ya?
Secondly, has this phenomena ever led to loss of control causing an accident? Not that I am aware of, so is it really a design flaw or structural inadequacy? - Most incidences of jack stall that I have heard about have involved aircraft close to MAUW and close to Vne. Are those "normal" operating conditions?? Generally accepted procedure is to back off collective and cyclic, and control is regained. Why would you want to be in a full speed cyclic descent anyway????
And Nick - is it really a structural issue as opposed to hydraulic??
Because if this is the case, wouldn't one expect to see cracked blades, splintered stars, or bent pitch links?? I have never heard of this happening as a result of jack stall.
The aircraft has been designed to be flown with out hydraulics if necessary, and is controllable at speeds of up to 70 knots, without damage to the rotor system. If you are incredibly strong and willing, probably more - you just aren't getting any help from the hydraulics.
I believe it is more of a 'characteristic', that perhaps should be investigated a little more thoroughly, same as LTE for the 206 series, the T/R problem with the 407, or the phenomena of mast bending in the 204,205,and 412 that led to the RIN and limited torque settings in the RFM limitations.
Is it necessary or practical to change a major design feature such as the hydraulic system?? I think I can answer for Eurocopter.
Knowledge and training I think are the key to this "issue".
After all its not what you know that will kill ya...........
Arm out the window...I'm with you on this one
Secondly, has this phenomena ever led to loss of control causing an accident? Not that I am aware of, so is it really a design flaw or structural inadequacy? - Most incidences of jack stall that I have heard about have involved aircraft close to MAUW and close to Vne. Are those "normal" operating conditions?? Generally accepted procedure is to back off collective and cyclic, and control is regained. Why would you want to be in a full speed cyclic descent anyway????
And Nick - is it really a structural issue as opposed to hydraulic??
The issue is not hydraulic, it is rotor structure. The Squirrel can bend and break its rotor if handled near stall. Weakening the hydraulics is the "fix" according to Gray Matter.
The aircraft has been designed to be flown with out hydraulics if necessary, and is controllable at speeds of up to 70 knots, without damage to the rotor system. If you are incredibly strong and willing, probably more - you just aren't getting any help from the hydraulics.
I believe it is more of a 'characteristic', that perhaps should be investigated a little more thoroughly, same as LTE for the 206 series, the T/R problem with the 407, or the phenomena of mast bending in the 204,205,and 412 that led to the RIN and limited torque settings in the RFM limitations.
Is it necessary or practical to change a major design feature such as the hydraulic system?? I think I can answer for Eurocopter.
Knowledge and training I think are the key to this "issue".
After all its not what you know that will kill ya...........
Arm out the window...I'm with you on this one
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Inadequate is the definition of a rotor that can be bent by the pilot during relatively normal maneuvers.
All that aside this is a not a real issue. The recovery from jack-stall is simple, ease the manoeuvre. It is not a safety issue if the pilot flys within the capability of the aircraft - just like any aircraft there are manoeuvre boundarys.
The argument from SASLess that he should be able to "put the controls to the mechanical stop...collective full up....cyclic full over and forward...and pedals full right" is frankly daft, at low speed you might get away with it but in the cruise or faster,with the contol authority of a semi-rigid head you would end up in a very hazardous situation.
GA
Gray Area,
I think you are missing the point....we are discussing the 350, not the Bell two bladed head. Not withstanding that, there are things that I will not do in various helicopters for various reasons. In any Sikorsky I or Bell helicopter I have flown....the hydraulics always kept up with the control inputs...take from that what you will. In the MBB products....except for some roll coupling...the hydraulics keep up with control inputs. In the Boeing-Vertol products I have flown...the hydraulics keep up with control inputs....it is only on the 350 we hear of this "Jacques Stall" event.
Yes, in the Bell two bladed heads...if you show your butt you can snap the mast off at the top....yes, if you enter negative "g" you can get into mast bumping and snap the head off...or lose control. Yes, in really aggressive maneuvering you can get yourself into a pickle in very high speed, high "g" pullups following a gun-run in a Cobra. Yes, you can over stress the Mast on the Bell 204-212 series if you pull too much power at too high an airspeed....but in all of these events...the hydaulics work with full control authority.
Your question "why would anyone want to operate near Vne at max weight?" Everyone of us who fly these things for a living will do that at some time. As long as the power utilized remains within the set parameters....we usually go for whatever speed we can get on long distance flights....Vne is the limit.....not near Vne....otherwise the Vne would be lower than it is.
There is no denying the fact....the controls should not enter "Jacques Stall" and remove the control of the aircraft away from the pilot. It is poor engineering at best in my humble opinion.
I think you are missing the point....we are discussing the 350, not the Bell two bladed head. Not withstanding that, there are things that I will not do in various helicopters for various reasons. In any Sikorsky I or Bell helicopter I have flown....the hydraulics always kept up with the control inputs...take from that what you will. In the MBB products....except for some roll coupling...the hydraulics keep up with control inputs. In the Boeing-Vertol products I have flown...the hydraulics keep up with control inputs....it is only on the 350 we hear of this "Jacques Stall" event.
Yes, in the Bell two bladed heads...if you show your butt you can snap the mast off at the top....yes, if you enter negative "g" you can get into mast bumping and snap the head off...or lose control. Yes, in really aggressive maneuvering you can get yourself into a pickle in very high speed, high "g" pullups following a gun-run in a Cobra. Yes, you can over stress the Mast on the Bell 204-212 series if you pull too much power at too high an airspeed....but in all of these events...the hydaulics work with full control authority.
Your question "why would anyone want to operate near Vne at max weight?" Everyone of us who fly these things for a living will do that at some time. As long as the power utilized remains within the set parameters....we usually go for whatever speed we can get on long distance flights....Vne is the limit.....not near Vne....otherwise the Vne would be lower than it is.
There is no denying the fact....the controls should not enter "Jacques Stall" and remove the control of the aircraft away from the pilot. It is poor engineering at best in my humble opinion.
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SASless
Applying that line of reasoning then to other aircraft...............
You should be able to be low and slow and heavy in a 206............
You should be able to punch in as much pedal as you want in a 407......................
You should be able to push over a teetering system into low G.........
You should be able to fly into icing conditions.....................
Is fuel REALLY necessary??................................
Point is, every aircraft has its deficiencies, quirks, characteristics etc etc, and granted some are of grave enough concern that they eventually find their way into RFMs as a pilot procedure, or a limitation, while others remain as a known phenomenon to be discussed, taught, trained.
Vortex ring state, or settling with power, doesn't imply a design flaw on a particular helicopter (or does it???)
I do see your point on a system that maybe should perform better, but if it is a known characteristic, isn't the first and obvious fix not pilot technique?? As in not pushing over a teetering head, not putting yourself into LTE, or getting into settling with power?
Applying that line of reasoning then to other aircraft...............
You should be able to be low and slow and heavy in a 206............
You should be able to punch in as much pedal as you want in a 407......................
You should be able to push over a teetering system into low G.........
You should be able to fly into icing conditions.....................
Is fuel REALLY necessary??................................
Point is, every aircraft has its deficiencies, quirks, characteristics etc etc, and granted some are of grave enough concern that they eventually find their way into RFMs as a pilot procedure, or a limitation, while others remain as a known phenomenon to be discussed, taught, trained.
Vortex ring state, or settling with power, doesn't imply a design flaw on a particular helicopter (or does it???)
I do see your point on a system that maybe should perform better, but if it is a known characteristic, isn't the first and obvious fix not pilot technique?? As in not pushing over a teetering head, not putting yourself into LTE, or getting into settling with power?
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I've been flying, among others, A stars for 18 years now and have to say that I've experienced jackstall only twice on B models and when I was doing quite an agressive flying. Never had any more on twins (F's and N's) although I have to say that it's been a long time since I don't fly the hard way anymore. So for me it has not been an issue but I've never flown them -25 ºC and it seems that some pilots have encountered that situation in normal flight envelopes
, if really so it should be something to take care of.
I fly my AS 355 N with total confidence in flight controls. Just my 2 cents
Buen vuelo
, if really so it should be something to take care of.I fly my AS 355 N with total confidence in flight controls. Just my 2 cents
Buen vuelo
Sandy,
In response....in each situation you mentioned...the pilot has the control....not the aircraft. When the controls quit working...the pilot does not have control.
LTE...the aircraft is fully functional...the controls work...might be the tail rotor does not have the ability to cope with the yawing moment but the controls are working. Judgement is the main issue there....keep your nose into the wind...don't let a yaw rate develop.
407 and its tail rotor....seems like the controls work too good there.
Bell Helicopters and their tail rotors are much akin to the "Jacques Stall" issue. Thus you will not get much argument from me about those issues.
Zero "G"....again the controls got you there....judgement is the issue.
Icing....the controls are working....judgement got you into the ice.
Low, slow, and heavy in a 206.....again...judgement got you there.
Fuel....pilot judgement again.
In the 350....with "Jacques Stall"....too many reports of it happening for it to be a simple judgement thing....gets back to engineering and the controls not working all the time.
In response....in each situation you mentioned...the pilot has the control....not the aircraft. When the controls quit working...the pilot does not have control.
LTE...the aircraft is fully functional...the controls work...might be the tail rotor does not have the ability to cope with the yawing moment but the controls are working. Judgement is the main issue there....keep your nose into the wind...don't let a yaw rate develop.
407 and its tail rotor....seems like the controls work too good there.
Bell Helicopters and their tail rotors are much akin to the "Jacques Stall" issue. Thus you will not get much argument from me about those issues.
Zero "G"....again the controls got you there....judgement is the issue.
Icing....the controls are working....judgement got you into the ice.
Low, slow, and heavy in a 206.....again...judgement got you there.
Fuel....pilot judgement again.
In the 350....with "Jacques Stall"....too many reports of it happening for it to be a simple judgement thing....gets back to engineering and the controls not working all the time.
I got hydraulic feedback in a Huey once while manoeuvering 'positively' to avoid hitting someone else in a formation, which felt just like the dreaded Jack Stall - unusually fast and large cyclic movement leading to forces through the controls which went away as soon as the severity of the manoeuvre was reduced.
That's the same thing as we're talking about with the Squirrel, isn't it?
That's the same thing as we're talking about with the Squirrel, isn't it?
For sure hydraulics or pylon mount issues that felt like feedback...or mast bumping....? Used to get hydraulics failure on the Alouette III in severe turbulence....hit a real down draft...all the fluid went to the top of the resevoir....pump cavitated....feedback in the controls...till the down draft was replaced with more normal forces.
Jack Stall in the AH-1T
During testing at Patuxent River we experienced a form of Jack Stall in the AH-1T (PT-6 powered AH -1 with a 214 rotor and tail rotor). Even with a 3000PSI hydraulic system the servos were not able to react the flight loads during a symmetrical 3 g pull up. During this maneuver we experienced significant levels of control feed back in pitch. Review of the data also revealed that we exceeded test cards imposed limit of 3 g's. I do not believe that the weak hydraulic system is actually capable of protecting the airframe. Limitations do that.
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The "B" series used to be called "Falling Stars". However, paco is right: the newer version of the LTS101 is apparently much better.
See:
http://www.pprune.org/forums/showthr...ghlight=lts101
See:
http://www.pprune.org/forums/showthr...ghlight=lts101
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SO who knows what the AS350C was ?. One of the early Canadian ships shows c to d to b on its registration.
Mark C-GMEY Serial No 1004
Common Name Aerospatiale Type Certified Model AS 350B
Identification Plate Model AS350C TRANS D TRANS B
Base Of Op. - Country CANADA
Base Of Op. - Province Quebec
Base Of Op. - Location Les Cedres
File Location Dorval Basis for Eligibility for Registration Type Certificate - H83
Type of Registration Commercial
Category Helicopter Weight (Kgs) 1950
Manufacturer Societe Nationale Industrielle Aerospatiale
Year of Manufacture 1979
Country of Manufacture FRANCE
Link to all you need to know about AS350 models
http://www.aviationtoday.com/cgi/rw/...=1003as350.htm
Mark C-GMEY Serial No 1004
Common Name Aerospatiale Type Certified Model AS 350B
Identification Plate Model AS350C TRANS D TRANS B
Base Of Op. - Country CANADA
Base Of Op. - Province Quebec
Base Of Op. - Location Les Cedres
File Location Dorval Basis for Eligibility for Registration Type Certificate - H83
Type of Registration Commercial
Category Helicopter Weight (Kgs) 1950
Manufacturer Societe Nationale Industrielle Aerospatiale
Year of Manufacture 1979
Country of Manufacture FRANCE
Link to all you need to know about AS350 models
http://www.aviationtoday.com/cgi/rw/...=1003as350.htm
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I read somewhere recently that a soloy conversion is on the way for the AS-350 using the updated LTS engine with much increased output and twin channel fadec which will give even the B3 a run for its money with MUCH lower DOC's.....would be a great conversion.
With regard to the AS-350 series all the basic airfames are more or less the same not including the engine / airframe interface parts, the t/rotor compensator fitted from the B1 onwards and some minor frames added to the underside of the tranny deck for a/frames modded from B upwards...... The vertical and horizontal stabs are a little different for almost all models. There is a fence on the tailboom of the B1 and B2 that must not have achieved a whole lot because it is not to be found on the B3....
With regard to the AS-350 series all the basic airfames are more or less the same not including the engine / airframe interface parts, the t/rotor compensator fitted from the B1 onwards and some minor frames added to the underside of the tranny deck for a/frames modded from B upwards...... The vertical and horizontal stabs are a little different for almost all models. There is a fence on the tailboom of the B1 and B2 that must not have achieved a whole lot because it is not to be found on the B3....
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OCTANE100,
I beleive also that Bell will introduce a version of the LTS 101 into the 407 from 2006 thereabouts!..should be interesting.
Here in NSW the National Parks have a 350BA with a C-30 Fitted to it
I beleive also that Bell will introduce a version of the LTS 101 into the 407 from 2006 thereabouts!..should be interesting.
Here in NSW the National Parks have a 350BA with a C-30 Fitted to it
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Soloy (pappilon ownes the soloy/ STC ) does have a STC for the LTS101, they are calling it a B2 101 or someting. They had one at the show this year. Supposedly the 101 is a super eng now. One thing about the 101 in the d model is it burns dirty, turns the tailboom black in a hurry.
The 101 DOC is a fair bit lower than the french eng.
rb
The 101 DOC is a fair bit lower than the french eng.
rb