AS350 Astar / AS355 Twinstar [Archive Copy]
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Uh, Oh, I might have to agree with Lu on this. heedm, note the date and time!
Jack stall is a sign of a servo system with too little force capability, and is not acceptable in modern helicopters, as a rule. It is caused when the stall of the retreating blade causes the blade to change its pitching moment sharply downward, which makes the blade try to dive. The strong downward force is fought by the pitch change links, swashplate and servos. At Sikorsky, we set the design requirement of the servos so that with one stage failed, the other has the full capability to fly the flight envelope. That means that we have twice as much servo force capability as needed in normal unfailed circumstances.
I personally set the S-76 flight test points to prove this, with max weight, one servo turned off, we pulled over 2 g's at Vne with no change in stick feel.
A helicopter that shows jack stall is on the edge of taking over for the pilot, and turning him into a passenger for what could be a very short ride. Treat all jack stall cases as bad ju-ju, because the difference between a stick that throbs a few cycles, and one that thrashes around and allows the aircraft to go ape is a very small difference in maneuver load factor.
Jack stall is a sign of a servo system with too little force capability, and is not acceptable in modern helicopters, as a rule. It is caused when the stall of the retreating blade causes the blade to change its pitching moment sharply downward, which makes the blade try to dive. The strong downward force is fought by the pitch change links, swashplate and servos. At Sikorsky, we set the design requirement of the servos so that with one stage failed, the other has the full capability to fly the flight envelope. That means that we have twice as much servo force capability as needed in normal unfailed circumstances.
I personally set the S-76 flight test points to prove this, with max weight, one servo turned off, we pulled over 2 g's at Vne with no change in stick feel.
A helicopter that shows jack stall is on the edge of taking over for the pilot, and turning him into a passenger for what could be a very short ride. Treat all jack stall cases as bad ju-ju, because the difference between a stick that throbs a few cycles, and one that thrashes around and allows the aircraft to go ape is a very small difference in maneuver load factor.
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Nick,
2G equates approximately to a sustained level turn at 60 degrees of bank, if I remember correctly.
The manoeuvres I have experienced as required to induce jackstall are beyond that.
If the aircraft are flown within their published limits there is no problem.
However, I may well agree that Sikorsky aircraft may be built with more margin in hand in some areas, obviously in the case of the S-76 and other aircraft with an input from your good self. It doesn't mean to say that another manufacturer's product is unsafe though.
2G equates approximately to a sustained level turn at 60 degrees of bank, if I remember correctly.
The manoeuvres I have experienced as required to induce jackstall are beyond that.
If the aircraft are flown within their published limits there is no problem.
However, I may well agree that Sikorsky aircraft may be built with more margin in hand in some areas, obviously in the case of the S-76 and other aircraft with an input from your good self. It doesn't mean to say that another manufacturer's product is unsafe though.
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To get transparency in the AS 350, the manouevers are so severe that you could fly without ever experiencing it, i have had it demonstrated and as one of the other posters said,it is quite a deal to set it up, I don't see it as a design flaw, it was designed at the time with the technology available, its an excellent aircraft and an absolutely stable platform to work from. Ive flown up to and including the B2, i havn't seen or read the B3 data, but if it was a serious concern, the B3 may have changed.
Anyone who operates an As 350 outside the performance specs and limitations is asking for trouble, doing anything, its a light helicopter with limits, the manufacturer has identified them for the pilot, fairly straightforward.
It is an extremely violent manoeuver to get to transparency. I have only had it when its demonstrated, never encountered it in normal ops or had other pilots experience it in normal ops.
Anyone who operates an As 350 outside the performance specs and limitations is asking for trouble, doing anything, its a light helicopter with limits, the manufacturer has identified them for the pilot, fairly straightforward.
It is an extremely violent manoeuver to get to transparency. I have only had it when its demonstrated, never encountered it in normal ops or had other pilots experience it in normal ops.
Funny term, transparency.
You would think that in the normal course of events, the servos would feel 'transparent', i.e. you wouldn't know they were there, so to speak.
I'd say that jack stalling would be when they weren't transparent!
You would think that in the normal course of events, the servos would feel 'transparent', i.e. you wouldn't know they were there, so to speak.
I'd say that jack stalling would be when they weren't transparent!
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Shytorque,
I agree that the 2 g's is not terribly severe, but recall that is with half the total servo force, since we had turned one system off prior to the maneuver.
The test pilots who took the AS-365 through air combat trials frequently experienced jack stall to the point that the aircraft would wind up tightening its own turn. This occurred at 2.4 g's or less, which is not terribly far out in the spectrum of possible maneuvers. One can argue if this is acceptable or not, but the ideal helicopter should not have the ability to out-fight its pilot, in my humble opinion. None of this should be interpreted as impuning a very fine helicopter, just stating what we should be striving for.
In any case, the concept of jack stall is clearly understood by the bunch, we can argue (politely, of course!) the specific level at which it should occur (clearly far out in the envelope).
Like weak tail rotors (which create the need for careful LTE training), jack stall is a fact of life, but I hope we all get to help raise the bar and make it something we tell newbies about with the phrase, "Sonny, I remember the time when...."
[ 08 December 2001: Message edited by: Nick Lappos ]
I agree that the 2 g's is not terribly severe, but recall that is with half the total servo force, since we had turned one system off prior to the maneuver.
The test pilots who took the AS-365 through air combat trials frequently experienced jack stall to the point that the aircraft would wind up tightening its own turn. This occurred at 2.4 g's or less, which is not terribly far out in the spectrum of possible maneuvers. One can argue if this is acceptable or not, but the ideal helicopter should not have the ability to out-fight its pilot, in my humble opinion. None of this should be interpreted as impuning a very fine helicopter, just stating what we should be striving for.
In any case, the concept of jack stall is clearly understood by the bunch, we can argue (politely, of course!) the specific level at which it should occur (clearly far out in the envelope).
Like weak tail rotors (which create the need for careful LTE training), jack stall is a fact of life, but I hope we all get to help raise the bar and make it something we tell newbies about with the phrase, "Sonny, I remember the time when...."
[ 08 December 2001: Message edited by: Nick Lappos ]
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Hey Nick : I always wondered why the S-76
has such High Hydraulic pressure (3,000 psi)for a helicopter with a Gross Weight under 12,000 Lbs. Is it because the servo actuators are relatively small ? ?
has such High Hydraulic pressure (3,000 psi)for a helicopter with a Gross Weight under 12,000 Lbs. Is it because the servo actuators are relatively small ? ?
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Nick,
I certainly agree that a combat aircraft should be able to endure more than its pilot can stomach.
But the AS-350 could hardly be described as a combat aircraft!
I certainly agree that a combat aircraft should be able to endure more than its pilot can stomach.
But the AS-350 could hardly be described as a combat aircraft!
Not a combat aircraft? - dont say that around the French!
Nick, What you are saying makes sense, but again I harp on the severity required to enter jack stall in the AS350 (not the 365), I am guessing from experience, but I would say around 3 Gs, or slightly less. As you say - jack stall occurs in or approaching RBS, but that is the point we have been trying to make - why are you flying the aircraft into RBS? Fighter maneuvering aside of course!! Thus the majority opinion was that as it only results from gross misshandling - perhaps calling it a design flaw was a bit over the top. Does this level of severity have to occur during certification? Or do you restrict it to 2 or so Gs as you indicated for the S76?
Lastly, do you think that the RBS under these conditions is a G stall?
Nick, What you are saying makes sense, but again I harp on the severity required to enter jack stall in the AS350 (not the 365), I am guessing from experience, but I would say around 3 Gs, or slightly less. As you say - jack stall occurs in or approaching RBS, but that is the point we have been trying to make - why are you flying the aircraft into RBS? Fighter maneuvering aside of course!! Thus the majority opinion was that as it only results from gross misshandling - perhaps calling it a design flaw was a bit over the top. Does this level of severity have to occur during certification? Or do you restrict it to 2 or so Gs as you indicated for the S76?
Lastly, do you think that the RBS under these conditions is a G stall?
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IHL,
The higher hydraulic pressure allows more energy to be transmitted, and it allows smaller piston areas in the servo for a given force, so it saves weight. 3,000 pounds per square inch is now considered old hat. The S-92 is 4,000 psi, and the V-22 is 5,000 psi (!!) The tradeoff is against the leak potential and the need to protect against line burst.
ShyTorque,
The real issue is a subject dear to my heart. Our machines should not execute the pilot for an error, I think, but the levels of jack stall we are discussing are really just annoying characteristics, so I really agree with the group, I think.
Helmetfire,
Generally, few helicopters can pull 3 g's, and I'll bet the 350 cannot. High g capability robs hover performance, so designers give it out gingerly. The Black Hawk can pull 3.5, and an Apache can get close to that, Comanche can pull almost 4. I have hit 2.7 in the S-76, doing stuff that would make many pilots toss their cookies (I used to demonstrate helo aerobatics to the Army when they were deciding how to specify LHX maneuvers). Estimating g's is hard, I really can't without a g meter.
Max G capability is actually easily estimated based on blade chord, tip speed and diameter. I can give you a reference, if you'd like.
The issue here is really the nature of carefree handling. As long as jack stall does not cause control loss, it is not a major issue, and we really agree. If it robs the pilot of control, it should be fixed, even if the maneuver is considered extreme. FAR states that we must test to the maximum the aircraft will experience in flight, so if someone comes back and pulled more, we didn't test enough. Flight manual cautions and the "pilot error" rubber stamp are quick outs for poor designs.
We used 2 g's with a servo failure in the S-76 to assure that nobody would ever get jack stall, reasoning that folks would not pull near stall loads after a failure. With both servos on, the controls can never get to jack stall under any case, as is true with the Black Hawk.
Something I must calrify is the notion that any helicopter can hit any g if the pilot gets wild enough. The max g's for a helo are set by the rotor design, especially the solidity (amount of blade area relative to the disk area). The rotor can only pull a few g's before it stalls, and sometimes the maneuver can be quite mild. The typical rotor stall g level drops quickly with altitude, so if the maneuver took 3 g's at sea level, it might stall at 2 g's at 10,000 feet DA, a much more achievable level, and near Vne, it might stall at only 1.5 g's.
If my helicopter could lose control in jack stall at 1.5 g's, I'd find another!
You ask about g stall as opposed to speed stall, I think. There is no difference, really. The relationship between g and speed is that the stall g drops with speed until at some speed beyond Vne, the aircraft stalls at 1 g. I will be glad to email you some charts of this relationship, or give you some references, if you'd like.
You ask, "Does this level of severity have to occur during certification? Or do you restrict it to 2 or so Gs as you indicated for the S76?" Please note that the S-76 is jack stall free with only 50% of its servo strength, and jack stall with both systems healthy is impossible. The manufacturer must test to a maneuver level that he then declares to be the maximum (the phrase is that the test maneuvers are extreme enough so that the probability of exceeding them in service is "extremely remote" which is FAA speak for 1 in 10e9 hours. In other words, if 1,000 helos are building 1,000 hours per year, in 1,000 years we will have one event! Using this definition, it is not good design to experience jack stall (to loss of control) in service, having certified that your tests were so thorough.
The higher hydraulic pressure allows more energy to be transmitted, and it allows smaller piston areas in the servo for a given force, so it saves weight. 3,000 pounds per square inch is now considered old hat. The S-92 is 4,000 psi, and the V-22 is 5,000 psi (!!) The tradeoff is against the leak potential and the need to protect against line burst.
ShyTorque,
The real issue is a subject dear to my heart. Our machines should not execute the pilot for an error, I think, but the levels of jack stall we are discussing are really just annoying characteristics, so I really agree with the group, I think.
Helmetfire,
Generally, few helicopters can pull 3 g's, and I'll bet the 350 cannot. High g capability robs hover performance, so designers give it out gingerly. The Black Hawk can pull 3.5, and an Apache can get close to that, Comanche can pull almost 4. I have hit 2.7 in the S-76, doing stuff that would make many pilots toss their cookies (I used to demonstrate helo aerobatics to the Army when they were deciding how to specify LHX maneuvers). Estimating g's is hard, I really can't without a g meter.
Max G capability is actually easily estimated based on blade chord, tip speed and diameter. I can give you a reference, if you'd like.
The issue here is really the nature of carefree handling. As long as jack stall does not cause control loss, it is not a major issue, and we really agree. If it robs the pilot of control, it should be fixed, even if the maneuver is considered extreme. FAR states that we must test to the maximum the aircraft will experience in flight, so if someone comes back and pulled more, we didn't test enough. Flight manual cautions and the "pilot error" rubber stamp are quick outs for poor designs.
We used 2 g's with a servo failure in the S-76 to assure that nobody would ever get jack stall, reasoning that folks would not pull near stall loads after a failure. With both servos on, the controls can never get to jack stall under any case, as is true with the Black Hawk.
Something I must calrify is the notion that any helicopter can hit any g if the pilot gets wild enough. The max g's for a helo are set by the rotor design, especially the solidity (amount of blade area relative to the disk area). The rotor can only pull a few g's before it stalls, and sometimes the maneuver can be quite mild. The typical rotor stall g level drops quickly with altitude, so if the maneuver took 3 g's at sea level, it might stall at 2 g's at 10,000 feet DA, a much more achievable level, and near Vne, it might stall at only 1.5 g's.
If my helicopter could lose control in jack stall at 1.5 g's, I'd find another!
You ask about g stall as opposed to speed stall, I think. There is no difference, really. The relationship between g and speed is that the stall g drops with speed until at some speed beyond Vne, the aircraft stalls at 1 g. I will be glad to email you some charts of this relationship, or give you some references, if you'd like.
You ask, "Does this level of severity have to occur during certification? Or do you restrict it to 2 or so Gs as you indicated for the S76?" Please note that the S-76 is jack stall free with only 50% of its servo strength, and jack stall with both systems healthy is impossible. The manufacturer must test to a maneuver level that he then declares to be the maximum (the phrase is that the test maneuvers are extreme enough so that the probability of exceeding them in service is "extremely remote" which is FAA speak for 1 in 10e9 hours. In other words, if 1,000 helos are building 1,000 hours per year, in 1,000 years we will have one event! Using this definition, it is not good design to experience jack stall (to loss of control) in service, having certified that your tests were so thorough.
Thanks for your response Nick. I should have clarified the G stall - what I was asking was: do you think the RBS we are talking about here was primarily induced by the G loading being experienced (as opposed to the retreating blade speed)?
your point about having the pilot executed by the machine design is well said, and I do not dispute, but I am curious as to where the limits of manuever harshness during testing are set. For example, you stated that you tested the s76 to two Gs with half the servos because you couldn't imagine anyone pulling to the stall with a servo failure. This is the point being made above - very few (none of the above so far) AS350 pilots can imagine pulling so hard as to experience jack stall, it is as you say: a manuever in which you mightlose your cookies! So if the Bell teetering head can get away with not being termed a design flaw because it can come off during gentle manuevering, and fixed wing stalling can too - jack stall is surely not a design flaw, or at least labelling it as such is a little harsh isnt it?
your point about having the pilot executed by the machine design is well said, and I do not dispute, but I am curious as to where the limits of manuever harshness during testing are set. For example, you stated that you tested the s76 to two Gs with half the servos because you couldn't imagine anyone pulling to the stall with a servo failure. This is the point being made above - very few (none of the above so far) AS350 pilots can imagine pulling so hard as to experience jack stall, it is as you say: a manuever in which you mightlose your cookies! So if the Bell teetering head can get away with not being termed a design flaw because it can come off during gentle manuevering, and fixed wing stalling can too - jack stall is surely not a design flaw, or at least labelling it as such is a little harsh isnt it?
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This is truly a study in sufficiency, because you are quite right, the issue is subjective. The jack stall we are discussing is a benign type, where control is not compromised, so it could be termed a marginal but acceptable characteristic.
Regarding the differences between retreating blade stall and g stall, there really is none. The stall is at the retreating blade, and is due to too much angle of attack. This could be achieved at 1.25 g at Vne, or 2.0 at 80 knots, the cause and results are the same. If you plot the slope between those two hypothetical points, that is the relationship between thrust and speed that defines retreating blade stall. If you toss in the effects of density altitude, you create a parallel line that is at lower g for higher altitude. Another parallel line could represent the effects of lower rpm.
In other words, more g or more speed or lower rpm or higher altitude all effect retreating blade stall.
Regarding the differences between retreating blade stall and g stall, there really is none. The stall is at the retreating blade, and is due to too much angle of attack. This could be achieved at 1.25 g at Vne, or 2.0 at 80 knots, the cause and results are the same. If you plot the slope between those two hypothetical points, that is the relationship between thrust and speed that defines retreating blade stall. If you toss in the effects of density altitude, you create a parallel line that is at lower g for higher altitude. Another parallel line could represent the effects of lower rpm.
In other words, more g or more speed or lower rpm or higher altitude all effect retreating blade stall.
"Just a pilot"
In my paranoid imaginings (result of this thread) I'm wondering where in "Chickenman's" flying life he could expect this problem to roast him?
Lots of cyclic demand, even at normal G? I can envision being rather busy if I suffered complete antitorque failure at a high hover- what with the throttle on the floor and probably over a hover hole...
Lots of cyclic demand, even at normal G? I can envision being rather busy if I suffered complete antitorque failure at a high hover- what with the throttle on the floor and probably over a hover hole...
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Clue #1. It usually works for me. Go to the website www.eurocopter.com,www.europterusa.com, www.eurocopter.ca, www.eads.net
If you cant find the info there, ask them they usually will send some fancy brochure...
or find a dealer, he may think you want to buy one and take you out to lunch......ha ha
If you cant find the info there, ask them they usually will send some fancy brochure...
or find a dealer, he may think you want to buy one and take you out to lunch......ha ha
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interesting discussion.
i also used to fly the as350 and i used to do aerobatics in it (different environment so settle down!) and teach others to do them. i believe that jack stall was an intentional design feature and i believe that it was a carry-over from the gazelle.
the facts are that jack stall was progressive and you could fly through it if necessary. i saw it as the rotary equivalent of the plankwing "buzz" that accompanied impending stall - in other words you knew you were at the limit and if you continued there were identifiable consequences.
after my AS 350 experience with jack stall, i had cause to rethink some previous experiences in uh-1 gunships where we thought we were regularly getting thrown out of maneuvers due to retreating blade stall. some might have been rbs, but i came to believe that many of them could have been jack stall (the benign ones) and others could have been jack stall followed by rbs when we couldn't back off in time.
anyway, despite the lu hysteria, it still seems to me that "transparency" is a good design feature because it alerts you progressively to an impending limtation that in effect is being sensed through the feedback load on the control horn.
i also used to fly the as350 and i used to do aerobatics in it (different environment so settle down!) and teach others to do them. i believe that jack stall was an intentional design feature and i believe that it was a carry-over from the gazelle.
the facts are that jack stall was progressive and you could fly through it if necessary. i saw it as the rotary equivalent of the plankwing "buzz" that accompanied impending stall - in other words you knew you were at the limit and if you continued there were identifiable consequences.
after my AS 350 experience with jack stall, i had cause to rethink some previous experiences in uh-1 gunships where we thought we were regularly getting thrown out of maneuvers due to retreating blade stall. some might have been rbs, but i came to believe that many of them could have been jack stall (the benign ones) and others could have been jack stall followed by rbs when we couldn't back off in time.
anyway, despite the lu hysteria, it still seems to me that "transparency" is a good design feature because it alerts you progressively to an impending limtation that in effect is being sensed through the feedback load on the control horn.
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I took this from a discussion forum on www.canadianaviation.ca.....
"except the only time I ever got into the "Servo Transparency" in my 2,000 + Astar hours was in a B model (Approx 4000 lb AUW) in a gentle turn around a fire on a calm August day at 4,000 Ft....go figure that one out??? "
I only mention it because somebody said that it only happens under extreme conditions. I have found that things like this that could happen often do just when you don't want them, despite what designers and test pilots say. In that respect, I think it should have been fixed before now. The accumulator is there to allow reduction in speed in a timely manner without going to the expense of adding a second hydraulic system.
And talking about hangovers from gazelles.... our Twinstar has a crap electrical system as well, but I won't go there....
phil
"except the only time I ever got into the "Servo Transparency" in my 2,000 + Astar hours was in a B model (Approx 4000 lb AUW) in a gentle turn around a fire on a calm August day at 4,000 Ft....go figure that one out??? "
I only mention it because somebody said that it only happens under extreme conditions. I have found that things like this that could happen often do just when you don't want them, despite what designers and test pilots say. In that respect, I think it should have been fixed before now. The accumulator is there to allow reduction in speed in a timely manner without going to the expense of adding a second hydraulic system.
And talking about hangovers from gazelles.... our Twinstar has a crap electrical system as well, but I won't go there....
phil
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scrubba,
Save us from such wonderful design features, please! The issue is that the hydraulics are too weak to keep the blades from arguing with you. As Paco relates, the incidence of stall can occur at relatively low maneuver states.
You have been lucky that the "transparency" occurred where the recovery is simple. The problem is that the mild stick wiggles you have felt are nothing compared to what could be dealt to you in other circumstances. Should the stick simply whip around the cockpit and let the aircraft suddenly take over, you would probably not declare that a design feature! The 365 family does that, and the maneuver ends when the aircraft finally runs out of airspeed, so control can be regained. Should the aircraft find some comfortable dirt or rock to nestle into before it lets you become PIC again, the flight might come to a rapid halt, thanks to that handy-dandy design feature you like so much.
I hate to agree with Lu (and I think hard about it, believe me!) but let's all push for power steering that works all the time, and helos that don't stall too early.
I hear the same apology for LTE in this group ("crummy pilots deserve to be punished"), and I ask us all to please seek helos that don't require budding Astronauts to keep them safe. The helicopter mission is hard enough, with the demands for extra judgement, fine motor skills and great airmanship to keep the outside world from hurting us and our machines. Let us at least ask our machines to be our partners, and not our adversaries, in the quest for better safety. If our safety record can't be raised, we might always be a mere sidelight in the world of aviation.
Paco, that incidence illustrates what I was talking about above in this thread - that stall is stall, it is not g stall or speed stall. The August day was warm, I'll bet, and the aircraft was heavy, and that turn crossed the stall line by a bit.
[ 15 December 2001: Message edited by: Nick Lappos ]
Save us from such wonderful design features, please! The issue is that the hydraulics are too weak to keep the blades from arguing with you. As Paco relates, the incidence of stall can occur at relatively low maneuver states.
You have been lucky that the "transparency" occurred where the recovery is simple. The problem is that the mild stick wiggles you have felt are nothing compared to what could be dealt to you in other circumstances. Should the stick simply whip around the cockpit and let the aircraft suddenly take over, you would probably not declare that a design feature! The 365 family does that, and the maneuver ends when the aircraft finally runs out of airspeed, so control can be regained. Should the aircraft find some comfortable dirt or rock to nestle into before it lets you become PIC again, the flight might come to a rapid halt, thanks to that handy-dandy design feature you like so much.
I hate to agree with Lu (and I think hard about it, believe me!) but let's all push for power steering that works all the time, and helos that don't stall too early.
I hear the same apology for LTE in this group ("crummy pilots deserve to be punished"), and I ask us all to please seek helos that don't require budding Astronauts to keep them safe. The helicopter mission is hard enough, with the demands for extra judgement, fine motor skills and great airmanship to keep the outside world from hurting us and our machines. Let us at least ask our machines to be our partners, and not our adversaries, in the quest for better safety. If our safety record can't be raised, we might always be a mere sidelight in the world of aviation.
Paco, that incidence illustrates what I was talking about above in this thread - that stall is stall, it is not g stall or speed stall. The August day was warm, I'll bet, and the aircraft was heavy, and that turn crossed the stall line by a bit.
[ 15 December 2001: Message edited by: Nick Lappos ]
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Yup, stall is stall, as many beaver pilots have found when turning low and slow...
here's another from the same thread, a sobering thought...
"110 kts, straight and level, collective bottomed, 500 lbs below max gross, descent off the top of the mountain - wind sheer, a/s up to 155kts, a/c snapped to the right 90 degrees. both arms could not pull it back, cyclic was solid. you can get ST any number of ways."
You know, I don't like aircraft that bite. I know the Astar is a good machine, and has had a lot of good stuff built in from the design stages, but that sort of thing should have been fixed. To my mind a limitation is something that results from natural causes, such as something that all engineers know about, such as, say helicopters don't fly faster than a certain maximum speed. This is a design flaw. like the electrics, but I'm not going there...
Phil
PS Design features are a Microsoft euphemism for bugs
[ 16 December 2001: Message edited by: paco ]
here's another from the same thread, a sobering thought...
"110 kts, straight and level, collective bottomed, 500 lbs below max gross, descent off the top of the mountain - wind sheer, a/s up to 155kts, a/c snapped to the right 90 degrees. both arms could not pull it back, cyclic was solid. you can get ST any number of ways."
You know, I don't like aircraft that bite. I know the Astar is a good machine, and has had a lot of good stuff built in from the design stages, but that sort of thing should have been fixed. To my mind a limitation is something that results from natural causes, such as something that all engineers know about, such as, say helicopters don't fly faster than a certain maximum speed. This is a design flaw. like the electrics, but I'm not going there...
Phil
PS Design features are a Microsoft euphemism for bugs
[ 16 December 2001: Message edited by: paco ]