Loss of Tail Rotor Effectiveness, recovery etc
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No sweat, Crab, your post was right on I think. The point is that some residual thrust is needed to assure control.
I do know that the official FAA reading at the time the 206 was certified was that full yaw control inputs were permitted during trimmed maneuvers as long as the aircraft was inside the envelope and the control was developing a positive yaw rate while against the stop! If you were hard against the pedal stop, but developing 1 degree per second of yaw rate, you were ok.
Regarding VRS in tail rotors, the resulting sideward speed is surprisingly small. On an S-76, it is perhaps 25 knots of left side flight, on an Agusta 109 I flew it was about 22 or so. You can tell if you simply fly sideward at ever increasing speeds to the left. VRS is where the pedals dance like crazy and suddenly shift by about 25% as the flow reverses through the tail rotor.
I do know that the official FAA reading at the time the 206 was certified was that full yaw control inputs were permitted during trimmed maneuvers as long as the aircraft was inside the envelope and the control was developing a positive yaw rate while against the stop! If you were hard against the pedal stop, but developing 1 degree per second of yaw rate, you were ok.
Regarding VRS in tail rotors, the resulting sideward speed is surprisingly small. On an S-76, it is perhaps 25 knots of left side flight, on an Agusta 109 I flew it was about 22 or so. You can tell if you simply fly sideward at ever increasing speeds to the left. VRS is where the pedals dance like crazy and suddenly shift by about 25% as the flow reverses through the tail rotor.
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Not trying to defend the indefensibly small tail rotor on the 206, but the H-500 early models aren't exactly sparkling in the tail rotor department.
And I'm sure there are others that have had LTE as well - just not as prevelant as the 206 / OH-58.
And I'm sure there are others that have had LTE as well - just not as prevelant as the 206 / OH-58.
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From the training side, I as well as others are confused by the FAA's Practical Test Standards (ATP Helo) that require pilots to have adequate knowledge of normal and abnormal procedures i.e.powerplant, electrical, hydraulics, but wait....there towards the bottom is "Loss of Tail Rotor Effectiveness" What's the normal procedure? How do you query a pilot on an aircraft that has NO history of LTE i.e. SK-76?
Keith
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Skymaster19,
It might seem confusing, but it is true that some helos get LTE and some don't, even when an FAA publication makes you have to teach it to everyone.
The Apache, S-92, S-76 and Black Hawk are aircraft that have tail rotors designed with enough thrust margin that LTE is not at all probable, but you still have to teach LTE. How do you query a pilot on an S-76? Ask him/her "What do you do for LTE?"
The test standard is a testiment to the LTE crowd who made it part of the lingo, for reasons stated in posts above. I personally pushed back hard at an FAA wish to put those recovery words in every helicopter flight manual, because I did not want the typical pilot to believe that every helicopter could get LTE.
It might seem confusing, but it is true that some helos get LTE and some don't, even when an FAA publication makes you have to teach it to everyone.
The Apache, S-92, S-76 and Black Hawk are aircraft that have tail rotors designed with enough thrust margin that LTE is not at all probable, but you still have to teach LTE. How do you query a pilot on an S-76? Ask him/her "What do you do for LTE?"
The test standard is a testiment to the LTE crowd who made it part of the lingo, for reasons stated in posts above. I personally pushed back hard at an FAA wish to put those recovery words in every helicopter flight manual, because I did not want the typical pilot to believe that every helicopter could get LTE.
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Could Nick, Shawn or some other airworthiness guru explain to all of us why the issue of ineffective tail rotors have not been addressed in the Continuing Airworthiness process?
This thread appears to indicate that a basic design flaw is being ignored and substituted by a requirement for LTE training; or am I being naïve?
This thread appears to indicate that a basic design flaw is being ignored and substituted by a requirement for LTE training; or am I being naïve?
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Mars,
Very astute question. The answer is somewhat mired in the politics of how these changes come about. I was on the FAR/JAR 27/29 harmonization team for the HQ area, and found one company that absolutely stonewalled any consideration of sharpening the regs about TR margins, notwithstanding that they had the vast majority of LTE accidents.
At that same time (1997?) that company was actually certifying several of their aircraft with NO tail rotor thrust beyond zero wind hover. Look at the Bell 412/430 performance data for those peculiar charts that describe hover with wind within 45 degrees of the nose. The reduction in TR capacity that reduced crosswind capability from 17 knots to 0 was cashed in as increased hover performance! The people who were doing that had no intention of allowing TR requirements to be increased.
The problem with PPruneFan#1's point of view (all cats are gray in the dark) is that when you call all TR control symptoms LTE, you obscure the ability to solve the problem. With a marginal TR, a pilot comes to a routine hover under conditions that are inside the envelope and finds himself spinning around - that is LTE. With any helo, even one with high TR margins, when he pulls the rotor rpm down below his ankles, it is not LTE. If we blur the issue we learn nothing from it.
Very astute question. The answer is somewhat mired in the politics of how these changes come about. I was on the FAR/JAR 27/29 harmonization team for the HQ area, and found one company that absolutely stonewalled any consideration of sharpening the regs about TR margins, notwithstanding that they had the vast majority of LTE accidents.
At that same time (1997?) that company was actually certifying several of their aircraft with NO tail rotor thrust beyond zero wind hover. Look at the Bell 412/430 performance data for those peculiar charts that describe hover with wind within 45 degrees of the nose. The reduction in TR capacity that reduced crosswind capability from 17 knots to 0 was cashed in as increased hover performance! The people who were doing that had no intention of allowing TR requirements to be increased.
The problem with PPruneFan#1's point of view (all cats are gray in the dark) is that when you call all TR control symptoms LTE, you obscure the ability to solve the problem. With a marginal TR, a pilot comes to a routine hover under conditions that are inside the envelope and finds himself spinning around - that is LTE. With any helo, even one with high TR margins, when he pulls the rotor rpm down below his ankles, it is not LTE. If we blur the issue we learn nothing from it.
Nick sez:
No, I just can't stand pedantic people. Whether you call it LTE or not, the result and the escape are the same.
It absolutely does not matter to the pilot whether he is inside or outside the envelope, or whether he is in an aircraft with a hugely strong tail rotor or a wimpy little one. The only problem that needs to be solved is if a helicopter pilot comes to a hover and cannot maintain directional control with full anti-torque pedal stuck in. At that point, as the water-bomber Skycrane pilot found out, he *is* in LTE. Period. The corrective action is the same for a Skycrane as it is for a 206: maintain full pedal, reduce torque, attempt to gain airspeed.
We know that the 206 has a weak tail rotor. Constantly bitching about it does not change that fact. It is a limitation that is not the sole proprietorship of the 206. Other helicopters also have weak tail rotors; early Hughes 500's and Enstroms for two, and the FH1100 was no monster either in that department. ISTR that the SA-341G fit in that group too and could quite readily get into LFE (you work it out). However it is only the 206 that seems to have acquired the dreaded appellation "LTE."
I have flown plenty of helicopters into situations where my left American boot was firmly pressed against the pedal stop, ready to input the corrective action if a yaw rate developed. Whether that yaw rate was the result of a too-small tail rotor or other factors is really moot. The issue of whether the tail rotor is being effective back there is certainly not blurred for me.
But if you chaps want to split hairs and get all technical just to denigrate one particular aircraft to the exclusion of all others, well, have at it.
The problem with PPruneFan#1's point of view (all cats are gray in the dark) is that when you call all TR control symptoms LTE, you obscure the ability to solve the problem. With a marginal TR, a pilot comes to a routine hover under conditions that are inside the envelope and finds himself spinning around - that is LTE. With any helo, even one with high TR margins, when he pulls the rotor rpm down below his ankles, it is not LTE. If we blur the issue we learn nothing from it.
It absolutely does not matter to the pilot whether he is inside or outside the envelope, or whether he is in an aircraft with a hugely strong tail rotor or a wimpy little one. The only problem that needs to be solved is if a helicopter pilot comes to a hover and cannot maintain directional control with full anti-torque pedal stuck in. At that point, as the water-bomber Skycrane pilot found out, he *is* in LTE. Period. The corrective action is the same for a Skycrane as it is for a 206: maintain full pedal, reduce torque, attempt to gain airspeed.
We know that the 206 has a weak tail rotor. Constantly bitching about it does not change that fact. It is a limitation that is not the sole proprietorship of the 206. Other helicopters also have weak tail rotors; early Hughes 500's and Enstroms for two, and the FH1100 was no monster either in that department. ISTR that the SA-341G fit in that group too and could quite readily get into LFE (you work it out). However it is only the 206 that seems to have acquired the dreaded appellation "LTE."
I have flown plenty of helicopters into situations where my left American boot was firmly pressed against the pedal stop, ready to input the corrective action if a yaw rate developed. Whether that yaw rate was the result of a too-small tail rotor or other factors is really moot. The issue of whether the tail rotor is being effective back there is certainly not blurred for me.
But if you chaps want to split hairs and get all technical just to denigrate one particular aircraft to the exclusion of all others, well, have at it.
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PPRUNE FAN#1,
You must think people who don't agree with your simplistic view of flying as pedantic.
You foolishly blurted:
"It absolutely does not matter to the pilot whether he is inside or outside the envelope, or whether he is in an aircraft with a hugely strong tail rotor or a wimpy little one. The only problem that needs to be solved is if a helicopter pilot comes to a hover and cannot maintain directional control with full anti-torque pedal stuck in. "
As a matter of simple fact, it does matter if his aircraft bites him when he is inside the envelope. We sign an agreement with our aircraft for ourselves and our passengers. We agree to obey the rules, and we ask our aircraft to have adequate control and reliability to keep its end of the bargain. The statistics show that 95% of all "LTE" accidents are suffered in ONE type. This type is notoriously weak in tail rotor control, in any case. We will never improve our industry, and our safety records if we insist on trusting fate and relying on special skills instead of demanding of our machines some honest predictable characteristics. And we will get no changes if we allow those pesky rubber stampers to put "Pilot Error" on accidents that are caused by inadequate control margin.
You say that it does not matter to you when an aircraft loses control within its envelope. With that attitude, when you take out your next insurance policy, please list me a benificiary. I will pay the premiums!
You must think people who don't agree with your simplistic view of flying as pedantic.
You foolishly blurted:
"It absolutely does not matter to the pilot whether he is inside or outside the envelope, or whether he is in an aircraft with a hugely strong tail rotor or a wimpy little one. The only problem that needs to be solved is if a helicopter pilot comes to a hover and cannot maintain directional control with full anti-torque pedal stuck in. "
As a matter of simple fact, it does matter if his aircraft bites him when he is inside the envelope. We sign an agreement with our aircraft for ourselves and our passengers. We agree to obey the rules, and we ask our aircraft to have adequate control and reliability to keep its end of the bargain. The statistics show that 95% of all "LTE" accidents are suffered in ONE type. This type is notoriously weak in tail rotor control, in any case. We will never improve our industry, and our safety records if we insist on trusting fate and relying on special skills instead of demanding of our machines some honest predictable characteristics. And we will get no changes if we allow those pesky rubber stampers to put "Pilot Error" on accidents that are caused by inadequate control margin.
You say that it does not matter to you when an aircraft loses control within its envelope. With that attitude, when you take out your next insurance policy, please list me a benificiary. I will pay the premiums!
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LTE and TR-VRS
Nick
Interesting discussions and ideas sofar (except for some false tunes...)
Coming back to your TR-VRS figures : 22-25 Kts, I tried to do impuls theory on the tail rotor (assuming MR-polar efficientcy between 10-15) and came with the following figures (for instance for a R44)
Induced speed MR : 6.6 - 7.5 m/s, Induced speed TR: 13-16 m/s
Assuming the max danger zone at 0,8 induced speed this would give the TR VRS- danger area in the range of 10-12 m/s which is exactly the figures you give. This is of course a very rough calculation to determine orders of magnitude. Is it correct ?
As far as practical tests you referred to is concerned, what is a safe set up ?
d3
Interesting discussions and ideas sofar (except for some false tunes...)
Coming back to your TR-VRS figures : 22-25 Kts, I tried to do impuls theory on the tail rotor (assuming MR-polar efficientcy between 10-15) and came with the following figures (for instance for a R44)
Induced speed MR : 6.6 - 7.5 m/s, Induced speed TR: 13-16 m/s
Assuming the max danger zone at 0,8 induced speed this would give the TR VRS- danger area in the range of 10-12 m/s which is exactly the figures you give. This is of course a very rough calculation to determine orders of magnitude. Is it correct ?
As far as practical tests you referred to is concerned, what is a safe set up ?
d3
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Delta3,
I used the S-76 TR which is highly loaded, and assumed 600 lbs of thrust on an 8 foot disk for a hover (about half the thrust of an R-22 main rotor?!!) to derive 29 knots as the downwash speed. Your estimate of .8 for the onset of VRS is good, I think.
To fly this, one must do what we call sideward flight. From a hover, carefully accelerate to the side, using a slight bank angle. Maintian height with collective, and carefully maintain heading at 90 degrees to the flight path, using pedals. The aircraft will naturally stop accelerating at a speed for the bank angle, and requires more bank to go past that speed. We generally use a pace car that has a calibrated spedometer, and we fix our flight path on that car, so it is frozen relative to the aircraft, thus the aircraft has the car's speed. On a calm morning, this gives us very good data on the crosswind/sideward handling qualities.
For many helos, the tail rotor is good for about 17 knots sideward (regulations wisely call for that as a minimum, except for those somewhat flakey "9 passenger or less" approvals had for some machines). At the maximum speed, the pedal will be close to the stops, and the aircraft cannot go any faster sideward, because the pedal cannot maintain the perpendicular. The aircraft slips out of sideward flight and the nose starts to swing toward the direction of flight.
For those helos which have powerful enough tail rotors, the max sideward flight speed can be as high as 50 knots (the S-76 family has 51 knots to the right and 57 to the left at MGW!). I have often demonstrated Black Hawks at 120 KM/HR, as shown on the doppler navigator. This is why I feel as I do about the LTE label being applied to all helos!
As the S-76 is accelerated beyond about 25 knots to the left, the nose twiches a bit, and the pilot must dance on the pedals to make it stay at 90 degrees. By about 25 knots, the pedals make a 2 inch shift in position, which is where the tail rotor shifts to windmill brake state and the downwash shifts from blown to the lefy to blown to the right.
Notwithstanding the type of test, a helicopter bombing about at 25 knots to the side is in a precarious place if an engine quits, so the pilot must carefully weigh the safety for himself. Also, if one gets diverted and allows the skid height to drift too low, a roll-over is a real concern, with disasterous results.
I used the S-76 TR which is highly loaded, and assumed 600 lbs of thrust on an 8 foot disk for a hover (about half the thrust of an R-22 main rotor?!!) to derive 29 knots as the downwash speed. Your estimate of .8 for the onset of VRS is good, I think.
To fly this, one must do what we call sideward flight. From a hover, carefully accelerate to the side, using a slight bank angle. Maintian height with collective, and carefully maintain heading at 90 degrees to the flight path, using pedals. The aircraft will naturally stop accelerating at a speed for the bank angle, and requires more bank to go past that speed. We generally use a pace car that has a calibrated spedometer, and we fix our flight path on that car, so it is frozen relative to the aircraft, thus the aircraft has the car's speed. On a calm morning, this gives us very good data on the crosswind/sideward handling qualities.
For many helos, the tail rotor is good for about 17 knots sideward (regulations wisely call for that as a minimum, except for those somewhat flakey "9 passenger or less" approvals had for some machines). At the maximum speed, the pedal will be close to the stops, and the aircraft cannot go any faster sideward, because the pedal cannot maintain the perpendicular. The aircraft slips out of sideward flight and the nose starts to swing toward the direction of flight.
For those helos which have powerful enough tail rotors, the max sideward flight speed can be as high as 50 knots (the S-76 family has 51 knots to the right and 57 to the left at MGW!). I have often demonstrated Black Hawks at 120 KM/HR, as shown on the doppler navigator. This is why I feel as I do about the LTE label being applied to all helos!
As the S-76 is accelerated beyond about 25 knots to the left, the nose twiches a bit, and the pilot must dance on the pedals to make it stay at 90 degrees. By about 25 knots, the pedals make a 2 inch shift in position, which is where the tail rotor shifts to windmill brake state and the downwash shifts from blown to the lefy to blown to the right.
Notwithstanding the type of test, a helicopter bombing about at 25 knots to the side is in a precarious place if an engine quits, so the pilot must carefully weigh the safety for himself. Also, if one gets diverted and allows the skid height to drift too low, a roll-over is a real concern, with disasterous results.
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Nick,
thx, I did similar flights using large taxi ways on an airfield nearby practising the change over from forward to sideways. I was not precisely aware of the exact speeds since all my attention went to controlling the MR-blows (cfr your comment of steering the cyclic in the wind in case of lte pirouettes in on other discussion). So I never really figured out what the speed exactly was (15-20-25?). I could have watched GPS of course, but all my attention was fixed on IAS -to anticipate transitions- and attitude.
Your set up is indeed much more controled.
For S-76-C I get around 17,4 m/s at full load and assuming a ratio of 15 on the polar (which is approx 700 lbs) giving 35knts*0,8=28 knts
Doing these calculations makes me think now that those early exercices were dangerous, since I now understand there is a big difference between right and left for other reasons that I first assumed, namely TR-power versus TR-VRS and I do now remember left slips produced extra vibrations...
d3
thx, I did similar flights using large taxi ways on an airfield nearby practising the change over from forward to sideways. I was not precisely aware of the exact speeds since all my attention went to controlling the MR-blows (cfr your comment of steering the cyclic in the wind in case of lte pirouettes in on other discussion). So I never really figured out what the speed exactly was (15-20-25?). I could have watched GPS of course, but all my attention was fixed on IAS -to anticipate transitions- and attitude.
Your set up is indeed much more controled.
For S-76-C I get around 17,4 m/s at full load and assuming a ratio of 15 on the polar (which is approx 700 lbs) giving 35knts*0,8=28 knts
Doing these calculations makes me think now that those early exercices were dangerous, since I now understand there is a big difference between right and left for other reasons that I first assumed, namely TR-power versus TR-VRS and I do now remember left slips produced extra vibrations...
d3
Last edited by delta3; 5th Sep 2004 at 18:22.
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Delta3,
Except for the possibility of ground contact, there is little danger as long as the flight maintains the sideward/crosswind limits of the flight manual. Power actually goes down with sideward speed, since the rotor really does not care about wind azimuth, only about velocity.
Your estimate of TR thrust is quite close! You can calculate the required anti-torque for any helo, if you know the total power needed, since the MR torque is a function of the total HP and the rpm. Then you can calculate the TR thrust by taking the anti-torque moment, and dividing by the distance from the main rotor to the tail rotor.
Except for the possibility of ground contact, there is little danger as long as the flight maintains the sideward/crosswind limits of the flight manual. Power actually goes down with sideward speed, since the rotor really does not care about wind azimuth, only about velocity.
Your estimate of TR thrust is quite close! You can calculate the required anti-torque for any helo, if you know the total power needed, since the MR torque is a function of the total HP and the rpm. Then you can calculate the TR thrust by taking the anti-torque moment, and dividing by the distance from the main rotor to the tail rotor.
Dr. Nick wrote:
Nick, I'm going to cut you some slack, because I know you don't have all that much flight time (compared to some of us) and you have ZERO commercial/civilian time...you know, real-world flying.
I can assure you that real, working helicopter pilots sometimes run up against performance limits. In my long and varied career (10,000+ hours) which includes scores of survey/photo flights, I have hit collective (power) limits, run out of pedal and even touched a cyclic stop or two in different kinds of helos. Never did I feel like I was teetering on the precipice of disaster. Never did the aircraft depart controlled flight. So put your pompous, holier-than-thou attitude away, okay? Not all of us are know-nothing R-22 students bowing at your feet.
Your prejudice against and dislike of the 206 is well-known and documented. But let me ask you a simple question: What would you prefer, the complete grounding of the 206 fleet? You act like every airborne 206 is an LTE accident waiting to happen- that at any time the pilot of such a deathtrap terminating his approach to a hover might discover to his horror that his pedals have somehow become ineffective even though he is right in the middle of the flight envelope! Eek!
Some of you guys act like the 206 is the only aircraft to experience LTE, and moreover that this mysterious "LTE" is strictly a function of a poorly-designed helicopter. The fact that 95% of all LTE accidents happen to one particular type of helicopter and the fact that until recently this particular helicopter just happened to be the most popular helicopter in general use seems to elude people. I'd wager that if OH-6's were being used like the OH-58 scouts were (heavy, OGE hovering over trees with little respect for wind) you'd all be shrieking about the miserable tail rotor on the OH-6 and how it ought to be legislated out of existence.
In all of my flying in the 206 (around 8,000 hours- just about your total time, eh Nick?) , I got into "LTE" exactly once. I was messing around up high in a downwind hover, trying to get an accurate power check in an L or L-1 (forget which...whichever one needed zero airspeed and pull to the TOT limit). When it snapped around, it caught me by surprise. But by keeping full pedal in, lowering the collective and banking slightly into the spin, we flew out of it easily. No big deal. In fact, one need not be a test pilot to realize that the 206's big vertical fin blanks off a lot of t/r inflow air during certain flight conditions.
As one who's flown at relatively low altitudes, I have never been "surprised" and run out of pedal. Similarly, I've never had the nose yaw and not been able to stop it with a bootful of left pedal. Then again, I'm pretty diligent about keeping the wind on the nose or off my left. If I ever did get into a condition in which my left leg was sticking straight out, I didn't bother to look at a chart to see whether I was within the flight envelope or not. The fact that I was approaching a control limit was enough to tell me that I was in a corner of it. (Actually, I'd be worrying about overtorquing the ship.)
Luckily, that Skycrane fire pilot who experienced LTE knew what to do. Maybe he'd flown 206's at some point in his career, eh? I wonder if he checked to see whether he was within his flight envelope or not? Good thing he didn't go, "Blimey! Can't be LTE, not in this bird! Must be a bleedin' tail rotor failure!"
As a matter of simple fact, it does matter if his aircraft bites him when he is inside the envelope. We sign an agreement with our aircraft for ourselves and our passengers. We agree to obey the rules, and we ask our aircraft to have adequate control and reliability to keep its end of the bargain. The statistics show that 95% of all "LTE" accidents are suffered in ONE type. This type is notoriously weak in tail rotor control, in any case. We will never improve our industry, and our safety records if we insist on trusting fate and relying on special skills instead of demanding of our machines some honest predictable characteristics. And we will get no changes if we allow those pesky rubber stampers to put "Pilot Error" on accidents that are caused by inadequate control margin.
You say that it does not matter to you when an aircraft loses control within its envelope. With that attitude, when you take out your next insurance policy, please list me a benificiary. I will pay the premiums!
You say that it does not matter to you when an aircraft loses control within its envelope. With that attitude, when you take out your next insurance policy, please list me a benificiary. I will pay the premiums!
I can assure you that real, working helicopter pilots sometimes run up against performance limits. In my long and varied career (10,000+ hours) which includes scores of survey/photo flights, I have hit collective (power) limits, run out of pedal and even touched a cyclic stop or two in different kinds of helos. Never did I feel like I was teetering on the precipice of disaster. Never did the aircraft depart controlled flight. So put your pompous, holier-than-thou attitude away, okay? Not all of us are know-nothing R-22 students bowing at your feet.
Your prejudice against and dislike of the 206 is well-known and documented. But let me ask you a simple question: What would you prefer, the complete grounding of the 206 fleet? You act like every airborne 206 is an LTE accident waiting to happen- that at any time the pilot of such a deathtrap terminating his approach to a hover might discover to his horror that his pedals have somehow become ineffective even though he is right in the middle of the flight envelope! Eek!
Some of you guys act like the 206 is the only aircraft to experience LTE, and moreover that this mysterious "LTE" is strictly a function of a poorly-designed helicopter. The fact that 95% of all LTE accidents happen to one particular type of helicopter and the fact that until recently this particular helicopter just happened to be the most popular helicopter in general use seems to elude people. I'd wager that if OH-6's were being used like the OH-58 scouts were (heavy, OGE hovering over trees with little respect for wind) you'd all be shrieking about the miserable tail rotor on the OH-6 and how it ought to be legislated out of existence.
In all of my flying in the 206 (around 8,000 hours- just about your total time, eh Nick?) , I got into "LTE" exactly once. I was messing around up high in a downwind hover, trying to get an accurate power check in an L or L-1 (forget which...whichever one needed zero airspeed and pull to the TOT limit). When it snapped around, it caught me by surprise. But by keeping full pedal in, lowering the collective and banking slightly into the spin, we flew out of it easily. No big deal. In fact, one need not be a test pilot to realize that the 206's big vertical fin blanks off a lot of t/r inflow air during certain flight conditions.
As one who's flown at relatively low altitudes, I have never been "surprised" and run out of pedal. Similarly, I've never had the nose yaw and not been able to stop it with a bootful of left pedal. Then again, I'm pretty diligent about keeping the wind on the nose or off my left. If I ever did get into a condition in which my left leg was sticking straight out, I didn't bother to look at a chart to see whether I was within the flight envelope or not. The fact that I was approaching a control limit was enough to tell me that I was in a corner of it. (Actually, I'd be worrying about overtorquing the ship.)
Luckily, that Skycrane fire pilot who experienced LTE knew what to do. Maybe he'd flown 206's at some point in his career, eh? I wonder if he checked to see whether he was within his flight envelope or not? Good thing he didn't go, "Blimey! Can't be LTE, not in this bird! Must be a bleedin' tail rotor failure!"
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It's a pity some interesting threads get a bit personal.
I had my first helicopter ride 49 years ago in the Malaysian hills with an army friend. Naturally I was excited and asked numerous questions about the controls and what the footrests were for. Even that long ago he was able to point out the problems of LTE which of course didn't mean a thing to me. Later when I was a student, the problems of LTE were driven home to me and demonstrated.
In those days most of the helicopters were underpowered and depending on the wind, OAT and altitude, it was impressed on us to lead with rudder pedal just slightly before you applied power which seemed to prevent LTE. Years later I had to land a 206A with a C18 engine at 12000 ft and using that technique, had no LTE problems.
I'm sure a lot of problems, such as LTE & others, occured because there were more civilian students going through the system than in my youth. This IS NOT a bash against civilian students, I've had plenty of very good ones. It is just a question of the AMOUNT of training received as well as the quality. In other words a doctor who gets 6 years training should be better qualified than one who gets 3 years. It doesn't mean that one is smarter that the other, just had access to more training. That is the real difference between military and civilian training, the quantity.
As already suggested by others, some helicopters get LTE easier than others but if the pilot knows how to prevent that happening or takes the correct remedial action if he does get LTE, then the chances of it becoming a disaster should be reduced.
I had my first helicopter ride 49 years ago in the Malaysian hills with an army friend. Naturally I was excited and asked numerous questions about the controls and what the footrests were for. Even that long ago he was able to point out the problems of LTE which of course didn't mean a thing to me. Later when I was a student, the problems of LTE were driven home to me and demonstrated.
In those days most of the helicopters were underpowered and depending on the wind, OAT and altitude, it was impressed on us to lead with rudder pedal just slightly before you applied power which seemed to prevent LTE. Years later I had to land a 206A with a C18 engine at 12000 ft and using that technique, had no LTE problems.
I'm sure a lot of problems, such as LTE & others, occured because there were more civilian students going through the system than in my youth. This IS NOT a bash against civilian students, I've had plenty of very good ones. It is just a question of the AMOUNT of training received as well as the quality. In other words a doctor who gets 6 years training should be better qualified than one who gets 3 years. It doesn't mean that one is smarter that the other, just had access to more training. That is the real difference between military and civilian training, the quantity.
As already suggested by others, some helicopters get LTE easier than others but if the pilot knows how to prevent that happening or takes the correct remedial action if he does get LTE, then the chances of it becoming a disaster should be reduced.
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Nigel,
You are quite correct, (as is pprune fan, although please don't tell him) in that we must train to care for the yaw control, and LTE concepts help that training.
What we must not do, I believe, is accept the case that any helo can get "LTE" within its envelope. That is simply not true. But more importantly, it lets off the hook those helos that are underdesigned, and therefore hopefully obsolescent.
I believe with clear facts, our purchase choices will force the manufacturers to make good helicopters. I also believe that with macho bull about how we all should be able to fly crappy helos, and even the boxes they came in, we will not improve our lot.
BTW, pprune fan#1, with 25 years of experimental helicopter test, I have more time against the pedal stops than you probably have on the crapper. So let me buy you a beer at the next meeting, and have you tell me some of the good stories you have to tell! Where we differ is that I think you should place some emphasis on making better helos, so your son doesn't have to risk what you did getting those 8,000 hours in 206's.
You are quite correct, (as is pprune fan, although please don't tell him) in that we must train to care for the yaw control, and LTE concepts help that training.
What we must not do, I believe, is accept the case that any helo can get "LTE" within its envelope. That is simply not true. But more importantly, it lets off the hook those helos that are underdesigned, and therefore hopefully obsolescent.
I believe with clear facts, our purchase choices will force the manufacturers to make good helicopters. I also believe that with macho bull about how we all should be able to fly crappy helos, and even the boxes they came in, we will not improve our lot.
BTW, pprune fan#1, with 25 years of experimental helicopter test, I have more time against the pedal stops than you probably have on the crapper. So let me buy you a beer at the next meeting, and have you tell me some of the good stories you have to tell! Where we differ is that I think you should place some emphasis on making better helos, so your son doesn't have to risk what you did getting those 8,000 hours in 206's.
...we seem to have run out of directional control........
ppruneF: I think it is fair to say that you just want one label to describe many situations because the recovery is the same - but others prefer to call a spade a spade in the hope that correct identification of the problem can lead to efforts to correctly address them. As we know, the BEST solution to any problem is to engineer them out, ie create a system that cannot suffer that error. The next best is to define the problem, recognise onset conditions and avoid them. The third best is to rote learn techniques to recover after onset. And that is where we are at: we have designed new helicopters that are not susceptible. We have defined the onset conditions in older susceptible machines to help avoid it. Finally, we have devised a recovery technique for those who suffer it. If you just want to focus on the recovery - great. But let everyone else gain an understanding at a deeper level if they want to.
Unfortunately, all the above requires a level of pedanticism. You get that.
ppruneF: I think it is fair to say that you just want one label to describe many situations because the recovery is the same - but others prefer to call a spade a spade in the hope that correct identification of the problem can lead to efforts to correctly address them. As we know, the BEST solution to any problem is to engineer them out, ie create a system that cannot suffer that error. The next best is to define the problem, recognise onset conditions and avoid them. The third best is to rote learn techniques to recover after onset. And that is where we are at: we have designed new helicopters that are not susceptible. We have defined the onset conditions in older susceptible machines to help avoid it. Finally, we have devised a recovery technique for those who suffer it. If you just want to focus on the recovery - great. But let everyone else gain an understanding at a deeper level if they want to.
Unfortunately, all the above requires a level of pedanticism. You get that.
