LTE, Wind Direction Preference
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LTE, Wind Direction Preferance
Just looking for a few opinions.
In the B206, what direction would you take a cross-wind landing if given the choice, right, or left?
Of course there are many places where you don't have that luxury, but given the choice do you prefer riding the right or left pedal on the way in, and why. Also, thoughts on Critical Wind Azmuth's/LTE directions and how they affect this choice would be appreciated - especially at altitude.
Thanks in advance,
AR
In the B206, what direction would you take a cross-wind landing if given the choice, right, or left?
Of course there are many places where you don't have that luxury, but given the choice do you prefer riding the right or left pedal on the way in, and why. Also, thoughts on Critical Wind Azmuth's/LTE directions and how they affect this choice would be appreciated - especially at altitude.
Thanks in advance,
AR
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Neat question.
Depends on whether you are concerned about running out of tail rotor control, or handling (i.e having a lot of yaw oscillations).
If you think you're close to the limit on tail rotor, then a wind from the left is not a good thing.
On the other hand, if you are concerned that you will be yawing a lot, and that you have to hold heading precisely, then a wind from the aft right is not a good choice.
No easy answer.
Depends on whether you are concerned about running out of tail rotor control, or handling (i.e having a lot of yaw oscillations).
If you think you're close to the limit on tail rotor, then a wind from the left is not a good thing.
On the other hand, if you are concerned that you will be yawing a lot, and that you have to hold heading precisely, then a wind from the aft right is not a good choice.
No easy answer.
Left. No doubt about it.
I learnt to fly in Franklin-engine Bell 47's and Enstrom F-28A's with the tail rotor on the "wrong" side. Neither aircraft was blessed with an overabundance of power and the wise pilot became very careful about not getting into a right crosswind in a hover lest the ship begin a right yaw that full pedal could not stop.
Now, eons later, I've flown with inexperienced pilots who get all antsy about left crosswinds. They'll recall the critical wind azimuth chart and tremble with fear that a left crosswind will put them into LTE. They forget about things like weathervaning tendency. Good thing it's not a factor anymore.
A right crosswind will require more left pedal in the hover than a left crosswind. So as Shawn says, if you're confident about your tail rotor power, go for it. Keep in mind that the 206 does not exactly have the World's Most Powerful Tailrotor.
However, a right crosswind will always require more engine power to hover. The difference between a left and right crosswind can make a big difference in hover power. I'll take all the available engine power I can, thank you. I fly primarily at low altitudes but it always seems that I am at MAUW.
Left crosswinds do produce some "yaw instability" as the vortex from the main rotor randomly interferes with the tail rotor. Big deal. So the pilot must actually stay awake and on his toes to keep the nose straight. In all my years of flying 206's, I've never found the workload overly objectionable, burdensome or excessively demanding of my meager skills.
There is one final consideration, the size and importance of which will be yours to decide: Let us assume that we are making a "normal" approach with a fair amount of power pulled and a relatively low airspeed (i.e. not autorotative). If the engine decides to quit during this time, which way will the nose snap? Righty-o, to the left. That being the case, I'd rather that the nose yaw into the wind instead of away from it.
Now, I know that we all think that we are Yeager-reincarnate and will instantly and correctly react to every emergency. We all probably assume that if the engine were ever to quit in real life, we'd automatically boot in enough right pedal that the nose wouldn't even yaw enough to wag the turn needle for a split second. The truth is, even I don't think I'm that good. Your mileage may vary.
Again, planning for a power failure may not be very important anymore, and so it may not matter to you which way the nose will yaw when this unlikely event does not happen. But it's something that I think about as I fly.
Shawn is right; assuming that into-the-wind is not an option, the question of left or right crosswind is interesting. Sometimes it will not matter much. And there may be times when right is preferable over left. But for me, those times would be few.
I learnt to fly in Franklin-engine Bell 47's and Enstrom F-28A's with the tail rotor on the "wrong" side. Neither aircraft was blessed with an overabundance of power and the wise pilot became very careful about not getting into a right crosswind in a hover lest the ship begin a right yaw that full pedal could not stop.
Now, eons later, I've flown with inexperienced pilots who get all antsy about left crosswinds. They'll recall the critical wind azimuth chart and tremble with fear that a left crosswind will put them into LTE. They forget about things like weathervaning tendency. Good thing it's not a factor anymore.
A right crosswind will require more left pedal in the hover than a left crosswind. So as Shawn says, if you're confident about your tail rotor power, go for it. Keep in mind that the 206 does not exactly have the World's Most Powerful Tailrotor.
However, a right crosswind will always require more engine power to hover. The difference between a left and right crosswind can make a big difference in hover power. I'll take all the available engine power I can, thank you. I fly primarily at low altitudes but it always seems that I am at MAUW.
Left crosswinds do produce some "yaw instability" as the vortex from the main rotor randomly interferes with the tail rotor. Big deal. So the pilot must actually stay awake and on his toes to keep the nose straight. In all my years of flying 206's, I've never found the workload overly objectionable, burdensome or excessively demanding of my meager skills.
There is one final consideration, the size and importance of which will be yours to decide: Let us assume that we are making a "normal" approach with a fair amount of power pulled and a relatively low airspeed (i.e. not autorotative). If the engine decides to quit during this time, which way will the nose snap? Righty-o, to the left. That being the case, I'd rather that the nose yaw into the wind instead of away from it.
Now, I know that we all think that we are Yeager-reincarnate and will instantly and correctly react to every emergency. We all probably assume that if the engine were ever to quit in real life, we'd automatically boot in enough right pedal that the nose wouldn't even yaw enough to wag the turn needle for a split second. The truth is, even I don't think I'm that good. Your mileage may vary.
Again, planning for a power failure may not be very important anymore, and so it may not matter to you which way the nose will yaw when this unlikely event does not happen. But it's something that I think about as I fly.
Shawn is right; assuming that into-the-wind is not an option, the question of left or right crosswind is interesting. Sometimes it will not matter much. And there may be times when right is preferable over left. But for me, those times would be few.
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Thanks for the responses.
I personally have taken the left X-wind option when available for many of the reasons outlined by PPrune Fan. The loss of power, while not near as common as it used to be, is still something to be taken into consideration - both for your clinet's and company's sake.
I have found that at high wieghts riding the right pedal allows for quite an increase in available torque in the hover, and so far I can't find a reason to do it the other way. As far as main rotor vortex interferance, I agree that if you are aware of it and anticipating the a/c's reaction, you shouldn't have too much trouble.
Another reason I have been given for the left wind direction is that the tail rotor is operating in relatively undisturbed air, anyone care to comment on this?
Thanks
AR
I personally have taken the left X-wind option when available for many of the reasons outlined by PPrune Fan. The loss of power, while not near as common as it used to be, is still something to be taken into consideration - both for your clinet's and company's sake.
I have found that at high wieghts riding the right pedal allows for quite an increase in available torque in the hover, and so far I can't find a reason to do it the other way. As far as main rotor vortex interferance, I agree that if you are aware of it and anticipating the a/c's reaction, you shouldn't have too much trouble.
Another reason I have been given for the left wind direction is that the tail rotor is operating in relatively undisturbed air, anyone care to comment on this?
Thanks
AR
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X wind e.g
All great answers, but i would like to stick my neck out here just a liiiiitle.
Would it not depend on the type of 206 you were driving?, i mean if you were concerned about losing tail rotor authority, would this not be a factor in chosing the type of 206 to drive. I mean in relation to earlier types or later types. Now correct me if i am wrong, but is there not a difference in tail rotor size from the earlier to the later (68" to 72") tail rotor diameter, thus aiding with tail rotor authority?
The second point i was going to touch on, was that it seemed that it was noted that maybe tail rotor vortex ring state, was a question, but my statment to that is that if you are flying in such conditions to warrent that, wouldn't you be better off home with the wife and kids ALIVE?
Just some sultry points, which i am sure will be covered swiftly by the big boys here
MD
P.S Left is the wind i would have chosen too, as in agreement with pprune Fan#1
Would it not depend on the type of 206 you were driving?, i mean if you were concerned about losing tail rotor authority, would this not be a factor in chosing the type of 206 to drive. I mean in relation to earlier types or later types. Now correct me if i am wrong, but is there not a difference in tail rotor size from the earlier to the later (68" to 72") tail rotor diameter, thus aiding with tail rotor authority?
The second point i was going to touch on, was that it seemed that it was noted that maybe tail rotor vortex ring state, was a question, but my statment to that is that if you are flying in such conditions to warrent that, wouldn't you be better off home with the wife and kids ALIVE?
Just some sultry points, which i am sure will be covered swiftly by the big boys here
MD
P.S Left is the wind i would have chosen too, as in agreement with pprune Fan#1
"Just a pilot"
Tail left, slow, low power and descending, are the danger points. Like the stereotype vortex ring, you can reduce your risk by minimising degree of exposure in any of those states. Having real exit options and an abort plan *could* allow you to take it to the edge of control authority, safely.
Some suggestions, based on experience with the "big" tail rotor variety 206, only-
Point the nose into the wind and shoot the approach sideways. (See danger points, above.) Remember, it's a helicopter. At the hover, when you have to put the skids down, turn the aircraft whichever way you wish. This should be done cautiously, especially yawing nose right more than 45 degrees, see initial danger conditions.
You'll run out of TR thrust yawing left in a stiff breeze, although playing with the collective can help a little. S-L-O-W rates of yaw, either direction, are critical in my experience.
If the yaw rate varies unexpectedly, deal with it immediately, and have options- don't play with limited control authority in a hover hole.
The 206 will hold more crosswind than you can turn the tail into at the hover. You have to be meticulous in heading at all times.
Finally, if your approach path has sufficient clearance, you can shoot the approach pointed into the wind as above, and yaw right to the desired heading while power reduced short final, just before losing ETL. You have to be able to abort by reducing power and accelerating simultaneously to use this technique!
Some suggestions, based on experience with the "big" tail rotor variety 206, only-
Point the nose into the wind and shoot the approach sideways. (See danger points, above.) Remember, it's a helicopter. At the hover, when you have to put the skids down, turn the aircraft whichever way you wish. This should be done cautiously, especially yawing nose right more than 45 degrees, see initial danger conditions.
You'll run out of TR thrust yawing left in a stiff breeze, although playing with the collective can help a little. S-L-O-W rates of yaw, either direction, are critical in my experience.
If the yaw rate varies unexpectedly, deal with it immediately, and have options- don't play with limited control authority in a hover hole.
The 206 will hold more crosswind than you can turn the tail into at the hover. You have to be meticulous in heading at all times.
Finally, if your approach path has sufficient clearance, you can shoot the approach pointed into the wind as above, and yaw right to the desired heading while power reduced short final, just before losing ETL. You have to be able to abort by reducing power and accelerating simultaneously to use this technique!
Airplane pilots are lucky. Their approach options are relatively few compared to ours. I suppose a book could and probably should be written on all of the different types and kinds of approaches that helicopters make. But such a book would be necessarily incomplete because there are uncountable variations.
The beauty of...and the trouble with...helicopters is that we take them to strange places that airplanes cannot go. Land into the wind? Yes, whenever possible, although it is not always. Simply abandon a landing because it might involve operating in a small corner of the flight envelope? Hey, all of life involves some risk. Good helicopter pilots are very flexible in their thinking.
Not to brag, but I have made over 50,000 landings in helicopters...maybe 60,000 depending on whether I use five or six landings per hour. Let's say five. Whatever. It's a lot of landings. And virtually every one of those helicopter landings was improvised; I made them up as I went along.
Unlike airplanes, every helicopter approach is an improvisation. We tailor the speed, angle and azimuth to the specific situation. Our "finals" may or may not be straight and there is no "standard" approach angle to use when landing off-airport. This need to improvise seems lost on a lot of pilots who cannot break free of regimented thinking and flying.
Recently, I flew with a new turbine owner, who's only other practical flight time was in Robbies. Aside from flying his approaches at Robbie speeds (i.e. too fast), he was a pretty good stick and I felt comfortable with him flying the turbine. ...Except for one thing.
The LZ at his property was tight but not unsafely so. He'd been in there before, so I let him show me his procedure. Instead of landing right at his house, we made a very nice approach to a huge nearby field. I was impressed but puzzled. To transition to his "front yard" parking spot, we would have had to hover over a large stand of 75 foot trees that blocked our path. When it was apparent that he intended to do just that, I called foul. I asked, "Do you mean to tell me that you're going to hover over those trees?" He did indeed. "Not with me in the ship," I said.
We took off and circled around and I taught him a real-life steep approach, not the theoretical ones we make at the airport during training. High-recon, low-recon, then set it up into the wind, aiming for that spot there and fly down to it. It was kind of a one-way-in sort of place, and the wind gods were smiling on us that day. There were good areas all around us to plop into if the engine quit, and it worked out perfectly with very little pitch-pull at the bottom. At least, worked for me.
No, we did not maintain 60 knots all the way down. Yes, we were probably in the shaded area of the H-V chart for a portion of the approach. Oh well. Better than a 100' OGE hover over friggin' trees with a nearly-vertical descent on the other side.
Clearly, this guy was more comfortable hovering at 100' over trees than making a steep approach. My approach worked on that day because the wind was favorable for the best path in. Tomorrow it may not be. Or now that I'm gone, he may simply go back to doing it his way, or whichever way he's most comfortable with. Which is fine I guess. He's a fully rated Commercial pilot and has to live (or die) with the consequences of his actions.
The more conservative among us would question his need to keep his helicopter at home. They would suggest that he simply park it at the nearest airport. But you know what? People like having their helicopters where they live, when they can. Is it unreasonably dangerous for this guy to operate out of his house, which is way out in the country with no close neighbors? I don't think so.
If we wanted to fly from airports all the time, we'd fly airplanes. We like and fly helicopters because of their versatility. But along with that characteristic, it is imperative that we learn to properly take advantage of it...and do it safely. To do that, we must know how to tailor each approach to the existing conditions. It's not something that you can learn from an internet website. Some things only come through experience.
The beauty of...and the trouble with...helicopters is that we take them to strange places that airplanes cannot go. Land into the wind? Yes, whenever possible, although it is not always. Simply abandon a landing because it might involve operating in a small corner of the flight envelope? Hey, all of life involves some risk. Good helicopter pilots are very flexible in their thinking.
Not to brag, but I have made over 50,000 landings in helicopters...maybe 60,000 depending on whether I use five or six landings per hour. Let's say five. Whatever. It's a lot of landings. And virtually every one of those helicopter landings was improvised; I made them up as I went along.
Unlike airplanes, every helicopter approach is an improvisation. We tailor the speed, angle and azimuth to the specific situation. Our "finals" may or may not be straight and there is no "standard" approach angle to use when landing off-airport. This need to improvise seems lost on a lot of pilots who cannot break free of regimented thinking and flying.
Recently, I flew with a new turbine owner, who's only other practical flight time was in Robbies. Aside from flying his approaches at Robbie speeds (i.e. too fast), he was a pretty good stick and I felt comfortable with him flying the turbine. ...Except for one thing.
The LZ at his property was tight but not unsafely so. He'd been in there before, so I let him show me his procedure. Instead of landing right at his house, we made a very nice approach to a huge nearby field. I was impressed but puzzled. To transition to his "front yard" parking spot, we would have had to hover over a large stand of 75 foot trees that blocked our path. When it was apparent that he intended to do just that, I called foul. I asked, "Do you mean to tell me that you're going to hover over those trees?" He did indeed. "Not with me in the ship," I said.
We took off and circled around and I taught him a real-life steep approach, not the theoretical ones we make at the airport during training. High-recon, low-recon, then set it up into the wind, aiming for that spot there and fly down to it. It was kind of a one-way-in sort of place, and the wind gods were smiling on us that day. There were good areas all around us to plop into if the engine quit, and it worked out perfectly with very little pitch-pull at the bottom. At least, worked for me.
No, we did not maintain 60 knots all the way down. Yes, we were probably in the shaded area of the H-V chart for a portion of the approach. Oh well. Better than a 100' OGE hover over friggin' trees with a nearly-vertical descent on the other side.
Clearly, this guy was more comfortable hovering at 100' over trees than making a steep approach. My approach worked on that day because the wind was favorable for the best path in. Tomorrow it may not be. Or now that I'm gone, he may simply go back to doing it his way, or whichever way he's most comfortable with. Which is fine I guess. He's a fully rated Commercial pilot and has to live (or die) with the consequences of his actions.
The more conservative among us would question his need to keep his helicopter at home. They would suggest that he simply park it at the nearest airport. But you know what? People like having their helicopters where they live, when they can. Is it unreasonably dangerous for this guy to operate out of his house, which is way out in the country with no close neighbors? I don't think so.
If we wanted to fly from airports all the time, we'd fly airplanes. We like and fly helicopters because of their versatility. But along with that characteristic, it is imperative that we learn to properly take advantage of it...and do it safely. To do that, we must know how to tailor each approach to the existing conditions. It's not something that you can learn from an internet website. Some things only come through experience.
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Just to clarify a point. There is no requirement in a Part 27 helicopter to stay out of the HV curve. Part 29, 10 passengers or more, there is a limitation on it.
There is also no HV curve information for a descent situation - the HV curve is published for takeoff power at a heavy weight, high density altitude from the hover to the 'knee' of the curve.
So, there is no requirement to stay out of the avoid curve in a descent to landing. There is a requirement that the takeoff distance (measured and if published) as well as the recommended takeoff flight path stay clear of the HV, but nothing else.
There is also no HV curve information for a descent situation - the HV curve is published for takeoff power at a heavy weight, high density altitude from the hover to the 'knee' of the curve.
So, there is no requirement to stay out of the avoid curve in a descent to landing. There is a requirement that the takeoff distance (measured and if published) as well as the recommended takeoff flight path stay clear of the HV, but nothing else.
Shawn Coyle:
Oh? 'Scuze me Shawn, but where exactly is this explained or established in the RFM? The ones I've used and perused make no mention of where or when the H-V curve applies or does not. This business of, "the H-V chart only applies for MGW take-offs" is interesting and I've heard it a lot from quasi-authoritative sources, but might as well be an urban legend for all I know. Is that one of those nudge-nudge, wink-wink things? Maybe Bell, Eurocopter, et.al, plaster each chart with "FOR INFORMATIONAL PURPOSES ONLY!"
See, to us dumb pilots (you know, those of us who are not test pilots), a chart is a chart is a chart. Without those little eyesight-straining explanations at the bottom, we might logically be expected to assume that the chart was applicable to all flight regimes.
Furthermore, I think asking pilots to disregard performance charts- even those "non-mandatory" ones like the H-V, is dangerous and irresponsible. Not to be insufferably pedantic (pretentious, moi?), but if the manufacturers or the FAA want us to believe and act as though the H-V curve only applies in certain flight conditions, they can come out and say so.
Just to clarify a point. There is no requirement in a Part 27 helicopter to stay out of the HV curve. Part 29, 10 passengers or more, there is a limitation on it.
There is also no HV curve information for a descent situation - the HV curve is published for takeoff power at a heavy weight, high density altitude from the hover to the 'knee' of the curve.
There is also no HV curve information for a descent situation - the HV curve is published for takeoff power at a heavy weight, high density altitude from the hover to the 'knee' of the curve.
See, to us dumb pilots (you know, those of us who are not test pilots), a chart is a chart is a chart. Without those little eyesight-straining explanations at the bottom, we might logically be expected to assume that the chart was applicable to all flight regimes.
Furthermore, I think asking pilots to disregard performance charts- even those "non-mandatory" ones like the H-V, is dangerous and irresponsible. Not to be insufferably pedantic (pretentious, moi?), but if the manufacturers or the FAA want us to believe and act as though the H-V curve only applies in certain flight conditions, they can come out and say so.
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I'm with you Fan, the HV diagram appears to apply to the landing phase; one of the elements that is covered in AC 29-2C is 'high hover' test which is conducted with 'power required to hover' - this is probably more related to landing than take-off.
In the absence of better guidance, it would be somewhat foolish to place the aircraft within the HV diagram - even on landing.
In the absence of better guidance, it would be somewhat foolish to place the aircraft within the HV diagram - even on landing.
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The HV Curve relates to take-off. See MD 600 RFM 5-8.
'Airspeed/altitude combinations to be avoided in the event of an engine failure during take off are shown in the height-velocity diagram' Quote
Agusta don't say whether it is for take off or landing. So one must assume it covers both profiles.
I don't have the B206/Enstrom/Robinson or Schweizer manual to hand. So I cant quote from them.
I've always taken it to be for both t/o and landing.
'Airspeed/altitude combinations to be avoided in the event of an engine failure during take off are shown in the height-velocity diagram' Quote
Agusta don't say whether it is for take off or landing. So one must assume it covers both profiles.
I don't have the B206/Enstrom/Robinson or Schweizer manual to hand. So I cant quote from them.
I've always taken it to be for both t/o and landing.
PF#1 - as usual you were doing really well and passing the benefits of your experience to others with less knowledge - right up to the point when Shawn pointed out some facts with which you do not agree. You are only a 'dumb pilot' when you won't listen to those who do know better - we have been round the origins of the HV curve argument before on this forum - it is created by test pilots so why not listen to a test pilot when he tells you its application.
From various test points of height and speed the throttle is chopped, an appropriate delay is applied and then the TP puts the aircraft into auto and attempts to achieve a configuration from where a survivable engine off landing can be made. Where it can be done you are outside of the HV curve, from the point the TPs assess it can no longer be achieved you are inside the HV curve.
There would simply be too many graphs and information if all configurations of climb/cruise/descent were included, therefore they do the tests in level flight/hover only and accept that in a climb with higher power you will be worse off and in a descent with lower power you will be better off.
PS why didn't the guy with the private site just chop the trees down instead?
From various test points of height and speed the throttle is chopped, an appropriate delay is applied and then the TP puts the aircraft into auto and attempts to achieve a configuration from where a survivable engine off landing can be made. Where it can be done you are outside of the HV curve, from the point the TPs assess it can no longer be achieved you are inside the HV curve.
There would simply be too many graphs and information if all configurations of climb/cruise/descent were included, therefore they do the tests in level flight/hover only and accept that in a climb with higher power you will be worse off and in a descent with lower power you will be better off.
PS why didn't the guy with the private site just chop the trees down instead?
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pprune fan#1
You have pointed out an area that only adds to the relative lack of information on the HV curve. And that lack of knowledge breeds misinformation in many areas.
If you get a copy of the Advisory Circular 27-1, it explains quite nicely how the HV curve is determined for certification purposes. Unfortunately, that information is not presented anywhere in the flight manuals, and until my books were published (unabashed advert for same), it wasn't explained anywhere.
Above the 'knee', the test is done from power for level flight, with a one-second intervention between throttle chop and collective intervention. Below the 'knee', the power is takeoff power and no intervention is used between failure and pilot action (the logic is that you had better have your hand on the collective on takeoff...)
So, it is not reasonable to expect the HV curve to apply to a landing profile where you are decelerating and at a lower power setting than level flight.
As far as I know, there is also no operating rule (at least in the FAA world) that requires you (in the Part 27 or Part 29 <9 pax world) to stay outside the HV curve at any time - can't remember the CAA rules, but you might check for them.
Terrain underneath will make a mockery of the HV curve even if you're outside of it in mosts cases anyway.
But your message about 'where is this written down?' is a valid one.
wish it were otherwise.
You have pointed out an area that only adds to the relative lack of information on the HV curve. And that lack of knowledge breeds misinformation in many areas.
If you get a copy of the Advisory Circular 27-1, it explains quite nicely how the HV curve is determined for certification purposes. Unfortunately, that information is not presented anywhere in the flight manuals, and until my books were published (unabashed advert for same), it wasn't explained anywhere.
Above the 'knee', the test is done from power for level flight, with a one-second intervention between throttle chop and collective intervention. Below the 'knee', the power is takeoff power and no intervention is used between failure and pilot action (the logic is that you had better have your hand on the collective on takeoff...)
So, it is not reasonable to expect the HV curve to apply to a landing profile where you are decelerating and at a lower power setting than level flight.
As far as I know, there is also no operating rule (at least in the FAA world) that requires you (in the Part 27 or Part 29 <9 pax world) to stay outside the HV curve at any time - can't remember the CAA rules, but you might check for them.
Terrain underneath will make a mockery of the HV curve even if you're outside of it in mosts cases anyway.
But your message about 'where is this written down?' is a valid one.
wish it were otherwise.
God, I should not post while at work...
Crab crabbed:
Crab, you can kiss my ass. Frankly, I don't give a...wait...deep breath now...I don't care what Shawn, Nick or God hisself *says.* What I care about is what my RFM says...or in this case doesn't say. I'm not quite sure why you don't understand that a "fact" isn't a fact if it does not appear in the RFM, especially when it concerns a performance chart published by the manufacturer. Then again, you may not be a pilot. It wouldn't be the first time someone with limited knowledge of aviation posted on this board.
Having said that, I'm fully aware that in most helicopters, adherence to the H-V chart is not mandatory and that the shaded area most certainly would be "smaller" for a descent than for a full-power take-off at MAUW. But as I've often said, I fly in the real world - the one full of lawyers and FAA types who maybe interpret rules differently from one region to another.
As Shawn says about my original point:
So do I, Shawn, so do I. Think we can convince Bell to amend the H-V chart in their 206 manual with a statement that the it only applies on max-gross take-offs?
One other issue that I've always wondered about concerns helicopters equipped with the RR/Allison C-20 series engine. These engines have a "scheduled decelleration" which defines the minimum time that it must take the engine to go from full throttle to 62% N1. Thus, the power comes off "softly" no matter how quickly you snap the throttle shut. I've never had a real engine failure in a ship equipped with a C-20, but those who have had one tell me that the power goes away in a drastically different manner from those oh-so-easy autos we practice in Training. So I question the validity of the FAA's "wait one second" methodology in determining the limits of the H-V chart and the accuracy of the results produced, especially at MAUW.
Your thoughts, Shawn?
PF#1 - as usual you were doing really well and passing the benefits of your experience to others with less knowledge - right up to the point when Shawn pointed out some facts with which you do not agree. You are only a 'dumb pilot' when you won't listen to those who do know better - we have been round the origins of the HV curve argument before on this forum - it is created by test pilots so why not listen to a test pilot when he tells you its application.
Having said that, I'm fully aware that in most helicopters, adherence to the H-V chart is not mandatory and that the shaded area most certainly would be "smaller" for a descent than for a full-power take-off at MAUW. But as I've often said, I fly in the real world - the one full of lawyers and FAA types who maybe interpret rules differently from one region to another.
As Shawn says about my original point:
But your message about 'where is this written down?' is a valid one.
wish it were otherwise.
wish it were otherwise.
One other issue that I've always wondered about concerns helicopters equipped with the RR/Allison C-20 series engine. These engines have a "scheduled decelleration" which defines the minimum time that it must take the engine to go from full throttle to 62% N1. Thus, the power comes off "softly" no matter how quickly you snap the throttle shut. I've never had a real engine failure in a ship equipped with a C-20, but those who have had one tell me that the power goes away in a drastically different manner from those oh-so-easy autos we practice in Training. So I question the validity of the FAA's "wait one second" methodology in determining the limits of the H-V chart and the accuracy of the results produced, especially at MAUW.
Your thoughts, Shawn?
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It's also necessary to understand that the FM is not intended as a 'how to fly' book, nor will it contain everything you need to know to fly the machine. Lots of stuff that would be useful is not in the 'approved' section, as it doesn't need to be to be certified. Range and Endurance information, if it appears, is in the 'manufacturer's data' section and is not subject to any scrutiny by the FAA or any other certification authority.
Getting more info in the HV section is, sadly, wishful thinking. The FAA isn't going to demand it of a helicopter that was certified more than 40 years ago, and Bell isn't going to provide it for (pick any one of the following)
liability reasons,;
cost of obtaining the data reasons;
usefulness to operators reasons;
and so on.
As for the 'real' engine failure being different than the deceleration of the engine with a throttle chop - during the certification program, the airframe manufacturer would have to show the FAA that the engine deceleration was similar enough to a real engine failure as to be representative- if not, they would have to demonstrate at least one HV point with a 'real' engine failure to show similarity. (Pretty gutsy point to do). But it would be done.
We had to use the training mode switch on the 427 to simulate engine failures, having proved that it was identical to the real engine failure, and that throttle chops were nowhere near the same as the real thing.
So it does happen.
Getting more info in the HV section is, sadly, wishful thinking. The FAA isn't going to demand it of a helicopter that was certified more than 40 years ago, and Bell isn't going to provide it for (pick any one of the following)
liability reasons,;
cost of obtaining the data reasons;
usefulness to operators reasons;
and so on.
As for the 'real' engine failure being different than the deceleration of the engine with a throttle chop - during the certification program, the airframe manufacturer would have to show the FAA that the engine deceleration was similar enough to a real engine failure as to be representative- if not, they would have to demonstrate at least one HV point with a 'real' engine failure to show similarity. (Pretty gutsy point to do). But it would be done.
We had to use the training mode switch on the 427 to simulate engine failures, having proved that it was identical to the real engine failure, and that throttle chops were nowhere near the same as the real thing.
So it does happen.
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These discussions tend to always focus on the theoritical rather than the practical.
The HV curve is valid for both the take-off and landing/descent profiles. It is very, very conservative during descent and landing, but the curve remains valid nonetheless. The "recommended take-off profile" corridor works forwards or backwards, climbing or descending. take-off or landing.
The bottom line, real world result of an engine failure within the low speed avoid area of the HV curve during an approach to landing where the collective pitch angle is considerably less than that on a maximum power take-off is that the pilot will have a greater chance of landing without damage or injury.
Does any helicopter pilot really need a manufacturer to tell them that?
The HV curve is valid for both the take-off and landing/descent profiles. It is very, very conservative during descent and landing, but the curve remains valid nonetheless. The "recommended take-off profile" corridor works forwards or backwards, climbing or descending. take-off or landing.
The bottom line, real world result of an engine failure within the low speed avoid area of the HV curve during an approach to landing where the collective pitch angle is considerably less than that on a maximum power take-off is that the pilot will have a greater chance of landing without damage or injury.
Does any helicopter pilot really need a manufacturer to tell them that?
Rich - it would appear that PF#1 does need everything to be written down and stated unequivocally - he was the one who called himself a 'dumb pilot' after all.
PF#1 -if the only acceptable 'facts' are those quoted in your RFM then it must be one hell of a big book - I presume you have been quoting from your RFM in your many long winded posts on this forum where you have stated many 'facts' - which in fact turned out to be simply your opinion.
PF#1 -if the only acceptable 'facts' are those quoted in your RFM then it must be one hell of a big book - I presume you have been quoting from your RFM in your many long winded posts on this forum where you have stated many 'facts' - which in fact turned out to be simply your opinion.
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250' AGL, 40kt and 80% power in a climb is way different than 250' AGL, 40kt and 40% power in a descent. In the first case, the RRPM will drop much more, and it will take longer for the autorotative airflow to develop. Given the choice, I'd much rather be inside the curve in a low-power descent than a little outside the curve in a high-power climb.
In fact, it would be very difficult to make normal approaches and stay out of the H/V curve. IMHO, the only time you truely enter the curve in approach is on a steep approach, where you are operating at a relatively high power setting while still pretty far from the ground.
In fact, it would be very difficult to make normal approaches and stay out of the H/V curve. IMHO, the only time you truely enter the curve in approach is on a steep approach, where you are operating at a relatively high power setting while still pretty far from the ground.