If you understand LTE there is no such thing as "unanticipated yaw" as you will be expecting the increase in pedal work in those conditions and thus be prepared for it. This has kept my nose straight for twenty years,...and in some pretty nasty winds too. As far as recovery goes, I don't know about his FAA textbook, but mine (the Rotorcraft Flying Handbook) mentions pushing in opposite pedal as well as forward cyclic, and even mentions lowering collective to help. It also mentions autorotation as a possible solution too, depending on the situation. Anyway, be mindful of the wind and stay awake on those pedals. :-)
Congratulations for this video, finally someone talks about, this is a real Myth and constant discussions with some pilots, training needs to be modified to feeling instead of reading, and known how the Aerodynamics works in detail, also understanding all the helicopters are different, cheers
Is there a trainer/simulator in existence that is dedicated to unanticipated yaw? Perhaps a wind tunnel with a decommissioned helicopter on a pivot where the main rotor is replaced with simulated counterforce to the tail rotor, but with a fully functioning tail rotor. Vary the landing directional conditions in the wind tunnel while incorporating a visible mist to observe tail rotor responses to variable wind conditions. This would also allow observations of the physical responses of the pilot during the unanticipated yaw simulation. Often my question is this: when the helicopter is in an unanticipated yaw spin, what are the physical responses of the body of the pilot? Does the pilot accidentally influence the cyclic with their legs (causing the helicopter to tip over)? Do the forces inside a spinning helicopter allow the pilot to still accurately operate the pedals? Does a pilot tend to brace both feet against the pedals in anticipation of a crash, rather than input counter forces to the pedals to stop the spin? Do computer simulators work as well as a real life simulation?
So we say there is no wind and potential rotational sitation of the helicopter, where the tailrotor is not powerful enough to stop it.... unless, the helicopter is power limited? Full left is always sufficient (as in "always")? I reserve a tiny bit of doubt here. I do easily believe many pilots do not put in full left - but I can also easily imagine a situation were full left is not sufficient for more than one rotation - too much eventually, to prevent ground impact. Of course not letting the heli spin in the first place, by not letting a considerable rotation rate develop prevents any hard to stop rotation, But that has been taught all along with the description LTE. Maybe the "effectiveness" part is just worded misleading - it is not that the tail rotor is not equally as effective as it always is - it is just sometimes not effective enough in relation to the already developed rotation of the helicopter (that might have developed by slow reaction to weathercocking for example).
well, if you get caught by surprise and slam the power pedal and start to droop, you will not have enough TR to stop it. The curve looks pretty on a power point but does it take into consideration overpitching? 1% in the MR is 6% on the tail, pretty sure that pedal curve would change?
If I understand correctly (not guaranteed), the curve represents the trim position of the pedal to maintain that amount of offset from the wind direction. In the stable zone, increasing right pedal trim is required for increasing right offset from the wind. As the aircraft turns further, the trim position required on the pedals tends back towards the left. So we are talking stable trim positions here... with the highest right trim being a pedal position of 50%. Maximum right pedal is 100%, way above these stable positions. Of course it could be you are asking why the required right pedal position decreases as you leave the stable zone - I think the shape of the pedal trim curve is dictated by a number of dynamic factors, including airflow over the fuselage, incident airflow over the tail rotor, interactions between the main and tail rotors, air density, temperature, weight. The different factors combine to produce this shape.
LTE is not a myth. I wonder if people who think LTE is a myth are those who've never flown a B model JetRanger? I flew them Mon-Fri for almost 12 years and can verify that LTE is EXACTLY as stated in the manual. I think the video should have been titled "Complete" LTE is a myth (and even then, it is a complete loss if you begin the spin without applying fast forward cyclic without full pedal and you're also too close to the ground to not get out of it; it would be a complete loss at that point because you have no other option other than a hovering auto and hope for the best). There is almost always zero discussion about this topic regarding what the forward cyclic actually does. Everyone thinks the forward cyclic is to begin flying out of the LTE by gaining forward motion after you begin spinning. Really: when done quickly, the tail is rotated up vertically so fast that clean air runs across the tail rotor in a vertical fashion to move the tail out of the VRS that's built on the TR blades at the time. Much like the reason Vuichard's VRS technique is so effective. For Vuichard's technique the sideways pulling of the tailrotor with coupled sideways cyclic gets the MR disc out of disturbed air quickly... with LTE the fast application forces the tailrotor in an upward direction very quickly getting clean air from a new direction which acts across the TR disc itself. Obviously, stomp on the pedal if you're not at the top of your TQ range and simultaneously apply aggressive forward cyclic and you'll be out of it in a heartbeat. Did it all the time. As a flight instructor, where you're always on your guard as a student approaches a limit and have to be prepared to react, I'd see this at least once a month and would point out to the student "be ready... you're right in that range" and when the nose came close to snapping right I'd typically have to take the controls to show them how to get out of it. 90-95% of the time just some full pedal applied quickly did the trick (probably why people think LTE is a myth), but there was 5% of the time where the forward cyclic was critical (i.e. pretty sure the nose would have kept going right and we would have been in a spin). But regardless the cyclic had a drastic impact and the nose immediately stopped and the pedals had effectiveness again. I've had friends get into fully developed LTE with a Schweizer 300 (or whatever the latest model it was that Sikorsky bought) in Saudi Arabia as well as two MD530 friends say they've gotten into it (all 3 said aircraft spun 1 to 3 times before diving out of it with a lot of forward cyclic). All three were near hills and they had room to dive and fly out of them. So yes, LTE can happen to other aircraft as well. LTE is NOT a myth.
VRS may only exist on a rotor in purely axial flight and will be exited as soon as an inplane speed component exists. Forget the idea that LTE ('poor and misleading wording, prefer unanticipated yaw) is entering permanent tail rotor VRS. This does not exist. Your testimony is the proof that AC90-95 is unclear. It only says that large tail rotor thrust variations take place in conditions where VRS occurs, but does not explain how it leads to unanticipated yaw.
If you understand LTE there is no such thing as "unanticipated yaw" as you will be expecting the increase in pedal work in those conditions and thus be prepared for it. This has kept my nose straight for twenty years,...and in some pretty nasty winds too.
As far as recovery goes, I don't know about his FAA textbook, but mine (the Rotorcraft Flying Handbook) mentions pushing in opposite pedal as well as forward cyclic, and even mentions lowering collective to help. It also mentions autorotation as a possible solution too, depending on the situation.
Anyway, be mindful of the wind and stay awake on those pedals. :-)
Congratulations for this video, finally someone talks about, this is a real Myth and constant discussions with some pilots, training needs to be modified to feeling instead of reading, and known how the Aerodynamics works in detail, also understanding all the helicopters are different, cheers
Very interesting presentation and very insightful. Is there a downloadable document on this subject?
Is there a trainer/simulator in existence that is dedicated to unanticipated yaw?
Perhaps a wind tunnel with a decommissioned helicopter on a pivot where the main rotor is replaced with simulated counterforce to the tail rotor, but with a fully functioning tail rotor.
Vary the landing directional conditions in the wind tunnel while incorporating a visible mist to observe tail rotor responses to variable wind conditions.
This would also allow observations of the physical responses of the pilot during the unanticipated yaw simulation.
Often my question is this: when the helicopter is in an unanticipated yaw spin, what are the physical responses of the body of the pilot? Does the pilot accidentally influence the cyclic with their legs (causing the helicopter to tip over)? Do the forces inside a spinning helicopter allow the pilot to still accurately operate the pedals? Does a pilot tend to brace both feet against the pedals in anticipation of a crash, rather than input counter forces to the pedals to stop the spin? Do computer simulators work as well as a real life simulation?
So we say there is no wind and potential rotational sitation of the helicopter, where the tailrotor is not powerful enough to stop it.... unless, the helicopter is power limited? Full left is always sufficient (as in "always")? I reserve a tiny bit of doubt here. I do easily believe many pilots do not put in full left - but I can also easily imagine a situation were full left is not sufficient for more than one rotation - too much eventually, to prevent ground impact. Of course not letting the heli spin in the first place, by not letting a considerable rotation rate develop prevents any hard to stop rotation, But that has been taught all along with the description LTE. Maybe the "effectiveness" part is just worded misleading - it is not that the tail rotor is not equally as effective as it always is - it is just sometimes not effective enough in relation to the already developed rotation of the helicopter (that might have developed by slow reaction to weathercocking for example).
well, if you get caught by surprise and slam the power pedal and start to droop, you will not have enough TR to stop it. The curve looks pretty on a power point but does it take into consideration overpitching? 1% in the MR is 6% on the tail, pretty sure that pedal curve would change?
This is a very intriguing video! In the pedal curve diagram, why doesn't the maximum right pedal correspond to the 90 degree right heading?
If I understand correctly (not guaranteed), the curve represents the trim position of the pedal to maintain that amount of offset from the wind direction. In the stable zone, increasing right pedal trim is required for increasing right offset from the wind. As the aircraft turns further, the trim position required on the pedals tends back towards the left.
So we are talking stable trim positions here... with the highest right trim being a pedal position of 50%. Maximum right pedal is 100%, way above these stable positions.
Of course it could be you are asking why the required right pedal position decreases as you leave the stable zone - I think the shape of the pedal trim curve is dictated by a number of dynamic factors, including airflow over the fuselage, incident airflow over the tail rotor, interactions between the main and tail rotors, air density, temperature, weight. The different factors combine to produce this shape.
LTE is not a myth.
I wonder if people who think LTE is a myth are those who've never flown a B model JetRanger? I flew them Mon-Fri for almost 12 years and can verify that LTE is EXACTLY as stated in the manual. I think the video should have been titled "Complete" LTE is a myth (and even then, it is a complete loss if you begin the spin without applying fast forward cyclic without full pedal and you're also too close to the ground to not get out of it; it would be a complete loss at that point because you have no other option other than a hovering auto and hope for the best).
There is almost always zero discussion about this topic regarding what the forward cyclic actually does.
Everyone thinks the forward cyclic is to begin flying out of the LTE by gaining forward motion after you begin spinning. Really: when done quickly, the tail is rotated up vertically so fast that clean air runs across the tail rotor in a vertical fashion to move the tail out of the VRS that's built on the TR blades at the time. Much like the reason Vuichard's VRS technique is so effective. For Vuichard's technique the sideways pulling of the tailrotor with coupled sideways cyclic gets the MR disc out of disturbed air quickly... with LTE the fast application forces the tailrotor in an upward direction very quickly getting clean air from a new direction which acts across the TR disc itself.
Obviously, stomp on the pedal if you're not at the top of your TQ range and simultaneously apply aggressive forward cyclic and you'll be out of it in a heartbeat. Did it all the time.
As a flight instructor, where you're always on your guard as a student approaches a limit and have to be prepared to react, I'd see this at least once a month and would point out to the student "be ready... you're right in that range" and when the nose came close to snapping right I'd typically have to take the controls to show them how to get out of it.
90-95% of the time just some full pedal applied quickly did the trick (probably why people think LTE is a myth), but there was 5% of the time where the forward cyclic was critical (i.e. pretty sure the nose would have kept going right and we would have been in a spin). But regardless the cyclic had a drastic impact and the nose immediately stopped and the pedals had effectiveness again.
I've had friends get into fully developed LTE with a Schweizer 300 (or whatever the latest model it was that Sikorsky bought) in Saudi Arabia as well as two MD530 friends say they've gotten into it (all 3 said aircraft spun 1 to 3 times before diving out of it with a lot of forward cyclic). All three were near hills and they had room to dive and fly out of them. So yes, LTE can happen to other aircraft as well.
LTE is NOT a myth.
VRS may only exist on a rotor in purely axial flight and will be exited as soon as an inplane speed component exists. Forget the idea that LTE ('poor and misleading wording, prefer unanticipated yaw) is entering permanent tail rotor VRS. This does not exist.
Your testimony is the proof that AC90-95 is unclear. It only says that large tail rotor thrust variations take place in conditions where VRS occurs, but does not explain how it leads to unanticipated yaw.
@@andre-micheldequin9518 well said.