LTE, Wind Direction Preference
"Just a pilot"
From the peanut gallery-
My experience is that the dead man’s curve, a/k/a “H/V chart”, is most useful as advisory. Think “VFR flight not recommended” in your WX briefs for a comparison. Adherence is not required, but if you’re officially interviewed, you’d better have bullet-proof reasons for failing to heed.
There are plenty of sound reasons why a pilot might operate in the shaded area: Confined areas, or almost any unimproved landing surface; Elevated pads; Tail rotor strike hazards proximal to the point of intended landing; External loads; Etc. These situations would be much more dangerous if not impossible were the H/V chart regulatory. It's information to guide your decision.
At least it's a known point to refer to- it's a new aircraft with a highly skilled pilot extrapolating. I know I'm, sub-par some days, I'm not operating over a smooth hard surface, and that pile of parts on the pad isn't perfect...
P.S. Real world power failures can be gradual losses, or sudden and complete. The aircraft comes down like a brick without engne idle thrust, especially as you cushion and land. Be somewhere with options.
My experience is that the dead man’s curve, a/k/a “H/V chart”, is most useful as advisory. Think “VFR flight not recommended” in your WX briefs for a comparison. Adherence is not required, but if you’re officially interviewed, you’d better have bullet-proof reasons for failing to heed.
There are plenty of sound reasons why a pilot might operate in the shaded area: Confined areas, or almost any unimproved landing surface; Elevated pads; Tail rotor strike hazards proximal to the point of intended landing; External loads; Etc. These situations would be much more dangerous if not impossible were the H/V chart regulatory. It's information to guide your decision.
At least it's a known point to refer to- it's a new aircraft with a highly skilled pilot extrapolating. I know I'm, sub-par some days, I'm not operating over a smooth hard surface, and that pile of parts on the pad isn't perfect...
P.S. Real world power failures can be gradual losses, or sudden and complete. The aircraft comes down like a brick without engne idle thrust, especially as you cushion and land. Be somewhere with options.
If the H/V curve was an operational limitation, then surely it would be in the "Limitations" Section of the Flight Manual?
I simply use it as a guide for any height/airspeed combo to be able to say to myself "At this combo I should be able to land OK if the power fails, but at this combo I might hit hard" and of course stay out of it if possible.
Back to the original thread, I can dig the left crosswind thing for giving you a bit more power at the bottom, albeit with a bit more yaw instability.
But if your shooting an approach with a left crosswind, presumably its to clear obstacles, and I'm not sure if I agree with the benefit of having the nose yaw further left into wind should the power fail in that situation. Wouldn't you then be totally crossed up to your original approach path with nowhere to go, if it happened on short final? I can't really see the benefit of that, personally I'd rather still be vaguely pointing at the orginal landing area I'm committed to, rather than sideways, if I'm going down. Just a thought.
I simply use it as a guide for any height/airspeed combo to be able to say to myself "At this combo I should be able to land OK if the power fails, but at this combo I might hit hard" and of course stay out of it if possible.
Back to the original thread, I can dig the left crosswind thing for giving you a bit more power at the bottom, albeit with a bit more yaw instability.
But if your shooting an approach with a left crosswind, presumably its to clear obstacles, and I'm not sure if I agree with the benefit of having the nose yaw further left into wind should the power fail in that situation. Wouldn't you then be totally crossed up to your original approach path with nowhere to go, if it happened on short final? I can't really see the benefit of that, personally I'd rather still be vaguely pointing at the orginal landing area I'm committed to, rather than sideways, if I'm going down. Just a thought.
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Thanks for all the responses. Good pespectives.
The original question was in reference to pads, ridges, or toe-ins on steep terrain and usually at altitude. Of course into wind is the best option, but often an up-valley wind in the afternoon will set up a situation where you have to accept a stiff x-wind on the last phase of the approch. Again, you want to minimize that time as you are then fairly commited, but avoiding it altogether is not often possible.
The H/V debate was an interesting one as well. I think if you spend most of your time hovering on the (100ft.) line, it's an arguement that really doesn't matter much, does it?
AR
The original question was in reference to pads, ridges, or toe-ins on steep terrain and usually at altitude. Of course into wind is the best option, but often an up-valley wind in the afternoon will set up a situation where you have to accept a stiff x-wind on the last phase of the approch. Again, you want to minimize that time as you are then fairly commited, but avoiding it altogether is not often possible.
The H/V debate was an interesting one as well. I think if you spend most of your time hovering on the (100ft.) line, it's an arguement that really doesn't matter much, does it?
AR
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left or right?!!!!
hello guys
lets talk about anti-clockwise rotorcrafts,,,,
if we are in a hover flight and an adverse wind condition, and the wind is from the left side of the helicopter which could cause tail rotor vortex ring state, and if the wind is from the right side of the heli, will reduce power of the aircraft, and may lead to a full left pedal.
so what do you think is better, if we don't have the choise to be head wind, to put the wind left or right????
lets talk about anti-clockwise rotorcrafts,,,,
if we are in a hover flight and an adverse wind condition, and the wind is from the left side of the helicopter which could cause tail rotor vortex ring state, and if the wind is from the right side of the heli, will reduce power of the aircraft, and may lead to a full left pedal.
so what do you think is better, if we don't have the choise to be head wind, to put the wind left or right????
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If we talk about "left-turn" rotors (for example Bell etc...), always choose left wind. Bell flight manual tell you to avoid operations from some right-rear angle ...
But, when you are in "hot & High" conditions, low speed, and high TOW, be carefull when you have wind from 11 o´clock, possibility of LTE (loss of tail rotor efficiency)...you can recognize that situation during the flight, for example in Bell 206, when you start with speed reducing, you can feel, lack of left pedal is coming ...
But, when you are in "hot & High" conditions, low speed, and high TOW, be carefull when you have wind from 11 o´clock, possibility of LTE (loss of tail rotor efficiency)...you can recognize that situation during the flight, for example in Bell 206, when you start with speed reducing, you can feel, lack of left pedal is coming ...
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In the R22 I would rather have a right crosswind, being that the vertical stabilizer is so small, and tail rotor authority is high.
The JetRanger however, has a a giant vertical stabilizer which eats up a ton of torque in a right crosswind situation, in addition to low tail rotor authority to begin with, so I would rather have a left crosswind.
just my 2 cents
The JetRanger however, has a a giant vertical stabilizer which eats up a ton of torque in a right crosswind situation, in addition to low tail rotor authority to begin with, so I would rather have a left crosswind.
just my 2 cents
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I have seen lots of talk on left or right turning rotors on helicopters-Forget all that,Fly heading and don't get lazy on the foot peddles, Know the querks of each machine. Even the same manufacture and type can feel different. Be more than a stick wiggler. Be safe.
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thx guys
your comments are so meaningful
but in most aerodynamics books like "principles of helicopter flight", the most dangerous areas are from 330 deg to 210 deg from the nose and can lead to tail rotor vortex ring state which is similar to the main rotor vortex ring state, and in other way a full loss of tail rotor effectiveness. And this discussion regardless of the vertical fin.
In several mountains flights, we can't terminate our approach head wind, we have to put the wind a little bit to the right or left.
your comments are so meaningful
but in most aerodynamics books like "principles of helicopter flight", the most dangerous areas are from 330 deg to 210 deg from the nose and can lead to tail rotor vortex ring state which is similar to the main rotor vortex ring state, and in other way a full loss of tail rotor effectiveness. And this discussion regardless of the vertical fin.
In several mountains flights, we can't terminate our approach head wind, we have to put the wind a little bit to the right or left.
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Loss of Tail Rotor Effectiveness
this link may give a sufficient explenation about tail rotor vortex ring state
this link may give a sufficient explenation about tail rotor vortex ring state
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http://www.pprune.org/newreply.php?d...te=1&p=6815974
this link may help in "tail rotor vortex ring state" explanation
this link may help in "tail rotor vortex ring state" explanation
Don't call it tail rotor VRS because it most certainly isn't - we used to show this on the Wessex to highlight a wind from the 10 o'clock would cause yaw deviations and could lead to overtorque, especially at high AUM. On Bells like the 206 it just leads to LTE.
To get VRS on a rotor it has to be moving into its own downwash at a minimum of half the speed of that downwash - normal yaw manoeuvres and crosswinds don't even come close to that speed.
To get VRS on a rotor it has to be moving into its own downwash at a minimum of half the speed of that downwash - normal yaw manoeuvres and crosswinds don't even come close to that speed.
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Evil Twin - thx for sharing us this interresting video
crab - the tial rotor vortex ring state, is similar to the main rotor vortex ring state; if we have a left cross wind (anti-clockwise), the induced flow of the tail rotor is encountered by the left cross wind which reduces the induced flow and increases the angle of attack to reach the critical angle and the blade looses its efficiency; it's similar to the main rotor vortex ring state(settling with power). But this is not our objective of discussion, this is a fact, but between the two evils: the left cross wind(resulting T/R VRS) and the right cross wind(resulting reduction of power) which evil do you choose?
Your thoughts guys ?
crab - the tial rotor vortex ring state, is similar to the main rotor vortex ring state; if we have a left cross wind (anti-clockwise), the induced flow of the tail rotor is encountered by the left cross wind which reduces the induced flow and increases the angle of attack to reach the critical angle and the blade looses its efficiency; it's similar to the main rotor vortex ring state(settling with power). But this is not our objective of discussion, this is a fact, but between the two evils: the left cross wind(resulting T/R VRS) and the right cross wind(resulting reduction of power) which evil do you choose?
Your thoughts guys ?
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Avoid right wind (if you, for ex. fly 206), fly into the wind and dont think to much. Just fly.
Don˙t be so impressed with LTE and left wind. But it is good to know about that, and be aware of that when you are on MTOW and "hot&high" (off course, in Jet Ranger)
Don˙t be so impressed with LTE and left wind. But it is good to know about that, and be aware of that when you are on MTOW and "hot&high" (off course, in Jet Ranger)
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All things considered, in a Bell, I would take the left crosswind because the ships hangs left skid low, and it will be easier to land with the left crosswind, Also, as I approach and crab left into the wind, I have better visibility of my LZ sitting in the right seat.
Having done Private, Commercial and ATP ratings and check rides at the Bell School, and many recurrent courses, Bell ground school and flight instructors state that the HV curve does not apply to descent/landing.
Having done Private, Commercial and ATP ratings and check rides at the Bell School, and many recurrent courses, Bell ground school and flight instructors state that the HV curve does not apply to descent/landing.
1aviator1 - thankyou, I am well aware what VRS is and how it is caused - I was trying to explain that a crosswind or a yaw manoeuvre is very unlikely to produce sufficient airflow to cause VRS in a TR.
The thread is concerned with which crosswind to accept and that is straightforward, you take a crosswind from the retreating side of the disc (from the left on an anti-clockwise rotor) if you are short on power because you use right (non-power) pedal to stop the aircraft weather-vaning into wind.
If you have control authority problems - running out of pedal or lateral cyclic (poor design or a large tail fin) then don't try to hover crosswind.
Winds from the 10 o'clock or 2 o'clock (depending on the direction of rotation of your rotor) can cause the MR tip vortices to disrupt the flow into the TR/fenestron giving yaw and Tq fluctuations.
Winds from the aft quadrants on either side will try to weathercock (weather vane) you into wind - (the helicopter fuselage is designed to fly forwards) - and so will always cause problems with heading control.
The thread is concerned with which crosswind to accept and that is straightforward, you take a crosswind from the retreating side of the disc (from the left on an anti-clockwise rotor) if you are short on power because you use right (non-power) pedal to stop the aircraft weather-vaning into wind.
If you have control authority problems - running out of pedal or lateral cyclic (poor design or a large tail fin) then don't try to hover crosswind.
Winds from the 10 o'clock or 2 o'clock (depending on the direction of rotation of your rotor) can cause the MR tip vortices to disrupt the flow into the TR/fenestron giving yaw and Tq fluctuations.
Winds from the aft quadrants on either side will try to weathercock (weather vane) you into wind - (the helicopter fuselage is designed to fly forwards) - and so will always cause problems with heading control.
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GeorgeMandes- thx for sharing us ur thoughts it's verry interesting
Jet Ranger-
in some cases especially in mountains flights, we can't terminate our approaches into the wind
during flight, we don't have to think to much-it's true- cz we don't have enough time to think, but if we want to return to our bases or helipads or whatever..safe, we have to think before every flight, and think a lot
crab- I appreciate that you are a good pilot maybe I didn't understand ur thought well now it's pretty clear
the only benefit of right cross wind is to provide more power when we operate in high gross weight, but the danger of left cross wind always exists especially in high density alt and high temp.
If we all agree with this consept, if we are operating in high alt/temp it's better to avoid T/R VRS and keep the wind to the right, and if we have high TOGW we have to take the risk of T/R VRS but to enforce the power with left cross wind? can we consider it true?
Jet Ranger-
fly into the wind and dont think to much. Just fly
during flight, we don't have to think to much-it's true- cz we don't have enough time to think, but if we want to return to our bases or helipads or whatever..safe, we have to think before every flight, and think a lot
crab- I appreciate that you are a good pilot
maybe I didn't understand ur thought well now it's pretty clearthe only benefit of right cross wind is to provide more power when we operate in high gross weight, but the danger of left cross wind always exists especially in high density alt and high temp.
If we all agree with this consept, if we are operating in high alt/temp it's better to avoid T/R VRS and keep the wind to the right, and if we have high TOGW we have to take the risk of T/R VRS but to enforce the power with left cross wind? can we consider it true?
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If we all agree with this consept, if we are operating in high alt/temp it's better to avoid T/R VRS and keep the wind to the right, and if we have high TOGW we have to take the risk of T/R VRS but to enforce the power with left cross wind? can we consider it true?
I can´t agree with that statement. If you fly for example Bell 206, if you choose wrong wind
(right wind, from 60-220 degrees relative), in that high alt conditions, you can stay without power (TQ) and may crash! (not enough left pedal). Flight Manual, Performance section, tells you - avoid hover operations from that relative wind operations 
! That is no.1!Left wind is very OK. Gives you low-left pedal and good TQ. LTE is something new, 20 years ago nowbody knew nothing about that-and fly. It is good to know about that ! But, thats no.2 problem.
Only my opinion. JR
A left crosswind in a 206 will be something of a compromise between LTE and weathervaning tendency. If the wind is strong enough to push the MR vortices into the tail rotor (as in in the video of the OH-58 model) then there will be enough weathervaning tendency that LTE won't be a worry. Weathervaning tendency in a 206 is strong.
But remember that wind is hardly ever constant like in a wind tunnel. In real life, the flow through the rotor systems (main and tail) is fairly chaotic. The instances of LTE will only be transitory. The tail rotor will not summarily "stall" and stop working altogether, allowing the fuselage to spin like a top. Yes, your feet will be "busier" with a wind from the left-front but you'll have more pedal available (than with a right crosswind) should a yaw rate start to develop. I will always take a left crosswind in a 206. Landing with the wind from the right is just asking for trouble, especially at higher MGW's.
But remember that wind is hardly ever constant like in a wind tunnel. In real life, the flow through the rotor systems (main and tail) is fairly chaotic. The instances of LTE will only be transitory. The tail rotor will not summarily "stall" and stop working altogether, allowing the fuselage to spin like a top. Yes, your feet will be "busier" with a wind from the left-front but you'll have more pedal available (than with a right crosswind) should a yaw rate start to develop. I will always take a left crosswind in a 206. Landing with the wind from the right is just asking for trouble, especially at higher MGW's.