Vortex Ring / Settling with power (Merged)
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One of the principles that has to be used when writing emergency procedures or insisting on warning or caution lights is that the symptoms must be clear and easily understood so that the correct action can be taken.
Can't have two separate and distinct procedures for the same indications, for example. Also can't have the same indications for two different problems.
Hence the question - what are the symptoms, in the cockpit, that the pilot will see to know whether he has 'settling with power' or 'vortex ring state'?
Given that many helicopter pilots can't describe what they'll see in the cockpit with VRS to begin with, how can we help to educate them about the difference.
Having re-read this wonderfully done discussion, my suggestion would be:
Symptoms:
Power / Engine Indications - at maximum power or engine limits
Airspeed - zero to 20 KIAS
Rate of Descent - 200-500 fpm/ Not slowing down / Not being arrested
Rotor RPM - May be decreasing
This might be called 'settling with power' but most probably should be called 'power required exceeds power available'.
Recovery action - maintain collective position, increase throttle in piston engine helicopter / lower collective to regain rotor RPM apply forward cyclic to gain airspeed. Reconsider attempt to land.
Symptoms
Vibrations - low frequency airframe buffeting
Airspeed - less than 20 KIAS
Airframe - may have uncommanded pitch, roll and yaw
Rate of descent- greater than 500' fpm
Power - initially may be less than any limits of airframe or engine
Raising collective results in increase in rate of descent
May be downwind if wind is known
Recovery action - apply forward cyclic and hold till airspeed increases, simultaneously increase collective (this based on Nick's advice)
I realize this appears to violate the first part of my post- the recovery action appears to be much the same for the two situations, but they are slightly different.
Further suggestions?
Can't have two separate and distinct procedures for the same indications, for example. Also can't have the same indications for two different problems.
Hence the question - what are the symptoms, in the cockpit, that the pilot will see to know whether he has 'settling with power' or 'vortex ring state'?
Given that many helicopter pilots can't describe what they'll see in the cockpit with VRS to begin with, how can we help to educate them about the difference.
Having re-read this wonderfully done discussion, my suggestion would be:
Symptoms:
Power / Engine Indications - at maximum power or engine limits
Airspeed - zero to 20 KIAS
Rate of Descent - 200-500 fpm/ Not slowing down / Not being arrested
Rotor RPM - May be decreasing
This might be called 'settling with power' but most probably should be called 'power required exceeds power available'.
Recovery action - maintain collective position, increase throttle in piston engine helicopter / lower collective to regain rotor RPM apply forward cyclic to gain airspeed. Reconsider attempt to land.
Symptoms
Vibrations - low frequency airframe buffeting
Airspeed - less than 20 KIAS
Airframe - may have uncommanded pitch, roll and yaw
Rate of descent- greater than 500' fpm
Power - initially may be less than any limits of airframe or engine
Raising collective results in increase in rate of descent
May be downwind if wind is known
Recovery action - apply forward cyclic and hold till airspeed increases, simultaneously increase collective (this based on Nick's advice)
I realize this appears to violate the first part of my post- the recovery action appears to be much the same for the two situations, but they are slightly different.
Further suggestions?
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Shawn: wouldn't VRS be noticed/happen earlier in athe approach
( you would need the altitude to get into fully developed VRS) while settling with power would be evident during the latter stages just prior to touch down.
( you would need the altitude to get into fully developed VRS) while settling with power would be evident during the latter stages just prior to touch down.
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Good point, IHL. We could probably go a step further and say that SWP is avoided by confirming power, checking charts, and proper recce's while VRS is avoided by using proper technique.
My point is that if you're properly educated, both of these shouldn't occur, or at the very least surprise you.
Matthew.
My point is that if you're properly educated, both of these shouldn't occur, or at the very least surprise you.
Matthew.
I think you are hitting the nail on the head Shawn. As I posted in the Black Hawk threads, I feel there really needs to be a change of terminology to avoid what is clearly confusing the hell out of everyone. That terminology was changed in Oz more than 20 years ago, and nowadays it is rare to hear this endless discussion and all its misunderstandings.
As I suggested in the Black Hawk thread, we can clean up the terminology simply by calling the situations what they are, and thus promote increased understanding (which is the ultimate goal anyway):
Vortex Ring State should be called Vortex Ring State, and no longer called settling with anything - because it is far from a "settling experience".
Running out of power should be called Insufficient Power because that is what it is. The fact that you then settle to the ground also happens with engine failures - but we dont refer to them as settling without any power! I go for "insufficient power" in preference to Shawns suggestion of "power required exceeds power available" because it says the same thing with more brevity.
Thus the bloke who tries to come to the hover and then smites the ground would NOT be "suffering" power settling or settling with power, he would have entered VRS or he would have attempted a manoeuvre with insufficient power, depending upon the circumstances which, (as should be blindingly obvious by now) are vastly different for each case.
Whaddyareckon?
As I suggested in the Black Hawk thread, we can clean up the terminology simply by calling the situations what they are, and thus promote increased understanding (which is the ultimate goal anyway):
Vortex Ring State should be called Vortex Ring State, and no longer called settling with anything - because it is far from a "settling experience".
Running out of power should be called Insufficient Power because that is what it is. The fact that you then settle to the ground also happens with engine failures - but we dont refer to them as settling without any power! I go for "insufficient power" in preference to Shawns suggestion of "power required exceeds power available" because it says the same thing with more brevity.
Thus the bloke who tries to come to the hover and then smites the ground would NOT be "suffering" power settling or settling with power, he would have entered VRS or he would have attempted a manoeuvre with insufficient power, depending upon the circumstances which, (as should be blindingly obvious by now) are vastly different for each case.
Whaddyareckon?
Something for you instructors !!
Just for interest while talking about vortex ring. Last week did lesson 15 vortex ring with a student in a 300. Normal briefings and demos from 3000 ft. Asked the student to hold 18 inches MP and height so he obviously is pulling back the speed. As we came below about 20 kts ias with 18" the ac began its normal vibration followed by pitching and rolling with rod at 700fpm. Asked student to recover, he did by snapping the lever up to 25"map. I was't expecting his yank so couldn't initally couldn't overcome the increased pitch!!!!
The result was impressive language, a 300 falling back to mother earth on its side ( very unerving looking out of the side window directly down). To recover was full lever down and full forward cyclic, it took a long time to ( seemed) get the ac out of vrs with about 500 ft to spare before stuffing in.
Result now take a strong pair of cycle clips and alot of pressure on collective to stop it coming up !!! I would have to agree with other posts in incipient vrs cylic first, in full vrs collective down followed by cylic and hope you have the height !!
Just for interest while talking about vortex ring. Last week did lesson 15 vortex ring with a student in a 300. Normal briefings and demos from 3000 ft. Asked the student to hold 18 inches MP and height so he obviously is pulling back the speed. As we came below about 20 kts ias with 18" the ac began its normal vibration followed by pitching and rolling with rod at 700fpm. Asked student to recover, he did by snapping the lever up to 25"map. I was't expecting his yank so couldn't initally couldn't overcome the increased pitch!!!!
The result was impressive language, a 300 falling back to mother earth on its side ( very unerving looking out of the side window directly down). To recover was full lever down and full forward cyclic, it took a long time to ( seemed) get the ac out of vrs with about 500 ft to spare before stuffing in.
Result now take a strong pair of cycle clips and alot of pressure on collective to stop it coming up !!! I would have to agree with other posts in incipient vrs cylic first, in full vrs collective down followed by cylic and hope you have the height !!
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Settling with power
I once deliberately entered a Vortex ring, as a demonstration to a student, in an Iroquois (Bell 204) at about 3000 ft. The entry was achieved by hovering downwind, descending and introducing power. When established the aircraft descended at approx 2500 ft/min, shook and rattled, and the cyclic was slack and ineffective. A moment of panic ensued when I discovered that the supposed recovery technique of selecting forward cyclic had no effect whatsoever, and we had already lost more than 1000 ft. I selected full pedal (left I think), and after a second or so the aircraft suddenly spun around into wind, and I was able to dive out and recover. From then on the Vortex ring topic was discussed in the classroom only, as far as I was concerned.
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It is a while since I have done ab-initio instruction, but the point was made during my instructor training that the aim was to show the symptoms of the incipient stage of VR, and then the recovery. It seems to me that there is a real purpose and value in going this far for the student - if for no ther reason than to make himm/her aware.
I remember several occasions when instructors I knew were flying together vying with each other to get a higher and higher rate of descent in VR before recovery - it was never a game that I joined in on. My experience of even the incipient stage was that it was so unpredictable that I really did not want to go further. I am not at all sure that we know enough about VR to play with it in this way - certainly an area for the test pilot in my book, and a high starting altitude to the exercise!
I remember several occasions when instructors I knew were flying together vying with each other to get a higher and higher rate of descent in VR before recovery - it was never a game that I joined in on. My experience of even the incipient stage was that it was so unpredictable that I really did not want to go further. I am not at all sure that we know enough about VR to play with it in this way - certainly an area for the test pilot in my book, and a high starting altitude to the exercise!
It's funny, really, to hear all the theoretical discussions of SWP/VRS. Those of us who've actually gotten into true VRS know (like Ross and "Hughes 500" found out) that VRS can be pretty...let's call it "anxiety-producing" since we pilots don't like to admit that something was scary.
Let's be honest, if you get into actual VRS below 500 feet you are going to crash.
On the other hand, SWIP ("settling with insufficient power") is probably more recoverable due to the fact that the rotor is still behaving in a conventional, predictable manner. All you need to do is get through ETL and you're flying again. But does it matter?
The trouble is, the line between SWIP and SWVRS is a hazy, indistinct one. The former can turn into the latter in a heartbeat. It matters not whether you think your a/c is more susceptible to one or the other. Operationally, the technique used to avoid both is the same.
And that is? Simple really. Pilots who find themselves on approach to an LZ with very low airspeed and power applied (i.e. non-autorotative) better be on their toes. You better know where the wind is coming from, and you better be super-attentive to the cues coming from the ship.
I absolutely hate downwind, back-below-ETL approaches. In the course of my career (60,000 landings, conservatively), I've had to make a few when no other alternative was available. They make me very uncomfortable. And I hope I never do get comfortable doing them. Because I never want to be sitting there thinking, "Is this just SWIP or true VRS?" If that thought ever crosses my mind, it means that I've screwed-up, big time. For whatever reason (luck?) I've yet to think it.
Let's be honest, if you get into actual VRS below 500 feet you are going to crash.
On the other hand, SWIP ("settling with insufficient power") is probably more recoverable due to the fact that the rotor is still behaving in a conventional, predictable manner. All you need to do is get through ETL and you're flying again. But does it matter?
The trouble is, the line between SWIP and SWVRS is a hazy, indistinct one. The former can turn into the latter in a heartbeat. It matters not whether you think your a/c is more susceptible to one or the other. Operationally, the technique used to avoid both is the same.
And that is? Simple really. Pilots who find themselves on approach to an LZ with very low airspeed and power applied (i.e. non-autorotative) better be on their toes. You better know where the wind is coming from, and you better be super-attentive to the cues coming from the ship.
I absolutely hate downwind, back-below-ETL approaches. In the course of my career (60,000 landings, conservatively), I've had to make a few when no other alternative was available. They make me very uncomfortable. And I hope I never do get comfortable doing them. Because I never want to be sitting there thinking, "Is this just SWIP or true VRS?" If that thought ever crosses my mind, it means that I've screwed-up, big time. For whatever reason (luck?) I've yet to think it.
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Either case (Settling with insufficient power or vortex ring state) are unlikely to sneak up and bite you, as both take a reasonable amount of cue-ignoring by the pilot.
For "insufficient power" the training technique that helps might be something I have taught for a while - the controlled power approach. Simply said, it is a progressive slow down and power check as you make the approach so that you never find yourself committed to a hover while overloaded. Most instructors teach something like this, perhaps not formally, but certainly trying to spark the judgement. These techniques are obvious to experienced pilots who have flown overloaded helos for a living. I operated an AH-1G in Vietnam that could never hover above 1 foot at max power, any technique but the one below spelled doom:
1) know the power you can pull, the max power, before you start the approach. Easy way, at 500 feet above the landing, just increase collective, climb, and note the max power (where you reach the first limit, of course). Since you are somewhat higher than the landing point, the check will be slightly conservative. Note that power, and don't forget it.
2) As you enter the approach, spot the max power on the gage. As you slow the aircraft down and keep on the approach line, watch the torque begin to increase. Slow down gradually and note the power increase as you pull up on collective to keep the approach angle constant.
3) As you get quite slow, perhaps in the 25 knot range, the power will start approaching the max power that you observed. Slow down carefully, feeling yourself increasing power as you slow. One knot is an appreciable change. If the power gets within 5% torque of the max, be very careful not to slow any further unless you are SURE things are healthy. Most insufficient power accidents are made right there, when the pilot slows abruptly and inadvertantly commits to the hover, without having enough hover power.
4) If you reach the max without assurance of being able to arrest things in the hover, go around. Simply keep the power where it is, gently lower the nose a hair, and you will start to accelerate. Increase power to the max and you will gently climb. It is impossible to "fall through" on approach if you keep the power and speed under your direct control.
5) recall that a bit of ground effect will help you at the bottom, so if you have almost max power and a very gentle descent rate, all will calm itself as you wash into the hover. Note that the peak power you pull should be at about 10 feet or so, and it should be almost exactly the hover power (maybe 1% more at the most) if you have done things right. I have made this a game with students, to see if they could sneak the aircraft into a hover with only hover power as the max pulled. It is great sport, and teaches the soft technique that will keep you able to fly at the edge of your aircraft's performance.
6) Note something interesting as you practice the sneaking into a hover - the control that causes you to pull too much power at the bottom is almost never the collective, it is the cyclic, because you are decelerating too rapidly, and the "whoa, Nelly!" flare at the bottom will always cost you more power than a steady hover.
7) As solid confirmation that you have the controlled power approach down pat, try making a go around during the approach with your hand off the collective. Here's how - at some point, just remove your hand from the collective, and then gently lower the nose maybe 1 degree. As you accelerate, the extra speed will get you closer to best rate of climb speed, so you will start to gently climb. If you are rushing the approach, you will sink quite a bit before you climb, a sign that the approach is a bit too fast for a maximum performance technique.
8) You are ready for graduate school in this technique if, on a calm morning you can actually plan a touchdown at a spot with your hand off the collective while decelerating through the 30 knot point. Gentle speed changes will change your approach angle, and the smooth cyclic control will help you a bunch.
Here is some discussion on VRS:
http:www.s-92heliport.com/vrs.htm
For "insufficient power" the training technique that helps might be something I have taught for a while - the controlled power approach. Simply said, it is a progressive slow down and power check as you make the approach so that you never find yourself committed to a hover while overloaded. Most instructors teach something like this, perhaps not formally, but certainly trying to spark the judgement. These techniques are obvious to experienced pilots who have flown overloaded helos for a living. I operated an AH-1G in Vietnam that could never hover above 1 foot at max power, any technique but the one below spelled doom:
1) know the power you can pull, the max power, before you start the approach. Easy way, at 500 feet above the landing, just increase collective, climb, and note the max power (where you reach the first limit, of course). Since you are somewhat higher than the landing point, the check will be slightly conservative. Note that power, and don't forget it.
2) As you enter the approach, spot the max power on the gage. As you slow the aircraft down and keep on the approach line, watch the torque begin to increase. Slow down gradually and note the power increase as you pull up on collective to keep the approach angle constant.
3) As you get quite slow, perhaps in the 25 knot range, the power will start approaching the max power that you observed. Slow down carefully, feeling yourself increasing power as you slow. One knot is an appreciable change. If the power gets within 5% torque of the max, be very careful not to slow any further unless you are SURE things are healthy. Most insufficient power accidents are made right there, when the pilot slows abruptly and inadvertantly commits to the hover, without having enough hover power.
4) If you reach the max without assurance of being able to arrest things in the hover, go around. Simply keep the power where it is, gently lower the nose a hair, and you will start to accelerate. Increase power to the max and you will gently climb. It is impossible to "fall through" on approach if you keep the power and speed under your direct control.
5) recall that a bit of ground effect will help you at the bottom, so if you have almost max power and a very gentle descent rate, all will calm itself as you wash into the hover. Note that the peak power you pull should be at about 10 feet or so, and it should be almost exactly the hover power (maybe 1% more at the most) if you have done things right. I have made this a game with students, to see if they could sneak the aircraft into a hover with only hover power as the max pulled. It is great sport, and teaches the soft technique that will keep you able to fly at the edge of your aircraft's performance.
6) Note something interesting as you practice the sneaking into a hover - the control that causes you to pull too much power at the bottom is almost never the collective, it is the cyclic, because you are decelerating too rapidly, and the "whoa, Nelly!" flare at the bottom will always cost you more power than a steady hover.
7) As solid confirmation that you have the controlled power approach down pat, try making a go around during the approach with your hand off the collective. Here's how - at some point, just remove your hand from the collective, and then gently lower the nose maybe 1 degree. As you accelerate, the extra speed will get you closer to best rate of climb speed, so you will start to gently climb. If you are rushing the approach, you will sink quite a bit before you climb, a sign that the approach is a bit too fast for a maximum performance technique.
8) You are ready for graduate school in this technique if, on a calm morning you can actually plan a touchdown at a spot with your hand off the collective while decelerating through the 30 knot point. Gentle speed changes will change your approach angle, and the smooth cyclic control will help you a bunch.
Here is some discussion on VRS:
http:www.s-92heliport.com/vrs.htm
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still dont understand why the VRS graphs say that a 0 airspeed decent is less lickley to enter VRS than at 5- 10 knots?? maybe it enters auto before VRS can develope?
anyone expain?
anyone expain?
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Charlie,
Some things to remember about VRS is that the airspeed and ROD required to enter VRS change depending on the aircrafts weight, density altitude, and rotor loading.
A lightly loaded helicopter is more likely to get into VRS at a slower ROD, but conversely will experience ETL and leave VRS at a lower airspeed. The same helicopter with a heavy load will need to be descending at a higher rate in order to experience VRS. But then this helicopter has to travel faster to achieve ETL and escape VRS.
A heavily loaded rotor versus a lightly loaded rotor works in the same fashion. The higher the rotor loading, the faster the ROD must be for this helicopter to enter VRS but the airspeed must also be higher to experience ETL and escape VRS.
The higher the density altitude, the greater the ROD must be to enter VRS. But again, the airspeed to achieve ETL and leave VRS is higher.
Vorticey,
Yes, the rate of descent that you will enter VRS decreases slightly as you increase forward speed, then it increases slightly before hitting ETL. This has to do with the fact that your rotor is now tilited forward and your vertical downwash is lessened. Since your downwash is now slower, you will experience VRS at a slower ROD than at 0 airspeed.
Some things to remember about VRS is that the airspeed and ROD required to enter VRS change depending on the aircrafts weight, density altitude, and rotor loading.
A lightly loaded helicopter is more likely to get into VRS at a slower ROD, but conversely will experience ETL and leave VRS at a lower airspeed. The same helicopter with a heavy load will need to be descending at a higher rate in order to experience VRS. But then this helicopter has to travel faster to achieve ETL and escape VRS.
A heavily loaded rotor versus a lightly loaded rotor works in the same fashion. The higher the rotor loading, the faster the ROD must be for this helicopter to enter VRS but the airspeed must also be higher to experience ETL and escape VRS.
The higher the density altitude, the greater the ROD must be to enter VRS. But again, the airspeed to achieve ETL and leave VRS is higher.
Vorticey,
Yes, the rate of descent that you will enter VRS decreases slightly as you increase forward speed, then it increases slightly before hitting ETL. This has to do with the fact that your rotor is now tilited forward and your vertical downwash is lessened. Since your downwash is now slower, you will experience VRS at a slower ROD than at 0 airspeed.
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It is somewhat frustrating to know that those who write the guide books for various governments, as well as those who write the tests are schooled in the same pop-aerodynamics course.
There is no helicopter on the planet that will experience VRS at 35 knots. (The end of that sentence is a period)
Take a gander at the plots shown at the web site I posted a while back, when this thread was young:
http://www.s-92heliport.com/vrs.htm
The data is excellent stuff, created by some good NAVAIR engineers in briefings on VRS in the V-22.
There is no helicopter on the planet that will experience VRS at 35 knots. (The end of that sentence is a period)
Take a gander at the plots shown at the web site I posted a while back, when this thread was young:
http://www.s-92heliport.com/vrs.htm
The data is excellent stuff, created by some good NAVAIR engineers in briefings on VRS in the V-22.
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Charlie,
What do they say the correct answer is?
Nick,
Several helicopters can experience VRS at 35 knots. Helicopters with highly loaded rotors at gross weight and high altitude may experience VRS will above 35 knots. However, it won't be at 300 or even 500 feet ROD. For example, an CH-53E at gross weight and 10,000 feet can experience VRS up to 38 knots. The ROD however, would have to be between 3800 and 4800 fpm.
What do they say the correct answer is?
Nick,
Several helicopters can experience VRS at 35 knots. Helicopters with highly loaded rotors at gross weight and high altitude may experience VRS will above 35 knots. However, it won't be at 300 or even 500 feet ROD. For example, an CH-53E at gross weight and 10,000 feet can experience VRS up to 38 knots. The ROD however, would have to be between 3800 and 4800 fpm.
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Nick, the page you referred shows data for VRS on the V22 occurring between 30 and 42 KIAS.
I completely agree with the written test creators being students only of "pop-aerodynamics" courses. I believe this is the greatest hurdle in explaining many things helicopter. The introduction and conclusion of those courses should include a caveat explaining that the discussion is meant to be simple not truthful.
I completely agree with the written test creators being students only of "pop-aerodynamics" courses. I believe this is the greatest hurdle in explaining many things helicopter. The introduction and conclusion of those courses should include a caveat explaining that the discussion is meant to be simple not truthful.
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I appreciate the idea that a helo or tilt rotor can "experience" vrs, or that it "occurs" at 30 or 40 knots, but let's define "experience" or "occurrence".
The data shows that the V-22 had nibbles (5 to 10% torque variability - the blue data points) at about 45 knots (at a speed equal to the downwash velocity). This is not VRS, it is the beginnings, where they wanted to stop the tests to avoid losing roll control. Note that the reds were at about .75 to .85 of the downwash speed, where the torque variability is 10% and the tests were aborted. This is not VRS, it is the first sign of it.
For a helicopter, with disk loadings about 1/4 that of the V22 (2 to 7 lbs per sq foot instead of 22 to 25 psf) the downwash speed is much less, and so the vrs forward (and downward) speed is much lower. In a Bell 206 you would have to slow to about 10 or 12 knots forward speed to experience real VRS, and could get some nibbles at 15 to 18 knots.
The written test question is simply wrong, fellows. The idea that 35 knot flight is close to VRS is another way of perpetuating the myth, and allowing misunderstanding and superstition to cloud the learning experience.
When I took my FAA Flight Instructor written, I refused to answer one question. It asserted that in a climb lift was greater than weight (the least-wrong multiple choice). I wrote a brief critique of the question, with an explanation of why, and I got credit for a correct answer.
I know the regulators in several countries. Good people, professional aviators and great instructors, but they get their aero from the old piloting texts written by those who they follow. Few aero engineers dabble in the training publication world. A guy like Gordon Lieshman or Gareth Padfield could help square these publications away. Maybe I'll ask them to do so next time I communicate with them!
BTW let me congratulate the ppruners here, this is a great discourse, with erudite observations and sharp minds. I love it when someone posts something and someone else reads it, goes beyond it and makes us all actually think!!
The data shows that the V-22 had nibbles (5 to 10% torque variability - the blue data points) at about 45 knots (at a speed equal to the downwash velocity). This is not VRS, it is the beginnings, where they wanted to stop the tests to avoid losing roll control. Note that the reds were at about .75 to .85 of the downwash speed, where the torque variability is 10% and the tests were aborted. This is not VRS, it is the first sign of it.
For a helicopter, with disk loadings about 1/4 that of the V22 (2 to 7 lbs per sq foot instead of 22 to 25 psf) the downwash speed is much less, and so the vrs forward (and downward) speed is much lower. In a Bell 206 you would have to slow to about 10 or 12 knots forward speed to experience real VRS, and could get some nibbles at 15 to 18 knots.
The written test question is simply wrong, fellows. The idea that 35 knot flight is close to VRS is another way of perpetuating the myth, and allowing misunderstanding and superstition to cloud the learning experience.
When I took my FAA Flight Instructor written, I refused to answer one question. It asserted that in a climb lift was greater than weight (the least-wrong multiple choice). I wrote a brief critique of the question, with an explanation of why, and I got credit for a correct answer.
I know the regulators in several countries. Good people, professional aviators and great instructors, but they get their aero from the old piloting texts written by those who they follow. Few aero engineers dabble in the training publication world. A guy like Gordon Lieshman or Gareth Padfield could help square these publications away. Maybe I'll ask them to do so next time I communicate with them!
BTW let me congratulate the ppruners here, this is a great discourse, with erudite observations and sharp minds. I love it when someone posts something and someone else reads it, goes beyond it and makes us all actually think!!
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Nick,
Who is defining experience and occurance here? And what's the definition of nibble?
If a helicopter begins to experience VRS at 35 knots, no matter how small the loss of lift, the helicopter will slow down. By slowing down, it enters VRS more deeply. So corrective action must be initiated no matter how small the experience, occurance, or nibble.
I definitatly wouldn't call VRS a myth.
Who is defining experience and occurance here? And what's the definition of nibble?
If a helicopter begins to experience VRS at 35 knots, no matter how small the loss of lift, the helicopter will slow down. By slowing down, it enters VRS more deeply. So corrective action must be initiated no matter how small the experience, occurance, or nibble.
I definitatly wouldn't call VRS a myth.
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CJ,
The myth is that at 35 knots a helo can experience VRS. As long as the guidebooks our students use have that bunk in them, our students will not understand what they are doing. This is second cousin to the now-standard belief that a 300 fpm descent can trigger VRS.
The data I posted shows that the max you can get at 18 knots in a helicopter is a 5% torque fluctuation. That is what I said, and what the data proves.
If you want to believe that a helo at 35 knots can experience VRS, please go ahead, nobody will stop you. Maybe you could even write some exams while you are at it!
You will be wrong, but nobody will stop you, after all, they didn't stop the last guys who did it, the ones that charlie used when he started this topic!
The myth is that at 35 knots a helo can experience VRS. As long as the guidebooks our students use have that bunk in them, our students will not understand what they are doing. This is second cousin to the now-standard belief that a 300 fpm descent can trigger VRS.
The data I posted shows that the max you can get at 18 knots in a helicopter is a 5% torque fluctuation. That is what I said, and what the data proves.
If you want to believe that a helo at 35 knots can experience VRS, please go ahead, nobody will stop you. Maybe you could even write some exams while you are at it!
You will be wrong, but nobody will stop you, after all, they didn't stop the last guys who did it, the ones that charlie used when he started this topic!