What the heck happened here?

[JDHelicopterPilot]

It is for the reason that the Rotorcraft Flying Handbook (which uses the terms as interchangeble) that I stated it was not SWP. I think the FAA needs to clearify this a little as this is an FAA document. There really should be two clearly different terms.

 

Here is something I was told long ago by several pilots some of which were very high time, they called it Power Settling. While not an official term it was how they described a situation such as the one in question where the helicopter simply didn't have enough power for level flight and looses altitude as a result.

 

I still feel the cause of the accident was the pilots failure to maintain Main Rotor RPM. Contributing factors were those as stated by Mike already.

 

When pilots encounter low RPM the recovery as taught is to lower the collective and add throttle if they can. Lowering the collective will result in a loss of altitude. When low to the ground there may not be enough time (altitude) to recover lost RPM prior to hitting the ground. In any case, lowering the collective and adding throttle (if any left) is still the right thing to do.

 

If I ever found myself in this situation I would rather have a simi-controlled loss of altitude into the ground(IE: controlled crash) than to stall the main rotor after which there is no control or recovery of. Remember the RPM at which the main rotor stalls is reduced with altitude. Much like the so called "coffin corner" that affect jets at altitude.

Edited January 20, 2013 by JDHelicopterPilot

[eagle5]

Since both of you are from the SWP=VRS camp…

 

1. How about Tail Rotor Vortex Ring State, is that the same as SWP too?

 

2. Were did the term Vortex Ring State originate from?

 

3. If SWP=VRS why can we have one without the other?

 

1. I have heard CFIs refer to that as "settling with power for the tail rotor".

 

2. I have no idea.

 

3. If you are settling because your in VRS you're settling because you've descended into your own downwash (like the video they show at RHC where the R44 has a hard landing on a rooftop, and then falls off from dynamic rollover) NOT because you've run out of power, which is why its called "settling with power".

 

If you start to settle BECAUSE you've run out of power (like the R44 in this video) then it makes no sense what so ever, to call it "settling with power"!

 

...and by the way, every CFI/DPE I have flown with (and there have been several), when asking me to demonstrate VRS recovery, has called it SWP!

Edited January 20, 2013 by eagle5

[eagle5]

It is for the reason that the Rotorcraft Flying Handbook (which uses the terms as interchangeble) that I stated it was not SWP. I think the FAA needs to clearify this a little as this is an FAA document. There really should be two clearly different terms

 

I'm with you!

[iChris]

2. I have no idea.

 

At the beginning of the vertical flight ear, it was thought that the helicopter would operate from confined sites where vertical climbs and descents of a thousand feet or more would be standard practice. Going straight up was no problem; however, going straight down was surprisingly difficult because of unpredictable control and power changes required to maintain a steady descent rate.

 

The most unusual characteristic was the unpredictably high sink rates with power. The pilots called it “power settling” based on their observation, that in some cases, the helicopter would keep coming down even though full engine power was being used.

 

The theory was that as the descent rate increases, the net flow through the rotor should decrease with little or no flow unsteadiness. Wind tunnel test made at Georgia Tech in the early 1950s, however, indicated that a real rotor doesn’t follow the theoretical line. The results showed that for moderate rates of descent, the net flow through the rotor is significantly higher than theory would indicate.

 

The tests also showed the characteristic flow unsteadiness starts at about 25%, peaks at 75%, and disappears at 125% of the hover induced velocity. In other words, as the rotor descends through this region, the net flow through the rotor increased in order to hold a constant thrust and descent rate, directly opposite of the theory.

 

Much flight and wind tunnel testing went into investigating this condition. The unsteady recirculating flow has even been seen during wind tunnel tests of model rotor using smoke for flow visualization. In 1950, a Dutch student, Jan Drees, made a movie of flow through a helicopter rotor using smoke for visualization (see clip below). As a consequents of these numerous tests, this flow state condition became known as “vortex-ring state” because of its resemblance to a smoke ring’s flow.

 

]

A rotor is operating in vortex ring state when it is descending at low forward speed with a vertical velocity that approaches the value of the wake-induced velocity at the rotor disk. In this condition the rotor tip vortices are not convected away from the disk rapidly enough, and the wake builds up and periodically breaks away. The tip vortices collect in a vortex ring, producing a circulating flow down through the rotor disk, then outward and upward outside the disk. The resulting flow is unsteady, hence a source of considerable low frequency vibration and possible control problems. For descent at forward speeds sufficiently high enough that the wake is convected away from the rotor, vortex ring state does not develop. - Model For Vortex Ring State Influence on Rotorcraft Flight Dynamics, Wayne Johnson, NASA Ames Research Center; Moffett Field, California.

 

Edited January 21, 2013 by iChris

[superstallion6113]

I like it when experienced pilots debate each other on here. Lots of good info to take in.

Edited January 21, 2013 by superstallion6113

[ridethisbike]

I agree wholeheartedly with the more experienced on here. VRS and SWP are definitely NOT the same thing.

 

I disagree, however, that it should be referred to as "settling with insufficient power" only because it makes it sound as if you just have insufficient power applied and can therefore remedy it with a little more up collective, which is obviously not the case. Although a bit longer, maybe "settling with max power applied" would be more accurate. I can see flaws in both terminologies though, so maybe we should just stick with the name we have and just better explain it to the students. NR's explanation in post 43 was pretty accurate and was easy to follow.

[JDHelicopterPilot]

I agree there are two different things going on here and that SWP and VRS are not really the same. However, in the Rotorcraft Flying Handbook the FAA published they use those terms as though they are one and the same.

 

I think we are all in agreement for the most part and that it really just comes down to semantics as far as terminology. Despite that we all see to agree there are two different situations here and we seem to understand that.

 

The important thing that students need to know that one can still get in a bind even though they are not in VRS.

[eagle5]

I disagree, however, that it should be referred to as "settling with insufficient power"

 

How about calling it, "Oh' sh*t, I forgot I don't have the power to do this!", or OSIFIDHTP, for short?

 

By the way, when you have an accident like this, what kind of logbook entry do you make?

[JDHelicopterPilot]

Just put the ending Hobbs and go have a beer.

[ridethisbike]

How about calling it, "Oh' sh*t, I forgot I don't have the power to do this!", or OSIFIDHTP, for short?

 

 

BAAHHAHAHAHA!

 

 

Oh, and JD. The new Helicopter Flying Handbook is no different. I'm sure you knew that already, but thought it worth mentioning.

[iChris]

Nick Lappos, former Sikorsky/Bell famous person, He suggested that we call SWP "settling with INSUFFICIENT power."

 

 

Along that same line, for those of us who operate helicopters at max gross for a living, here’s a few techniques from Nick Lappos that we should always remember.

 

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 judgment. 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 inadvertently 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.

Edited January 22, 2013 by iChris

[iChris]

“The general misunderstanding that the backside of the power curve is unstable with respect to power and airspeed, accounts for most of the accidents blamed on the so-called boogeyman, "Settling With Power”

“Never find yourself committed to a hover while overloaded.”

“Most insufficient power accidents are made right there, when the pilot slows abruptly and inadvertently commits to the hover, without having enough hover power.”

“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.”

http://youtu.be/vnulmMRFdpQ

Edited November 12, 2018 by iChris

[Spike]

Respectfully,

 

Back in my instructor days, I had some students attempt to critically dissect certain areas of helicopter aerodynamics. When this happened, I’d draw a straight line across the whiteboard and put “average Joe” on one end and “Ray Prouty” on the other. I’d plot where I thought I landed on my “scale of knowledge”. It was usually near the center but closer to “average Joe” then to Mr. Prouty. I then would ask the student how far they wanted to go paying me $14 an hour and, if they wanted to be closer to Mr. Prouty, they were probably in the wrong school…..

 

In my opinion, politically correct and/or academic discussions don’t help. SWP and/or VRS did not cause this to happen. Simply put, aerodynamic phenomenon is the what. Not the how. Understanding the how will aid in prevention. The what tends to be after the fact. And, I can guarantee, as the machine was about to hit terra-firma, the pilot wasn’t thinking “is this SWP or VRS?”……..

Edited January 22, 2013 by Spike

[Fred0311]

Im still hoping to hear what those with direct experience with this incident have to say about it versus the vrs swp debate being rehashed. And I'd like to add I appreciate their comments looking at this as a learning opportunity for others.

Edited January 22, 2013 by Fred0311

[280fxColorado]

This accident was discussed in another thread after it happened with links to several other video angles:

http://helicopterfor...liops-accident/

 

It seems pretty clear that the pilot grossly exceeded the capabilities of the R44 on that day, "settled with insufficient power," and had insufficient height/distance to clear the terrain and make a clean escape. Or, as Gordy said on the PPRUNE discussion, "He ran out of "Pitch, Power and Ideas" all at the same time...."

http://www.pprune.or...do-may-8-a.html

 

At the time, the rumor mill in Colorado was saying (I make no claims about the validity..):

• The pilot did ZERO performance planning for that flight and scrambled to put one together after the accident for NTSB investigation, revealing how far outside the envelope he was trying to operate.
  
• The RPM horn was blaring on the way down. Perhaps an incorrect initial up-collective reaction to the settling?
  
• The morning of the accident, the pilot was observed at a local airport flying in a manner someone described as reckless- hot approach to a flare into a crowded ramp, making rapid snap pedal turns on the ramp with 3 pax onboard and spectators within 100ft, rapid pickups and setdowns and bouncing around inside the cockpit like he'd drank the whole pot of coffee.
  

So to address the original question of this thread, "What the heck happened here?" It has very little to do with equivocation of terms SWP/VRS or misunderstanding the aerodynamic concepts. 'What happened?' - Seems to be poor pilot judgement and a perfect example of the FAA's classic Hazardous Flight Attitudes.

 

Anti-Authority - "Performance planning, who needs that?"

Impulsivity - "Oh yeah, this looks good! Let's just put 'er in a hover right here."

Invulnerability - "10,800'DA OGE hover in an R44, 2300lbs, who cares."

Macho - "I got this, no problem."

Resignation - "Goin' down!"

Edited January 23, 2013 by 280fxColorado

[iChris]

Respectfully,

 

In my opinion, politically correct and/or academic discussions don’t help.

 

Simply put, aerodynamic phenomenon is the what. Not the how. Understanding the how will aid in prevention.

 

 

That all sounds good on the surface; however, lets take a closer look at those two words, “what” and “how.”

 

“What” and “how” are Interrogative words or question words, used to ask a question, such as what, when, where, who, why and how. They are sometimes called wh-words, because in English most of them start with wh-.

 

You’ve got it a little backwards; aerodynamics helps you understand and answer both those two questions, why and how. Pilot error thrives on the lack of knowledge and understanding.

 

When you don’t have a sound understanding of the true nature and character of the aerodynamics under which the helicopter operates and in which it was designed, you’re in a poor position with respect to accident prevention.

Edited January 23, 2013 by iChris

[eagle5]

When you don’t have a sound understanding of the true nature and character of the aerodynamics under which the helicopter operates and in which it was designed, you’re in a poor position with respect to accident prevention

 

You ain't got ta know notin' bout' no aireedymamics to read a simple performance chart!

 

,...thought those mountain pilots were supposed to be better than the rest of us!

[bintheredonethat13]

Bad mistake. He or she will pay for that mistake for years to come. Too bad.

[Wally]

Along that same line, for those of us who operate helicopters at max gross for a living, here’s a few techniques from Nick Lappos that we should always remember.

 

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 judgment. 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 inadvertently 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.

 

EXACTLY!

 

(Edit)

What's not explicitly stated in this is that you recognize that turns, that is- flight track redirection, all use energy, as does adding antitorque pedal, and stopping the yaw started by allowing torque turns.

Edited January 23, 2013 by Wally

[RkyMtnHI]

damn jon, tell us how you really feel...

 

i can tell you that two of the rumors you posted are of course untrue (but you probably already knew that).. the one’s about him snapping the tail and such are laughable, especially if you know me (i simply don’t stand for that sh*t, just ask the pilots that fly with you that we asked to leave).. there were NO tours that day, i was at home and i’ve only missed one tour day in three years cuz i was at air venture. The horn did come on, i remember it from the video, but not sure about when and where, i am looking for that info.

 

So, speaking of rumors, am i to go by the ‘Colorado rumor mill’ when people call me for references on you?? Or would you rather i just tell them what i know from personal experience? In the past when they called i never said a thing about the rumors about you (just rumors) i only told them what i personally knew which was that it seemed that your attitude had improved lately... i hope i wasn’t wrong or that hasn’t changed.

 

This is something everyone reading this should get, there are people on this forum, some that NEVER post and some that do, that hire a lot of pilots, or know folks that hire a lot of pilots or both, they pay attention to your posts, your attitudes and professionalism... and people call us and ask ‘i got a resume from a pilot, he’s from your State but you are not listed as a reference, why is that’... this is a small community, and a lot of us know each other and talk, email or txt constantly (i talked to seven or eight operators last week trying to help two great pilots move up). i’ve even had recruiters call and ask who is who on this forum (more than once). If you are going to post, do it positively and nicely, one thing i do is to type it out on word and print it out, take it with me to work, read it a few times to make sure i’m not coming off as a dick (yeah, i do care about that).. it’s hard sometimes i know, but this is a GREAT resource and asinine posts only show us who you really are (and we talk about that) and this sort of sh*t keeps some of the really good contributors from staying involved. I looked back over the links jon provided and saw some members that are no longer posting, sad really, because some of them were great. I hear more and more members saying how the few are ruining it for the many. i for one appreciated the ones that care about this resource and hang in there with us low timers to make our industry better.

 

jon, from your great posts in the recent past i was thinking that you were growing up a bit... in the future you might want to try my technique.

 

i will post my comments on the crash today or tomorrow, it’s four pages and i want to make sure i’m correct on stuff as much as possible and i don’t want to hurt anyone trying to help others.

[Spike]

That all sounds good on the surface; however, lets take a closer look at those two words, “what” and “how.”

 

“What” and “how” are Interrogative words or question words, used to ask a question, such as what, when, where, who, why and how. They are sometimes called wh-words, because in English most of them start with wh-.

 

You’ve got it a little backwards; aerodynamics helps you understand and answer both those two questions, why and how. Pilot error thrives on the lack of knowledge and understanding.

 

When you don’t have a sound understanding of the true nature and character of the aerodynamics under which the helicopter operates and in which it was designed, you’re in a poor position with respect to accident prevention.

 

You are correct. I should have used the word why….

 

The why is the essential aspect of accident prevention. A Master’s Degree in Aerodynamics is just that…. A Degree….

[Helijason]

SWP and VRS most definitely should be taught as two seperate things. Even though when experienceing VRS you are technically sttling with power. SWP is most times due to high DA, high gross weight and definitely high power settings while VRS is easiest to get into with low gross weight and low power settings. In fact the lower your power setting the less your rate of decent has to be to get into it because the recirculating air isnt being pushed down as far. Ive been in VRS twice and both times were decending for a pick up with an empty 100' longline on. Shat my pants both times.

 

Its also worth noting that VRS is recoverable but if you try and use those recovery techniques when settiling with power, they will likely make it much worse.

 

sorry for being late to the party haha

Edited January 24, 2013 by Helijason

[ridethisbike]

Helijason, I'm curious to know what your particular indicators were that you were in VRS? What was the thing that made you realize "oh crap I'm in a bad way" and get out of it?

 

In training I know what we get taught, but the problem is we're being taught so we're actually looking for the indicators. It's easy to spot something when you're expecting it, whole different story when you're not.

 

Also, you make it seem as if the recovery techniques are different for the two conditions. Can you elaborate?

[Helijason]

well both times were pretty simmilar. vertical decent into a small confined area with a 100' longline on. close to the end of the day after moving many loads all day and feeling pretty confident but definitely getting complacent. Coming in, decending a bit too fast maybe 200-300fpm, which is nice on a normal approach but not really where you want to be when verticaling down at 120 feet. Felt a bit of a shudder and then it felt like a trap door opened up under me. Of course instant reaction is to pull collective but it did nothing but almost overtorque the helicopter with no results and made the cyclic feel really spongey. So i pushed the collective down and made a pretty heavy sideward input and got out of the vortex and ended up in about a 30 foot hover. The ground crew were standing there staring at me. I'm not sure who was more scared. we called it day after that.

 

As far as the differences in recovery, they can be similar in such a way that IF you have lots of altitude you can recover either by lowering your colective and pushing the cyclic forward to get airspeed.

At lower altitudes you can recover VRS by sideward or forward cyclic to escape the vortex or full down collective to break the vortex or most likely a combination of both.

 

If you are settling with power because you tried to hover or land without consulting the performance charts in the flight manual then there isnt a lot that can help you without having sufficient altitude to nose over and get airspeed. Just hope the ground cushion slows you down enough so that you dont spread the gear.

 

Thats my take on it anyway.

 

edit: I should also add that both of these conditions are completely preventable and avoidable. So if you find yourself getting close to encountering either of these, you better, as the kids say these days, check yourself before you wreck yourself.

Edited January 24, 2013 by Helijason

[280fxColorado]

Let me apologize for the first post.  My intent was to shed some light on the human factors that led to this unfortunate event with some personalized background to the story.  I tried to paint a caricature using the FAAs Hazardous Attitudes model with comical irreverence which, I see now, may have been a bit crass.  Trusting in rumors is inappropriate and I was not  being fair to the pilot with my account.  I certainly wouldn't want to find myself subject to that kind of loose speculation.  The point I wanted to make is that the most important thing to be learned from this crash is not a lesson in aerodynamics--although the distinction should be clear.  As Mikemv discussed earlier, an accident chain of human factors led this previously outstanding pilot to make one very unfortunate mistake.  That's not something we'd wish upon any of our peers.  But it is something we are all susceptible to and something we all fear.   A personal analysis of why the pilot ended up in this situation might help others to avoid the same misfortune.  Hopefully those who were more involved can paint a more accurate picture.

 

Respectfully,

-JMc

Edited January 24, 2013 by 280fxColorado