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Vuichard again

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Vuichard again

Old 6th Apr 2022, 17:21
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You know the NTSB report about it? I would like to read that one. But damn, doing an approach for a photo shoot from the wrong direction sounds like really bad planning and a pilot wanting giving in to the demands of a non aviation person. Not the first and not the last.
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Old 6th Apr 2022, 17:37
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Originally Posted by Rotorbee View Post
You know the NTSB report about it? I would like to read that one. But damn, doing an approach for a photo shoot from the wrong direction sounds like really bad planning and a pilot wanting giving in to the demands of a non aviation person. Not the first and not the last.
Sorry, all I know is from the discussion on the video. I don't remember what year it happened, or in what city. I only know that I first saw the video in 2005 and that they still showed it at the RHC Course in 2020.
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Old 6th Apr 2022, 17:44
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PK-BAT. 4. of March 2003. Jakarta. No report in their database. We would need a lot more information to understand what happened.
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Old 6th Apr 2022, 17:44
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Originally Posted by Rotorbee View Post

c. As Robbie said from his own experience, when you get in there, especially as a relatively new pilot, the stress level might be too high, to do all the mental decisions in a short time. The . If you use what you learned as you describe it, in an H120, H125, H130, H155, H160, H175, H215, H225 or anything MiL, you’r in for a surprise, because you would have pushed the wrong pedal.

.
Couple few things.

Yeah, I know about that other pedal thing (good job with the list, so much more dramatic). Airbus wants you to use it in certain scenarios, like when you are about to hit the ground. It's possible there are so few VRS accidents because most of us have been trained in avoidance, recognition and recovery. Don't hold your breath waiting for any "scientific papers" be written on this because it's not going to happen. I already said Airbus don't want you to practice VRS in flight. If you are in full on VRS (depending on your altitude), neither one is probably going to save you. If you go forward because you have an external load and crash, you still did the wrong thing. The quickest way out it is the Vuichard. If you can't figure out what's going on when you raise the collective and the opposite of what you expect to happen, happens, and you don't know how to react, find another line of work.
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Old 6th Apr 2022, 18:02
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It's pretty simple: if you are low to the ground, the quickest way out of VRS is the Vuichard. Do that. There is no question about it. If you don't recognize it fairly quickly, neither method may help you. If it happens at altitude, do whichever one you want. And if you find yourself plummeting to earth in full on VRS because you fly around with your head up your a**, apparently pushing the cyclic forward is the only thing that works because reasons and I hope it works out for you in time.
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Old 6th Apr 2022, 18:10
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If you can't figure out what's going on when you raise the collective and the opposite of what you expect to happen, happens, and you don't know how to react, find another line of work.
Funny you say that, because in most VRS accidents I read, the pilots did just that. They did not realise what was going on. You know, that brain of ours is very easy to confuse. We have some really bad issues with fixation.
I already said Airbus don't want you to practice VRS in flight.
You did? And I thought I brought that Safety Notice up. Silly me.
Don't hold your breath waiting for any "scientific papers" be written on this because it's not going to happen.
See, we agree on something already. That's exactly what I told Crab a few posts ago.
Anyway, I just ordered a paper on flapping in VRS written not so long time ago. We will see what comes of it.
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Old 6th Apr 2022, 18:19
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Originally Posted by Rotorbee View Post
Funny you say that, because in most VRS accidents I read, the pilots did just that. They did not realise what was going on. You know, that brain of ours is very easy to confuse. We have some really bad issues with fixation.
Thanks for that. It is now safe to conclude doing nothing is also a bad idea. I can't wait to hear about the flapping thing as I'm sure it will change everything.
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Old 6th Apr 2022, 18:25
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Na, it probably will not, but I have a very unhealthy relationship with aerodynamics of helicopters and physics in general. But who knows, at least it could give me new insights into the VRS subject. Sometimes I have these "Aha" moments. Worth living for.
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Old 6th Apr 2022, 18:47
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You don't know this and you are guessing.
yes I do and no I'm not. I know a lot of mil pilots who have experienced VRS for real and nearly died - the only thing that saved them was the 'standard' technique.

It used to be taught in the UK military - full VRS not the incipient version. Pulling power and cross controlling wasn't possible because in full VRS you have almost lost control of the helicopter.

Early recognition and the Vuichard method will get you out faster.
Only from the very early stages and, as I have tried to point out, just raising the lever will do that.

Ever been in a helicopter at the onset of VRS and did the normal recovering and sat there while nothing happened?
No because as soon as I pushed the cyclic forward the recovery started, whether or not I lowered the lever as well.

It's pretty simple: if you are low to the ground, the quickest way out of VRS is the Vuichard.
You should stop saying VRS when you mean IVRS and any technique will get you out of IVRS. The only time the cross controlling might help is if you are dead downwind - as per the Airbus advice.

You carry on doing what you want if it makes you feel safe but Vuichard is only of use in combination with early recognition - and if you recognise it early you can just raise the lever and achieve the same result - go on, I dare you to try it.
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Old 6th Apr 2022, 19:13
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Nobody is saying the standard technique won't save your life IF you have enough altitude. Sounds to me like they almost killed people in training. Either way, since "a lot" of people were *almost* dying, they were obviously doing something wrong.

Last edited by helonorth; 6th Apr 2022 at 20:06.
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Old 6th Apr 2022, 19:43
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Getting in to fully developed VRS intentionally for demonstration purposes can be actually quite difficult.
Plus it is very hard on the machinery and was not something the designers of the machine would thought anyone would do intentionally and repeatedly when determining component lives.

Most of the time people only get to experience the edge of IVRS and it doesn't have the impact on just how bad it can get.

Then one day when you least expect it..............................

BTW there is one highly automated machine out there that can drop you in automatically without too much trouble.
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Old 6th Apr 2022, 20:20
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It's rare when I agree with helonorth. The temperature in hell must be awfully cold right now, because I think helnorth has the best handle on this VRS thing and how to extricate oneself from it. Look, fully-developed VRS is not fun. As Crab notes, you have almost lost control of the helicopter (except for the tail rotor, if you have one). 1) If you're up high (e.g. external load work), then do whatever you need to do to get air flowing laterally through the disk. 2) If you're down low and don't recognize it in time, you're probably going to crash. And if you're too late in employing that Vuichard technique, you're probably going to crash going sideways.

VRS events that result in a crash/hard-landing usually don't happen way up high (duh). They happen down low at the bottom of a screwed-up approach. If you're even halfway awake, you can catch the VRS while it's still in the I-VRS stage and bail out if you can. But if you're already close-in and have maximum (or nearly so) power applied...well. The BO105 was horrible in this regard. With respect to that "R-44 rooftop scenario"... at some offshore oil installations, due to the placement of the helideck, you just cannot get into the wind on final. So you'd sit there, downwind (more or less) with the machine vibrating like crazy (as all Bolkows do as their rotor passes back through ETL) and your left arm is finely tuned to any "disconnect" between collective movement and rate of descent.

Just as we don't do full stalls in swept-wing jets anymore, real VRS is not something that should be practiced. It is something that should be avoided.
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Old 7th Apr 2022, 05:16
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Since we are nice and calm now and I had a bit of time at hand, I think there are few informations about VRS, that might be interesting to some of you.
First, ONERA with Pierre-Marie Basset et.all did a research paper on VRS in 2006 for a better prediction of the VRS boundary with flight tests and everything.

One of their findings with flight test data.VH: rotorcraft horizontal velocity
Vih: rotor-induced velocity
Vz: vertical speed



The important thing to take away from this is, when you reach a vertical speed (no forward speed) of about 1.5 the rotor induced velocity, you are out of VRS (no more big vortices). In fact, now it is an autorotative decent and the rotor does get energy from the inflow. You may still call that deep VRS, for what I care, but the thingy with the eddies is over. Depending on the experiment, or helicopter, the boundary changes. But -2 is probably a good rule of thumb.
What is different from your normal autorotation, is that the AOA on the blade is much higher and therefore the driving region is smaller, but the stalled and driven regions are larger. Which explains nicely, why you have so little control in certain helicopters. That the whole thing is not very smooth comes from the fact, that there is still a lot of turbulence hitting the rotor and produced by it. But VRS is gone.
What is also remarkable, Vz stabilises at the VRS boundary. At least for me, that explains, why for the love of god I never could get the R22 descend more than around 2000 ft/min during demos.
This has been know for a long time as the vertical wind tunnel experiments of NASA have shown the same. Or Prouty.

The thing that I find a bit more interesting, is a paper from the Naval Postgraduate School by Rumsey from 2003 about the Vortex Ring State in a water tunnel.
Here is the blade bending load:

H-34 Flapwise Bending Moment At R/R=0.575
That is really hard on the components and while it is positif over the tail boom, it is negative at a substantial part of the disc.
There you have it. At a certain Vz, VRS is gone, deep VRS is in reality an autorotation and the flapping in VRS is quite erratic.
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Old 7th Apr 2022, 08:09
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Originally Posted by helonorth View Post
You don't know this and you are guessing. Early recognition and the Vuichard method will get you out faster. Ever been in a helicopter at the onset of VRS and did the normal recovering and sat there while nothing happened? But sure, tell me how pushing that mush cyclic forward in full on VRS is going to save your ass in time.
Having experienced this in “fright” in a medium twin and light helicopter operationally plus instructing and looking for it this is exactly what I found effective. An ample amount of forward cyclic to give positive accelerative attitude (at least 10deg nose down) with a slight decrease on collective works instantly in IVRS, I would be surprised if any less so than Vuichard. It also recovers to forward flight with no further input and the better side of the power required curve.
As you have stated any later than the early stages of IVRS is likely to to ineffective for both techniques and require more height to recover than it’s likely to have.
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Old 7th Apr 2022, 08:18
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Nobody is saying the standard technique won't save your life IF you have enough altitude. Sounds to me like they almost killed people in training. Either way, since "a lot" of people were *almost* dying, they were obviously doing something wrong.
No the 'almost killed' was a reference to encountering full VRS on operational flights.

For example, many years ago in Oman there was high ground (several thousand feet) above the valley floor and the tactic to get down was a tight spiral descent with low speed and moderate AoB which gave a high rate of descent and made tracking with SAMs or small arms difficult. At the bottom it was necessary to roll wings level and increase speed slightly before pulling in power to reduce the RoD. I know one pilot who just raised the lever and effectively put himself in VRS and crashed - luckily surviving it.

I cannot emphasis enough that Vuichard technique will not recover you from full VRS.

An analogy from fixed wing - incipient vs full spin recovery - incipient spin is easy to recognise and easy to recover from, you actually have to mishandle the aircraft badly to get into a fully developed spin.

The recovery from a full spin is not instantaneous and requires specific techniques. The recovery from an incipient spin is to centralise the controls - almost let go and do nothing works.

Vuichard is effectively marketing incipient spin recovery but selling it as a full spin recovery.

Incipient VRS recovery is easy - raise the lever (the first part of Vuichard) - full VRS recovery is not easy and if you get into it at low level NOTHING will save you except divine intervention or extreme good luck.

If you want to use Vuichard at the early stages, be my guest, but I think encouraging pilots to fly close to VRS parameters, especially at lower levels, in the mistaken belief that Vuichard's 'technique' will save them if it gets worse is just WRONG and UNSAFE.
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Old 7th Apr 2022, 08:19
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Convince me Vuichard would have helped here. Extreme I know but if the helicopter was sideways it would have rolled and the guys in the back would not be jumping out.
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Old 7th Apr 2022, 08:29
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Convince me Vuichard would have helped here. Extreme I know but if the helicopter was sideways it would have rolled and the guys in the back would not be jumping out.
That is confusing SWP as per the video title, with VRS.

Whilst at that low level the symptoms are the same - you get the shudder and a rate of descent - a recovery with power isn't possible because there isn't enough available (hence the term settling with power).

However, a pilot experiencing that scenario who mistakenly decides to employ the Vuichard technique because he thinks it is IVRS - will, as SLMFS says, crash and roll over.
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Old 7th Apr 2022, 08:39
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Originally Posted by [email protected] View Post
That is confusing SWP as per the video title, with VRS.

Whilst at that low level the symptoms are the same - you get the shudder and a rate of descent - a recovery with power isn't possible because there isn't enough available (hence the term settling with power).

However, a pilot experiencing that scenario who mistakenly decides to employ the Vuichard technique because he thinks it is IVRS - will, as SLMFS says, crash and roll over.

Oh dear now we have the SWP agreement in. You are correct Crab re the title but surely this one is early stages of VRS? Downwind approach with flare sounds like the set up to me.
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Old 7th Apr 2022, 08:45
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Having just watched tim tucker and the R44 i am not convinced that is VRS. Surely he comes to a high hover with not enough power ( or maybe he does ) Looks like he over pitches it to me. As for the " new " technique " well if he had power to pull ( then why was he going down ) even if he did which seems unlikely as soon as he hit the power pedal to fly left he would already have the horn going as he is now definitely overpitched and rapidly losing rrpm. So he is on a hiding to nothing. Yes he might have recovered from IVRS but then due to Vuichard he is in a position of flying sideways with an overpitched rotor, with little chance of getting airspeed back. Personally I think i would prefer to stick it on its nose , that way at least if you have over pitched as well as IVRS you have a chance of dumping the lever to get rrpm back as she gets out of the vortex. In the military was always taught RRPM is life. You can all shoot me down now. Having done 1000's of hours on a longline, I would always elect to go forwards if I could, safer for ground crew and much more likely to get back translational lift back.
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Old 7th Apr 2022, 08:54
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Has been discussed on Redit and I tend to agree with them. Since the collective in this fast deceleration is way down (I assume, here), you can not get into VRS. I think he run out of power to stop the descend.
Anyway, perfect example, why we should fly into the crash and stay straight and level, if possible. An by far not enough time to process all what is going on, to decide on the right method. Classic method saves the day more often than not.
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