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.

PK-BAT. 4. of March 2003. Jakarta. No report in their database. We would need a lot more information to understand what happened.

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.

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.

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.
You did? And I thought I brought that Safety Notice up. Silly me.
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.

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.

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.

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.

Only from the very early stages and, as I have tried to point out, just raising the lever will do that.

No because as soon as I pushed the cyclic forward the recovery started, whether or not I lowered the lever as well.

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.

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.

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.

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.

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


https://cimg2.ibsrv.net/gimg/pprune....a255b2ceda.png
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:
https://cimg1.ibsrv.net/gimg/pprune....e6863b691a.png
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.

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.

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.

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.

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.

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.

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.

I wonder, if Vuichard's method has ever saved anyone?

It is one of the classic configurations used to showcase entry to VRS but I have done this myself (early days as a junior Sqn pilot into a field in NI full of troops) - my ambition exceeded my talent and I overtorqued the aircraft arresting the RoD before we hit the ground, coming to a low hover with a high heartrate!

The 412 is probably into IVRS - as was I - but I pulled enough power to muscle out of it, either he didn't pull hard enough or he did run out of engine muscle.

Rotorbee
why dont you ask Mr Vuichard ?

How do you know there isn't enough power available here? Isn't it possible that the power he had couldn't stop his decent because he was in the vortex ring state?

because he crashes with a manageable RoD and the RRPM droops as he pulls pitch.

If he had another 100' feet or so to get to the ground it could well have developed into full VRS and been a much harder landing.

As I said, I have done this myself but without hitting the ground thanks to a surplus of power in the Wessex.

There are many words that don't survive the crossing of the Atlantic but descent isn't one of them usually.:)

If the rpm droops as he pulls pitch, then doesn't that just mean he was too heavy to hover?

No. he might have had enough power to come gently to an OGE hover. However, he went for the very punchy quickstop arrival (which may well have been downwind) - that needs a shedload more power to stop and is why he then fell out of the sky.

Look at the disc tilt and think about the Total Reaction arrow of thrust the rotor can produce - then tilt it and see how much the vertical component - which is required to oppose weight - reduces.

Is this a problem only common to large helicopters, because the situation seems strange to me?

​​​​​

Robbiee, when you were at the Robinson Safety course, didn't they show you the video what happened during certification? The one were an FAA pilot did very low level autorotations?
That ended it the same way, upright, bent blades and the prototype was toast. It ends with the pilot jumping out and throwing his helmet down. He seemed to be slightly upset.
I asked Nick Lappos, if that was VRS, he said, no that was HTG - Hit The Ground, as you can not have VRS with the lever down. Doing it right, you can even have that in a R22. Inertia can be such a b*****.

No. The situation is not strange, just the severity of the manoeuvre.

Plenty of light singles run out of power trying to come to an OGE hover - the accident stats are there for SWP and it is often because they are overloaded, haven't done any pre-flight performance calculations or have been caught out by wind (or lack of it).

Sudden onset of excess gravity affects all sizes of helicopters.

Explaining the various causes of such sudden onsets is where it gets complicated.

SWP, IVRS,VRS, Excess Weight, Density Altitiude, Wind Direction and Velocity, Turbine Lag, Mechanical Failure, Pilot Technique.....and combinations of several factors will find you making an interesting arrival at your final landing spot.

Prevention is the key....perferably learned in a classroom or training environment and not by Trial and Error.

Some video can begin to show what the most likely cause of such landings might be....but a full analysis should be the basis for accurate assessment.

transient droop recovery

The only way I can wrap my head around this concept of running out of power even though I'm not too heavy to hover is that I must be coming in like a screaming banchi and just wait too long to put on the brakes.

Is this it?

Pretty much Robbiee - when you are pushed for power, you need to make a gentle, level decel to an OGE hover so you are using power to balance weight/mass and a little to slow you down. gentle application of aft cyclic will tilt the disc a little and not reduce the vertical component of that rotor thrust and you will have a small benefit from flare effect.

With a screaming Jesus quickstop, you are initially holding the aicraft up with lots of flare effect which generates enough rotor thrust to balance the weight/mass and slow you down.

As the flare effect reduces with speed in the decel, you need to replace it with collective pitch to keep balancing the weight/mass and increase the rotor thrust.

In an ideal world, you gradually feed in the power and reduce the flare until you get to your OGE hover with no problem.

If you are late with the lever, the aircraft is starting to sink and now you need a big, rapid application of power to stop you AND control the height - it can require more power than you have available and that's when settling with power kicks in, the Nr starts to decay, more lift is lost and down you go as per the 412 video.

It is really about controlling inertia - if you ease off the gas in your car a long way ahead of a stop light you can brake gently all the way to the stop. If you keep the gas pedal down until the last moment, you'd better have really good brakes.

The analogy with the 412 video is that drove like he had carbon ceramic brakes when he really had sh8tty drum brakes that needed new shoes.

FWIW, as one who has made countless FR approaches, the 412 could hover OGE under the conditions of the video.

This is not VRS. It doesn’t even appear to be settling with power, unless one considers the reduced Nr.

This is primarily a demonstration of transient rotor droop.

Anyone care to count the duration of the 0 to max-up collective pull?

Never discount the V-squared term in the equation of lift.

The 412 has a bit of inertia built up as it falls into hover attitude and needs arresting.

An over-torque may have saved the bacon but a PT6T probably won't let you.

NO IVRS, NO VRS, NO SWP. I am sure there is more than enough power to hover.

Just a massive "handling error".

I'd have to disagree Jim - I've flown plenty of manoeuvres like that in a 412 and airtested a few of them as well - the Nr doesn't droop more than a % or two when you haul in collective.

that's for sure.

These were my thoughts too Crab. I can’t say I’ve been in the position that aircraft was in but I have never really experienced significant NR droop in a 412. Almost all my time is in EP’s so I’m not sure if it’s more of an issue in the earlier models. Quick stops isn’t something we get to play with often but I’ve always found the EP rock solid on power changes.
I can’t pick up any change of rotor speed in the video, well not until he’s just about to hit the ground.

my thoughts too - Nr in the video looks stable

PS can the thread title be edited to add an ‘!’at the end?

I will probably get a lot of flak for this but:
I was doing a job which entailed a lot of climbing, descending and hovering at high altitudes AGL.
I discovered that it is possible to enter VRS from a steady hover.
It was a great surprise the first time.
Due to the job it happened a lot. So I got the chance to try various things out.
Maintaining a vertical descent pulling power just increased the rate of descent.
Controls got sloppy but the aircraft did not enter any unusual attitudes.
There were no torque or RPM fluctuations.
Recovery was simple, Initiate forward or sideways movement and exit the column of descending air.
The aircraft was very light during these operations just myself and sometimes 1 passenger and around half fuel.
It warned you it was going to enter VRS. You would be happily sitting there at about 80%Q. The VSI would flicker (not even to 100FPM down) Altimeter would hardly move. If you did nothing it would enter VRS shortly thereafter. Pull a bit of collective and it usually entered VRS immediately and fully.
It only happened in calm wind conditions.
As we were hovering, climbing or descending on a ‘Laser’ beam you were never moving more than 2 feet in the horizontal from ground level to as much as 7000 AGL. Usually we only climbed 2000-4000 ft.
If you lost the ‘Laser’ beam you had to descend to ground level in order to reacquire it so sometimes I remained in VRS to descend.
The aircraft was being observed using a 50x theodolite so the surveyors could see the aircraft depart downwards. They would have me in the crosshairs as I hovered and suddenly I would depart downwards. They thought it was very funny to watch.
Just for info the aircraft had a cowling just abut under the fwd seats. The cowling had a screen on the bottom. Inside the cowilng was a video camera focused on the screen and a small 3 inch square monitor was installed on the instrument panel. A 10 amp gyro stabilized ‘Laser’ was placed on the ground pointed vertically upwards. You hovered low over the ‘Laser’ and placed the aircraft over it until you saw the ‘laser’ dot on the screen. You then initiated a climb at about 6-800 FPM keeping the dot as close to the center of the screen as possible. If you rapid control movements failed in this and you lost the dot you had to return to ground level and start over again. It took a lot of practice to learn the technique usually about 5 -10 hours. Some guys caught on quickly, some never could. The customer paid fro the training. They also allowed you to go out and practice if you didn’t do a shot for a day or two as it was a skill that required constant practice. Totally an eye, hands, feet coordination thing…if you had to think about it the dot was gone.