I have great respect for Nick and don't for a minute think I know more than he does about aerodynamics, but all I'm saying is that the S61 can and does get into VRS with WAY less than 1000 ROD than you suggested, that is from personal experience and I will not attempt to explain that in aerodynamical terms, only underwear changing ones ;)

crab is correct. Disc loading has a significant impact on establishing at what ROD the rotor system enters VRS. It takes a lesser ROD with an empty helicopter at the end of the fuel cycle vs. a helicopter at max gross weight.

To make a slight correction to VF's contention that the Vulchard method doesn't work in fully developed VRS: in a tandem rotor helicopter it is the smartest method, no matter on your ROD. Also, an S-64 Aircrane responds very quickly to a lateral control input to exit VRS vs. a longitudinal recovery. I've seen RODs larger than 5,000'/min and the Vulchard method works like a charm. Loggers have been doing this since the '70s.

with 50' recovery as advertised?????

Sideways recovery on a tandem rotor makes sense - both rotors in clean air

Thanks Mast Bumper (I hope You're not bumping to often) I've never flown twins let alone a Chinook, so no comment......it is not my contention alone, many others have come to the same conclusion as I! I have many times tried & tested this method on a 350, 125, 130, 206, 407 & G2 & it didn't work at all in fully developed VRS, it did have some positive effect in IVRS. The 70's aye; then Vulchard didn't invent this at all, stole an old idea claiming it was his own invention, hmmmmm :=

Have You tried this method in a light single?

Happy landings

VF

that makes a ton of sense!

But with two sets of Rotors...how many possibilities of VRS are there....Forward head only, Aft Head only, both Heads involved?

Outwest - out of interest, were the two occasions you experienced VFRs in the S61 in the same flight profile ie flaring to the high hover?

It's certainly possible. I know an RAF Chinook pilot who had a student get both fore/aft into VRS on final for a pinnacle landing in Afghanistan.

VF - not to dispute your experiences, but I personally have had good results from sideways recoveries, even at late VRS stages - that's in a Squirrel and G2 - as you say, only testing, no real-world brown underwear scenarios. Side note; I know a few instructors here in Switzerland that also have played around with both techniques over time and found the Vuichard recovery to be the better option assuming no obstacles.

In the Chinook....clever use of the yaw pedals during takeoff can produce additional lift as you accelerate the aft rotor into clean air not disturbed by the forward rotor.

I wonder how that would work in dealing with a VRS situation.

In all of the VRS demo's I ever performed during conversion training for. new pilots....I do not recall it being all that easy to get into a full blown VRS descent.

I know it was not one of the demo's that caused much excitement as I recall it being a rather benign maneuver.....but always done at 3,000 feet AGL.

In the early A model...turning off the SAS in a steepish turn was not for the faint of heart....feeling the aircraft trying to swap ends at 100 Knots was far more exciting.

I may have been misleading, I have been in it twice, once in the 61 and once in a 205. The 61 was not what you would call a flare, a simple slowing of airspeed to come to a hover at altitude, and upon noticing that what I would call a small ROD I used a small application of collective to arrest the decent and that fast we were coming out of the sky. The strange thing was the VERY experienced instructor never told me why he wanted me to come to a hover at that altitude, but he knew ( I guess from all the others he checked out) what would happen.

The other time was on a seismic longline job. I was going down the cutline ( downwind) looking for the drill and realized I had passed it. I lowered the collective and pitched up to slow to make my turn into wind and approach the drill. We had no flight instruments ( AS) on the left side or a means to jettison the belly hook from the left side so ( luckily for me) we were flying 2 crew. I obviously came to a very low AS but since I was going downwind I didn't realize this. The next thing I knew we the greased manhole cover and when I got my head back in from the bubble window both low rotor lights ( Yellow and red) were on. By this time the turn was completed and we were into wind. VERY luckily the other highly experienced pilot was pumping the collective to regain RRPM. We were now with the skids almost going thru the tree tops, and yes the longline was still attached ( remember I could not kick it off) how it did not wrap around a tree and drive us into the ground still haunts me to this day.

I have a very LARGE respect for VRS.......

Outwest - very brown trousers on that last event I am sure:ok:

NigelH - did they do a comparison of the Vuichard vs 'standard' recovery? When they used the Vuichard, did they recover in 50'?

Kiwi500 - I don't know, other than using Nick Lappos' graph, if you can put numbers on it.

However, you could liken it to a FW stall in as much as there is light buffet, which gradually increases if you don't recognise it - it gradually worsens and then finally gets to the nose drop/wing drop stage which would be roughly the equivalent of IVRS going into full VRS.

The 30 kts 500'/min RoD figures have been taught for many years as a way to avoid even IVRS but they were based on low disc loading helicopters. Each aircraft will have different figures based on its disc loading and even they will vary with AUM and DA.