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-   -   Vuichard technique for settling with power? (https://www.pprune.org/rotorheads/557861-vuichard-technique-settling-power.html)

Bellrider 19th Nov 2015 13:32

sorry for that question! IŽam a littlle confused!
Hovering HOGE with max power available, heli starts decending due to not enough power availible. In that case i canŽt increase power or left pedel (still full forward).
Settling with power and Vortex are quite close togehter. But canŽt get out of settling with power with that method..

Thomas coupling 19th Nov 2015 15:36

The other thing to be very clear about with Tim Tuckers description of VR is that it isn't Vortex Ring that he talks of. He should be more circumspect and call it: Incipient vortex ring state (IVRS).

For starters he talks about "commencing this above 1000 feet" Yeah - good advice Tim. Like VR induces 3-4-5000 feet per minute descent.

Secondly - Fully developed VR causes intermittent LOSS of CONTROL of the cyclic and or the collective inputs. Its a game of luck as and when the controls respond inside FDVR. So "applying the Vuchard technique".....how?

Thirdly. The VT is another means of departing the vortices, correct? So too, is the normal response to recovery, except instead of popping out to the 3 or 9 o clock, you bugger off to the 12 o clock.

Vuchard technique....my arse! Vuchard buchard......:ugh:

jymil 19th Nov 2015 20:20

@Bellrider and TC: you both talk about situations in which the VT is not relevant. If you havenŽt got the power to hover, youŽll settle no matter what. And if youŽre in a 5000ft/min uncontrollable descent, then it might be too late anyways.

VT is for when youŽll be guaranteed to crash with the standard recovery because youŽre too close to the ground. At 100 feet AGL, it does make a huge difference whether you need 30 feet to recover or 150 feet.

Thomas coupling 19th Nov 2015 21:23

jymil

Here we go again - or rather.....no we don't. I'm not going to waste any more time on VRS, SWP et al.
Suffice to say once and for all, the following:
IVRS is identified by buffeting, vibration and unintended height loss under power.
Atleast several hundred feet will be lost before any half awake pilot will identify they are in IVRS.
Once they initiate recovery using normal or VR technique, atleast 1 or 2 hundred feet will be lost. Overall - no-one here has ever recovered from IVRS in less than 2 or even 300 feet. If you have - you did not enter IVRS.

If you find yourself in FDVRS, then goodbye several thousand feet height loss - minimum, while you battle to regain full response from the cyclic/collective (Yaw not normally affected).

Don't ever convince yourself that any of these aerodynamic phenomena will only lose you 50 - 100 - 150 feet. You're in la la land sunshine.
Bye di bye....................:ugh::ugh::ugh:

Hughes500 19th Nov 2015 22:41

I have spent a long time trying to work this out
1. How can you get out of VR with a loss of 20 to 30 ft ???? I can assure you having been in Fully developed VR where the ac was pitched up by about 75 degrees falling on its tail with IVSI off the clock ( goes to 3000 ft a minute ). My only recovery after trying cyclic in every direction ( result sweet FA ) Lever fully down ( result FA ) only thing left was full right pedal that then put ac into about 80 degrees nose down regained speed, nearly pulled head of the 300 pulling out of dive with about 200 ft to spare. Please someone tell me how full right cyclic and virtual max power with loads of left pedal do anything when you have 3000 ft plus rate of descent with ac pitched about 75 degrees nose up ??? Let alone come out of it with a loss of 20 to 30 ft. How powerful is your f..ing rotor system that is going to stop a high ROD in just 20 to 30 ft ?????
2. I can perhaps understand getting into incipient vortex ring this technique will work but having tried it no real difference to putting nose forward.
3. It appears to me that a lot on this forum don't really understand the difference between Incipient vortex ring, fully developed vortex ring or come to that running out of power. This goes for the books themselves. Last week put a Hu 300 into " VR" 20 inches of MP 10 kts downwind 700 ft min rate of descent ( according to most books you get VR with 300 to 500 ft min ROD ) pulled lever to max power trying to get into VR and guess what the ac climbed back up, certainly not what the student was expecting !
I am some what concerned that some people who appear to be highly experienced don't have a clue here, what does this say to the younger inexperienced pilot.
I will eat my hat if I am wrong but want to see some actually factual information rather than what appears to be hearsay

Vertical Freedom 20th Nov 2015 02:25

Crikey Hughes500 ~ couldn't have said it better....thanks :ugh:

==============================================

Pole forward with Power applied; it Works !!! Just Pole Forward !!! ;) It doesn't need fixing, so please get some Airspeed back into Your flight, rather than just a jiggle & dance := recovered in 50' hahahahahahahahahahahaaar :}


Fly always at ETL, or above, whenever conditions permit :confused:

VF

rotorfossil 20th Nov 2015 06:18

Bearing in mind that the vast majority of VR/settling with power events occur in the latter stages of an approach, the chances of recovery using any technique are unlikely. To reiterate the obvious, avoidance and awareness of the conditions likely to lead to it are the answer.
To add some experience to this discussion, the only time I have got into this situation was from an unrealised downwind approach. The only reason I got away with it (using the stick forward and easing the lever down) was because I had an escape route downhill.
On the above subject, I've noticed over the years that there often is an element of an unrealised downwind approach in the accident reports. I think this is due to the assumption that the wind was so and so at departure and is the same at the destination. Very noticeable at coastal locations where sea breezes can reverse the gradient wind.
Sadly, use of VSI readings as a guide to the likelihood of VR is a bit of a trap due to the large lag in the readings.

ShyTorque 20th Nov 2015 07:02

I did some very basic maths to try to understand the claim that it's possible to recover from VRS with such a small altitude loss.

3,000 fpm = 34 mph
4,000 fpm = 45 mph

To try to put this in context, I looked up car braking distances. Most sources state these braking distances (dry road surface):

Speed 30 mph = 75 feet.
Speed 40 mph = 118 feet
Speed 50 mph = 175 feet

These are essentially "emergency stop" distances and anyone who drives a car will understand the dynamics of such a manoeuvre. I fail to see how anyone can claim that a helicopter can level off in around one third of those distances from similar vertical speeds.

Hughes500 20th Nov 2015 07:05

Shy

I had that exact conversation with one of my pilots yesterday, hence my comment on how f..ing powerful is your disc to stop rod in 20 to 30 ft
We really need ETPS at Boscombe to check this out:ugh:

ShyTorque 20th Nov 2015 07:15

H500, Seems that some don't know the difference between VRS and running out of power!

[email protected] 20th Nov 2015 12:29

If Mr Vuichard and his acolytes are demonstrating recovery from VRS with less than 1000'/min RoD before recovery then they are nowhere near VRS in the first place.

Nick Lappos posted a chart many years ago highlighting that you have to be descending at approximately 65 % of your downwash speed to even start to get close to incipient VRS - for the full blown event it is 75 to 80%.

The trouble is that people have no idea of their downwash speed and the 500'/min figure comes from the days when disc loading was very low (due to low engine power) and so, therefore, was the downwash speed.

It can be calculated but it is surprisingly high - I know for the Sea King and similar helicopters it is in excess of 2000'/min which happens to be the same as the RoD in autorotation.

If your RoD in auto is a reasonable guide then no modern helo will get into VRS with less than 1000'/min RoD - try stopping that in 50 -75 feet.

Utter bollocks this Vuichard stuff.

Vertical Freedom 20th Nov 2015 15:00

Hey [email protected] Love Your work :ooh:

If your RoD in auto is a reasonable guide then no modern helo will get into VRS with less than 1000'/min RoD - try stopping that in 50 -75 feet.

Utter bollocks this Vuichard stuff

jymil 20th Nov 2015 16:45

Any discussion about >3000fpm sink rates and whether you call it incipient VRS or whatever is not really the point. The point is when you come in at e.g. 500 fpm and then you pull collective at 100ft agl just to figure out your descent rate goes the other way. Before you reach a >3000fpm sink rate, you'll have crashed.

Interesting to see how stubbornly some people rebuke this as utter nonsense. If that was the case, they certainly wouldnt teach it at the Robinson safety course. Try it out for yourself, talk is cheap.

[email protected] 20th Nov 2015 17:29


The point is when you come in at e.g. 500 fpm and then you pull collective at 100ft agl just to figure out your descent rate goes the other way
So it is not a VRS recovery at all since you are not in VRS - it is at best a IVRS recovery, in the very earliest stages.

Hughes500 20th Nov 2015 17:48

jymil
Quite frankly I don't give a diddly squat what they teach at Robinson ( this is the same company that can't even make a set of main rotor blades properly and then come up with a micky mouse solution to repair the **** they put out )
If you care to check some of the posts you will realise that a lot of so called high hour experienced people are talking bolloc.s Tim Tucker included.
Come down and see me I will put a 300 or 500 into what you would call vortex ring < 15 kts, > 500fpm rate of descent pulling power. I will then invite you to recover by simply pulling the collective up. Guess what you will recover, because YOU ARE NOT IN VORTEX RING
Please explain to me if you are in vortex ring, greater than 1000fpm decent how does any rotor system able to halt that within 30 ft. Just engage the grey matter here !

claudia 20th Nov 2015 18:50

Hughes 500 Refreshing and accurate facts from your goodself.
Exactly why you are so highly regarded as an instructor/ tre.
Also concerned about the knowledge of some of the" experienced"
people on this topic.

jymil 20th Nov 2015 19:53

It seems possible to get a Super Puma into VRS starting from >500 fpm rod and <30kts according to the accident report from G-WNSP.

Now, back to using your grey matter: recovery #1 requires you to lower the collective, push nose forward and then raise collective again. Recovery #2 requires you to bank into the upstream of the vortex and not lower the collective, but raise it directly. Which one of the two do you think would lead to less altitude loss ?

jellycopter 20th Nov 2015 20:04

In fully developed VRS, #1 will lose less height. Raising collective will 'deepen' the VRS.

Having lost 6500ft in an out of control Puma due to VRS, I can tell you categorically that in my experience, the Vuichard technique is bollocks. My VRS was so well developed that the cyclic had no effect on aircraft attitude, even at full deflection. I'm convinced that the only reason we got any speed at all to fly out of the situation was due to the very high RoD resulting in an upward force on the horizontal stabiliser thus pitching the aircraft nose down. The cyclic did bugger all, despite trying to force it through the instrument panel! Lateral cyclic would have been cock all use.

JJ

jymil 21st Nov 2015 04:22

If you are in a fully developed VRS out of control: how exactly is the standard recovery technique helping there?
Both recovery methods are only applicable when you still have some control over your aircraft. You should do something about it as soon as you detect that things don't go the way you want.

n5296s 21st Nov 2015 04:53

I'm just a novice in all this, but I did start the thread so... if Vuichard only works for IVRS, just how exactly does it differ from the conventional recovery? (a) You go sideways instead of forwards (b) you pull collective straightaway instead of drop-wait-pull.

(a)... so what? The rotor doesn't know or care about sideways, forwards or backwards. I guess maybe the tail rotor thrust potentially makes the translation happen a bit faster.

(b)... as long as you get out of the downwash rapidos and you were only ever in IVRS, dropping the collective probably doesn't make much difference. In fact my original instructor said something like "do it for the checkride but in truth there's no point because by the time you've dropped it you've recovered anyway" (which was ironic because he was also my examiner, but that's another story).

So the advantage, if any, of Vuichard is (a) you may get out of the downwash a tiny bit faster thanks to help from the TR and (b) you don't have the brief loss of lift due to dropping the collective.

If the difference between flying away and disaster is 20 feet, then I guess these may help. For FDVRS it's academic, but then what were you doing there anyway?


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