Mi-8 Crash in Gelendzhik, Russia

[JohnDixson]

VRS Boundary Chart

RVDT, the chart is in direct conflict with Ray Prouty on this subject ( see page 102 ). His book is certainly in agreement with the various VRS tests on SA machines ( and one other ) that I have been involved with. Curious.

Thanks,
John

[cpt]

The point is that, because we hardly meet VRS in the course of our pilot carrers, we tend to store it in the back of our mind, that makes it even more treatorous.... wasn't it the case in this late 332L2 accident in the Shedlands ?

Just for the sake of experience sharing, I recently put myself in a VRS ( I already have experienced peharps 3 or 4 VRS all along my helicopter flying years)

I was training a "young" S76 pilot, speed variations with one engine in the "manual-trim" mode and the "ALT" function engaged to maintain a constant altitude.
at one stage, our target was a speed reductiion to 60 Kts, but the preset torque was obviously too low, IAS dropped increasingly quickly below 40, the coupled "ALT" couldn't maintain altitude and we started to sink with our speed reducing in a blink of the eye, to almost nothing, then all the symptoms followed in sequence, vibrations, sluggish reaction with flight controls (it made it harder to build up speed again) and down we went.

We started at 1500' and managed a recovery just below 1000'... I must admitt I wasn't very convinced about the VRS scenario in the "Shedland" case, now .... I understand much better how this could have happened, sadly, at much lower height.

I also can say that the S76 simulator reproduces the VRS very faithfully...

Once again the popular wisdom quote saying that your horse will kick you when you will not expect it, is verified with Helicopters and VRS.

[Helilog56]

On occasion while instructing VRS will be demonstrated for any student or pilot that wants to gain the real world experience. I will not even consider doing it less than 4,000 agl as vertical descents can be in excess of 6,000 fpm....which can leave minimal time to recover when deep into VRS.
I am dismayed by the lack of knowledge from pilots that can not see the difference between VRS and settling with power (FAA term), which really should be insufficient power.....it is still taught in the US, that they are one and the same....!!!?!?!

[RVDT]

cpt,

Value for money - 2 traps in the same flight!

[fijdor]

In reference to Helilog56 post, here is what TC (Transport Canada) has to say about VRS and SWP. Not the whole thing but part of it.

JD

You should note that an increase in collective alone may not result in a recovery and indeed may only serve to increase the rate of descent. This increase in blade pitch will cause the vortices to intensify in strength and will result in a more rapid descent.

There are some uninformed pilots who use “settling with power” to describe vortex ring, in fact some publications use the terms interchangeably. Confusion results when symptoms are related that do not describe true vortex ring but rather describe “settling with insufficient power”. This may occur when a pilot attempts to arrest a rapid, low power descent only to find that he has insufficient power available to bring the helicopter to either a hover or a no-hover landing without exceeding the engine limits. However, this is not a vortex ring situation.

Another situation, ‘over-pitching’ is often misinterpreted as vortex ring. This is where the pilot rapidly increases collective considerably and the engine cannot produce enough power to overcome the large, swift increase in drag on the rotor system. The result is that the rotor system quickly slows down and loses efficiency causing the helicopter instantly to sink. Again, this is not vortex ring.