So, what DID happen ?

[The Nr Fairy]

I've been trying to puzzle this one out for a few weeks, and despite asking around haven't come close to an answer which seems right.

Imagine a short finals in a B206 to a site which is actually on your left hand side. Wind is between 10 and 20 knots, occasional gusts, from your right hand side. Arrive in a top of IGE / bottom of OGE hover, with the site still to your left, and the wind still from your right.

Next thing, you've turned 90 degrees nose left, and are heading towards the landing area. Adrenaline rush time, but all turns out well.

So, back to the question - what did happen ? Someone watching said there was a large gust at the time I arrived, other than that nothing else - power requirements when departing the same site a few minutes earlier (pleasure flying, you see) was about 95% TQ, no TOT or N1 limit.

[Droopystop]

Need more info on this one.

Re read your post objectively - you might be opening yourself up for critism, and you know how vicious the pprune secateurs are .

[NickLappos]

Stand fast, Nr Fairy, we will protect you from the onslaughts. Show me a pilot who has not had a dozen such stories, most self-induced, and I will show you a liar! We learn from our mistakes, and by examining them closely.

A jump to the left can only occur for the reason that you temporarily had too much anti-torque. Was there a collective pitch reduction in process while you experienced a burst of wind reduction (an un-gust?) while just at the critical 17 knot point of main rotor speed?

[[email protected]]

Sounds like you might have just been weathercocked to the downwind position rather than to into wind by the gust.

[The Nr Fairy]

Some thoughts I've had:

1. Weathercocking - I thought that was unlikely, since an larger gust would have put the nose more to the right but see below.

2. LTE - no, because the nose would have gone right again, and the Nr was up at the top of the green.

3. Collective pitch reduction - not that I recall, I was just coming to the hover and the lever was coming up to a "normal" position for the power required.

Only thing I can think of is that with the wind from the right, and a relatively heavy a/c I had a LOT of left pedal in. If the gust was just BEFORE I arrived and dissipated as I came to the hover, then I would instantaneously have had far too much pedal.

Droopystop - what more info is needed, I'm quite happy to provide it.

[ThomasTheTankEngine]

By the sound of things I would say you applied to much left pedal.

I would be very careful (Ex in a 206) with the wind on the right side on approach and an unexpected 90° pedal turn as you reach a hover, This gives you a tail wind requiring more engine power.

Watch out for the TOT it raise’s quite a lot if you pedal turn to fast in a 206. Try and keep those pedal turns slow and controlled especially when heavy.

[Gerhardt]

Now THIS is the big benefit of pprune. I'm impressed that everyone's full of good cheer and helpful in solving the problem.

[PPRUNE FAN#1]

The baffling thing about helicopters is that they simply defy efforts to absolutely quantify their performance. In other words, they sometimes do weird and inexplicable things.
Pilot: "It did this.
Designer: "It's not supposed to do that."
Pilot: "But it did."
Designer: "Oh well."

Personally, I'd go with the "too much left pedal for the ungust" theory. Or maybe the wind was more variable than you thought. When you get down low like that (high IGE/low OGE) the wind can do some crazy sh...uhh, stuff. Chalk it up to experience.

[Matthew Parsons]

Maybe your tail rotor had lost some effectiveness throughout the final stages of your approach since it was blowing its washing directly into a 10-20 knot wind. The wind dropped and you lost the loss of effectiveness :), becoming more effective.

Other ideas
- was there any unusual configuration ie floats, doors off?
- hydraulics on the tail rotor acting up?
- Yaw SAS acting up (don't know if this is even a B206 option)?
- maybe it was typical LTE and you turned 270 degrees right :O

[skitzs]

Nr fairy

seems to me you nearly answered it your self on the last post.
Your first post seems clear to me (im sure some will disagree),
"a boot full of left pedal' to pull up of coarse wasnt needed soon after especialy when the collective was also lowered as you level, then a little lazey on the feet possibly? caused your left swing into a gusty tail wind which leads to the nose droping more than you had the authority to stop, or while your thinking "wayhey" whats happening, instead of staying one step ahead and not running out of aft control. :O take it easy, :ok:

[The Nr Fairy]

All doors on, non-hyd tail rotor - as far as I'm aware, no SAS on this 206, and I think I'd have noticed 270 degrees :)

[Gomer Pylot]

If you have a choice, always approach with the wind on your left. It requires less power, because it requires less left pedal. High torque and almost full left pedal will bite you in the rear very quickly. When you lose ETL while holding lots of left pedal, and also lose the right crosswind momentarily, you have to be very fast on the pedals. My advice with a 206 has always been to keep the feet very busy, and the hands very still, at least as much as possible. If you let your feet become the slightest bit passive, you'll get surprised, sooner or later.

[overpitched]

If you left the area a few minutes earlier and were heavy enough to need 95% tq and were planning to return with a right crosswind and a downwind termination than you were probably lucky that a 90 degree turn to the right was the only problem you experienced. Did you get a look at the tq guage during the excitement ??

If there were trees in the area you may have been shielded by them during the later stages of the approach. Always has the potential to be bad if you are heavy or a bit slow to react.

The gust that was reported may have been a willy willy. Don't know if you get them in the UK. But they can be a big problem here late in an approach.

[Flingingwings]

Could Ian offer no suggestions:confused:

With the benefit of hindsight, reckon the problem started long before the a/c turned :uhoh:

We can always learn from these little incidents, so thanks for sharing.

But ,IMO avoidance in this case would have been a better option.

[The Nr Fairy]

I was trying to avoid a downwind approach into a site with limited options by coming to a controlled stop before turning left to hover taxi to the landfing area. It seems I got bit in the arse, and I'll make my feet work harder next time !

[skitzs]

its all about learning, as most say we never stop.
Good comment on your last NR.F. well done.
Happy flying.:ok:

[SASless]

As Nick so rightly stated....hang on...this is just one of many more events that will get you to thinking. That is part of working a helicopter. The trick is to learn from them as The Man said.

[delta3]

Based on the information, my guess would be wind sheer : by getting lower, the wind coming from the right side, which required extra left pedal dropped away. Could be amplified by a local wind shift caused by buildings/trees.

Just my pennies worth...

D3

[[email protected]]

NR - sounds like you ended up downwind in the end pointing at the LS - so back to my comment about being weathercocked downwind. If you are holding left pedal to counter the crosswind and then the crosswind turns into a cross/downwind, there is only one way the aircraft is going to turn - which is how you described it.

[Joker's Wild]

Don't all skewer me right away, but what are the numbers again for the critical wind azimuth on a 206? I've simply forgotten, but I do remember always having that illustration in my head when I was still driving around in Jetboxes.

And, as one might expect, we were into plenty of "odd" sites out in the sticks, where some of the more unpleasant character traits of a 206 out of wind became evident.

JW

[The Nr Fairy]

JW:

Critical azimuth (from the POH) is 050 to 210. However, the POH states

Tail rotor control margin and/or control of engine parameters (TOT and torque) may preclude operation in AREA B of the Hover Ceiling charts when the wind is in the Critical Wind Azimuth Area.

On the day, looking at the HOGE chart just to be pessimistic, I was nowhere near AREA B, but was well in the Critical Azimuth - assuming +35 celcius, 1000' pressure alt, and 3200lbs.