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Val d'Anniviers Airplane Crash

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Val d'Anniviers Airplane Crash

Old 16th Feb 2011, 11:13
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It still looks to me as if the aircraft has flown into a severe pocket of sinking air.
That would explain the crash sight a lot.
Unless you have experienced such a downdraght you cannot appreciate the helplessness of sitting there going down like a lift.
Other posts point out the good weather but even on good weather you can get peculiar localized phenomena.
Other than that ? God knows!

Pace
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Old 16th Feb 2011, 12:40
  #82 (permalink)  

 
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The very first photo, taken from the chopper seems to indicate that the roof was like that because of the crash.

I know what you mean Pace, I've had 1500 fpm decents full power (trying to climb) with the stall warner chirping while flying in the mountains, followed by 1500 fpm climbs with power at idle very shortly after. It was pretty windy though - 30kt plus according to Garmin. I remember reading an accident report of a glider / tug combo which encountered moutain waves causing the tug to break up and the glider to experience 14g (and land safely).

But I still don't see how on an apparently good weather day (good enough for the chopper to by flying there) you could get such dangerous down drafts above the ridge (they must have been above it to hit it with that much impact). If you had 20+ kts of wind at the top of these mountains there would be significant wind blown snow in the lee I should imagine and I'd have though that would have been a good clue to the pilot to stay high.

Wouldn't Avgas have the effect of melting the snow had the tanks ruptured with a lot of fuel onboard, or would it evaporate quickly. I can't see any obvious signs of fuel spill in any of the photos.

I am only speculating because I am keen to know why this happened so that it doesn't happen to me.
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Old 16th Feb 2011, 12:58
  #83 (permalink)  
 
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But I still don't see how on an apparently good weather day (good enough for the chopper to by flying there) you could get such dangerous down drafts above the ridge (they must have been above it to hit it with that much impact). If you had 20+ kts of wind at the top of these mountains there would be significant wind blown snow in the lee I should imagine and I'd have though that would have been a good clue to the pilot to stay high.
To say this you can't have done much flying around mountains.
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Old 16th Feb 2011, 13:10
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wanna bet I normally stay above them though.
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Old 16th Feb 2011, 23:27
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Er, is it me or is the speculation on here a bit crazy?

The aircraft has hit a ridge, a typical alpine accident. There may have been 20kt winds aloft and in the mountains these can be incredibly variable and localised. As an example, yesterday on the Kleine Matterhorn and at Schwarzsee (Zermatt, not a stone's throw from the accident site) there was 73 km/h of wind. At the Gornergrat, not 3 miles away and similar height, there was 22 km/h of wind.

Occam's razor suggests we take the simplest likely explanation. He may well have been in a downdraft and may have been in a position where he was unable to turn away. This happens frequently, unfortunately. And to see how simply and quickly such a thing can happen, even without a downdraft, I am posting the chilling Cessna Bird Dog video from Colorado for those few who haven't seen it:

YouTube - Fatal Airplane Crash From Instrument Panel Mounted Camera Colorado 1984

I don't understand the compulsion to postulate that the pilot may have been doing aerobatics (in a twin, in one of the tightest, most precipitous alpine valleys you can imagine, with 4 passengers!).

???
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Old 17th Feb 2011, 00:59
  #86 (permalink)  
 
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Absolutely right QDM^3 - any lack of forward speed is most likely due to a last-ditch attempt to pull-up and avoid the inevitable, trading the last bit of speed for height into the stall.

As for the O2 theory, the seats themselves show no sign of having been in the middle of any such explosion. It's much more likely that the big rock visible in the middle of the cabin is responsible for ejecting the seats.
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Old 17th Feb 2011, 05:56
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QDM

Totally agree too. I can remember skiing up at Val Disere. It was a calm clear blue sky day and we were on one of those lifts which pull you up the mountain side.
All of a sudden a huge gust came from no where whipping up to what must have been 70 mph in seconds. We clung on for dear life until the wind subsided.
The gust was so strong that it tripped the lift. It stopped and stayed stopped. We had to Ski back down. This was a calm day.

That film is a shocking warning about the dangers of mountain flying even on what appear to be good days.

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Old 17th Feb 2011, 07:57
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I don't think anyone (serious) mentioned aerobatics in a Baron.

It is kind of rare to see a "high end" aeroplane involved in a crash caused by a stupid mistake, and Twins generally are involved in far less accidents than SEPs such as low power Cessna Bird Dogs messing around with rising terrain and high density altitude. That is why I am interested.

Most of the deaths in Twins are in IMC conditions (CFIT) - check the NTSB if you want proof. Most of the pilots are more experienced (have to be for insurance if nothing else). I've been snowboarding in the Alps many times and know what it is like at the top of some of these mountains in windy conditions though to be fair if it gets too windy (30kts) they shut the chair lifts. This is rare too.

However there are many glorious, sunny, still days too and you get lots of para-skiers going from the tops without issue. You also get loads of balloons going over the Alps as well as medical choppers flying between the mountains regularly. This looks like one of those sunny days to me.

I doub't very much the pilot "just flew into a ridge" unless he was showing off and trying to get some good photos. Again I doubt this. Also had he hit the ridge at speed, the wings would have been bust. Had he been trying to climb, the tail would be bust.
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Old 17th Feb 2011, 08:39
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It's the lack of the forward speed which is weird.

BTW which photo shows a rock inside the cockpit? I thought the stuff visible in the back were seats, but you may be right.
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Old 17th Feb 2011, 10:20
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It's the lack of the forward speed which is weird.

10540

The lack of forward speed suggests sinking air. It is possible the pilot was giving his PAX a good view of the mountains by either flying close or even below ridge heights because he considered conditions to be favourable.
We all know in summertime you can get calm days and a whirl wind can appear from no where.

I appreciate this was not summer but certain mountain shapes can take a large volume of air moving relatively slowly and force it through a smaller area effectively accelerating that volume of air to considerable speed in a localised area.

I have seen that effect many times.

No one should be under the illusion that because there is little wind that they are safe from violent downdraughts in large mountain areas.
This is what I think has happened here.

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Old 17th Feb 2011, 10:25
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The lack of forward speed suggests sinking air
Sinking air will give you a negative vertical speed but it won't kill your forward speed.

Pulling back on the yoke (to maintain altitude) will reduce the forward speed but only to the point of stall.

It will be quite difficult to reduce forward speed much below Vs.

And of course you will have the stall warner and the whole orchestra going off so only somebody deaf and blind will carry on doing that.
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Old 17th Feb 2011, 10:34
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That was the point I was thinking of earlier but obviously I didn't put it across very well. In a down draft, the aeroplane still has forward velocity, and the only way NOT to have forward velocity is to stop flying.

I believe the stall on the B55 is about 75 kts so if as described, hitting a down draft one would still expect to see the result of a 75 kt head on - wings ripped off for example.
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Old 17th Feb 2011, 10:51
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Optical illusion.
Snow covered mountains in the distance masking nearer and identical but unseen similar coloured terrain. Usually occurs in good weather.
Seen at the last minute... violent pull up into the steeply rising ground...
See pic 1.

Ask any military pilot, they have a phrase of it which I cannot recall atm.
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Old 17th Feb 2011, 11:40
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Sinking air will give you a negative vertical speed but it won't kill your forward speed.
10540

It most certainly will kill your forward speed purely through the laws of triangulation. That is presuming that you do not try to maintain altitude and go for maintaing IAS in sinking air.

Trying to maintain altitude will kill your forward speed as well as quickly reducing to stall speed.

Trying to maintain your IAS will also result in an increase in VS as well as a decrease in forward speed as stated due to triangulation.

You can only maintain forward speed by maintaining altitude.Take a stupid example. You are flying level at 100 kts you hit a pocket of air descending at 200 kts are you going to travel the same distance forward as if you were still maintaining 100 kts in the horizontal plane?

The angle you would have moved forward would probably be without working it out about 30 degrees from the vertical rather than 90 degrees in level flight. Your vertical speed would also have increased dramatically over the 200 kts aircurrent trying to maintain your IAS.

Regardless an aircraft in severly descending air is going one way and thats down. It would be natural for the pilot to see ground fast approaching to minimise the impact by pulling back to near the stall.

His vertical speed would reduce as would his forward speed at impact point.

My concern here is the belief that you can fly mountains when winds are low and be immune to severe down draughts unless CBs are also present.
This is far from the truth and a dangerous conception in mountain flying.

Pace

Last edited by Pace; 17th Feb 2011 at 12:13.
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Old 17th Feb 2011, 12:18
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??

The aeroplane doesn't know it is going up or down, only AoA on the wings. If you fly at max alpha in calm conditions, you might climb at 1000 fpm. If the air is decending at 1000 fpm the net climb AGL is zero and if the air is going down at 2000 fpm, then you have a net 1000 fpm decent...right?

Through that parcel of air you are still moving forward at your same forward speed, which in the Barons case is a minimum of 73 kts if still flying. If not flying then it is stalled. It is possible that the aeroplane stalled into this ridge as a result of a down draft as the pilot trying to outclimb it (panic at seeing the ridge, yank back maybe?). Seems like it has happened to some famour pilots over the years. But over the peak of a mountain you normally find rising air. The descending air is to be found in the lee. To impact a ridge with high VS then the aeroplane must have been above the ridge to start with, either that or he cleared the ridge then stalled it and fell onto the ridge........which is why I don't think weather conditions were a factor in this.

Looking at the pics, the aeroplabne obviously hit in a nose down attitude. Due to the extent of the damage it doesn't look like a "just cleared the ridge, panic, stall" to me, but a fall from some considerable height. The fact the wings haven't sheared off is a mystery and indicates a low forward speed, as does the fact the engine blocks are still in the vicinity of the aircraft final resting place.

Just my view, I may well be wrong but that is how I interpret what I am seeing.
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Old 17th Feb 2011, 12:34
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Yes I take your point but we are looking at impact! His vertical impact would be far higher in this situation than his horizontal impact and that is what I thought we were talking about???

His horizontal impact speed ie his speed forward would not be 100kts but a lesser figure.

His verical impact speed would be the 200 kts vertical air plus a greater figure as a portion of his IAS.

Obviously maintaining 100 kts his speed in the air would stay at roughly 100 kts but not in a horizontal plane.

That determines your horizontal impact and that is what I thought we were talking about not your speed through the air which accepted stays at 100 kts if you mainatin that.


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Last edited by Pace; 17th Feb 2011 at 12:48.
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Old 17th Feb 2011, 12:47
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Pace, I know what you are saying, and of course it is possible...but

I doubt it because there would not have been a 200kt vertical down draft , but likely 15 kts max based on weather reports around. Secondly that down draft has to stop when it contacts the ground and dissipate sideways and finally and most puzzling is that the back end of the aeroplane is in one piece, showing a nose down (i.e. not trying to outclimb a draft) pitch.

I really don't know what happened here, I'd like to find out because I do a reasonably amount of flying around mountains and into mountain airports and I'd like to know if it was pilot error, airframe failure, or simply being too close to mountains.

I'll shut up now
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Old 17th Feb 2011, 12:54
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The nose down would probably have been caused by a panic stall trying to reduce the vertical impact with the ground. As you said the aircraft doesnt know its in moving air and will behave the same Ie STALL.
Forget triangulation for a moment.

You are in a speed boat travelling at 10 kts against a 15kt current ie 5kts against the riverbank.
Turn around and you will be travelling at 25kts against the river bank which way would you rather be going when you hit the river bank
Now cut across the current at 45 degrees and drive down river into the bank.
Do you still think your collision speed with the bank will be 25kts?? going 45 degrees??? across

Why 15kts? if you take a mass of air which is moving at 15 kts funnel it into a spout will the air accelerate through the spout or remain at 15 kts? Mountain shapes can do the same.

I fly into an airfield surrounded by hills!On approach I always avoid a certain point even in light winds as there is always turbulence at that point.
On a stronger wind day I forgot went through that point lifted out of my seat and put a 2 inch cut in the top of my head.

Everywhere else that day the wind was infact 15 kts but not at that point WHY???

Pace

Last edited by Pace; 17th Feb 2011 at 13:04.
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Old 17th Feb 2011, 14:33
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opinions please:

Is it possible in a sudden downdraft when reacting by pulling hard on the control column with a view to clearing the ridge to "overstall" the plane in the sense of pulling so hard to climb that the nose drop below the horizontal occurs at a much lower speed than stall speed due to the momentum of the movement?

I am thinking of a more than 45 degree cross over a ridge (assume 60 degrees for the argument), a serious downdraft at a moment when it s too late to veer away from the ridge, pulling very hard on the control column whilst trying to also slightly turn away from the ridge.

The reason for my question is that it is not only peculiar that the plane apparently crashed without forward motion but also apparently alongside the ridge as opposed to the 45 degree angle we would expect of a failed ridge crossing
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Old 17th Feb 2011, 14:56
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A trawl of the web reveals this footage of the aircraft flying into - Geneva??

YouTube - FLIGHT BEECH BARON 55 SWITZERLAND
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