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BA911 G-APFE Mt. Fuji crash

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BA911 G-APFE Mt. Fuji crash

Old 10th Mar 2016, 12:12
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India Four Two,
Thanks for your description. When you have a conical mountain rather than a mountain chain, is it possible to have a rotor trailing downwind rather like the vortex off a wing tip?
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Old 10th Mar 2016, 13:09
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Bergerie,

You can get something called a Karman Vortex Street, which is different from a wingtip vortex. See the very nice animation under Analysis here:
https://en.m.wikipedia.org/wiki/Kármán_vortex_street

And here is real-life example:

Last edited by India Four Two; 10th Mar 2016 at 13:24.
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Old 10th Mar 2016, 14:25
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India Four Two,

Thanks. Yes - I have seen those before. What I was wondering about was the possibility of having a powerful horizontal vortex downwind from the shoulder of a conical mountain.
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Old 10th Mar 2016, 21:41
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India four two, many thanks for your instructional explanation of your experiences with wave and rotor. Most interesting. I've even nicked it for my blog! I hadn't realised that rotor usually doesn't exist above summit line.
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Old 10th Mar 2016, 22:31
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Bergerie1,

I don't know the answer. I'm making some enquiries.

SSD,
Thanks for the compliment. Plagiarism is the sincerest form of flattery.
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Old 11th Mar 2016, 09:38
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Bergerie1, I would expect not. A wingtip type vortex is related to pressure differences in a vertical plane i.e. top and bottom of a wing in an airstream. I can't imagine a mountain causing such a pressure differential. Just my instinct.
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Old 11th Mar 2016, 13:18
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A U.S. Navy A-4 Skyhawk that was sent up shortly after the accident to search for the wreckage encountered extreme turbulence in the accident area. The aircraft registered peak acceleration values of +9 and -4 "g", causing temporary loss of control, and leading the pilot to believe his aircraft would also break-up in the turbulence. The pilot regained control and landed safely, but the aircraft was grounded for post-flight inspection by maintenance personnel.
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Old 12th Mar 2016, 04:30
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Mount Rainier is visible from Boeing Everett on a clear day and I can remember two lenticulars forming just inland being pointed out to me by one of the local glider pilots. It's a wonder that a similar accident hasn't happened as it seems to be common practice to route flights over the mountain.
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Old 12th Mar 2016, 09:29
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But as I-42 pointed out, the destructive rotor which caused the accident only exists at or below the height of the mountain, unlike the wave (indicated by the lenticulars) which can be many times summit height but is non-destructive.
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Old 12th Mar 2016, 11:19
  #50 (permalink)  
 
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Didn't the same 'upside down switch' scenario apply to at least one 1-11 on the BEA fleet? It (or they) were different to the rest having been acquired when another airline was merged with BEA?
I seem to remember G-ANCD, one of 4 Britannias in IAS, having the "reversed" switches. It was built originally for Northeast in the USA, but never delivered to them. It was a 307 with a grey flight deck interior and an accident waiting to happen with all those switches.
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Old 12th Mar 2016, 13:34
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The aircraft registered peak acceleration values of +9 and -4 "g",
Megan,

When you are not expecting it, that would be staggering, even for a fighter pilot!

ICT_SLB,

Lee waves are very common all over the western US and Canada, when the wind direction, topography and air masses are conducive to their formation. They routinely extend into the stratosphere. The Canadian glider altitude record is 34,400' (Cowley, AB) and the US record is 49,000' (California City CA). At altitude, the wave flow is laminar and very smooth. Turbulence is unusual. The risk of turbulence increases at lower levels, at or near the mountain tops and so it is typically during climb and descent that commercial aircraft encounter.

However, the turbulence, while uncomfortable for the passengers, hardly ever reaches the "severe" classification. I've only experienced severe turbulence on a couple of flights, for very brief periods.

The turbulence associated with the Mt. Fuji accident was extreme. It would certainly make me think twice about flying downwind of a volcano.

I live in Calgary, about 50 nm downwind of the Rockies. On "blue wave" days, with no lenticulars, it is quite common to see the contrails of E-W jets appearing and disappearing as they fly through the peaks and troughs of high altitude waves.
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Old 12th Mar 2016, 14:21
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I remember years ago being in the jump seat of a 737 to Tenerife South. The island, dominated by its volcano, Mount Teidi, was visible for many miles as we approached from the north, and the wind was southerly.

I remember the captain being wary of 'what the mountain might be doing' and we gave it a wide berth as we ran down the east coast of the island some miles out.
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Old 12th Mar 2016, 14:44
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the destructive rotor which caused the accident only exists at or below the height of the mountain
SSD,
I was rereading the accident report and I was surprised to see that the 707 was at 16,000', more than 3000' above the summit, which is higher than I assumed. However, this was clearly a day with unusual and extreme conditions.
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Old 13th Mar 2016, 17:56
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Originally Posted by Shaggy Sheep Driver
But as I-42 pointed out, the destructive rotor which caused the accident only exists at or below the height of the mountain, unlike the wave (indicated by the lenticulars) which can be many times summit height but is non-destructive.
Such a tragic accident.

Just looking at my glider logbooks. I see a number of flights over 10000' msl in waves from the low ridges of the central and northern Appalachians. I often noted the turbulence as well in my logs. Some of these flights were from airports where the upwind ridges are no more than 1000' above valley level (typically 600-800 msl on the airport).

Very familiar (and satisfying) experience to be working the ragged lift of the turbulent zone well above ridge level, and then climbing into the laminar wave.

Could be the poster quoted above is correct about the rotor zone. I'm not sure if this turbulence I've flown in is strictly "rotor" or how it occurs. I'm just offering a PIREP that it's there, well above the height of the peaks, and wondering about its mechanism...
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Old 22nd Mar 2016, 08:02
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Rotor and wave.
Some excellent posts but I would like to add a bit more.
I have hiked Mount Fuji and flown over her. I have also soared three conical mountains.
The first, Hongorie, in the Alp maritine and in a glider.The second south of Auckland when my paraglider instructor imprudently threw me off in an El Nino year when everywhere else was blown out and the third is Sugar loaf in the Wicklow mountains last week.
India 4 2 posts are highly informative and Sugar loaf acted exactly like the Von Karman link on the windward face with the flow oscillating. Sugar loaf is a Marilyn, steeper than Fuji and in a 16 kph pressure gradient flow I was able to soar 150ft above the 660ft mountain - my paraglider has a sink rate of 1m/sec.
Similarly I was able to gain around 50% of the height of the NZ hill in a 30 kph wind (mind you my sphincter was going sixpence - half a crown at a great rate of knots).
Bearing in mind the relatively low Reynolds numbers the airflow over a conical mountain is influenced up to 50% of its height.

Rotor.
As shown in I-42 link it moves and can gallop off downwind...I would imagine there is a ducting effect with it bouncing of inversions.
I have flown in rotor many times and it's best described as being in a tumble dryer. My first trip in the Pyrenees had me spending around 9 hours over four days trying to climb into the wave system.
I had two unpleasant experiences - one where I was knocked unconscious during a transit of the Durance valley on a light wind day...I came too with the undercarriage hanging out and the airbrakes extended. The other was near the Cape gliding club where I found myself inverted at 200ft. There are several members of the club who have managed to put their head through a canopy - one twice.
It was suggested the Steve Fossett crashed due to rotor.
I have also seen a down burst in the lee of Tenerife which terminated 6ft above the road on a day when the wind was blowing force 6.
But I have flown on the lee side of the mountain in a Mistral less than a wingspan away from the southerly face - a technique taught by some of the best french glider pilots - one has to just stay very close and put on a thinking hat as to how and where to leave the lee.
Bergerie would probably remember the loss of a 747 skipper who died in Spain - Vic was one of the few guys who really loved flying and had started hang gliding in the mid 70s when we were both in BEA. He transitioned to paragliders in the mid 90s and was blown back into the rotor above take off at an altitude of 200ft where his wing had a series of collapses (I contacted the investigator). The point of this observation is that the rotor extends practically vertically above the leading edge. I have also witnessed a 200 ft plume of spray above the cliffs of Mohar.

WRT to wave for the curious.
The bars are stationary and parallel with the feature that sets them off. They aren't necessarily at right angles to the wind. I have had a difference of 80 knots on beats soaring the leading edge.
Two features will react similarly to a light interference pattern - the lift can cancel itself out or augment the climb - there is a hotspot over the A1 south of Sutton Bank.
Wave can also be set off by wind shear and there is a theory that cloud streeting is indicative of a sheer wave system. I do know someone who has soared above one side of a street.
I flew yesterday Sleive Gullion which is a part of the Ring of Gullion - either a weathered volcanic ring dyke.
Geology ? Ring of Gullion
In a NNE wind the lower edge throws off a rotor which can make flying interesting...rather curious as it's virtually an edge to a plateau and it's the downwind lip that throws off the turbulence and also forms a wave above the rotor.
To sum up rotor extends far further than many imagine and it can be bloody rough.
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Old 23rd Mar 2016, 12:26
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bp,

Your post was a graphic illustration of how turbulent rotor can be. Scarier events than I have ever experienced. Also, very interesting observations about "conical" mountains.

My experience with rotor has been exclusively at or below the mountain tops. All my wave flying above the tops (up to FL240), has been in completely smooth conditions. I asked a glider pilot friend of mine who is also a commercial pilot, about his experiences and how the autopilot manages in wave conditions. He sent me an extensive, very interesting reply, which I am quoting, with his permission:

Wave effects are quite noticeable. One of the big surprises of jet flying was how often we do see wave, and how widespread it is. Wave caused by strong wind over T-storm lines can be run into every month of spring, summer, and fall. None of the pilots I fly with, recognize the name Cowley [ed. known to glider pilots as "Canada's Diamond Mine"], but everybody knows where I am referring to, if I mention the speed bump on the way from Vancouver to Winnipeg. We often see wave around Thunder Bay, also. Sugarbush is a good place to see wave. I have seen lenticulars over every province, and territory, except maybe PEI.

The effect of wave is two fold - wave and turbulence. We don't see much turbulence due to wave - besides climbing/descending in and out of Calgary. Most turbulence is wind shear generated by the jet stream, although we can get some interesting interaction when a jet stream over-runs wave activity.

The autopilots maintain an altitude hold and the auto throttles maintain a Mach or IAS hold. The autopilots are very assertive about altitude, but the auto throttles are very damped. If I'm too busy to look at the airspeed in some situations, I will just start to push or pull the throttles in the opposite direction to the one they are trying to drive to.

A consideration for most jets is that we run very close to Mmo/Vmo. The other night we were showing an airspeed of 253 kts at 37,000', Vmo was 266 kts, and the stall buffet warning (the speed at which a "g" loading of 1.3 would stall the aircraft) was 231 kts. So, 35 knots between stall and over-speed warnings. At the first feel of the aircraft rising, pilots will put hands on power levers and at 5 knots or so will start adjusting the power, depending upon the rate of acceleration. Excursions of 7 knots or greater will usually see us reset the target speed to the middle of the band. The autopilot will usually hold within 100 feet. If the airspeed excursions start getting greater, we advise ATC and start flying attitude accepting the deviations to moderate the airspeed excursions. Maybe once every year or two, the excursions can be +/- 600' with speed changes of +/- 10-15 kts. The most extreme event I am aware of, was when a friend of mine ran into wave at Cowley and ended up 1600' above initial cruise of FL410 while “sharply" reducing power, and still getting the occasional over-speed alarm.
In a follow-up, I asked him about what altitudes he has experienced rotor turbulence, relative to the mountain tops:

Rotor turbulence will be significantly below the tops of the lenticulars of course. As a rough rule of thumb - coming into Calgary I figure when wave is possible - if it is smooth above 14,000' it will likely be rough below, if it is rough above 14,000', often it is smooth below. And it is a rapid transition from smooth to rough - rarely over 500' vertically. So that is 4-5,000' above the ridgeline tops. Driving further east past the foothills at 16,000' before letting down over the flat land (10 nm) will almost always avoid the majority of the rotor, unless the tertiary lennies are in serried ranks east of Calgary.

There are very interesting theories about the behaviour of single mountains vs ranges in wave conditions - with vortices/and all sort of singularities being identified - but the common thread is a narrow lift band and greatly disturbed flow up to near the heights found along ranges.
Finally, with reference to the Mt. Fuji accident, he made this observation about the relative strength of jets, compared to the towplanes we both fly:

The vertical "g' limits for certification in the transport category are (to a little airplane guy) frighteningly small, being just +2.5 to -1.0, compared to the +3.8 to -1.52 Normal category, and +4.4 to -1.76 Utility category. Both the 182 and Scout are certified Utility category at reduced weight. (Flaps down is +2/-0, but that's the same for pretty well all aeroplanes).
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Old 23rd Mar 2016, 14:38
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BCal had a severe turbulence incident in mountain wave/rotor conditions over the Andes. You can read about it here:- BCal Flight over the Andes 1

They were very lucky.
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Old 23rd Mar 2016, 18:32
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India 4 2... 100% behind your post.
My first experience with wave over the Alps heading South when I was extremely wet behind the ears...I went out to answer the call of nature and when I sat back down noticed the speed was low...added a touch of power and looked at the Doppler map and my nav log...next second over speed alarm went off - only time I heard it on the Trident (but not so on the DC9 with ex Luftwaffe starfighter guys).. I yanked open the airbrakes as per our SOP...complete over kill...supposed risk of tuck under.

Only used the Turb mode on the DC10 with one of those "heros" one occasionally get who dispite Shannon warning us that everyone else had descended below FL300 on the Nat Tracks we had to go through it cause the yanks are whoosies...

Hit the button which disconnected the auto throttle and the FD went into pitch attitude hold mode...both "sir" and engines kept switching the A/T back on...didn't even understand the basics.

The glider I got knocked out was a Phoebus C built by one of the Atafliegs...stress loaded to 12G and the first production glass glider..42:1 which flew the first 300km flight in the UK.
Sadly some of the modern microlight gliders aren't so well built as was at Coupe Icare when one folded and lost a very good mate ex French and American carriers when he had a wing fold near Gap.
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Old 6th Aug 2016, 07:10
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Does anyone know the source of the picture of PFE coming down? I know it was in Macarthur Job's book but it looks as if it must have been taken by someone local who had his/her camera to hand. I ask because I want to trace the copyright holder to see if I can get permission to use it in a book I am writing.
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Old 9th Aug 2016, 12:45
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Blind pew.
I have experienced high altitude rotor over the Pyrenees in an airliner and it was not funny at all.
Started at FL380. Climbed to 390 at Mmo/ idle power, followed by loss of I think 5000' with full power and intermittent stick shaker.



It was over a waypoint called TURBO. I guess there was a clue there, had I only known it.....

Strong northerly Jetstream of about 90kts.

It damaged the aircraft fin cap and scared us both ****less.

Luckily ATC warned us of 'Windshear' over the mountains, so we'd buttoned up the cabin. Was quite a ride though and it seemed to go on for ever.

I let the FO fly it!
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