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Air France crash at YYZ (Merged)

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Air France crash at YYZ (Merged)

Old 8th Aug 2005, 10:22
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Braking Power vs. Friction Coefficient

I suspect the deceleration will break down into a number of performance phases.

The major division will be between wheels sliding over water and wheels with grip on pavement. Friction coefficients may not be constant in either case.

Antiskid effects once pavement grip was obtained requires elucidation.

There may be an intermediate phase where the rear axles were on pavement while some of the fronts were not. What kind of braking modulation between axles is available in that case and would the couple tend to lift the rear axle?

Superimposed over that will be reverse and spoiler effects -- a big question being just how much of either was applied in the cockpit and obtained from the machinery.
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Old 8th Aug 2005, 10:42
  #402 (permalink)  
 
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Still very confused about where these "bystanders" or others may have come in. Is there a detailed boundary map anywhere? Either the a/c landed within the perimeter fence, in which case it should have been tricky for anyone to cut through it in either direction, or it crashed (sorry, can't find better word) through it.

I'm very interested in the discussion about over-runs, and have started a new thread in airports, airlines and routes (hope that's right place), to cover whether these should be applied to all busy airports, not just YYZ?

And lawyers may also be "fellow professionals", but this $62m compensation claim seems a little far fetched. As commented on earlier, it seems almost "cheaper" to have fatalities in these accidents.

Can I now sue this law firm for the stress that I, and millions of other passengers, may now have to experience every time our planes might now get diverted because of a few drops of rain falling on the runway surface?

Can those other 308 passengers and crew, who are presumably extremely grateful to be both alive and uninjured, also sue this law firm for the trauma that they must now suffer by having to potentially replay these events over and over again, presumably under cross examination in a court room?

Last edited by jabird; 8th Aug 2005 at 11:06.
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Old 8th Aug 2005, 12:14
  #403 (permalink)  
 
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one of those "bystanders" name is guy ledez, works for a company that rents out cars to the airport / airside and was handed from one tv station to the next after the crash... sounds pretty unbelievable but apparently confirmed by several accounts.

http://fullcoverage.yahoo.com/s/ap/2...ane_crash_hero

kind regards
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Old 8th Aug 2005, 12:21
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The more that PPRuNe's genuine, fair and reasonable contributors become engulfed and swamped by the speculative rantings of those who just want to slag off other professionals, the more likely it is that readers will turn away from PPRuNe and towards the aviation press in order to find authoritative, non-sensational information - without the amateurish cr@p.
Not really, the curious among us know that there is no way the press will have more than pure speculative talking heads in the first days follwing an accident. While by reading PPRune you will at least have a chance to sort out some good ideas and investigative considerations from the amatures wanting to be first to guess at the probable cause.
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Old 8th Aug 2005, 12:29
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Not really, the curious among us know that there is no way the press will have more than pure speculative talking heads in the first days follwing an accident.


That's why I said the "aviation press", not the mass media - who, granted, tend to go overboard with speculation.
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Old 8th Aug 2005, 12:39
  #406 (permalink)  
 
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The plot thickens:

"Ledez and the other man met up with the pilot and other passengers and ran to safety by Highway 401, Canada's busiest freeway, where they were met by emergency officials."

OK, maybe Ledez was originally on the service road, but apparently, he, the pilot and other passengers managed to get to Canada's busiest freeway.

So... where was the fence?
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Old 8th Aug 2005, 12:48
  #407 (permalink)  
 
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Mangled in the undercarriage of the aircraft I suspect.
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Old 8th Aug 2005, 12:52
  #408 (permalink)  
 
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The word within Airbus suggests that the cause of the event was the knob on the end of the sidestick.
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Old 8th Aug 2005, 13:16
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If the rain had just moved in, the runway surface could well have been more oily than wet.

The top part of pavement is full of petroleum-based products, mostly microscopic bits of tyres. When it first rains after a dry spell, those oily bits of petroleum float on the surface of the just-fallen rain, and that is when a paved surface is the most slippery. This is particularly true on those areas where the tyres are accelerating, decelerating, or turning (because thet's where they shed the most rubber). After it has been raining for a few minutes, the water/oil ratio grows large enough to eliminate the oil surface, and it's just a question of a wet surface.
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Old 8th Aug 2005, 13:20
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Somebody already mentioned it in this thread. The Lufthansa A321 runway overrun in Poland comes to mind considering the circumstances. Approach in rain and relatively strong and gusty winds, touched down pretty late and pretty fast.
Does anybody have the accident report on this, since I do not remember the details.
The only thing I remember is that either thrust-reversers or breaks or both could not be used for a critical perioed of time since with flap setting three (which was used for landing) a necessary precondition for their usage was not fullfilled (not enough weight on the main landing gear if I am not mistaken).

Anyway, would be grateful if somebody could find the report.
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Old 8th Aug 2005, 13:26
  #411 (permalink)  
 
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Report on the Accident to Airbus A320-211 Aircraft in Warsaw
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Old 8th Aug 2005, 13:51
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Now I know it's not a great way of stopping an aircraft, but the ravine did stop the Airbus from carrying straight on across a crowded highway.
No it didn't. As has been pointed out before on this thread, the highway runs almost parallel to the runway. The extended centreline of the runway does not intersect the highway until about 1km away. No over-running airliner is going to plough on that far. ( Overhead picture )
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Old 8th Aug 2005, 14:33
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Thanks ACL1011 that helped refresh my memory.

Quote from the report.

"The aircraft automatics comprises, for basic landing configuration if the
aircraft (i.e. with flaps extended to FULL position), the programme which
subjects actuation of all braking devices to some specific conditions. Ground
spoilers, when selected, will extend provided that either shock absorbers are
compressed at both main landing gears (the minimum load to compress one
shock absorber being 6300 kgs), or wheel speed are above 72 kts at both main
landing gears. Engine reversers, when selected, will deploy provided that
shock absorbers are compressed at both main landing gears.
Such a logics result in the lack of possibility of immediate actuation of two
mentioned above aircraft's braking devices without meeting the conditions
described."

Does anybody know if this sytem design has been changed in newer Airbus acft.

I think following this accident Airbus and LH agreed to change the landing gears of the 320s. The new type apparently required reduced load on the shock absorbers, if my memory serves me right.
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Old 8th Aug 2005, 16:33
  #414 (permalink)  
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Now I know it's not a great way of stopping an aircraft, but the ravine did stop the Airbus from carrying straight on across a crowded highway.
If you read through the thread, this was discussed in some detail. Both from the point of view of the extended centre line and that if the ravine was covered by a bridge, then that could support an overrun speed reduction system. Links to one manufacturer were posted.
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Old 8th Aug 2005, 16:55
  #415 (permalink)  
 
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To: greek-freak

From the report (aircraft landed in config full):

" B. Aircraft
1 The aircraft was serviceable and all it's basic documents were up-to-date and valid.
2 The aircraft was loaded within it's operational limits.
3 The aircraft automatics comprises, for basic landing configuration if the
aircraft (i.e. with flaps extended to FULL position), the programme which
subjects actuation of all braking devices to some specific conditions. Ground
spoilers, when selected, will extend provided that either shock absorbers are
compressed at both main landing gears (the minimum load to compress one
shock absorber being 6300 kgs), or wheel speed are above 72 kts at both main
landing gears. Engine reversers, when selected, will deploy provided that
shock absorbers are compressed at both main landing gears.
Such a logics result in the lack of possibility of immediate actuation of two
mentioned above aircraft's braking devices without meeting the conditions
described.
4 In emergency, the crew is unable to override the lock-out and to operate
ground spoilers and engine thrust reversers. "

and

" 4.2 For A320 aircraft manufacturer

4.2.1 Possibility should be analysed to introduce the emergency use of ground spoilers and thrust reversers independently of meeting the criteria imposed by aircraft logics.

4.2.2 The possibility should be considered to modify the thrust reverser system to enable use of more than 71% N1 in the emergency. "

--------------------------------------------------------------------------------

I believe that in config full manually selecting spoilers on landing will have no effect but in config 3 there will be extension of the flight spoilers.

Caveat emptor.

Last edited by Tree; 8th Aug 2005 at 18:03.
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Old 8th Aug 2005, 17:14
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Fence lines

I have looked at YYZ site maps, and as far as I can tell (some of the maps are a little hard to interpret), the aircraft would have crossed unpaved ground, then the 'South Service Road', then the primary security line fence, then more open ground, then the public road leading to the Infield Cargo Area (and Control Tower and other facilities), then stopped in the ravine.

There would be about 250 m of cross-country travel (i.e., 250 m if the ground were level) required to cross the distance between the freeway (Highway 401) and the crash site, and yes, there should be a chain-link fence at the edge of the airport property -- but this would be a 'non-security fence'. The public road inside the airport property would have been much closer, but would have much less traffic than the 401.

I suppose those people who did cross that outer fence got over it or through it the usual way -- they climbed it. I emphasize again that this would not have been the primary security line fence, since it was separating the highway right-of-way from a publicly-accessible portion of the airport property, so this may not have been too difficult for the physically-fit and adrenaline-charged.
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Old 8th Aug 2005, 17:16
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Could anyone check out this very complicated piece of arithmetic :

2500m-1200m=1500m

How can anyone in his own mind hope to stop a large aircraft on a wet runway with that little concrete left ahead ??
The aircraft was working fine. You put the sucker down on the mark or go around. End of story.
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Old 8th Aug 2005, 17:55
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Maybe a good juicy boeing arrival would have helped dissipate the remaining 79 kts and not one of those gay french touchy feely touchdowns that the big airbusses seem to do. Just a thought, and maybe not as daft as it sounds. Other wise no excuse really , probably an ego issue when all is said and one.
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Old 8th Aug 2005, 18:14
  #419 (permalink)  
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wallabie, old jumper.
That's what you HAD to do at LCY and there could be some really weird winds around those tall buildings.
regards from Absinthium.
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Old 8th Aug 2005, 18:23
  #420 (permalink)  


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PaxBoy

Thanks for the update. I frequently have to sufer a p1ss-poor internet connection (would you believe 16.8kb/s with frequent disconnexts!) so with nearly 30 pages I missed that.

When I get a bit of time free at the office I'll look through to find that info,

Cheers
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