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SAS Q400 gear collaps CPH 27/10

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SAS Q400 gear collaps CPH 27/10

Old 5th Nov 2007, 00:43
  #221 (permalink)  
 
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Hmm, a quick read of the prelim report on the O-ring makes me suspect that it would make William of Occam turn in his grave.
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Old 5th Nov 2007, 01:56
  #222 (permalink)  
 
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Lomapaseo,
Razors could be in short supply.
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Old 5th Nov 2007, 09:21
  #223 (permalink)  
 
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SAS to ground all Q400's?

http://www.abtn.co.uk/SAS_grounds_all_Q400s
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Old 5th Nov 2007, 11:06
  #224 (permalink)  
 
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aces low

Come on, catch up old boy!
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Old 5th Nov 2007, 11:26
  #225 (permalink)  
 
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Does anyone know what SAS are using at the moment to cover the Q400 routes?
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Old 5th Nov 2007, 11:46
  #226 (permalink)  
 
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Welcome to the thread, aces.
Better late than never.
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Old 5th Nov 2007, 12:36
  #227 (permalink)  
 
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I'm not a Q400 driver, but it seems to me that the overall design of the Q400 landing gear leaves something to be desired.
How is it that on three different occations something has disabled both the primary AND the alternate gear extension? This gear extends forward, into the wind, and presumably needs hydraulic pressure to extend?
Where is the redundancy when a small O-ring can cripple both systems?
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Old 5th Nov 2007, 12:52
  #228 (permalink)  
 
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How is it that on three different occations something has disabled both the primary AND the alternate gear extension?
It didn't. The gear extended properly on both the 1st and 2nd accident but didn't lock down on the starboard side. On the 3rd occasion there was something there that shouldn't have been (the O-ring), causing the system to malfunction and the starboard gear failed to deploy.

The most reasonable cause at the moment looks like a badly designed actuator on early Q400 aircraft causing accident's #1 and #2. With accident #3 caused by poor maintenance procedures and/or fitting of the new actuators.

SAS should have waited on the outcome of the 3rd accident before making their decision on the Q-400 which in hindsight looks like a mistake. Flybe's response was certainly well thought out and proper.
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Old 5th Nov 2007, 13:59
  #229 (permalink)  
 
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Sorry chaps...only took 12 pages for me to get the drift. I'm improving
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Old 5th Nov 2007, 15:07
  #230 (permalink)  
 
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You're right MP, but a free fall design would have taken care of scenario # 3.
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Old 5th Nov 2007, 15:22
  #231 (permalink)  
 
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the alternate extension is free fall!!
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Old 5th Nov 2007, 15:29
  #232 (permalink)  
 
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Do any aircraft have an actual "freefall" backup? Are the hydraulic actuators disconnected from the MLG in such a design?
If not, the gear wouldn't drop if the actuator was unable to both push oil out in one end, and draw oil in on the other end...
That's what valves are for, and if valves fail or gets blocked...
Well... That's what started this thread, isn't it...?

An actual freefall design would probably prevent all three accidents, as the MLG did freefall on the first two accidents, but it didn't lock..
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Old 5th Nov 2007, 15:46
  #233 (permalink)  
 
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bartender--the gear in the first two incidents did basically free fall as the acuator wasnt attached and look what happened!! it went right through the centre and tried to carry on but something had to give and lock it couldnt, cause it had nothing to lock to!!!
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Old 5th Nov 2007, 16:03
  #234 (permalink)  
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Does anyone know what SAS are using at the moment to cover the Q400 routes?
I have heard they are looking for DHC-6 Twin otters , as those are the only ones that will satisfy the current "gearmania" in certain spheres....
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Old 5th Nov 2007, 16:10
  #235 (permalink)  
 
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bartender--the gear in the first two incidents did basically free fall as the acuator wasnt attached and look what happened!! it went right through the centre and tried to carry on but something had to give and lock it couldnt, cause it had nothing to lock to!!!
Because it wasn't designed to freefall in the first place...
My point is, that calling alternate extension for "freefall" is at best an exaggeration, as:

A) It relies on valves to let the oil vacate the actuator in one end, and let oil (or any fluid for that matter) to enter the actuator at the other end.

B) It relies on the components listed in A to provide a dampening to prevent the mechanism to tear the locks apart at the end of the cycle..

As i understand it, on the last accident, "A" failed, and on the two first accidents, "B" failed...
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Old 5th Nov 2007, 16:12
  #236 (permalink)  
 
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Will SAAB start up the 2000 line again?

How long will it take for SAAB to start up the 2000 line again? This was a plane that was about 3 months late to market and got killed by the RJ from Bombardier.

Maybe the Scandianavian Airline System needs a Scandinavian airplane?
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Old 5th Nov 2007, 16:36
  #237 (permalink)  
 
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MP:

With accident #3 caused by poor maintenance procedures and/or fitting of the new actuators.
Maybe, just maybe, you're jumping slightly ahead of the Danish NTSB here. They haven't finished their investigation yet regarding who caused what, and you shouldn't speculate, if you consider yourself an aviation professional.

SAS should have waited on the outcome of the 3rd accident before making their decision on the Q-400 which in hindsight looks like a mistake. Flybe's response was certainly well thought out and proper.
SAS didn't make their decision based on the safety of Q400. They haven't questioned the safety. But they care about the brand "SAS" in the eyes of the costumers, and after 7 years of more or less lousy technical reliability, followed by 3 accidents in app. 1 month, they have come to the end of the road. Where do you suggest they draw the line, if not here?

Flybe, mind you, have NOT had 7 years of lousiness followed by 3 accidents, so no wonder, their costumers have a different view on Q400 than SAS'.

It's not THAT hard to put yourself in SAS' shoes, if you try just a little bit.
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Old 5th Nov 2007, 17:26
  #238 (permalink)  
 
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It's not THAT hard to put yourself in SAS' shoes, if you try just a little bit.
Not a problem at all but considering the latest press release below, they are indeed ill-fitting shoes
Aviation regulator clears Dash 8 of design flaw
Cologne, Germany - European Union aviation regulators said Monday they had found no evidence of a design flaw in the Dash 8 turboprop passenger aircraft. Scandinavian airline SAS Group decided last month to completely stop using its fleet of 27 Dash 8 planes, also known as the Q400 and made by Bombardier of Canada, after their landing gear collapsed three times.
But the European Aviation Safety Agency (EASA), which has its offices in the western German city of Cologne, said there was no proof this had been caused by any error of the manufacturer.
An EASA spokesman said the decision by Denmark, Sweden and Norway to cease use of the Dash 8 had created an "unsatisfactory situation" where three nations were temporarily out of line with the rest of the 31 EASA member nations.The Scandinavian nations acted last month after an outcry in the media and among politicians over the crash landings, in which one wingtip fell onto the runway and passengers and crew were shaken but not seriously hurt.
Preliminary reports from the first two such incidents in September said the accidents were believed to have been caused by corrosion of a bolt that secures the landing gear in a hydraulic cylinder.
http://www.earthtimes.org/articles/show/136536.html
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Old 5th Nov 2007, 17:53
  #239 (permalink)  
 
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Severe CAVOK, you have mis-quoted me there, what i said was:

The most reasonable cause at the moment looks like a badly designed actuator on early Q400 aircraft causing accident's #1 and #2. With accident #3 caused by poor maintenance procedures and/or fitting of the new actuators.
If you have a look at preliminary reports you will see that the O-ring should not have been there at all.

SAS didn't make their decision based on the safety of Q400. They haven't questioned the safety.
Of course they have questioned the safety. Otherwise they wouldn't have stopped flying them. Agreed, they had to do something because of the bad publicity being generated but it was done off the back of the final accident which at the moment doesn't look like it is Bombardiers fault. If anybody has "jumped ahead" of the AIB report, it's SAS.
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Old 5th Nov 2007, 19:03
  #240 (permalink)  
 
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bartender--the gear in the first two incidents did basically free fall as the acuator wasnt attached and look what happened!! it went right through the centre and tried to carry on but something had to give and lock it couldnt, cause it had nothing to lock to!!!
Is it positively known that the eyebolt ripped out of its threads already at gear extension, in the first two accidents? Or is it possible that it did not happen until the actual touchdown?

Just wondering, because I haven't seen this mentioned before and initial reports seemed to indicate the gear looked to be in its normal down position.

I'm certainly no expert on the Q400 landing gear, but it would seem possible that the wind pressure may actually cause a compression force on the actuator all the way during gear extension, keeping it in one piece. Pls correct me if I'm wrong
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