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SWISS LX40 [ZRH-LAX] diversion to Iqaluit

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SWISS LX40 [ZRH-LAX] diversion to Iqaluit

Old 12th Feb 2017, 23:10
  #221 (permalink)  
 
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Originally Posted by ATC Watcher
Super cold metal = another challenge is to unscrew fastened bolts torqued at or near standard temp I would say.
Sorry to be pedantic, because you have a good point.
It's just that you seem to have it around the wrong way; or so I think!

The difference in the coefficient of linear expansion for steel fasteners versus aluminium / magnesium alloy components probably means that removing bolts could actually be a little easier than at "normal" temperatures. Though there may be some "clamping" effect of aluminium alloy onto threaded fasteners.

However the inverse applies for tightening. And, at such low temperatures, you will also be entering the realm of ductile-brittle transition for some steel alloys. It is probably not so much of a problem for aluminium alloy under compression but fasteners under tension may well be affected, depending on the steel alloy used. Probably not a problem at all for any titanium alloys used.

Correct tightening values for fasteners at such low temperatures would (or should) certainly have been a consideration for this exercise.
I'm guessing that a re-torque later with everything at more normal temperatures would be on the cards.
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Old 23rd Feb 2017, 16:07
  #222 (permalink)  
 
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This press release from Antonov answers a couple of the questions asked earlier in the thread: Antonov Airlines transports world's most powerful turbofan engine to grounded aircraft in Canadian Arctic
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Old 24th Feb 2017, 01:05
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HB-JND, a Boeing 777-300 aircraft operated by Swiss International Air Lines, was conducting flight SWR40 from Zürich-Kloten, Switzerland (LSZH) to Los Angeles Intl, CA (KLAX). During cruise flight approximately 288 nautical miles North West of Iqaluit, NU (CYFB), the flight crew declared a Pan Pan due to the left engine (GE90-115B) shut down and requested a diversion to CYFB where it landed without further event at 2003Z with ARFF on standby.

After landing, the aircraft got trapped in the turn around bay of the threshold of Runway 16. The runway was closed by NOTAM until the aircraft was towed at 2110Z.
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Old 27th Feb 2017, 06:40
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Originally Posted by WingNut60
Sorry to be pedantic, because you have a good point.
It's just that you seem to have it around the wrong way; or so I think!

The difference in the coefficient of linear expansion for steel fasteners versus aluminium / magnesium alloy components probably means that removing bolts could actually be a little easier than at "normal" temperatures. Though there may be some "clamping" effect of aluminium alloy onto threaded fasteners.

However the inverse applies for tightening. And, at such low temperatures, you will also be entering the realm of ductile-brittle transition for some steel alloys. It is probably not so much of a problem for aluminium alloy under compression but fasteners under tension may well be affected, depending on the steel alloy used. Probably not a problem at all for any titanium alloys used.

Correct tightening values for fasteners at such low temperatures would (or should) certainly have been a consideration for this exercise.
I'm guessing that a re-torque later with everything at more normal temperatures would be on the cards.

Retorque. .. nope, that isn't happening.
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Old 28th Feb 2017, 00:17
  #225 (permalink)  
 
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Just asking ... you seem to suggest that you know emphatically that this is not happening - as compared to just thinking that it probably won't happen.
If so, can you offer an opinion about why a re-torque is not considered necessary, in this case?

Not a problem, re-torque or not, provided the low temperatures were taken into account and the installation procedures adjusted, if necessary.
And, every chance that it was not even necessary. But it should have been a consideration.

In any case, any necessity for re-torque would only apply to fasteners used during the engine change and installed at non-standard temperatures.
Other considerations would be any "stretch bolts or necked fasteners" that are normally torqued to or even exceeding yield, though these are usually single-use fasteners anyway.
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Old 14th Mar 2017, 17:27
  #226 (permalink)  
 
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The whole story in laymans' terms - well done too:
Replacing the World's Largest Jet Engine at 40-Below
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Old 14th Mar 2017, 17:43
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Re-torque

Re-torque after extreme cold maintenance?

My estimate is that for the work done in the inflated bubble, or the hangar (they claimed 10C/50F was maintained), no special treatment required. This is good because these bolts and studs (QEC & LRUs) are loaded in tension and are more critical.

Anything done on-wing in the cold will have more items that are shear-loaded, less so tensile, and thus less influenced by the cold when wrenched.
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