Further info on the free-flying fan...

Further info on the free-flying fan...

Joined: January 11th, 2016, 8:57 pm

April 14th, 2017, 1:31 am #1

The ATSB have released the preliminary report on the SAAB 340 propeller that got lost near Sydney. Looks like corrosion pitting in one of the flange dowel pin holes started a fatigue crack that ultimately broke the flange drive shaft at the gearbox bearing and released the fan. Most of the flange was still attached to the prop when they found it, but they removed it before transporting the prop so the flange wouldn't get damaged any further, hiding the root cause of the break. See:
http://www.atsb.gov.au/publications/inv ... -2017-032/
for words and pictures....
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Joined: September 11th, 2014, 4:45 pm

April 15th, 2017, 10:53 am #2

Finding out that something went bad on an aircraft that you maintained is no fun.
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Joined: August 16th, 2016, 11:47 am

April 15th, 2017, 11:26 am #3

But, an inspector isn't.

Don't they have a teardown and inspect cycle for this equipment?

I'll bet they get one if they didn't have one, or the time gets shortened if they have one now.
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Joined: November 19th, 2014, 12:50 pm

April 15th, 2017, 5:33 pm #4

Inspection was current and assembly was done properly. This is the only known failure of this kind on that particular gearbox.

GE is looking into it.
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Joined: January 11th, 2016, 8:57 pm

April 15th, 2017, 10:53 pm #5

One-off faults DO happen. Remember United 232 Heavy, the L1011 that crashed at Sioux City, Iowa, in 1989 when the 8-foot diameter front 'fan' on its center engine threw apart? That engine 'explosion' was ultimately traced back to a flaw the size of a grain of sand (.055" x .015") in a 370 pound titanium casting. The flaw had existed for over 17 years before it finally let go. There were two different tests to check for such flaws, but this flaw was apparently too deep for dye penetration tests to detect it, and too shallow for the ultrasonic test to detect it....

Statistically, such things are off the charts - a one in a billion occurance. Sometimes, though, shit happens, no matter what you do.

https://en.wikipedia.org/wiki/United_Ai ... Flight_232
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