Re: Qantas 737s in a pickle
Posted: 03 Nov 2019, 18:28
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As I understand the NG's anatomy , the pickle forks are actually on both front and rear spars, 4 per aeroplane. The cracks have been found, as I understand it, only on those securing straps holding the pickle forks on the rear spars . The front spars, which do not carry the same dynamic loads from the main gear on landing , do not seem to have been affectedChris Trott wrote: ↑03 Nov 2019, 12:25
The pickle fork structure is attached the front spar, not the rear. Also, my understanding is that it's a secondary "load relief" structure designed to help keep the fuselage located on the wing center section, thus why the repair isn't a major concern (i.e. immediate grounding). The other thing that I don't think has been determined is why these cracks are being found. There is some chatter that these cracks are actually from undetected or improperly assessed heavy landings as the most likely way to get a crack like this is the airplane's nose to be "slammed" down which could stretch the attachment, leading to a crack in the saddle.
I believe the original testing was done on wings without winglets. Conceivably these could increase the bending moment by improving the performance of the outer portion of the wing.Chris Trott wrote: ↑05 Nov 2019, 13:59Personally, I'm most interested in finding out if they discover why they're cracking at 1/3 of their life span. Heavy landing or not, having a part crack that early in its life is kinda odd, especially (as Juan said) the original testing showed they should make it well beyond 90,000 cycles before any issues.