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red750

Qantas urged to ground all 737's

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13 hours ago, Bruce Tuncks said:

I reckon that to denigrate litespeed for not being a lame is dead wrong. I know a really stupid lame, and it annoys me that the qualification is grossly over-regarded.

If I had my way,  the Standards lot  would be able to give and take qualifications based on testing.  I bet litespeed would beat lots of lames.

 

Thankyou, that is appreciated.

 

I never want to make those with greater qualifications or any, think I am deriding their knowledge or experience.

 

I am just looking at it from a I treated bystander perspective.

 

What I see I do not like. I agree cracks happen but this is a still major safety issue.

 

Given the number of effected airframes with even low hours been detected, my argument stands.

 

All should be grounded for inspection regardless of hours. They claim only a half day to inspect- so just do it.

 

No crack- no problem, check again in 500 cycles.

 

To wait till it is a Boeing mandated cycle number is asking for trouble and a number derived at by profit not safety.

 

It is not my intent to flame every aircraft with a crack. But when the manufacturer has a big reputation for been dodgy, non compliance and fraudulent paperwork, fake parts etc.

 

The concern is warranted.

 

Yes, parts can be repaired, but I still contend the special nature if the part, its shape and the placement of the cracked fastener make a proper repair difficult. It is not a flat simple surface.

 

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Who is/was Sainty.?  We can blame the bureaucracy, but the PUBLIC demand an accountable reliable system of required qualifications for many specialised operators  like electricians and I wouldn't like to see that just ignored. If it's knowledge based it won't be bought or depending on a favour from a mate. No harm in having a strong reliance on "practical" ability and experience, but we will always need proper accreditation processes and encourage  on the job updating as well Nev

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The problem with proper accreditation processes is that complete idiots can become accredited and other fully capable people do not try to become accredited.

In my last few years at work I took delight in failing accreditation exams only to be awarded the accreditation because failure was not allowed. As far as LAMEs go they mostly seem to be competent and look good compared with electricians and plumbers, also civil engineers.

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I am all for proper testing and accreditation with compliance of the rules been the norm.

 

It is the ability to be dodgy by bending rules or plain ignoring them, that have Boeing in this situation.

 

The effectual regulation gap in the USA  is so big Airbus could fly a A380 through it.

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 The FAA are equally to blame for the CURRENT situation with BOEING where profit has been placed ahead of Quality  Assurance and self regulation been a dismal failure. Ironically the damage from this may ruin the company which has been in the past the  pretty much leader of making "Good" aeroplanes in the world but has absorbed the internal competition and been spooked by Airbus' increasing sales, to put the emphasis in the wrong places. Cost cutting, regardless. Nev

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Four doors down from my place.

 

Now just a mechanics of slow cars.

 

Dainty was the quintisential Aussie creative engineer.

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At least it shows what they look like and where they are and sort of what they do. It's the same area where Fokker F 27's used to crack but they just had reinforced rings(semi Bulkheads to do the same job.. and the wings were above not below.. Nev

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9 hours ago, facthunter said:

At least it shows what they look like and where they are and sort of what they do. It's the same area where Fokker F 27's used to crack but they just had reinforced rings(semi Bulkheads to do the same job.. and the wings were above not below.. Nev

They would have been in tension then, not compression.

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The Fokker has no sweep back which very much complicates the issue with twist  on the Boeing but the job is to transfer the loads from the wings and distribute them to to the fuselage. in both cases. It's cycling loads that produce stress cracks. and not just in flight.  Nev.

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Of course, that makes sense - so on landing the direction is reversed in both cases.  (High wing goes from tension to compression, low wing from compression to tension).

 

So in the long run the forces creating the stresses are pretty much the same.

 

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The wheels are usually attached to the wings (except for Hercs ,747's and such). You can resolve the stresses in both instances and engineer/ design it appropriately and use the right materials but usage patterns and manufacturing variables can affect life of structure outcomes or the design analysis may have slightly miscalculated on the extent of  some the loads encountered in use. The initial flight testing of the B 727 found the ACTUAL MAX  flight loads in the tailfin were about 3 times what they had predicted from wind tunnel testing and also there were yaw problems that required gyroscopic sensed Yaw Dampers. This was an early "T" tail with short coupled tailfeathers and behaved very differently to the B707 it was based on. which had a problem with slower speed  Dutch Roll  oscillations. This is all related to swept back wings and how they react to yaw. Nev

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17 hours ago, Marty_d said:

They would have been in tension then, not compression.

As the wings transmit lift to the fuselage (that is their 'raison d'etre') then the bulk of force will be as Marty suggests. However I don't disagree that the short cycle reversal of stresses would actually create most fatigue on the structure.

I'm no engineer, simply trying to get a clear idea of what's happening. Don

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The design loads are always more for positive than negative loads in normal aircraft and structures are specifically designed for each situation. A column for compression loads is more complex than a rod for tension but if they didn't fluctuate/cycle there would be no cracks/ fatigue. Materials like carbon fibre don't like compression loads as an example. With a swept back wing the centre of lift could be near the rear wing root  attach point and there's lots of twisting force to cope with you don't get as much of with a straight(er) wing.  Nev

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