Heard on the radio this morning: New wing cracks... all on planes that are not in service yet. Ocurred at the Mitsubishi plant, where the wings are being made. The're altering the mfg. method to correct it. Will not alter the delivery schedule, Boeing says. Boeing reports wing cracks on 787 Dreamliners in production | Reuters I heard that Boeing is going back to more in-house mfg on the new 777. Specifically, Boeing will make the wings themselves.
The subject cracks are not in the wing panels but in the shear ties that join the panels to the interior structure. From what I understand, the shear ties are a 7000 series alloy and they have cracked from over-tightening the fasteners. The same thing happened 55 years ago on the 707 but not specifically the shear ties. Here is where in-house training, in-house quality control, and in-house surveillance comes in to play.
I hope MHI has to eat the whole mess. Irritates the crap out of me that we source out the most critical part of the plane, after the entire industry said it was a bad plan and they do it anyway. The entire management staff that went along with this mishigoss at Boeing should be fired. But - they won't be.
Specifically a lack of the above... Mitsu builds crappy, unreliable cars... why would their wing assembly be any better?
Mitsubishi has built some of the finest most well built aircraft the world has ever known. That's a FACT.
Yes, I know... the MU-2 is one of my favs... (you had one, didn't you?) The Zero was pretty good... Their cars are junk, tho, IMO.
Next to impossible to over-tighten a high-lok or lockbolt. Now a clamp-up issue I can believe. I read where they (MHI) had changed the design on the shear ties to trim some weight. Of course this was likely done with Boeing's blessing. The installation dwg should call out maximum gap allowances on fit up and requirements for use of shims. These requirements would need to be reviewed as the design changes. All airplanes, even those flying, probably have same fitment issues but the re-designed shear ties are more prone to stress corrosion cracking. Formed 7075-T6 parts have been known to crack due to stress corrosion from just sitting on a shelf. Boeing should be looking very carefully at the aircraft in-service. Airbus had a similar problem on the A380 fleet last yr (or so).
The incident of which I spoke re the 707 was exactly what you have mentioned here, trying to close the gap with the fastener instead of using the proper shim. In the case of the 707 it was the steel splice plate on the lower wing surface where it joined the stub. It lacked the correct shim thickness and was simply pulled up into place by tightening the fasteners. A slightly short bolt could still cause the problem.
Airbus uses multiple entities to produce substantial sections of an aircraft and it seems to have been a viable solution. Boeing has been using "partners" for portions of the aircraft for decades. It is part of how they use relationships to make sales in certain countries. Jeff
