with the respected manufacturer's submission leading the poor NTSB staff -- and then omitting the crucial information that might properly reveal the design-weakness.
With all due respect, I think you're letting your (justifiable) bad feeling regarding the Gibson incident lead you to assume that all investigations follow a similar path, when that's not the case. Obviously in that case, the lead investigator didn't follow up with enough vigour on the alternative propositions put forward, however that was but one investigation.
As I said above, the NTSB investigators of UA585 and US427 summarily rejected Boeing's proposal that the B737 rudder hard-over could be caused by inadvertent pedal manipulation by the crews concerned.
(eg, ntsb's Bob S. during the TWA800 investigation deserves recognition for his work)
He credited the UK AAIBs methods on the PA103 investigation as the basis for all the reconstruction-based analysis work the NTSB did there. Not denying it was a good bit of investigative work though!
In the thread-item about mid-way down, notice that the Boeing Submission subtly avoided discussing those failures in the automated features of the Electrical system -- then the NTSB Systems Engineer completely missed those technical problems omitted from the Boeing Submission
To be fair, you make a few assertions that ring a bit amiss:
Originally Posted by IGh
Recall the basis of the 2-Pilot concept: No Flight Engineer , no 3rd pilot would be needed in the B767 Cockpit (Douglas was working the MD80 development at the same time)
In fact the DC9 (from which the MD-80 series was developed) had *always* been designed around a two-person flight deck, as was the Jurassic B737 and the BAC One-Eleven. A 2-person crew has been nothing out of the ordinary in short-haul ops since the mid-'60s.
With reference to your talk of certification in that post, remember that as a derivative of the original DC-9 (as with later generations of the B737) the MD-80 is, I believe, given "grandfather" rights from the original 1960's certification regime for the DC-9, and thus is exempt from later regulations strengthening certain aspects of safety and redundancy.
It's also worth bearing in mind that whatever your feelings on the matter, Human Factors is a much better-understood aspect of investigation than it was in 1979.
If you take these factors into account, you can see why the St. Louis MD-80 investigation followed the path that it did - not, in my opinion, because of subtle shenanigans on the part of the manufacturer but because a central aspect of the aviation infrastructure allowing airliners to be given "grandfathered" certification from earlier variants is that the manufacturers' maintenance and operating procedures must be followed precisely, which they were apparently not in this case.