Originally Posted by
Kengineer-130
I would think that a brand new, modern, multi-billion dollar computer designed airliner that has been shaken down for the last 30 years would stand a better chance of surviving in that environment than a bodged up comet?
Would you? I wouldn't!
One of the reasons why a modern airliner is so much more efficient in its intended role than the 1950s incarnations is simply what you say - computer-aided engineering. We can now do stressing down to the individual part with decidedly complex load-paths and so very little of the airframe is only along for the ride - it all contributes. So the airframe is optimised to a MUCH higher degree than those of yesteryear. Heck, you only have to watch one fly through a mild bit of wake turbulence and the wings are flapping around like the tacoma narrows bridge.
In the Comet era we lacked the ability to do the hundred billion calculations needed to fully understand the stresses reacted by many curved surfaces and components. So the aeroplane structure was comprised of a "primary structure" of largely straight and easily-calculated elements with simple load paths wrapped up in an aerodynamic fairing of "secondary structure". By the 1950s we had started including *some* of the structural properties of the secondary structure, but only through what were essentially rules of thumb and so the values were heavily "discounted" in the stressing cases.
As a result the Nimrod was (compared to a modern airliner) built like a brick outhouse. And that's the primary reason why it was easily adaptable to the low-level manoeuvering needed for the ASW role. Not that it's that relevant for the MRA4, because that had an entirely new wing which was designed explicitly for the stresses of that role - something which could not be said of any current airliner.
It's time we learn from our mistakes, flogging the VC10 & Tristars on for as long as we did led to serious operational performance problems, not only from a (hideous) reliability point of view, but supporting the aircraft worldwide with no real back up from the manufacturers etc.. Operating a modified civil airliner has huge benefits that vastly outweigh any downsides.
This is one of those assertions which sounds reasonable until you challenge the core premise. It assumes that civil and military operations are they same, but they aren't. I've been involved with initiatives which try to use commercial solutions to military availability issues, and they all stumble because in the commercial world any shortfall can be both defined and recitfied in purely financial terms. This was a peripheral area in my second Masters dissertation, and the following extract (in the next post) shows why the assumption is invalid.
PDR