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Strategies & Market Trends : Strictly: Drilling II -- Ignore unavailable to you. Want to Upgrade?

To: Frank Pembleton who wrote (27251)	2/2/2003 1:31:43 PM
From: E. Charters	Respond to of 36161

Metal fatigue, corrosion coupled with other failures were in part responsible for the tails corroding off on Candain F-18's and the many tail failures of the 767. The 767 had a hydraulics problem that overloaded the rudder and tail assembly on occasion, but cracks had already started for form their and were aided in propagation by fatigue and corrosion. Killed a lot of folks in the case of the 767. Aircraft, for weight considerations are built at a 4 times safety factor on the known new, uncorroded strength of Reynolds 5xx. (By contrast standing structure and most machine parts are built to 10X safety to withstand shock loads.) After a few years, this slight margin of safety may be exceeded at certain key points during turbulence vibration. Vibration is like a micro-shock that is continuous, and in many designs stress riser points from the harmonics of surfaces under vibration are not calculated for, especially in their effect over time. It has been seen in bridge design that aeolian and other vibration loads are frequently not calculated, and this factor coupled with others over time has put supports at risk and required rebuilds. Most of the bridges in the US are not lasting their required lifespans. The finger has been pointed at the complexity of vibrational stress over time, and other factors such as erosion and corrosion. We don't know now what caused the accident. It may even be multivariant. There was tile damage. There may have been burn through. Or there may have been excess vibration causing other more critical tiles to separate as well. EC<:-}

To: Frank Pembleton who wrote (27251)	2/2/2003 9:19:49 PM
From: lh56	Read Replies (1) \| Respond to of 36161

Frank, i must make the point that the quality of performance in NASA is ultimately determined by the quality of support from the US congress. and that has been steadily eroding for 20+ years. if NASA is flying aging bolt buckets past their prime that's what the american taxpayers want and that's all that congress has allowed. if you're an american taxpayer then the target of your anger isn't really NASA, it's the flawed judgement of the holders of the budget purse. it terms everyone can understand: money talks and bullshit walks. in this case it kills. larry