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Old 27th Sep 2008, 16:56
  #2023 (permalink)  
PJ2
 
Join Date: Mar 2003
Location: BC
Age: 76
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HarryMann;
would be nice to know whay this default wasn't chosen?
Likely because it's a very old system and at the time no one thought it necessary to guard against such a "fundamental" error. A host of side-issues accompany any such designs, such as certification, robustness, likelihood of failure and risk-analysis of the consequences of failure, (ie, would a "single-point" failure cause "loss of the vehicle", to use NASA's terminology in examining the shuttle systems).

Likely in an engineer's mind there are many scenarios against which the design must protect itself in the various ground and flight regimes either through self-diagnosis and correction (switch-over to alternate system), or through warnings to operators, (crew, maintenance) and this scenario didn't make it at the time for the reason stated. "What if" is an expensive and time-consuming question and must be triaged as any risk-intensive endeavour. I suspect you probably know all this so I say this for the sake of the dialog.
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