From: email@example.com (ExpAero) Organization: America Online, Inc. (1-800-827-6364) Date: 22 Jun 95 03:07:36 References: 1
View raw article or MIME structure
>>Use of a single design of computer and software to drive the FBW - the >>possibilities of common mode failures must be obvious. The theoretical possiblity of common mode failures in complex systems may seem obvious but determining the probabity of simultanious occurrence of such failures it not. I assume you would prefer not to have two pilots on the same flight who are identical twins since they may have a "common mode failure" at the same time? Granted at this stage humans are a more complex system that a simple 777 flight control system but the issue is really the same. Further, in order to get redundant, asychronous, processors to operate together properly, the software requirements must be so detailed as to result in almost the same software (and errors) even if multiversions are developed. This issue could provide fodder for a whole string on it's own. I've not seen any literature that purports to prove that redundant system designs with multiversion software actually result in a lower probability of simultanious common mode errors of any kind. Some academic investigations into the subject have actually indicated otherwise. >>As I understand it,no protection against low energy (windshear) situations. I'm confused by this statement. Are you referring to some autothrottle feature that would automatically advance the throttles based on some signal from the windshear warning system? The 777 does have a windshear warning system with associated flight director cues. This is required for all commercial aircraft of its type operated in the U.S. Is there something more that you believe the 777 lacks?