Date: 27 Dec 96 13:32:19 From: firstname.lastname@example.org (Scott Odle) Organization: Earthlink Network, Inc. References: 1
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In article <airliners.1996.2792@ohare.Chicago.COM>, email@example.com says... > >The keynote speaker of the 1996 Pacific Northwest Software Quality >Conference reviewed the 10^9 (ten to the ninth power) problem. Years of >testing a PC program are required to believe that it won't fail within a >week of release. To meet the FAA standard of 10^9 hours of failure free >operation would require 100 years of testing assuming that one could >execute 1 test/sec (there are about 10^7 seconds in a work-year). > >He went on to say that because of the millions of lines of code written >for the 777 that it would be impossible to test all of the failure >conditions, and therefore was irresponsible to design and deploy such an >aircraft. He vowed never to fly on one... > >How was the 777 tested? Is it safe? Or is it "unsafe at any airspeed?" > It is not as simple as you make it sound. First of all, all failures are not required to be 10-9. Only those that are deemed "catastophic". Determination of failures is not necessarily done by testing. Hazard analysis and effects analysis is done to determine the effects of a given failure. As for software, there are very strict requirements. However, the level that the software is certified to based on if the a particular piece of equipment is critical, essential, or non-essential.