Subject: The Virgin Bus (Is it a Practicable Solution?) |
Date: Wed, 30 Dec 1998 16:27:11 +0800
From: John Sampson <sampson@iinet.net.au>
To: Mark Fetherolf <fetherolf@platinum.com>
Mark Fetherolf
wrote: (re: virgin.html
) Certainly sounds sensible to
me. Why do you think this isn't obvious and implemented in relatively modern aircraft? |
Mark, The reasons are reasonably evident and explicable. Firstly, many crews luck out by having their cockpit or cabin fires in relatively benign environments (i.e. good weather, day-time with a visual horizon to fly by, close to an emergency alternate airport; electrical design-friendly airframe etc). That means that 90% of crews get away with it and don't become a statistic. If there are no statistics, just incidents, then FAA can get away with such statements as: " To date we know of no passengers in the last ten years that have died because of a wiring fault etc". Statistics, when finely tuned, are true deviltry in the hands of a bureaucrat. Please read about last week's B737 total electric failure at: smokingun.html The Kaptonitis hazard is only now beginning to assume more significant proportions - because Kapton doesn't age gracefully.You can therefore expect an increasingly greater number of incidents actually attributable to Kapton -but the FAA will always be looking to allot the cause elsewhere (i.e. it's too hard a bullet to bite). Unfortunately such smithereening accidents as SR111 are very difficult to definitively attribute to a specific cause. The latest info I have is that the investigators are thoroughly confused by the revelations of the DFDR and its timelines. They have decided that a lot of the data on the DFDR has been corrupted by the electrical malfunction (i.e. a lot of the events on the DFDR didn't really happen). That is one of the really devilish things about electrical malfunctions - they throw everything into an anomalous frenzy and such devices as the DFDR begin to tell lies. However I think the word about aircraft wiring and Kapton is starting to become common property and more safety conscious airlines will be looking for a realistic solution to the conundrum. As has been said many times it is just not practical to rewire these many many aircraft. Besides loss of operating revenue for the three months (each) that it would take, it is tantamount cost-wise to totally dismantling an airliner and rebuilding it from scratch. Similarly you cannot afford to trash them with their low flying hours and initially high capital costs. The only real answer is the Virgin Bus. It could be designed and incorporated in fairly short order and should be a very, very safe fall-back position for a crew faced with an electrical "fire of unknown origin". It is designed to avoid the very time-consuming, unduly optimistic and potentially lethal style of checklist that's been around for decades. That checklist is even more inappropriate in today's "electric jets". Modern jet-liners have three times the wiring and electrical consumption of their 1960's equivalents (and now, only a two man crew in most instances). Passengers would feel very safe knowing that their flight-crew wasn't gambling against the clock with their lives while trying desperately to trace and isolate the source. It's always been an open-ended checklist that never ever told you what to do when you couldn't locate the source. Airline crews don't have any indepth training on their aircraft's electrical circuitry. All they know is that certain systems are powered by certain busses, the number of generators, batteries and backup devices (APU's, air-driven generators, Ram air Turbines). In many cases inflight access to circuit breakers is limited and/or operators have no procedures for crews to check or manipulate CB's. Indeed systems are nowadays so electronically complex and interrelated that "a little knowledge can be a very dangerous thing". Crew responses to circumstances are therefore limited to running checklists. In-depth systems knowledge died with the demise of the professional Flight Engineer. You might form the opinion that this makes modern flight crews very robotic and lacking in any scope for initiative. Simulator smoke reproductions normally degenerate to less of a realistic drill and more of a discussion - because dense smoke is hard to simulate and electrical fire malfunctions can anyways be so multi-faceted. There's no telling where, or how far, one will go. In the case of SR111 I think that my chain of likely events spelt out in: switcher.html
solution.html
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