Date: 13 Jan 97 18:35:33 From: Andrew Weir <100637.616@CompuServe.COM> References: 1 2 3 4 5 6 Followups: 1
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>Interestingly enough the first 767 delivered with PW4000 is the Lauda >Air 767 that went down in Thailand a few years ago. To this day I >don't the official accident report has ever been published, although it >apparently isn't any secret what happened. What they don't want to >talk about is what didn't happen. Aircraft should never have crashed, >major major screwup in the cockpit. There was an obviously solution to >the problem, and to this day, no one has any idea why they didn't do >it. It takes some 23 minutes from first indication until the aircraft >augers in, so isn't as if they didn't have time. Whoa, there! "23 minutes"? I think you must be thinking of a different accident. The plane crashed 15 minutes after take-off when a thrust reverser deployed without command, leading to an in-flight break-up. While we are getting on the backs of dead pilots, let us remember that the 767 was certificated for recovery from such a situation. Investigators questioned this when they attempted to reproduce the plane's problems in the sim. So, new wind tunnel tests were performed and these showed that instead of a lift loss of 10 per cent resulting from thrust reverser deployment, giving plenty of chance of recovery, the real figure was 25 per cent. Boeing's own engineering simulator was reconfigured to include this data and Boeing's chief test pilot found that if corrective action were not taken within 4 to 6 seconds after the event, recovery was impossible. The recovery manoeuvres were not, however, part of normal airline training. Uncommanded thrust reverser deployment sounds to me like a "major major screw-up" -- but not by the unfortunate pilots. All PW4000-powered 767s were subject to ADs to correct the problem, which seems to have been due to an overlooked failure mode in the thrust-reverser's electronic controls. As an aside for the FBW debate, this accident could not have happened on an older model plane with mechanical controls for thrust reversal.