A few pertinent points regarding the the Bac 1-11
The left windscreen had been replaced and the task certificated by the same Shift Maintenance Manager with the appropriate British Airways authorisation 27 hours before the accident flight and the aircraft had not flown since its replacement.
The replacement windscreen had been installed with 84 bolts (A21l-8C) whose diameters were approximately 0.026 of an inch below the diameters of the specified bolts (A21 1-8D), and 6 bolts (A211-7D) which were of the correct diameter, but 0.1 of an inch too short.
The windscreen fitting process was characterised by a series of poor work practices, poor judgements and perceptual errors, each one of which eroded the factors of safety built into the method of operation promulgated by British Airways.
A series of cues were available to the Shift Maintenance Manager to draw attention to the use of incorrect bolts but all went unnoticed or unheeded.
Although an independent final inspection would have had a high probability of detecting the error, the task of the windscreen installation was not designated a 'Vital Point' and consequently no duplicate inspection was called for and none took place.
The work of the Shift Maintenance Manager was not subject to review by another manager and thus the there was no backstop with any chance of detecting his errors. Errors that were made more likely by the sleep deprivation and circadian effects associated with the end of a first night shift.
The practices employed by the Shift Maintenance Manager which permitted such errors were not considered to be 'one-offs' but were symptomatic of a longer term failure on his part to observe the promulgated procedures.
The British Airways local management, Product Samples and Quality Audits had not detected the application of inadequate standards by the Shift Maintenance Manager, because they did not monitor directly the working practices of Shift Maintenance Managers.
The windscreen replacement task may have been unique in that it alone could accommodate the errors associated with its fitment, such that they were exposed so dramatically the first time that the windscreen was called upon to resist cabin pressure.
The Shift Maintenance Manager required mild corrective lenses to read small print or figures but did not use his glasses whilst performing the windscreen replacement.
A safety critical task, not identified as a 'Vital Point', was undertaken by one individual who also carried total responsibility for the quality achieved and the installation was not tested until the aircraft was airborne on a passenger carrying flight.
The Shift Maintenance Manager's potential to achieve quality in the windscreen fitting process was eroded by his inadequate care, poor trade practices, failure to adhere to company standards and use of unsuitable equipment, which were judged symptomatic of a longer term failure by him to observe the promulgated procedures.
The British Airways local management, Product Samples and Quality Audits had not detected the existence of inadequate standards employed by the Shift Maintenance Manager because they did not monitor directly the working practices of Shift Maintenance Managers.
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Fools rush in where Angels fear to tread
[This message has been edited by Golden Rivet (edited 25 February 2001).]