The Normalization of Deviance

The ‘accident’ involved a Gulfstream IV business jet that crashed in Bedford, Massachusetts in 2014 after the experienced crew attempted to takeoff with the gust-lock engaged. The gust-lock is a device that locks the controls to prevent damage from the wind whilst the aircraft is parked. The take-off was rejected at a very late stage which meant that the aircraft departed the end of the runway and broke apart with the ensuing fire killing all onboard.

The report’s Executive Summary concluded that the probable cause was the crew’s failure to perform a check of the flying control surfaces before take-off, their attempt to take-off with the gust-lock applied and their delayed actioning of the rejected take-off when they realised the controls were locked.

Contributing factors included the flight crew’s habitual non-compliance with checklists. In fact five checklists had not been completed and it had become standard practice within the organisation to not do them.

If the checklists had been done the gust-lock would have been removed prior to engine start and a full and free check of the controls would also have been completed.

To people who fly professionally, however, it is obvious that the report implies that the accident was caused by a theory called the 'Normalisation of Deviance’.

This term was first used by sociologist Diane Vaughan in her book on the Challenger Shuttle disaster ‘The Challenger Launch Decision: Risky Technology, Culture, and Deviance at NASA.’


Here is a link to the NTSB report.

Series of Errors by Flight Crew Caused Fatal Business Jet Crash, NTSB Says

Gee, isn’t it amazing how much that event has such parallels to another incident where the investigators, management, and even the public worked very hard to avoid the same conclusion.