Usability Disasters
American Airlines Flight 965
On 20th December, 1995, the schduled Flight 965 from Miami International Airport to Cali, Columbia crashed into a mountain killing all but four of the 156 passengers and 8 crew.
The full detail of the incident is quite convoluted but one pertinent aspect was the selection of a radio-navigation fix, named “ROZO”. The system returned a list of fixes begining with “R” and the pilot selected the first of these, whose latitude and longitude appeared to be correct. Unfortunately, the pilot selected “ROMEO” causing the flight to turn east whilst it was descending in north-south valley.
Whilst, the usability of the system was not blamed for the crash, it was a pertinent aspect. Had the system provided some feedback that the selected fix might not be the appropriate one then the pilot would have been more aware of his error.
Three Mile Island
On the 28th March 1979 Three Mile Island nuclear plant near Harrisburg, Pennsylvania suffered a partial core meltdown.
The accident resulted from a complex interplay of events but was exacerbated by poor user interface problems. An automatic relief valve had failed to close but the failure was not indicated to the operators who believed it had. The indicator light indicated what the valve had been commanded to do, not what it was actually doing and so it remained dark because the valve had been commanded to close.