Incident: Westjet B736 at Abbotsford on Jan 20th 2009, navigation system flies different route than pilots
The crew of a Westjet Boeing 737-600, registration C-GWSB performing flight WS-456 from Abbotsford,BC to Calgary,AB (Canada) with 104 people on board, noticed during an RNP (Required Navigation Procedure, precision RNAV navigation) departure, that the airplane was not following the programmed standard instrument departure route. The airplane was below minimum safe altitude. The crew contacted Victoria Terminal and was issued radar vectors away from high terrain. The airplane continued to the destination for a safe landing.
Subsequently it was established, that the engine out procedure had been inadvertently activated in the flight management system.
Now you see why a pilot might want to shoot the FMS?