A mishandled propeller overspeed in an SAS Bombardier Dash 8 Q400 on approach almost led to loss of control, says a new report by the Swedish accident investigation board. The board was critical of the crew, their training, SAS's maintenance, and the emergency checklist and operations manual for the type.
The incident took place on 6 April 2006 during an instrument landing system approach to Runway 16 at Kalmar, near Sweden's south-east coast, with four crew and 69 passengers on board. The report says: "During the flight a technical failure occurred, which meant that the right-side propeller overspeeded. According to the emergency checklist a number of actions are to be taken, ending with feathering the faulty propeller and switching off the engine to reduce the drag of the propeller.
"The commander decided, however, to keep that engine at flight idle during the approach, which meant that the angle of the propeller blades remained flat to the aircraft direction, thereby causing severe drag. This severe drag caused great control problems for the aircraft and the commander thus had to use a power output from the other engine that exceeded the maximum permitted power. The approach was not stabilised and the final stage was at a very low height."
According to the report: "The crew had not practised dealing with faults in this system during approach and landing, and considered that the emergency checklist was unclear. During the three-week period immediately preceding the incident, three failures of the same type occurred on this individual aircraft. In no case had the crew completely followed the instructions in the emergency checklist. Nor had the technical fault been located correctly."
The investigators have recommended that the European Aviation Safety Agency "makes efforts to set up a working group, with representatives of the manufacturer and the airline, and possibly other operators of the Q400. The purpose should be to improve both the content and the method of application of the emergency checklist for the Q400".