Narrative:

While configuring on approach; we began to notice that the aircraft was not responding to flight control inputs appropriately. When this first occurred we had just selected flaps 35 degrees and were slowing through 150 KTS. The captain described the situation as feeling like the set up for a cross controlled stall. We immediately noticed that the left outboard spoiler was deploying on the pfcs [primary flight control system display]. At about 1/3 deflection it was taking increased amounts of right aileron to fly straight. As the plane continued to slow we noted that the deflection of the spoiler increased to about 2/3 deflection. There was a gusty crosswind (25 KTS); so after a short discussion we elected to execute a go-around. As airspeed increased the spoiler retracted. Once reaching a safe altitude we ran the most appropriate checklist we could find; which was 'uncommanded roll.' we contacted maintenance control and dispatch. After discussions with both parties we decided that it would be best to follow the guidance of the checklist; which instructed us to land at an airport with a minimal crosswind component. On approach we elected to fly solid bug and flaps 15 since from what we had seen the spoiler did not deploy as high when the aircraft was at a higher speed. This proved to be correct. We elected to declare an emergency and have crash fire rescue equipment trucks standing by as a precaution. Additionally; we declared minimum fuel with approach since we would be landing with just over 30 minutes of fuel remaining at touchdown. During the event we discussed activating the spoiler push-off switch; but this was not driven by the checklist or suggested by maintenance control.

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Original NASA ASRS Text

Title: A Q400 flight crew experienced uncommanded left outboard spoiler extension during approach and elects to divert to an airport with minimal crosswind. During the diversion fuel becomes an issue.

Narrative: While configuring on approach; we began to notice that the aircraft was not responding to flight control inputs appropriately. When this first occurred we had just selected flaps 35 degrees and were slowing through 150 KTS. The Captain described the situation as feeling like the set up for a cross controlled stall. We immediately noticed that the left outboard spoiler was deploying on the PFCS [Primary Flight Control System display]. At about 1/3 deflection it was taking increased amounts of right aileron to fly straight. As the plane continued to slow we noted that the deflection of the spoiler increased to about 2/3 deflection. There was a gusty crosswind (25 KTS); so after a short discussion we elected to execute a go-around. As airspeed increased the spoiler retracted. Once reaching a safe altitude we ran the most appropriate checklist we could find; which was 'uncommanded roll.' We contacted Maintenance Control and Dispatch. After discussions with both parties we decided that it would be best to follow the guidance of the checklist; which instructed us to land at an airport with a minimal crosswind component. On approach we elected to fly solid bug and flaps 15 since from what we had seen the spoiler did not deploy as high when the aircraft was at a higher speed. This proved to be correct. We elected to declare an emergency and have CFR trucks standing by as a precaution. Additionally; we declared minimum fuel with approach since we would be landing with just over 30 minutes of fuel remaining at touchdown. During the event we discussed activating the Spoiler Push-Off switch; but this was not driven by the checklist or suggested by Maintenance Control.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.