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.
Synopsis
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.
Second reporter narrative
We flew this aircraft for two legs before our 'event leg'. I am suspicious that the spoiler was deploying on those flights as we noted performance was degraded in climb and descent... specifically about 40% torque rather than 26% midway down final was needed to maintain speed. By short final power settings were normal. On the 'event leg' everything appeared normal until we entered the traffic pattern. We were high as there was orographic turbulence and we were asked by Tower to turn an early base because there was inbound traffic on long final. I turned off the autopilot on downwind approaching base and entered the base turn. The flight controls felt strange. The base leg never really leveled out. It was a bank from downwind; rolling out; and then rolling onto final as the Tower had asked us to keep it in close. As we slowed the controls felt weirder and it felt like a cross controlled stall although we were nowhere near a stall. I mentioned the same and the First Officer noticed our L.O.[Left outboard] spoiler was deployed about 1/3rd up. This was a dynamic time so we monitored the spoiler as we continued to slow on final and it continued to increase to about 2/3rd deployment as we slowed. We elected to go around as we left with 10;000 LBS of fuel and had enough fuel to resolve the problem. The best checklist for our situation was 'uncommanded roll.' We contacted Maintenance Control and Dispatch and decided that it would be best to follow the guidance of the checklist. It instructed us to land at an airport with a minimal crosswind component. Some comment about our conversation with Dispatch. We were given the choice of two airports almost as simply as being asked if we wanted the chicken or the fish. This was a surprise to me as I thought we were going to get a direction. For me this was the beginning of a feeling of low latent stress which never went away until we touched down our final destination. As we diverted to the airport we talked with Dispatch about fuel burn to the airport and were given an airway routing fuel burn which didn't reflect our reality as we were going direct. We then asked for that information. We didn't really know how much fuel we would consume enroute to the airport so we did some back of the envelope calculations regarding our climb burn and time at altitude. We had a 100 KTS headwind to the airport so our remaining fuel was a concern. We determined we would be landing with about half an hour worth of fuel. I was privately concerned that if the spoiler acted up at altitude or an engine problem happened we wouldn't have fuel over mountainous terrain. I should have been more assertive getting info from dispatch. On approach to the airport we flew at flaps 15 since the spoiler did not deploy as high when the aircraft was at a higher speed. We asked for trucks from the airport in case the spoiler did act up and we went off the side of the runway. This necessitated an emergency declaration. Post flight thoughts:1. I thought that Dispatch would take greater charge. My need to 'pull' from them rather than expecting a 'push' from them. 2. Constant phone calls etc. for several hours after the termination of the leg. 3. Unanticipated fatigue which affected the remainder of the flight. Did not have the ability to 'self rescue'.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.