Narrative:

While on a usfs contract fire suppression mission I detected that the aircraft (L-P2V) had a small change in trim. It was yawing slightly left. This was completely controllable. This was; however; unusual since the aircraft had been handling very well balanced with the 3 trims zeroed for quite sometime. I felt it warranted aborting the mission and returning to base for investigation. History: the aircraft was fueled with the outboard mains topped and 200 gals in the inboard center tanks. After fueling I was made aware of maintenance's request to change the right jet fuel control and I assisted with jet engine runs. The total time of jet engine run and fuel burn was noted and agreed with my highest estimate of 200 pounds. (There is no published asymmetric fuel loading for this aircraft; and I have flown it with more differential wing weight than that). The estimated fuel burn agreed with the fuel quantity indication. The take-off and climb was normal with no noticeable roll or yaw problems. ATC instructions were to maintain runway heading for company traffic entering the left downwind and a company P-3 on a straight in. We advised both aircraft in sight and continued on the vector. All checklists were performed through the after take off; including spoilers on. We were closing rapidly with the traffic on final. ATC was making continuous transmissions. I asked the co-pilot to get our vector amended. I then made a moderate turn to the left to avoid getting too close to the head on traffic and show the P-3 my wing so they would see me. The range was about 3 miles; and altitude about 1;500 AGL. I am aware that the amount of roll input probably began integrating the turning spoiler activation; as the aircraft responded well. When we were cleared back on course (a right correcting turn) I noticed the control response behaved sluggishly. I was still flying the airplane first; my co-pilot was busy with ATC; as I began to look inside the airplane for some indication of an impending problem; as well as looking over the left wing and reciprocating engine. All power indications were evenly matched. Trims were still 0. I became aware that I was needing some right rudder input pressure (about a 2 inch pedal split and about 3-50) right yoke. I again scanned everything and as we were well clear of the airspace and restricted area. I began to roll in right rudder trim. It took about 4 degrees. I immediately realized this to be unusual. Engine power was still normal. I alerted the co-pilot of what was happening and called for a cruise check as I reduced power for the reciprocating engines and we initiated the jet shut down (as per normal operations for cruise as well as a chance to determine if a jet was somehow malfunctioning) at 9;500 MSL. We compared rudder pedals for agreement. I inspected my side and co-pilot her side. There was no change in flight characteristics; just a slight left yaw accompanied by a slight left roll tendency. I retrimmed the rudder to 0 and asked the copilot to turn the trim and I would tell her when it was adequate. She complied and I verified the trim took 4 degrees right. Once we were stabilized at cruise; I briefed the co-pilot of what I was experiencing and asked her to do a walk around inspection aft; as well as look out all the windows; taking time to look at the back of the engines for possibly missing cowling or panels. We continued on course and called a lead plane that was in the area. I asked him to look over the airplane. He complied and intercepted us. The lead plane intercept was performed in accordance with usfs and far standards. My plan was to make sure there were no apparent structural concerns before releasing the retardant. Then safely dispense the retardant; then to return to base. The lead plane pilot told us that everything looked normal. We told him that we were aborting our mission and would contact the incident for jettison instructions. All operations were still normal with the 1 exception. The load was jettisoned and we returned. I had the copilot ask approach if we could alert ground equipment without declaring an emergency. They complied. At approximately 10 miles out and nearing the final approach course; I asked my copilot to declare an emergency since there was a lot of traffic in the area (1 aircraft doing a practice approach and 1 additional for that runway. I think there were also 1 in the pattern and 2 more ready to depart.). I wanted to enhance our safety. I was maintaining 150 KIAS (below va) all the way from the jettison point with no flaps and in light to moderate chop. For the landing; I briefed my copilot to give me assistance on rudder and or aileron if I called for it or if I could not control an uncommanded roll or yaw. She could automatically assist until I told her to release control. I elected to make a no flap landing and briefed it. I did not want the jets; since I suspected jets; flaps or any unnecessary configuration change and a 2 engine reciprocating engine landing is considered normal. We lowered the gear at about 3-5 miles and slowed to 140 KIAS and props 2600 and about 25' map. The landing went uneventful. No serious discrepancies found. It may have been a stuck spoiler.

Google
 

Original NASA ASRS Text

Title: A P2V Pilot reported that a flight control anomaly developed during flight causing an excessive rudder trim requirement during what had been a normal flight. An emergency was declared and the aircraft returned to base with a suspected spoiler malfunction.

Narrative: While on a USFS Contract fire suppression mission I detected that the aircraft (L-P2V) had a small change in trim. It was yawing slightly left. This was completely controllable. This was; however; unusual since the aircraft had been handling very well balanced with the 3 trims zeroed for quite sometime. I felt it warranted aborting the mission and returning to base for investigation. HISTORY: The aircraft was fueled with the outboard mains topped and 200 gals in the inboard center tanks. After fueling I was made aware of maintenance's request to change the right jet fuel control and I assisted with jet engine runs. The total time of jet engine run and fuel burn was noted and agreed with my highest estimate of 200 LBS. (There is no published asymmetric fuel loading for this aircraft; and I have flown it with more differential wing weight than that). The estimated fuel burn agreed with the fuel quantity indication. The take-off and climb was normal with no noticeable roll or yaw problems. ATC instructions were to maintain runway heading for company traffic entering the left downwind and a company P-3 on a straight in. We advised both aircraft in sight and continued on the vector. All checklists were performed through the after take off; including spoilers ON. We were closing rapidly with the traffic on final. ATC was making continuous transmissions. I asked the Co-pilot to get our vector amended. I then made a moderate turn to the left to avoid getting too close to the head on traffic and show the P-3 my wing so they would see me. The range was about 3 miles; and altitude about 1;500 AGL. I am aware that the amount of roll input probably began integrating the turning spoiler activation; as the aircraft responded well. When we were cleared back on course (a right correcting turn) I noticed the control response behaved sluggishly. I was still flying the airplane first; my Co-pilot was busy with ATC; as I began to look inside the airplane for some indication of an impending problem; as well as looking over the left wing and reciprocating engine. All power indications were evenly matched. Trims were still 0. I became aware that I was needing some right rudder input pressure (about a 2 inch pedal split and about 3-50) right yoke. I again scanned everything and as we were well clear of the airspace and restricted area. I began to roll in right rudder trim. It took about 4 degrees. I immediately realized this to be unusual. Engine power was still normal. I alerted the Co-pilot of what was happening and called for a cruise check as I reduced power for the reciprocating engines and we initiated the jet shut down (as per normal operations for cruise as well as a chance to determine if a jet was somehow malfunctioning) at 9;500 MSL. We compared rudder pedals for agreement. I inspected my side and Co-pilot her side. There was no change in flight characteristics; just a slight left yaw accompanied by a slight left roll tendency. I retrimmed the rudder to 0 and asked the Copilot to turn the trim and I would tell her when it was adequate. She complied and I verified the trim took 4 degrees right. Once we were stabilized at cruise; I briefed the Co-pilot of what I was experiencing and asked her to do a walk around inspection aft; as well as look out all the windows; taking time to look at the back of the engines for possibly missing cowling or panels. We continued on course and called a lead plane that was in the area. I asked him to look over the airplane. He complied and intercepted us. The lead plane intercept was performed in accordance with USFS and FAR standards. My plan was to make sure there were no apparent structural concerns before releasing the retardant. Then safely dispense the retardant; then to return to base. The lead plane Pilot told us that everything looked normal. We told him that we were aborting our mission and would contact the Incident for jettison instructions. All operations were still normal with the 1 exception. The load was jettisoned and we returned. I had the Copilot ask Approach if we could alert ground equipment without declaring an emergency. They complied. At approximately 10 miles out and nearing the final approach course; I asked my Copilot to declare an emergency since there was a lot of traffic in the area (1 aircraft doing a practice approach and 1 additional for that runway. I think there were also 1 in the pattern and 2 more ready to depart.). I wanted to enhance our safety. I was maintaining 150 KIAS (below Va) all the way from the Jettison point with no flaps and in light to moderate chop. For the landing; I briefed my Copilot to give me assistance on rudder and or aileron if I called for it or if I could not control an uncommanded roll or yaw. She could automatically assist until I told her to release control. I elected to make a no flap landing and briefed it. I did not want the jets; since I suspected jets; flaps or any unnecessary configuration change and a 2 engine reciprocating engine landing is considered normal. We lowered the gear at about 3-5 miles and slowed to 140 KIAS and props 2600 and about 25' MAP. The landing went uneventful. No serious discrepancies found. It may have been a stuck spoiler.

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.