Narrative:

During approach; on an extended vectored downwind; I asked for flaps 7. A few seconds after the PNF selected flaps 7; I felt a 'thumping' from the elevator trim wheel (I'm tall; 6'4' and my leg almost always rests against the trim wheel). I looked down and saw the elevator trim indicator at its full forward limit. The autopilot appeared to still be trying to force more nose down trim; but had reached the forward limit of trim travel. I felt three 'thumps' (visually watched probably the last one) within about 2-3 seconds. I next firmly grabbed the control wheel and disconnected the autopilot. There was not a noticeable pitch up and the nose trim annunciator did not illuminate. I decided to continue to configure the aircraft and slow a few more knots as this tends to return the trim towards a more neutral position. I did not have any more trim problems for the remainder of the flight. I did not declare an emergency as there was no annunciator and the aircraft felt fine when hand-flown. I wrote up the aircraft immediately after landing. Additionally; I had written up the elevator trim two days prior (about 8 legs prior) for the trim indicator not moving through it's full range of the white trim travel indicator. I had no other problems the previous legs with the aircraft either hand-flown or with autopilot and I believe our weight and balance to be within the proper envelope. I am unsure how to avoid a recurrence of this event. As I stated above; I believed the aircraft was airworthy and that I was operating it within the proper specifications and limitations. While using flaps 7 is a non-standard procedure; there are some of us who occasionally use it when a long way from airport; but already slowed to below 200 KTS. It allows the large change in trim (that seems to be caused more from horizontal stab moving) from flaps zero to flaps 15 to be broken up into two separate changes that the autopilot can keep up with easier. In addition; it is less drag; thus lower power setting and therefore fuel saving; while allowing us to get the stab movement over and done with.

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Original NASA ASRS Text

Title: CE560 Captain experiences a thumping sensation from the elevator trim wheel when the flaps are selected to 7 on the downwind for landing with the autopilot engaged. The elevator trim indicator is noted at its full forward position and the autopilot is disengaged; anticipating a pitch up but none occurs. A normal approach and landing ensues.

Narrative: During approach; on an extended vectored downwind; I asked for Flaps 7. A few seconds after the PNF selected Flaps 7; I felt a 'thumping' from the elevator trim wheel (I'm tall; 6'4' and my leg almost always rests against the trim wheel). I looked down and saw the elevator trim indicator at its full forward limit. The autopilot appeared to still be trying to force more nose down trim; but had reached the forward limit of trim travel. I felt three 'thumps' (visually watched probably the last one) within about 2-3 seconds. I next firmly grabbed the control wheel and disconnected the autopilot. There was not a noticeable pitch up and the nose trim annunciator did not illuminate. I decided to continue to configure the aircraft and slow a few more knots as this tends to return the trim towards a more neutral position. I did not have any more trim problems for the remainder of the flight. I did not declare an emergency as there was no annunciator and the aircraft felt fine when hand-flown. I wrote up the aircraft immediately after landing. Additionally; I had written up the elevator trim two days prior (about 8 legs prior) for the trim indicator not moving through it's full range of the white trim travel indicator. I had no other problems the previous legs with the aircraft either hand-flown or with autopilot and I believe our weight and balance to be within the proper envelope. I am unsure how to avoid a recurrence of this event. As I stated above; I believed the aircraft was airworthy and that I was operating it within the proper specifications and limitations. While using Flaps 7 is a non-standard procedure; there are some of us who occasionally use it when a long way from airport; but already slowed to below 200 KTS. It allows the large change in trim (that seems to be caused more from horizontal stab moving) from flaps zero to Flaps 15 to be broken up into two separate changes that the autopilot can keep up with easier. In addition; it is less drag; thus lower power setting and therefore fuel saving; while allowing us to get the stab movement over and done with.

Data retrieved from NASA's ASRS site 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.