B737-700
Flight Crew Last 90 Days 152
Aircraft Equipment Problem Less Severe
Aircraft Aircraft Damaged; General Maintenance Action
Aircraft; Human Factors
During climb after departure; with flaps retracted and autopilot engaged; the FO noted that a larger than normal amount of right rudder trim was required to center the control wheel. I took control of the aircraft; disconnected the autopilot; and trimmed the aircraft using the AOM Aircraft Trim Technique with autopilot disengaged (i.e.; trimmed both aileron and rudder). Once trimming was complete; the aileron and rudder were trimmed one to two degrees to the right; the control wheel was level and the aircraft maintained a steady heading; but the PFD slip/skid indication showed a slip. In addition; the aircraft seemed slightly more sensitive to roll control input than normal. In all; the indications were slightly unusual; but certainly not in any way alarming. The aircraft was completely controllable at all times. I have seen similar trim conditions in other aircraft; particularly in the older [second generation] models. The greater sensitivity in roll was minor; perhaps similar to the difference between roll sensitivity with flaps at 30 and flaps at 40 degrees. We continued to our destination; which was about one hour and 30 minutes away. During Approach; with flaps extended to 30 degrees for landing; when the autopilot was disengaged; the FO (again the Pilot Flying) noted that it was necessary to trim the aileron and rudder back to the left to remove control pressures. Basically; the trim input required for flaps up had to be removed with flaps extended.Upon arrival; I decided to inspect the flaps and primary control surfaces to see if there were any discrepancies that could explain the trim changes between flaps up and flaps extended. During the inspection; I discovered that the right inboard trailing edge flap remained partially extended (perhaps six to eight inches) while all other flaps; on both wings; were fully retracted. I contacted local Company Maintenance; and made a logbook entry. While inspecting the flaps; the Maintenance Technicians discovered damage to the internal flap mechanism of the right inboard flap. As a comparison; the Maintenance Technicians also inspected the left inboard flap (which was fully retracted); and discovered similar; but lesser damage to that flap mechanism as well. The aircraft was removed from service. Throughout the entire flight; from preflight to postflight; the flightdeck indications were normal; there was no split in the flap indicator or any other abnormal flightdeck indications. Further; to the best of our knowledge; no flap overspeeds occurred during the flight.
The reporter indicated that the damage found could be consistent with a flap over speed; although none occurred on his flight. This was the first flight on this aircraft for the reporter but the First Officer had flown the previous leg with a different Captain who experienced similar trim anomalies; but no log entry was made. He also indicated that this aircraft was acquired from another carrier.
B737-700 Captain was informed by his First Officer that the aircraft had odd trim requirements during climbout; requiring one or two degrees of right rudder and aileron trim to fly wings level. When the flaps were extended for landing the trim settings needed to be zeroed. Post flight revealed that the right inboard flap was not fully retracted. Maintenance was contacted and found damage to the flap mechanism on both wings and the aircraft was taken out of service.