Date: 201303
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Flap Control (Trailing & Leading Edge)
Component problem: Malfunctioning; Improperly Operated
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Human-Machine Interface
Second reporter function: Pilot Flying; First Officer
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: After takeoff we retracted flaps on schedule and verified flaps in up 0 degrees position before selecting autobrakes off and gear handle to off position. After two hours in cruise we noticed a slight rolling moment followed by the illumination of the LE FLAPS TRANSIT amber annunciator light. Flaps indicated 1 degree with flap handle in the 1 degree position. This action was uncommanded by either pilot. The airspeed indicated 244 knots and at no time exceeded upper airspeed limit. Aural airspeed warning/overspeed was not heard. We then moved flap handle back to 0 degree position and the flaps again indicated 0 degrees. During approach we extended flaps from 0 to 1 degree and found the flap handle was difficult to move out of the 0 degree detent. It felt as though there was resistance to its movement. Selecting other extension positions was normal with no resistance. After landing and clearing runway; selected flaps up. Again; flap handle was difficult to position in the 0 degree detent/gate. We called Maintenance Control after gate arrival and explained what had happened. They advised there was no reported history of this problem on the aircraft and that there was no required flap inspection since a flap overspeed warning had not been detected. They advised that Maintenance would visually inspect the flap components and would operate/cycle the handle to verify its operation based on the logbook entry and what had happened. We made a logbook entry explaining the uncommanded extension and difficulty in operating the flap handle in and out of the 0 degree gate. We also made reference to the fact that the flaps had extended above FL200. Later; a representative recommended filing this report based because the flaps were extended above FL200. I suspect; based on the binding/resistance felt in operating the flap handle at this position; it had never fully seated in the 0 degree gate and that the flap handle migrated from 0 to 1 degree position over the course of two hours.


Second narrative: After clearing the runway and retracting flaps; I noticed that the flap handle had resistance the last 1/2 inch of travel before entering the 0 degree detent.


Synopsis: A B737NG flight crew was surprised when; while at cruise; the flaps extended to the one degree detent; apparently the result of resistance to fully engage the zero degree gate during retraction.