Date: 201404
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: Cessna 402/402C/B379 Businessliner/Utiliner
Operator: Air Carrier
Operating under: Part 135
Mission: Passenger
Flight phase: Landing
Aircraft component: Flap Control (Trailing & Leading Edge)
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Aircraft Equipment Problem Critical; Inflight Event / Encounter Unstabilized Approach
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: During approach to Runway 27 at 1;000 feet; I extended 15-degree Flaps; continued descent then extended full flaps at 400 feet MSL. I watched the Flap Position Indicator stop at the 'Full' position. I looked outside and heard the Flap Motor engage with the aircraft beginning to pitch-up. The Flap Position Indicator showed the flaps began to retract with the Flap handle in the full down position. Then the flaps began to extend again  descending through 200 feet. As I began to flare; the flaps again started to retract to the 30-degree position and stopped there. I then landed the aircraft with flaps in the 30-degree position. During 'after landing' flow; the flaps would not retract or extend and found Circuit Breaker (C/B) popped. Mechanic found Flap Position Selector wire broken.

Callback: Reporter stated the flaps are 'Full Down' at 45-degrees. The Circuit Breaker (C/B) that popped during landing had cut electrical power to the Flap Motor and that was why the flap position had locked-in at 30-degrees. Reporter stated he was fortunate he had a long runway; because he was concerned about the aircraft suddenly settling on the runway if the flaps continued to move uncommanded. The reporter stated he did not want to do a Go-Around; so he kepted engine power up and when the flaps seemed to stop at 30-degrees he let the plane land.Reporter stated the Flap Position Selector handle is basically a switch that sends an electric signal to move the flaps after the pilot selects a flap position. Some of their C-402's have a more solid detent feel in the Selector handle at each flap position while others have very little; he stated that his had very little.  The Flap Position Indicator is cable driven and scrolls down and up. Maintenance explained to the reporter that a wire had broken internally in the Selector handle switch and was contacting different flap position nodes inside the switch; causing the uncommanded flap extentions and retractions. The reporter indicated that in a worse case scenario; a short runway and IFR conditions would be a really challenging situation. He has not heard if other C-402 Pilots or Operators experienced similar flap problems.



Synopsis: A Captain describes his efforts to land a Cessna C-402 aircraft on a long runway while experiencing uncommanded flap retractions and extensions. The Flap Position Selector handle never moved from the 45-degree 'Full Down' handle position. Aircraft Maintenance Technician (AMT) found a broken wire in the Flap Position Selector handle switch.