Date: 202108
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Light Transport; Low Wing; 2 Turboprop Eng
Operator: Air Taxi
Operating under: Part 135
Flight plan: None
Mission: Passenger
Flight phase: Landing
Airspace: Class G ZZZ
ATC / advisory: CTAF ZZZ
Aircraft component: Rudder
Component problem: Improperly Operated
Reporter organization: Air Taxi
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Human-Machine Interface; Situational Awareness
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Runway
Detector: Person Flight Crew
When detected: Other Landing Roll Out
Result: General Evacuated
Contributing factors: Weather; Aircraft; Human Factors
Primary problem: Weather

Narrative: On Date about XA45 PM local time; during roll out after landing on Runway XX in ZZZ in Aircraft X; the plane veered to the right and exited the runway surface and came to rest in the soft mud just to the right of the runway. We departed ZZZ1 enroute to ZZZ; at XB25 local time on a part 135 passenger charter flight with passengers; their luggage; and groceries for ZZZ; and after a nice 2 hour and 20-minute VFR flight we arrived at ZZZ. We made a pass overhead of Runway XY to check the windsock; and then flew out about 3 miles and made a teardrop back to final to Runway XX. When we did our wind check I observed the windsock to be showing about 5 kts. or less of wind out of about 070 degrees. When we were on final to Runway XX; I again looked at the windsock and observed it to be showing about 10-15 kts. of wind at about a 30-degree right crosswind to the runway. After a normal approach and touchdown; during rollout while the tail was still in the air; I could feel the rudder starting to become less effective and the wind wanting to push the tail to the left; so as quickly as I could I got the tail wheel planted firmly on the ground to help with directional control. As the plane was slowing down through an estimated 35-40 kts. the plane started to veer to the right; I immediately applied full left rudder and pumped the left brake to make sure that we were getting maximum effectiveness out of the left brake. After rolling about another 100 ft.; I realized that it was not likely that we were going to be able to get the plane straight again; so then I applied maximum right brake also and was just trying to get the plane stopped before it went off the side of the runway. When we were about 100-150 ft. from going off the runway the Copilot also applied maximum braking; but nothing we did was able to keep the plane on the runway; we went off the right side of the runway about 1;000-1;200 ft. from the end. The plane stopped quickly in the soft mud that was just off of the runway. We then did a quick assessment of the passengers and after none of them reported any injuries we evacuated the passengers and then secured the aircraft. There were no known pre-accident mechanical issues with the aircraft. Of the passengers and 2 crew members on board; there were no reported injuries. After the incident was over as I was back on the ramp; I was able to observe the windsock for a while. I noticed that the wind would be anywhere between 5 and 15-20 kts. and the direction would shift between approximately 060 and 150 degrees. At the time we landed I would estimate that the clouds were about 2;000-2;500 ft. broken-overcast and greater than 10 miles visibility. The ceilings and visibility did deteriorate throughout the day.




Synopsis: Captain reported a runway excursion when the winds pushed the aircraft off the runway into soft mud.