Learjet 55
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 75; Flight Crew Total 9850; Flight Crew Type 3050
Situational Awareness
Ground Excursion Taxiway
General Maintenance Action
Airport; Human Factors; Weather
After landing I exited on Taxiway A3. As I made the right-hand turn onto Taxiway A; the right main gear departed the pavement and sank into soft mud. The effect was equal to applying full right differential braking and overpowered the nose wheel steering. In an instant; all three landing gear were in the mud. The aircraft had to be extracted with a tug and one taxiway light was knocked over. There was no damage to the aircraft. A combination of factors contributed to this incident: Patchy fog congregating at the edges of the runway and taxiways; my failure to keep the yellow stripe in sight and the nose-wheel on it; the unexpectedly sharp right turn (approximately 135 degrees) required and the resulting sharp point of unpaved area extending into the turn radius.
A landing was made and the aircraft exited on A3 which was the last high-speed taxiway. After clearing the runway I began the After Landing checklist and the Captain made a 135 degree right turn onto Taxiway A. While making the turn the aircraft cut the corner too tight and right main gear left the taxiway which yawed the aircraft to the right pulling all of the aircraft's wheels off of the paved surface. Since we stopped in soft mud we required an airport tug to pull us out. After getting pulled out of the mud we thoroughly cleaned the wheels with a high pressure water hose and carefully inspected the landing gear. No damage was found. I believe that poor visibility; low light; unfamiliarity with the airport were contributing factors. The incident would have been less likely to occur if the After Landing checklist was completed before we began taxi allowing the all attention of both crew members to be outside the aircraft while making the turn.
LR55 flight crew reports becoming stuck when the right main gear leaves the paved surface during a 135 degree turn from a high speed exit to the parallel taxiway. Darkness and fog contributed to the incident. A tug is required to extract the aircraft.