Narrative:

As I was taxiing for takeoff; my right landing gear came off the taxiway and got stuck in the mud. I was preparing the final takeoff checklist while the aircraft was rolling. I only took my eyes off the outside environment for what I thought was just a couple of seconds; but that was too long. The aircraft steered to the right without my catching it soon enough and the landing gear came off the concrete and into the mud. This was a self distracting situation and I should have completed the checklist prior to releasing the brakes. This thankfully did not disrupt operations at the airport.

Google
 

Original NASA ASRS Text

Title: A KING AIR BECOMES STUCK IN THE MUD AFTER THE R MAIN GEAR LEAVES THE PAVED SURFACE OF THE TXWY.

Narrative: AS I WAS TAXIING FOR TKOF; MY R LNDG GEAR CAME OFF THE TXWY AND GOT STUCK IN THE MUD. I WAS PREPARING THE FINAL TKOF CHKLIST WHILE THE ACFT WAS ROLLING. I ONLY TOOK MY EYES OFF THE OUTSIDE ENVIRONMENT FOR WHAT I THOUGHT WAS JUST A COUPLE OF SECONDS; BUT THAT WAS TOO LONG. THE ACFT STEERED TO THE R WITHOUT MY CATCHING IT SOON ENOUGH AND THE LNDG GEAR CAME OFF THE CONCRETE AND INTO THE MUD. THIS WAS A SELF DISTRACTING SIT AND I SHOULD HAVE COMPLETED THE CHKLIST PRIOR TO RELEASING THE BRAKES. THIS THANKFULLY DID NOT DISRUPT OPS AT THE ARPT.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.