A CESSNA CITATION'S R LNDG GEAR SANK INTO A VEGETATION SOFTENED RWY SURFACE AT 2R9.

Narrative

WHILE TAXIING FOR TKOF WE WERE NEARING THE DEP END OF THE RWY WHILE BACK TAXIING. NEEDING TO MAKE A 180 DEG TURN FOR TKOF; I NOTICED THAT THE NORMAL 60 FT WIDE RWY WAS GETTING NOTICEABLY NARROWER AS I NEARED THE END. THIS APPEARED TO BE FROM GRASS GROWING ON AND THROUGH SOME CRACKS NEAR THE EDGE OF THE RWY AND GROWING INWARD ABOUT 4-5 FT TOWARD THE CENTER OF THE RWY. AS THINGS LOOKED TO BE GETTING TIGHT FOR THE 180 DEG TURN; I TRIED TO STAY NEAR THE EDGE OF THE RWY SURFACE WHICH MEANT ROLLING OVER SOME OF THE GRASS. AS I APCHED THE TURNING POINT; THE R MAIN GEAR STARTED TO BECOME STUCK AND THE ACFT WOULD NOT TURN L. AS I TRIED TO TURN L; THE ACFT CONTINUED DRIFTING TO THE R AND GOT STUCK. AFTER EXITING THE AIRPLANE; WE SAW THAT WHAT WE THOUGHT WAS THE RWY WAS IN FACT THERE BUT THE ASPHALT CRUMBLED AND BROKE UNDER THE WEIGHT OF THE AIRPLANE. I CAN ONLY ASSUME THAT THE GRASS THAT GREW INTO AND ON THE RWY WEAKENED THE RWY SURFACE ENOUGH NOT TO BE ABLE TO SUPPORT OUR AIRPLANE. WE NEEDED ASSISTANCE TO GET THE AIRPLANE OUT OF THE SINKING AREA AND THEN CONTINUED ON AN UNEVENTFUL FLT. I WILL NEVER AGAIN TRUST THAT NEARING THE EDGE OF A RWY WITH GRASS GROWING THROUGH THE CRACKS; THAT IT STILL HAS ALL OF ITS STRENGTH. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INGO: PLT STATED THAT THE NORMAL RWY WIDTH IS 60 FT; BUT WHERE THE VEGETATION IS GROWING THROUGH THE RWY SURFACE; THE USABLE WIDTH IS ABOUT 48 FT. HIS ACFT WEIGHT AT THE TIME WAS ABOUT 11300 LBS. HE ESTIMATES THAT THE WHEEL WEIGHT WAS ABOUT 4500 LBS. IN ORDER TO FREE THE ACFT; THE VOLUNTEER FIRE DEPT USED AN AIRBAG UNDER THE WING. WHILE ATTEMPTING TO PULL THE ACFT OUT WITH A TUG; IT ACTUALLY BECAME MORE DEEPLY STUCK. THE ARPT HAS VERY LITTLE JET TFC; BUT DOES OCCASIONALLY.