PA60 DEPARTED RWY DURING TKOF ABORT.

Narrative

I WAS CLRED FOR TKOF ON RWY 34R. I HELD THE BRAKES AND ADVANCED THE THROTTLES TO 30 INCHES OF MANIFOLD PRESSURE. I CONFIRMED THAT OIL PRESSURE AND FUEL FLOW WERE CORRECT AND MATCHED ON BOTH ENGS; THEN I ADVANCED THE THROTTLE TO 42 INCHES MANIFOLD PRESSURE (TKOF PWR). I KEPT A SLIGHT AMOUNT OF PRESSURE ON THE BRAKES TO KEEP THE ACFT ALIGNED WITH THE CTR OF THE RWY (THE AEROSTAR'S RUDDER PEDALS DO NOT CTL THE NOSEWHEEL). UPON REACHING 40 KIAS ON THE TKOF ROLL; THE RUDDER BECAME EFFECTIVE; SO I USED IT INSTEAD OF THE BRAKES TO MAINTAIN LONGITUDINAL CTL. 1000 FT INTO THE TKOF ROLL; AT APPROX 65 KIAS; I FELT A 'SHUDDER' THAT SEEMED TO COME FROM THE WHEELS. MY FIRST THOUGHT WAS THAT I HAD ENCOUNTERED A POOL OF STANDING WATER ON THE RWY. THEN I FELT A SECOND SHUDDER LESS THAN A SECOND LATER. AT THIS POINT; I FELT AS IF I WAS LOSING DIRECTIONAL CTL; BECAUSE SOMETHING SEEMED TO BE IMPEDING THE WHEELS IN AN UNUSUAL WAY. GETTING THE ACFT INTO THE AIR WAS NOT AN OPTION; BECAUSE I WAS WELL BELOW ROTATION SPD. SO; I CHOSE TO ABORT THE TKOF. I CHOPPED BOTH THROTTLES. AT THIS MOMENT; I WAS STILL ALIGNED WITH THE CTR OF RWY. AGGRESSIVE BRAKING AT THIS POINT SEEMED INAPPROPRIATE; BECAUSE THE RWY WAS WET. I DIDN'T WANT THE ACFT TO SKID; AND I WASN'T SURE OF THE CONDITION OF MY WHEELS AND BRAKES. I WANTED TO COAST GENTLY DOWN THE RWY WITH MINIMAL BRAKING; BUT IN LESS THAN 2 SECONDS; I WAS ON RAIN-SOAKED SOD TO THE L OF THE RWY. IT HAD SNOWED 2 DAYS BEFORE; AND HAD RAINED STEADILY ALL DAY; SO THIS SOD WAS SOFT AND THOROUGHLY DRENCHED. UPON REACHING THE EDGE OF THE RWY; THE ACFT PIVOTED AND BEGAN SKIDDING SIDEWAYS; MAKING IT ALMOST IMPOSSIBLE TO CTL. IT SKIDDED 1000 FT AND CAME TO REST IN A DITCH 300 FT TO THE L OF THE RWY. 3 POSSIBLE CAUSES: 1) I TALKED TO A MANASSAS-BASED PLT; WHO SAID HE HAD EXPERIENCED VIBRATIONS FROM THE RWY SURFACE WHEN FLYING A CESSNA 182 ON RWY 34R. ARPT MGR SAID THE RWY IS SCHEDULED TO BE RESURFACED. HOWEVER; EVEN IF THE IRREGULAR RWY SURFACE CAUSED MY ACFT TO SHUDDER; THAT WOULD NOT EXPLAIN WHY IT DARTED TO THE L EDGE OF THE RWY; AND THE SENSATIONS I FELT DID NOT SEEM CAUSED BY AN IRREGULAR RWY SURFACE. 2) ARPT MGR POINTED OUT THAT MY PLANE HAD BEEN SITTING ON THE RAMP ALL WEEK. 2 DAYS PRIOR TO MY DEP; AN ICE STORM BLANKETED THE AREA. AT THE TIME OF MY DEP; THE TEMP WAS JUST ABOVE FREEZING IN LIGHT RAIN. HE SUGGESTED THAT A PIECE OF ICE MIGHT HAVE JAMMED 1 OR BOTH OF MY BRAKES. I DID NOT SEE ANY ICE DURING MY PREFLT INSPECTION; AND I HAD NO DIFFICULTY TAXIING THE ACFT MORE THAN 1 MI FROM THE FBO TO THE DEP END OF RWY 34L; BUT SOME ICE MAY HAVE MOVED INTO A COMPROMISING POS AS I ACCELERATED FOR TKOF. 3) I TALKED WITH A FORMER FACTORY TEST PLT FOR THE AEROSTAR COMPANY. HE SAID A CRACKED OR BROKEN STEERING COLLAR IS CONSISTENT WITH THE SCENARIO I DESCRIBED. I MENTIONED TO HIM THAT THE ACFT HAD BEEN MOVED BY A MANASSAS FBO; WHILE I WAS GONE. HE SAID MOVING THE ACFT COULD HAVE CAUSED SUCH DAMAGE IF IT IS FOUND.