A LEAR25 HYDROPLANES OFF THE RWY AT PWK; IL.

Narrative

WX CONDITIONS WERE APPROX 2600 FT BROKEN; 5 MI VISIBILITY; WINDS 190 DEGS AT 6 KTS; AND MODERATE RAIN SHOWERS. FLT CONDITIONS WERE IMC WITH NO TURB. I REDUCED THE THRUST LEVERS TO FLT IDLE AND MADE A SMOOTH AND CTLED LNDG AT VREF ON OR NEAR THE SECOND SET OF TOUCHDOWN MARKINGS. KNOWING THAT THE RWY CONDITIONS WERE WET AND THE LENGTH WAS SHORT; I IMMEDIATELY APPLIED PRESSURE TO THE BRAKE PEDALS UPON TOUCHDOWN. CAPT IMMEDIATELY EXTENDED SPOILERS ON TOUCHDOWN. DECELERATION OF THE ACFT APPEARED TO BE NORMAL. AT APPROX 3/4 OF THE WAY DOWN THE RWY ALL APPEARED TO BE NORMAL AND STOPPING THE ACFT PRIOR TO THE END OF THE RWY WAS NEVER QUESTIONABLE. AT ROUGHLY 200-400 FT PRIOR TO THE END OF THE RWY THE ACFT APPEARED TO STOP DECELERATING AS IT NORMALLY DOES. THERE IS A STRONG POSSIBILITY THAT THE ACFT BEGAN TO HYDROPLANE. AT APPROX 100 FT PRIOR TO THE END OF THE RWY; IT WAS APPARENT THAT I WOULD NOT BE ABLE TO COMPLETELY STOP THE ACFT. I DEPLOYED THE DRAG CHUTE; BECAUSE THE GRASS WAS WET AND I WISHED TO UTILIZE EVERY MEANS AVAILABLE TO ME TO STOP THE ACFT FROM SLIDING THROUGH THE FENCE. I WOULD HAVE APPROXIMATED THE ACFT SPD TO BE IN THE VICINITY OF 40-50 KTS. DEMONSTRATING THAT THERE WAS NO EFFECTIVE BRAKING IN THE LAST 200 FT. THE DRAG CHUTE OPENED FULLY JUST AS THE ACFT NOSEWHEEL LEFT THE RWY SURFACE AND MADE CONTACT WITH THE GRASS. I MAINTAINED DIRECTIONAL CTL ACCOMPLISHING A L HAND TURN 100 FT AND 80 DEGS BACK TOWARDS THE RWY. ONCE THE ACFT WAS CLOSE TO STRAIGHT; I APPLIED A SMALL AMOUNT OF PWR TO ENSURE FORWARD MOVEMENT AS TO NOT BECOME STUCK IN THE SOAKING WET GRASS. I TAXIED THE ACFT TO RE-ENTER THE RWY SURFACE. I WAS CLRED TO BACK TAXI ON THE RWY TO THE FBO. THERE WAS NO DAMAGE TO ARPT PROPERTY OR TO THE AIRPLANE. MAINT DID A THOROUGH INSPECTION OF THE ACFT; ITS BRAKING AND ANTI-SKID SYS; AND ITS TIRES PRIOR TO INITIATING RETURN HOME FLT. THERE WERE NO MALFUNCTIONS OR DEFICIENCIES TO ANY SYS AND NO FLAT SPOTS ON THE TIRES; WHICH WOULD INDICATE THAT HYDROPLANING DID OCCUR.