A PIPER PA34-200 WAS LANDED GEAR UP AFTER BEING DISTR BY AN OPEN CABIN DOOR.

Narrative

IT STARTED WHEN THE FRONT CABIN DOOR FLEW OPEN ON TKOF; ON DEP AT APPROX 500 FT AGL. AN IMMEDIATE REQUEST WAS MADE TO TWR TO RETURN FOR LNDG. I WAS INSTRUCTED TO MAKE R TFC FOR RWY 1. I WENT THROUGH MY PRELNDG CHKLIST; CONFIGURING THE AIRPLANE FOR A NORMAL LNDG. DUE TO THE STEEP DSCNT; I WAS IN A STEEP R BANK AND CONCERNED FOR THE PAX SEATED NEXT TO THE DOOR AND CTLING THE AIRPLANE. THE SHORT FINAL APCH; TO ME; SEEMED NORMAL WITH THE AIRPLANE IN THE LNDG CONFIGN. DUE TO THE SHORT APCH; THE FLT CONDITIONS AND THE DISTR OF THE OPEN DOOR; I DID NOT COMPLETE/REMEMBER COMPLETING MY FINAL LNDG CHK. I CAN STILL HEAR MY INSTRUCTOR'S WORDS 'FLY THE AIRPLANE.' IN THE LNDG FLARE; I FELT THE AIRPLANE IN GND EFFECT LIKE A NORMAL LNDG AND I WAS PREPARED FOR A GOOD/SMOOTH LNDG ROLL. THE AIRPLANE PANCAKED AND CONTINUED TO MOVE FORWARD AND I WAS UNAWARE OF WHAT HAD JUST HAPPENED -- LNDG GEAR UP. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS A PIPER SENECA PA34-200 AND INCURRED DAMAGE TO THE LOWER FUSELAGE AND PROPS. THE RPTR SAID SHE WAS NOT SURE IF THE LNDG GEAR WARNING SYS; HORN AND LIGHTS; WAS OPERATING. THE RPTR SAID HEARING WAS IMPAIRED BECAUSE OF THE OPEN DOOR AND JUST COULD NOT BE SURE ABOUT THE HORN. THE RPTR STATED THE ACFT WAS JACKED AND THE LNDG GEAR OPERATED NORMALLY. THE RPTR SAID THE LNDG GEAR WARNING HORN AND POS INDICATING LIGHTS ALSO OPERATED NORMALLY. THE RPTR STATED THE FAA SAFETY INVESTIGATOR HAS ADVISED THAT THE CASE IS CLOSED.