DIAMOND DA20 PLT HAD THE PAX DOOR FALL OFF THE ACFT.

Narrative

SEP/SAT/04; DURING CLBOUT FROM 5M0 AT APPROX 1800 FT MSL; I NOTICED AN ANNUNCIATOR PANEL LIGHT 'DOORS' WAS ILLUMINATED. NECESSARY ACTION WAS TAKEN; MAIN CABIN DOOR WAS CHKED AND FOUND TO BE SECURE. FOLLOWING MAIN CABIN CHK; THE REAR PAX DOOR WAS CHKED. INTERIOR DOOR CATCH WAS OBSERVED IN THE EXTENDED POS. UPON OBSERVATION OF EXTENDED LATCH; I REACHED BACK IN AN ATTEMPT TO SECURE CATCH. UPON PLACING FORWARD PRESSURE ON LATCH; THE REAR PAX DOOR THEN DEPARTED THE ACFT. FULL ATTN WAS THEN GIVEN TO ENSURE THE ACFT WOULD MAINTAIN CTLED FLT. ONCE THIS WAS DETERMINED; EXTERIOR WAS EXAMINED VISUALLY FOR ANY DAMAGE CAUSED BY DEPARTED DOOR. NONE WAS OBSERVED. ONCE THIS WAS PERFORMED; SUITABLE ARPTS WERE CONSIDERED. ACFT WAS THEN TAKEN TO APPROX 4500 FT TO ASSESS THE HANDLING CHARACTERISTICS OF THE ACFT IN PRESENT CONFIGN. UPON DETERMINING THE ACFT TO BE FULLY CTLABLE; SUITABLE ARPT WAS CHOSEN AND FLOWN TO; AFTER CONSIDERATION WAS GIVEN TO WX; TERRAIN AND OBSTRUCTIONS TO FLT. ARRIVED AT CHOSEN ARPT AND LANDED WITHOUT FURTHER INCIDENT. PRIOR TO FLT; THE REAR PAX DOOR WAS CLOSED AND LATCHED. I THEN WALKED TO FBO AND WAS AWAY FROM ACFT FOR AN ESTIMATED 30 MINS. UPON RETURN TO ACFT; A PROPER POH PREFLT WAS PERFORMED. UPON ENG START; I ANNOUNCED MY INTENTIONS AT 5M0 AND BACK-TAXIED TO RWY 36; WHERE I PERFORMED A RUN-UP AND FOUND THE ACFT SUITABLE FOR FLT. LATCHED THE MAIN CANOPY; CHKED INSTS; GAUGES AND ANNUNCIATOR PANEL FOR TKOF. EVERYTHING CHKED OK WITH ONLY THE PITOT LIGHT ILLUMINATED. TOOK ACTIVE RWY 36; AFTER ANNOUNCING INTENTIONS; AND DEPARTED THE ARPT. EXACT CAUSE OF DOOR DEP WAS NOT KNOWN. WE WILL FROM NOW ON TRIPLECHK THE PAX DOOR LATCH BEFORE TKOF ROLL. NO INJURIES WERE SUSTAINED BY EITHER MYSELF OR ANY PERSONS ON THE GND. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE DOOR FELL OFF ONTO A HOUSE. THE OWNER CALLED POLICE; AND AFTER AN INSPECTION; THEY CALLED THE FAA. THE FAA HAS BEGUN AN INVESTIGATION. THE ACFT MANUFACTURER IS REDESIGNING THE DOOR. THE MANUFACTURER WILL REPLACE THE DOOR WITH A REDESIGNED MODEL; FREE OF CHARGE.