PA23 PLT ABORTS TKOF AFTER PAX INADVERTENTLY OPENS ACFT DOOR.

Narrative

AFTER COMPLETING THE BEFORE TKOF CHKLIST; THE ACFT (PA23- 150) WAS CLRED FOR POS AND HOLD ON RWY 22R AT EWR. ACFT WAS CLRED FOR TKOF AND A NORMAL TKOF COMMENCED. AT APPROX 85 KIAS AND 20 FT ALT; THE PAX SITTING IN THE COPLT SEAT USED THE CABIN DOOR LATCH AS A HANDHOLD -- OPENING THE CABIN DOOR AS A RESULT. PIC IMMEDIATELY REDUCED PWR AND LANDED NORMALLY ON THE REMAINING RWY. CONTRIBUTING FACTORS: 1) INADEQUATE PAX BRIEFING -- ALTHOUGH I BRIEFED THE SINGLE PAX TO KEEP HIS SEATBELT FASTENED AT ALL TIMES; GENERAL CONDUCT OF THE FLT; AND EMER PROCS -- I DID NOT POINT OUT AND INSIST THAT HE SHOULD NOT USE THE DOOR LATCH AS A HANDHOLD. I WILL ENSURE THAT ALL FUTURE PAX ARE BRIEFED THAT IT IS OFF LIMITS ONCE SECURED VIA THE PRE TKOF CHKLIST UNTIL THE ACFT HAS LANDED AND COMPLETELY STOPPED IN THE PARKING AREA. 2) WHEN THE SINGLE DOOR LATCH IS SECURED IN THE PA23-150 IT IS IN THE HORIZ POS AND REALLY DOES LOOK LIKE A HANDHOLD. I AM GOING TO TALK WITH MAINT ABOUT PLACARDING OR WRAPPING IT WITH MAYBE YELLOW; BLACK OR RED TAPE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATES THAT THE NEWER ACFT HAVE 2 LATCHES; BUT THIS OLDER MODEL; AND OTHERS LIKE IT; HAVE ONLY 1 DOOR LATCH. THE RPTR WILL BRIEF HIS PAX IN THE FUTURE NOT TO TOUCH THIS LATCH; BUT WONDERS IF OTHER PLTS WILL DO THE SAME.