FLC OF BEECH 58 IS INVOLVED IN A POSSIBLE COLLISION INCIDENT WITH A LAHSO OP WITH A DASH 8 COMMUTER WHO WAS GIVEN THE LAHSO CLRNC. A GAR WAS INITIATED BY RPTR ACFT.

Narrative

AS PIC (PNF) OF BE58 (BARON) WE WERE CLRED TO LAND RWY 33 AT DCA WHILE A COMMUTER ACFT (DHC8) WAS CLRED TO LAND RWY 36 TO HOLD SHORT OF OUR RWY 33. COMMUTER WAS ON AN INTERSECTING (COLLISION) COURSE WITH US AS HIS RELATIVE POS DID NOT CHANGE FROM MY VIEW. TEMP WAS HOT (94 DEGS F) AND DHC8 APPEARED TO FLOAT EXCESSIVELY IN THE FLARE AND APPEARED TO BE TRAVELING AT A HIGH RATE OF SPD; EVEN AFTER TOUCHDOWN. THIS MAY HAVE BEEN DUE TO THE INCREASED DENSITY ALT AND HIGHER THAN NORMAL TRUE AIRSPD OVER STANDARD CONDITIONS. IT ALSO MAY HAVE BEEN INTENTIONAL AS THE COMMUTER GATES ARE ON THE N END OF THE ARPT AND A LONG TOUCHDOWN WOULD REDUCE COMMUTER'S TAXI TIME. I BEGAN TO WONDER IF THE COMMUTER WOULD BE ABLE TO STOP. WE WERE STILL ON INTERSECTING COURSE AFTER COMMUTER TOUCHED DOWN AND WE WERE XING THE ARPT BOUNDARY. I BELIEVED THE COMMUTER WOULD LIKELY BE ABLE TO STOP (APPROX 4500 FT AVAILABLE FOR THEM) HOWEVER; THERE WAS ENOUGH DOUBT THAT I CHOSE NOT TO PUT OUR FLT AND PAX AT RISK AND INSTRUCTED PF TO GAR. LAHSO OP WAS CONDUCTED IN ACCORDANCE WITH APPROPRIATE PLT AND AIR TFC PROCS WITH BOTH ACFT ADVISED OF THE OTHER'S POS AND INTENTIONS. COMMUTER TURNED OFF APPROX 1000 FT SHORT OF INTXN. PAX RECORDED EVENT ON VIDEO. WE WERE ASKED BY ATC IF THERE WAS A PROB AND TOLD THEM WE WERE UNSURE IF COMMUTER WOULD STOP. WE WERE INSTRUCTED TO ENTER DOWNWIND FOR RWY 3 AND PROMPTLY CLRED TO LAND. IN THIS CASE; ALL LAHSO PROCS WERE MET AND A COLLISION RISK AT A CRITICAL PHASE OF FLT STILL SEEMED APPARENT. UPON DEBRIEF; SIC INDICATED HE SHARED MY CONCERN REGARDING THE COMMUTER'S ABILITY TO STOP. LAHSO; EVEN WHEN CONDUCTED WELL; SEEMS TO PRESENT RISKS AND LACK SAFEGUARDS; UNLIKE OTHER FLT OPS. A CONTRIBUTING FACTOR IN MY DECISION TO GAR; WAS AT THE INTXN OF THE 2 RWYS; OUR ACFT SPD WOULD HAVE BEEN TOO SLOW TO FLY AND TOO FAST TO STOP; SO THE ONLY OPTION WOULD HAVE BEEN AN EVASIVE MANEUVER ON THE GND. I DIDN'T CONSIDER THIS ACCEPTABLE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT THIS LAHSO OP WAS ACCOMPLISHED STRICTLY 'BY THE BOOK' WITH ALL COM AND PROCS HANDLED QUITE WELL AND IT STILL TURNED OUT TO BE A PROB SIT. WITH A CLOSE INVOLVEMENT IN LAHSO OPS AND STUDY OF OTHER SUCH INCIDENTS THIS RPTR FEELS THAT LAHSO IS EXTREMELY DANGEROUS. ONE OF THE PAX IN THE ACFT HAD A VIDEO CAMERA AND VIDEO TAPED THE INCIDENT. REVIEW OF THE TAPE SEEMS TO CONFIRM THAT IT WAS UNSAFE TO CONTINUE THE APCH AND LNDG. THE GAR WAS THE ONLY SAFE OPTION.