AN SMT LNDG AT ARB; MI; LANDS CLOSE BEHIND AN SMA. CLOSE ENOUGH THAT A GAR WAS NECESSARY TO PROVIDE PROPER SEPARATION; HOWEVER; A THROTTLE OF THE SMT WAS UNABLE TO BE ADVANCED FOR GAR PWR.

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ARB; XX35 JUL/KK/97; DAYLIGHT; 10 MI VISIBILITY IN HAZE. WIND AT YIP AS RPTED BY ATIS 'CALM.' ARB TWR CLOSED. COMING INTO ARPT AREA AT APPROX 1800 FT MSL ON A COURSE THAT APPROXIMATED THE VOR/GPS RWY 24 APCH. (WAS MONITORING THE GPS APCH SEQUENCE ON THE GPS EQUIP.) CHKED YIP AND ARB ATIS APPROX 12 MI OUT. WINDS RPTED AS CALM AT YIP; ALTIMETER 30.09. SWITCHED TO ARB TWR/ADVISORY FREQ 120.3 APPROX 10 MI OUT. LISTENED TO A PORTION OF AN ACFT'S ANNOUNCEMENT 'FOR RWY 24 AT ANN ARBOR.' CALLED 'TWIN COMMANCHE #1 ACFT GPS INBOUND RWY 24 ANN ARBOR.' APPROX 2 MI NE OF THRESHOLD ON THE VOR COURSE; ANNOUNCED 'TWIN COMMANCHE #1 ACFT TURNING FINAL RWY 24 ANN ARBOR.' CESSNA ON BASE LEG ANNOUNCED 'CESSNA ON BASE TO FINAL RWY 24 ANN ARBOR. WE'LL BREAK OFF AND LET YOU GO AHEAD IF YOU'D LIKE.' #1 ACFT; 'NO; THAT'S OK; I'LL DO A 360 DEG TURN OUT HERE; YOU GO AHEAD (CONTINUE).' CESSNA THEN CALLED FINAL WITH ADDITIONAL INFO THAT IT WOULD BE TOUCH AND GO. EXECUTED A 360 DEG L TURN THAT STARTED ON A 180 DEG HDG NOW AS A RESULT OF A 20+ DEG L TURN TO CLR FOR THE CESSNA TURNING BASE TO FINAL. ROLLED OUT OF THE 360 DEG TURN; NOTED A CESSNA TAILDRAGGER ON DOWNWIND. THAT ACFT CALLED 'CESSNA; DOWNWIND FOR RWY 24 ANN ARBOR; WHERE'S THE TWIN COMMANCHE?' 'I'M AT YOUR 11 O'CLOCK; LOW; SBOUND #1 ACFT.' NO REPLY FROM THE TAILDRAGGER. EXECUTED A 300 DEG L TURN. TAILDRAGGER CALLED FINAL TO RWY 24; FULL STOP. #1 ACFT ROLLED OUT ON FINAL APCH HDG TO RWY 24; AND OBSERVED THE TAILDRAGGER LAND OVER THE NUMBERS AND ROLL OUT SLOWLY. WE EXPECTED THE TAILDRAGGER TO TURN OFF AT THE CTR TXWY; 12/30 TXWY; OR TURF RWY 12/30 AS ITS DECELERATION APPEARED TO BE COMPLETE WELL BEFORE THESE INTXNS. #1 ACFT CALLED '1/4 MI FINAL RWY 24 ANN ARBOR.' TAILDRAGGER CONTINUED TO TAXI STRAIGHT AHEAD ON RWY 24. #1 ACFT BEGAN TO ADVANCE THROTTLES; R THROTTLE BOUND UP A BIT; NOTED AIRSPD AT 100 MPH (BELOW BLUE LINE BUT ABOVE VMC). OPTED TO CONTINUE STABILIZED APCH WITHOUT AGAIN TRYING ASYMMETRICAL THROTTLE ADVANCE JUDGING THAT: 1) TAILDRAGGER WOULD CLR BEFORE TOUCHDOWN. 2) SUFFICIENT SPACING EXISTED BTWN THE 2 ACFT TO STOP #1 ACFT WITHOUT BRAKING SHOULD THE TAILDRAGGER STOP ON THE RWY AT ITS PRESENT POS. I COMMITTED TO THE LNDG SEQUENCE; THEN THE TAILDRAGGER SLOWED FURTHER. THE TAILDRAGGER WAS APPROX WITHIN THE LAST 300 FT OF THE 3500 FT RWY WHEN I TOUCHED DOWN. #1 ACFT ROLLED OUT WITHOUT THE USE OF BRAKES TO AID IN THE CLRING OF THE RWY FOR THE NOW APCHING TOUCH AND GO TFC. THE TAILDRAGGER CLRED THE RWY AND ANNOUNCED THE SAME. A DEPARTING ACFT ANNOUNCED ITS DEP AS #1 ACFT CLRED THE RWY BEHIND THE TAILDRAGGER. THE TAILDRAGGER TAXIED ABOUT 100 FT NE ON THE TXWY; STOPPED; ANNOUNCED A TAXI TO THE 'NW TEES;' PROCEEDED TO TAXI TO THE TURF RWY 12/30; AND TURNED L ONTO THAT RWY. #1 ACFT FOLLOWED TO THAT POINT; THEN TAXIED TO THE TERMINAL RAMP. CHAIN OF EVENTS -- HOW THE PROB AROSE: CLOSED TWR. BUSY TFC PATTERN. GPS APCH PATTERN NOT CONSISTENT WITH STANDARD VFR PATTERN. (THE MIXING OF VFR AND PRACTICE IFR PROCS AT A NON TWRED ARPT). CONTRIBUTING FACTORS: HIGH PERFORMANCE TWIN SHARING DISSIMILAR PATTERN WITH A LOW PERFORMANCE TAILDRAGGER. THE PIPER TWIN COMMANCHE THROTTLE QUADRANT HAS AN OVERLAID ALUMINUM PLACARD BTWN THE LEVERS THAT CAN FRAY ON ITS EDGE AND SLIGHTLY BIND THE LEVER MOVEMENT. HOW IT WAS DISCOVERED: SEE AND BE SEEN. CORRECTIVE ACTIONS: A 'SHARED' RWY LNDG RESULTED WHILE AVOIDING A POTENTIAL ASYMMETRICAL THRUST PROB DURING THE LNDG SEQUENCE. HUMAN PERFORMANCE CONSIDERATIONS -- PERCEPTIONS; JUDGEMENTS; DECISIONS: IT WAS PERCEIVED THAT THE TAILDRAGGER WOULD CLR THE RWY. WHEN THE TAILDRAGGER DID NOT EXIT AT THE CTR TXWY; A GAR WAS CONSIDERED UNTIL THE R THROTTLE LEVER BOUND UP. WITH SUFFICIENT SAFE DISTANCE BTWN THE 2 ACFT; A COMMITMENT TO LAND WAS MADE. ACTIONS OR INACTIONS: DID NOT EXECUTE A POSSIBLE ASYMMETRICAL THRUST GAR WITH SUFFICIENT AIRSPD AVAILABLE. DID NOT EXECUTE A LNDG AFTER THE FIRST CESSNA AND BEFORE THE TAILDRAGGER AS #1 ACFT WAS LOWER; CLOSER; AND FASTER TO THE THRESHOLD. (CONTRIBUTING FACTOR TO THIS WAS NO REPLY FROM THE TAILDRAGGER AFTER GIVING #1 ACFT POS.) FACTORS AFFECTING THE QUALITY OF HUMAN PERFORMANCE: PLT WAS PICKING UP 3 ADULT CHILDREN OF A TERMINALLY ILL CANCER PATIENT THAT HAD BEEN CALLED TO BE PRESENT AT THE PATIENT'S FINAL DAYS. ALL PERSONS KNOWN PERSONALLY BY THE PLT.