A C172 WAS CLRED FOR TKOF AT STS AND STOPPED SHORT OF THE RWY BECAUSE OF CONFLICTING TFC THAT HAD MADE A SHORT APCH; CATCHING THE TWR CTLR BY SURPRISE.

Narrative

NEAR MISS ON RWY APCH END. ACFT A CLRED FOR TKOF RWY 19; THE SECOND ACFT B CLRED FOR LNDG RWY 19; AND ACFT B MAKES A SHORT APCH. I WAS PIC IN A C172 (ACFT A) TAKING OFF RWY 19 WITH 3 (INCLUDING PLT) ON BOARD. THE SECOND ACFT (B) WAS A C172 LNDG RWY 19. I (ACFT A) WAS CLRED BY THE TWR TO CROSS RWY 14 AND TAKE OFF ON RWY 19. DURING ACFT A TAXI ON TXWY Y FROM THE RUN-UP AREA TO RWY 19; I LOOKED OUT TOWARDS THE APCH FOR RWY 19 TO CHK FOR OTHER ACFT (I ALWAYS LOOK). I SUDDENLY NOTICED ACFT B ON A 150 FT HORIZ (100 FT VERT) SHORT FINAL FOR RWY 19. I ACTUALLY WAS NOT SURE IF ACFT B WAS LNDG RWY 19 OR RWY 14. I (ACFT A) IMMEDIATELY STOPPED JUST SHORT OF RWY 14 BUT IN THE RWY ACTIVE AREA (BEYOND HOLD BARS BUT NOT ON RWY 14). ABOUT THE TIME I STOPPED; TWR SAID (IN A HURRIED VOICE) ACFT B GAR WHICH THEY DID IMMEDIATELY. TWR THEN SAID TO ACFT B; '...PLEASE TELL US IF YOU INTEND TO MAKE A SHORT APCH...!' ACFT B ACKNOWLEDGED. TWR HAD CLRED ACFT B (WHEN MID FIELD DOWNWIND) TO LAND ON RWY 19. TWR THEN CLRED ME (ACFT A) TO TAKE OFF RWY 19. TWR APPARENTLY BELIEVED THERE WAS ENOUGH TIME (AND SPACING) BTWN ACFT. IDEAS: TWR COULD ADVISE LNDG ACFT THAT THERE IS 'ONE DEP' PRIOR TO THE ACFT LNDG. I OFTEN HEAR THIS AT OTHER ARPTS. 2) DEPARTING ACFT ALWAYS LOOK TOWARD RWY APCH TO VERIFY THAT NO ACFT IS LNDG. 3) LAST RESORT -- DO NOT ISSUE LNDG AND TKOF CLRNCS SIMULTANEOUSLY.