PLT OF VINTAGE SMA REQUIRING MANUAL START PROC (HAND PROPPING) IS UNABLE TO RESTRAIN THE ACFT AFTER START. ACFT COLLIDES WITH A C170 PARKED NEARBY.

Narrative

THE PRIMARY ACFT INVOLVED IS A 1939 LUSCOMBE 8A (CERTIFIED WITHOUT AN ELECTRICAL STARTING SYS). THE NORMAL START PROC INVOLVES CHOCKING THE WHEELS; OPENING THE THROTTLE APPROX 1/4 INCH OR LESS; PRIMING THE ENG 2-3 STROKES; SETTING THE MAGNETOS TO THE 'BOTH' POS AND THEN HAND PROPPING THE ENG. I DID ALL OF THE ABOVE AND THE ENG SEEMED TO BE STARTING NORMALLY. AS I QUICKLY LEFT THE FRONT OF THE ACFT AND MADE MY WAY TO THE L SIDE PLT'S DOOR; THE ENG WENT FROM A COUGHING IDLE TO A SHORT BURST OF PWR. I HAD NOT YET REACHED THE COCKPIT BUT DID HAVE MY HAND ON THE L STRUT WHEN THE 'BURST' OCCURRED. THE ACFT JUMPED THE CHOCKS AND SPUN TO THE L HITTING A NEARBY C170'S WINGTIP. THE LUSCOMBE'S PROP MADE A NUMBER OF SLICES INTO THE WINGTIP PRIOR TO RETURNING TO A SLOWER IDLE AND STOPPING. A CONTRIBUTING FACTOR COULD HAVE BEEN AN OVERLY RICH INITIAL MIXTURE. ALTHOUGH THE ABOVE START SEQUENCE IS COMMONLY ACCOMPLISHED WITHOUT INCIDENT; IT WOULD ALWAYS BE BEST TO HAVE A SECOND PERSON IN THE ACFT AT THE CTLS IN CASE THERE WAS A RUN AWAY SUCH AS THIS.