At approximately 500 ft after take-off the engine began to run roughly.
The aircraft was immediately positioned for a landing back on to the departure runway. The engine was still developing sufficient power at this point to complete a climbing turn to 800 ft. Approximately mid-down wind, the engine began to run very roughly and then lost all power. In the subsequent forced landing, the aircraft touched down approximately one third of the way along the runway. The pilot was unable to bring the aircraft to a halt in the distance remaining to avoid overrunning the the end of the strip. The aircraft came to rest part way down the sloping sea wall at the end of the runway. All three occupants were able to evacuate the aircraft safely.
Examination of the engine found that the centre electrodes for both spark plugs in the number four cylinder were excessively lead fouled and unable to fire. The porcelain surrounding the electrode on the top spark plug for number two cylinder was also cracked and indications were that this plug was firing intermittently. No other faults were found that could have contributed to to the power loss.