Piper PA-28R-201T Turbo Cherokee Arrow III, G-BFLI
The aircraft was on its first flight after having had two new cylinders fitted to the engine. After approximately 90 minutes the engine started making an unusual sound and, fearing an imminent catastrophic engine failure or fire, the pilot elected to shut it down and make a forced landing. The aircraft came to rest in a lake; the pilot escaped with only minor injuries. The engine problem was attributed to the rocker for the No 4 cylinder inlet valve becoming detached due to failure of the stud bolts, causing the inlet valve to remain closed. Metallurgical examination of the fractures revealed evidence of a fatigue initiated failure mechanism in both bolts; this could not be attributed to any deficiency in the bolt material.