What happened
On 21 August 2003, a Piper PA-28R-200, registration G-BHIR, was conducting a private flight from Tatenhill Airfield to Liverpool. Shortly after takeoff, while climbing at approximately 850 feet, the engine began making a rumbling noise and suffered a sudden loss of power. The pilot attempted to restart the engine by switching fuel tanks and checking the magnetos, but the engine failed to recover. As oil began to spray onto the windscreen, the pilot declared a MAYDAY.
While attempting to locate a landing site, the pilot identified a long field but was forced to divert to a second, shorter field due to transmission lines obstructing the first. To minimize the risk of the aircraft flipping during the landing, the pilot opted to keep the landing gear retracted. Upon touchdown, the aircraft slid across the grass and entered a small wooded area. The impact with trees caused both wings to be torn from the fuselage. The pilot sustained a serious injury, specifically a fractured collarbone, caused by striking the control yoke.
The investigation
The AAIB examined the wreckage and the engine components. The investigation focused on the Avco Lycoming IO-360 engine, which had undergone a crankshaft replacement approximately 115 flying hours prior to the accident. Investigators found that the engine's No 2 connecting rod had detached from the crankshaft, punching a large hole through the crankcase.
Physical evidence showed that the engine's internal components had been severely damaged by the impact of the rod while the engine was running. While the extreme mechanical damage prevented a definitive conclusion, specialists identified fatigue cracking on one of the big-end bolts. This type of cracking was consistent with the bolt being subjected to high tensile stress due to an improperly secured nut.
Findings
- The engine failure was caused by the release of the No 2 connecting rod from the crankshaft.
- The separation of the big-end cap was driven by the fracture of the big-end bolts.
- Evidence indicated that at least one bolt had suffered low-cycle fatigue, which is consistent with the nut having been insufficiently tightened during the previous engine overhaul.
- The loss of critical components during the failure made it impossible to positively confirm the exact cause of the initial bolt loosening.