What happened
On November 13, 2018, at approximately 08:15 a.m., a Piper PA-25-235 agricultural aircraft, registration HI-191, was performing its second spraying mission of the day near the Peñuela Aerodrome in Esperanza, Valverde. While returning to the airfield, the aircraft experienced a sudden loss of engine power. The pilot attempted to troubleshoot the issue by checking the fuel mixture and magnetos and attempted a restart, but was unsuccessful. Consequently, the pilot performed a forced landing in a banana plantation located approximately one mile southwest of the runway. The pilot was uninjured, and the aircraft sustained minor damage, including propeller deformation and impact damage to the wings and nose. The landing resulted in the destruction of 2/21 banana plants in the field.
The investigation
The CIAA investigation focused on the mechanical integrity of the Lycoming O-540 engine. Following the accident, the engine was sent to an overhaul facility in Fort Lauderdale, Florida, for a detailed teardown inspection. This inspection was prompted by the impact damage sustained by the propeller during the landing. The investigation examined the aircraft's maintenance records, which showed the plane had been under a valid airworthiness certificate with its last 100-hour inspection completed in August 2018. The investigation also reviewed meteorological conditions, which were reported as favorable, with visibility exceeding 10km and moderate winds.
Findings
- The primary cause of the accident was a mechanical failure within the engine.
- A teardown analysis of the Lycoming engine revealed that a pin from a crankshaft counterweight had broken.
- The failure of this pin caused the loss of timing, leading to the sudden engine power loss and subsequent shutdown during flight.
- The impact of the engine failure caused secondary damage, including a bent camshaft and damage to four connecting rods, two counterweights, and the crankshaft gear.