What happened
On May 4, 2014, a Cessna 152, registration RP-C8847, operated by Omni Aviation Corporation, departed Clark Airfield, Pampanga, for a solo cross-country flight training mission. During the cruise phase of the flight, approximately two nautical miles southwest of Paniqui, Tarlac, the student pilot encountered intense engine vibrations originating from the front of the aircraft.
Upon notifying flight authorities, the pilot was advised to land at the nearest safe airfield rather than attempting to return to the home station. During the descent from 3,500 feet, the pilot observed that while oil pressure and temperature remained normal, the Cylinder Head Temperature (CHT) dropped to zero. The engine became unresponsive to throttle inputs, with RPM dropping significantly below standard levels. As the aircraft approached Paniqui Airstrip, the vibrations worsened, leading to a propeller stoppage. The pilot successfully executed an emergency forced landing at 1,300 feet, touching down on runway 2ss and coming to a halt near the mid-runway. The pilot sustained no injuries.
The investigation
Following the incident, maintenance personnel from the operator identified an excessive oil leak from the engine. AAIIB investigators subsequently examined the aircraft and discovered that the engine cowling had to be removed to reveal the source of the malfunction. Upon inspection, investigators found a broken and detached engine push rod located behind the propeller assembly.
Findings
- The primary cause of the engine power failure was a material failure involving a damaged engine cylinder number 3, which broke and detached from the main engine crankshaft.
- Maintenance and operational lapses contributed to the accident, specifically regarding the scope of pre-flight inspections. The existing 360-degree visual inspection protocol did not require removing the cowling, meaning internal engine components were not inspected regularly.
- The investigation identified the improper use of kerosene as an engine cleaning agent. The use of this unauthorized detergent caused corrosion on engine assembly bolts, compromising the structural integrity of the components.
Safety action
- The AAIIB recommended that the CAAP Flight Standards Inspectorate Service review flight school training procedures to mandate the opening of engine cowlings during pre-flight inspections.
- Maintenance protocols must be updated to ensure only authorized degreasers are used and to standardize the use of tap water for cleaning engine assemblies.
- The investigation emphasized the full implementation of the FAA Special Airworthiness Information Bulletin regarding Lycoming engine cylinder mounting studs.