What happened
On January 18, 2016, a Piper PA-28-180, registration HK1584G, was conducting a flight instruction mission from Perales Airport (SKIB) to Santiago Vila Aerodrome (SKGI). The flight was part of a training program involving touch-and-go maneuvers.
During the initial climb phase of a takeoff from runway 20, the aircraft experienced a sudden and significant drop in engine revolutions per minute (RPM). Unable to maintain altitude or return to the runway, the flight instructor executed an emergency landing in an unprepared field adjacent to the aerodrome. The aircraft struck the terrain with a forward impact and a leftward roll, resulting in the separation of the nose and left main landing gear, propeller blade deformation, and various structural damages to the fuselage and flaps. Both the instructor and the student survived the impact without injuries.
The investigation
The GRIAA investigation focused on the engine's performance and the crew's operational procedures. While the aircraft was found to be airworthy and maintained according to manufacturer standards, investigators noted that the aircraft had experienced engine starting issues the previous day, possibly related to the carburetor.
Post-incident inspections of the Lycoming O-360-A4A engine and its accessories, including the carburetor and magnetos, were conducted at an authorized workshop. These tests showed that the engine and its components were functioning normally and no mechanical defects were found in the engine itself at the time of the inspection.
Findings
- The investigation identified that the improper adjustment of the mixture or throttle controls by the student pilot, or a lack of sufficient supervision by the instructor during the takeoff phase, may have caused an incorrect air-fuel ratio.
- This improper mixture likely led to incomplete combustion, resulting in the observed loss of engine power.
- An alternative contributing factor considered was the incorrect regulation of internal carburetor components, such as the mixture needle or acceleration valve, which prevented the engine from responding to power demands during takeoff.