What happened
On November 21, 2022, a Piper PA-31-350, registration HK5121, was operating a non-scheduled passenger flight from Enrique Olaya Herrera Airport in Medellín to Pizarro, Chocó. The aircraft was carrying two crew members and six passengers.
Shortly after takeoff at approximately 10:14 local time, the crew reported an engine failure to Air Traffic Control. While attempting to manage the emergency, the aircraft lost altitude and drifted left, eventually striking the upper portion of a three-story building in an urban area of Medellín. The impact triggered a significant fire that consumed much of the aircraft. All eight occupants perished in the accident. The crash also caused structural damage to nearby residences, necessitating the evacuation of 17 people.
The investigation
The GRIAA investigation focused on the mechanical state of the engines and propellers, the aircraft's weight and balance, and the operator's maintenance and operational procedures. Investigators examined the wreckage of both engines and the propeller assembly, as well as the aircraft's weight logs and maintenance records. The investigation also reviewed the operator's compliance with Supplemental Type Certificates (STC) regarding structural modifications like winglets and vortex generators.
Findings
Investigators established that the primary cause of the loss of control was a reduction in minimum controllable airspeed and increased drag, resulting from the loss of power in the number one engine and a failure of the propeller feathering system. The investigation identified several critical factors:
- The number one engine suffered a power loss, likely due to a malfunctioning turbocharger.
- The propeller feathering system failed to function because of excessive grease accumulation in the blade coupling section, which prevented the blades from feathering quickly.
- The aircraft was overweight, exceeding its maximum takeoff weight by approximately 770 lb, which prevented the crew from maintaining sufficient climb performance.
- The operator failed to use exact weights for passengers and cargo, instead using averages that resulted in an underestimated takeoff weight.
- The operator failed to comply with specific STC requirements regarding the installation of winglets and vortex generators necessary for the increased weight limits.
Safety action
The GRIAA issued several recommendations to the operator, including the need to improve propeller inspection programs to detect grease buildup, and to implement stricter weight and balance procedures that record actual passenger weights. Additionally, the authority was advised to enhance oversight regarding structural modifications and the practical implementation of Safety Management Systems (SMS).