What happened
On June 29, 2000, at 19:40Q, a Piper PA-23-250 operated by Mundy Táxi Aéreo Ltda performed a forced landing in an open field approximately 2 km from the Dourados aerodrome in Mato Grosso do Sul, Brazil. The flight had departed from Dourados at 19:00Q, bound for Campo Grande, for the purpose of transporting bank mail.
During the cruise phase at FL055, the propeller on the left engine suddenly feathered. The crew attempted to restore normal engine operation through various maneuvers, including engine restarts, but were unsuccessful. The crew decided to return to the departure airport, but during the descent, the right engine also experienced a loss of power. The aircraft struck the ground with the landing gear retracted. Upon impact, a fire broke out in the right engine, spreading throughout the airframe and resulting in the total loss of the aircraft. Both crew members survived the accident without injuries.
The investigation
CENIPA's investigation focused on the mechanical failure of the propeller governor and the operational decisions made by the crew. Technical analysis of the left engine revealed that the propeller feathering was caused by the failure of the drive shaft in the propeller governor assembly. Laboratory testing indicated that the fractures occurred due to excessive stress, likely stemming from inadequate lubrication, which may have been a result of deficient maintenance practices. he investigation also examined the aircraft's weight and balance. While a formal cargo manifest was unavailable, the investigation noted a significant loss of altitude during the return leg, suggesting the aircraft may have been operating above its maximum takeoff weight, which would have compromised its ability to maintain altitude on a single engine. Furthermore, the investigation found that the crew did not follow standard emergency checklists, specifically failing to shut down the right engine prior to the forced landing.
Findings
- The left engine propeller feathered due to the collapse of the propeller governor's drive shaft assembly.
- Deficient supervision by the operator regarding maintenance records, crew training, and weight and balance oversight.
- The aircraft may have been overloaded, preventing sustained single-engine flight.
- The crew lacked sufficient experience in this specific aircraft model.
- The crew failed to implement proper emergency procedures, such as shutting down the remaining engine before impact.
- There was evidence of an inhibiting posture from the co-pilot toward the pilot, potentially affecting cockpit coordination.