What happened
On October 19, 2017, a Cessna 206T, registration HK5057, was performing a scheduled air taxi flight from Mitú to Monfort in the Vaupés department of Colombia. After successfully landing in Monfort to collect four passengers, the aircraft prepared for its return leg to Mitú.
During the takeoff from Monfort's runway 35, the aircraft failed to achieve a positive rate of climb. While the aircraft initially lifted off due to ground effect, it was unable to maintain sufficient airspeed as it climbed. The pilot attempted a left turn to avoid approaching trees, which induced a stall. The aircraft subsequently struck a dense cluster of trees in an inverted position. Despite the significant impact, all five occupants (one pilot and four passengers) were uninjured and were able to evacuate the wreckage on their own.
The investigation
The GRIAA investigation focused on the aircraft's performance and weight calculations. Investigators found that while the pilot's manifest recorded a takeoff weight of 3,285 lb, the actual weight was approximately 3,285 lb, which exceeded the specific performance limitations for the Monfort runway. Due to high temperatures and the limited runway length, the maximum allowable takeoff weight for this specific location was restricted to 3,230 lb.
Technical analysis of the wreckage showed significant damage to the landing gear, wing leading edges, and the empennage due to impact forces. The investigation also noted that the engine and propeller were in good working order and that meteorological conditions, communications, and navigation aids were not contributing factors to the accident.
Findings
- The primary cause was a loss of lift resulting from an improper takeoff technique caused by an incorrect weight and balance calculation.
- The aircraft was operating at an overweight condition, exceeding the runway-specific weight limit by approximately 55 lb.
- The pilot likely relied on ground effect to lift the aircraft, but the excess weight prevented the aircraft from accelerating to a safe flying speed once it left the ground effect zone.
- The pilot's attempt to maneuver around obstacles during the climb exacerbated the low-speed condition, leading to a stall.
- There was a lack of adequate risk analysis by both the pilot and the operator regarding the specific constraints of the uncontrolled Monfort airstrip, such as temperature and runway length.
Safety action
- The operator was advised to revise its General Operations Manual to implement stricter standards for weight and balance calculations, specifically accounting for environmental variables like temperature and runway length.
- Recommendations were made to implement a standardized risk analysis format for daily operations to identify hazards and mitigation measures for each flight.