What happened
On 15 July 2011, an L410UVP-E20, registration PR-NHC, operated by NHT Linhas Aéreas, departed from runway 33 at Curitiba Aerodrome (SBCT) bound for Caçador (SBCD). While climbing through approximately 400 to 500 feet AGL, the aircraft experienced a sudden loss of power in the right-hand engine, causing the aircraft to yaw to the right.
The pilot in command immediately took control of the aircraft and instructed the co-pilot to contact the Curitiba Tower to declare an emergency and initiate a return to the airport. Following the completion of emergency checklists and memory items, the crew successfully performed an emergency landing on runway 33. There were no injuries among the 15 passengers and 2 crew members, and the aircraft sustained no damage.
The investigation
CENIPA's investigation focused on identifying the cause of the right engine power loss. Flight Data Recorder (FDR) analysis confirmed a torque drop in the right engine at 400 feet AGL. While fuel contamination was ruled out through testing of the aircraft's fuel and the refueling truck, technical research involving GE Aviation Czech and LET Aircraft Industries provided critical insights.
Engine manufacturer tests revealed that when throttles are moved from takeoff power to a lower power setting without first switching off the water injection system, a flameout can occur. Specifically, tests showed a flameout in 16% of power reduction instances due to flame instability caused by a weakened air/fuel mixture. The investigation found that the crew and maintenance personnel were unaware of this specific limitation because the necessary alert from the engine's operation manual was not included in the operator's flight safety or standardization documents.
Findings
- The right engine failed during power reduction because the water-injection system was not switched off prior to reducing the power setting.
- The crew's training was insufficient, as it did not provide the necessary information regarding this specific engine limitation.
- A lack of organizational support contributed to the incident, as the operator's manuals and safety documents failed to incorporate the critical warning found in the engine manufacturer's operation manual.