What aircraft was involved and where did it happen?

The accident on 2019-08-29 involved a 42-500, registration HK5199, at Medellín, CO.

What was the probable cause of the accident?

The primary cause was the fracture of a blade in the first stage of the number 1 power turbine (PT1), which initiated a sequence of secondary blade fractures and engine imbalance, ultimately resulting in an engine fire due to ruptured oil lines.

Engine Failure and Fire on ATR 42-500 During Initial Climb

An engine failure and subsequent fire occurred on an ATR 42-500 during its initial climb from Medellín, resulting in an emergency return to the airport.

What happened

On August 29, 2019, an ATR 42-500, registration HK-5199, operated by Easyfly S.A., was performing a scheduled commercial flight from Medellín's Enrique Olaya Herrera Airport to Montería. During the initial climb, at an altitude of approximately 8,400 feet, the crew experienced a sudden smell of smoke, a loud noise in the cabin, and a significant yaw to the left.

The pilot identified an in-flight flameout of the number one (left) engine, accompanied by a fire warning. The crew immediately executed emergency memory items, which included activating the number one fire extinguisher. After declaring an emergency with air traffic control, the crew performed the single-engine operations checklist and prepared the aircraft for an emergency landing. The aircraft returned to the departure airfield and landed safely on runway 20. All 43 occupants (3 crew and 40 passengers) evacuated the aircraft without injury.

The investigation

The GRIAA investigation focused on the mechanical failure of the engine and the subsequent chain of events. Investigators examined the flight data recorder (FDR) and cockpit voice recorder (CVR), noting that engine parameters (torque, low-pressure rotor speed, and high-pressure rotor speed) dropped sharply following the failure.

Physical examination of the engine revealed extensive internal damage. The investigation established that the primary failure originated in the power turbine section. Specifically, all blades in the first stage of the power turbine (PT1) had fractured, leading to the destruction of blades in the second stage (PT2) and the low-pressure turbine (LPT). This fragmentation caused a severe imbalance in the turbine, leading the low-pressure rotor to contact the bearing housing. This contact severed the radial oil supply pipes, causing engine oil to leak into the nacelle, where it ignited upon contact with hot engine components.

While the investigation noted that maintenance personnel had used incorrect tools and torque values during previous engine work, these practices were not determined to be the cause of the blade fractures.

Findings

The primary cause of the incident was the primary fracture of a single blade in the number 1 power turbine (PT1) stage.
This initial fracture triggered a cascade of secondary failures, including the breakage of multiple other blades across several engine stages.
The resulting imbalance caused the low-pressure turbine rotor to strike the bearing housing, rupturing oil lines.
The subsequent release of engine oil onto hot engine parts led to the engine fire.