What happened
On October 31, 2021, a Boeing 727-214, registration CX-CAR, departed from Carrasco International Airport (SUMU) in Uruguay, bound for Ezeiza International Airport (SAEZ) in Argentina. The aircraft was operating a cargo flight with a crew of three.
Approximately six minutes after takeoff, while climbing through FL 160 west of Montevideo, the crew received a fire warning and saw the fire light for engine number three. The crew immediately executed emergency procedures, shutting down the engine and discharging the fire extinguishing agent. The crew declared an emergency with Montevideo Control and was provided with vectors to return to the airport. The aircraft landed safely on runway 24 without further incident.
The investigation
The CIAIA investigation focused on identifying the origin of the fire warning. Physical inspection of the aircraft revealed that the engine did not have an active fire, but rather heat marks inside the engine cowling. The investigation established that the fire detection system had been activated by hot air escaping from a compromised component.
Technical examination of the third engine identified a perforation in the 8th-stage compressor bleed air duct. The investigation found that the failure originated from within the component, making the defect invisible to standard external inspections. The investigation also confirmed that all maintenance records were up to date and that previous inspections of the duct had been performed correctly.