Date: October 23, 2023
Location: 30 nautical miles WSW of Barcelona, Spain
Aircraft: Airbus A321-200N, registration CS-TJL
Operator: TAP Air Portugal
Flight Number: TP-823
Route: Milan Malpensa (Italy) to Lisbon (Portugal)
Occupants: Unknown
Injuries: None reported
Summary of Events
On October 23, 2023, TAP Air Portugal Flight TP-823, an Airbus A321-200N enroute from Milan to Lisbon, experienced an engine failure while cruising at FL370 approximately 30nm west-southwest of Barcelona. The flight crew followed standard procedures, drifted the aircraft down, and diverted safely to Barcelona Airport, where it landed on Runway 24R approximately 50 minutes after the failure.
A replacement aircraft transported passengers to Lisbon, arriving with a delay of approximately 8 hours and 10 minutes.
Aircraft Details
• Type: Airbus A321-200N
• Registration: CS-TJL
• Engines: 2x CFM International LEAP-1A
• Configuration: Passenger aircraft
Sequence of Events
1. Cruise Phase:
• The aircraft was cruising at FL370 when the ECAM system displayed “ENG2 SHUTDOWN,” prompting the crew to execute engine failure checklists.
2. Descent and Diversion:
• The crew initiated a controlled descent to a lower altitude and decided to divert to Barcelona.
3. Landing:
• The aircraft landed safely on Barcelona’s Runway 24R approximately 50 minutes after the initial alert.
4. Replacement and Investigation:
• A replacement Airbus A321-200N, registration CS-TJK, completed the flight to Lisbon.
• Investigations revealed no immediate visible damage to the engine. The #2 engine fire push button was found to have been activated due to a mechanical issue with the retaining pin.
Initial Findings and Investigation
The Portuguese GPIAA (Gabinete de Prevenção e Investigação de Acidentes com Aeronaves e de Ferroviários) rated the occurrence as a serious incident. Initial findings included:
• Attempts to relight the engine in-flight were unsuccessful.
• Post-landing inspection revealed the #2 engine fire push button had popped out, leading to an uncommanded engine shutdown.
Probable Causes
The GPIAA identified the probable cause as a failure of the retaining pin in the fire push-button switch (PB-SW), which allowed the button to disengage during flight, resulting in an uncommanded shutdown of engine #2. Factors contributing to the failure included:
1. Improper Handling of the Fire Panel:
• Likely damage from a drop prior to June 2013 created a latent condition affecting the PB-SW retaining pin.
2. Inadequate Repair Process:
• The OEM repair process failed to identify or address damage to the retaining pin during previous maintenance.
3. Design Vulnerabilities:
• Lack of redundancy and manufacturing tolerances allowed a slight deformation (bent <6º) of the retaining pin to trigger the failure.
4. Flight Conditions:
• Turbulence and instantaneous accelerations contributed to the release of the retaining pin.
Safety Risks Identified
1. Design Weakness:
• The lack of a redundant retaining mechanism for the PB-SW increased the risk of uncommanded engine shutdown.
2. Maintenance Gaps:
• The improper repair process and undetected damage highlight the need for robust maintenance and inspection protocols.
3. Operational Impact:
• The shutdown necessitated the diversion of the flight, resulting in significant delays and operational disruptions.
Recommendations
1. Redesign of Fire Push-Button Switch:
• Incorporate redundancy and stricter manufacturing tolerances to prevent similar failures.
2. Enhanced Inspection Protocols:
• Develop specific guidelines to detect and address latent damage to critical components like the PB-SW retaining pin.
3. Turbulence Mitigation Training:
• Reinforce flight crew procedures for handling mechanical malfunctions during turbulence.
4. OEM Maintenance Standards:
• Improve repair and maintenance procedures to detect and rectify minor deformations or damages.
Safety Lessons
This incident underscores the importance of robust aircraft design, thorough maintenance practices, and comprehensive flight crew training in managing unexpected mechanical failures. The safe diversion and landing highlight the effectiveness of standard operating procedures but also reveal opportunities for improvement in design and maintenance practices to prevent similar occurrences.
Disclaimer
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Our investigation reports are based on all the evidence and facts we have at the time of writing and posting. We apologise if any details are missed or are not fully accurate.
