Flight AK-128 | Registration: 9M-AQG
Date: 26 March 2025 | Location: Kuala Lumpur International Airport (WMKK)
Introduction
On 26 March 2025, an AirAsia Airbus A320-200, registration 9M-AQG, operating flight AK-128 from Kuala Lumpur, Malaysia, to Shenzhen, China, experienced a left engine fire indication shortly after departure. The crew discontinued the climb at 4,000 feet, discharged the fire extinguisher system, entered a holding pattern to complete checklists, and safely returned to Kuala Lumpur International Airport (KLIA) approximately two hours after takeoff. All 171 occupants disembarked without injury.
Aircraft and Flight Details
• Aircraft Type: Airbus A320-216
• Engines: 2 × CFM International CFM56-5B6/3
• Registration: 9M-AQG
• Operator: AirAsia Berhad
• Flight Number: AK-128
• Callsign: AXM128
• Route: Kuala Lumpur (WMKK) to Shenzhen (ZGSZ)
• Occupants: 171 (passengers and crew)
• Departure Runway: 33
• Landing Runway: 33
• Altitude at Incident: 4,000 feet
• Time Airborne: Approx. 2 hours
• Emergency Declared: Yes – Engine fire indication
• Damage: Suspected damage to pneumatic duct and/or engine components
• Injuries: None
• Weather: VMC – clear conditions reported
Sequence of Events
Takeoff and Initial Climb
The aircraft departed Kuala Lumpur International Airport’s runway 33 and began climbing on its northeasterly route to Shenzhen. Shortly after becoming airborne, while passing through 4,000 feet, the crew received a fire warning associated with the No. 1 (left) engine – a CFM56-5B.
Crew Actions and Emergency Declaration
The crew immediately levelled the aircraft, declared an emergency to Kuala Lumpur ATC, and executed the ENG 1 FIRE checklist as per Airbus QRH (Quick Reference Handbook) procedures. One of the engine’s Halon fire suppression bottles was discharged.
The fire indication ceased after bottle activation, confirming extinguishment. The crew continued in a holding pattern to monitor engine parameters and prepare for return.
Diversion and Safe Landing
After approximately two hours airborne, including time spent in the hold and coordinating with ground emergency services, the aircraft conducted an uneventful landing on runway 33 at KLIA. Emergency response vehicles were on standby. Upon landing, the aircraft taxied to a remote stand where all 171 occupants disembarked safely.
Post-Flight Assessment and Investigation
AirAsia confirmed the incident and stated that a preliminary engineering investigation attributes the fire warning to a burst pneumatic duct in the left engine nacelle. The pneumatic system routes high-pressure air (bleed air) used for environmental control and anti-icing. A duct rupture can result in high-temperature air leaking into the engine compartment, which may trigger a fire detection loop.
Although no external fire was observed, the fire warning system was activated, and the onboard extinguishing system operated automatically. No visible damage to the engine cowling was reported immediately following landing, though full maintenance inspections are ongoing.
As of the latest update, 9M-AQG remains grounded at Kuala Lumpur for in-depth inspection and component replacement.
Replacement Aircraft and Operational Impact
A replacement aircraft, Airbus A320-200 registration 9M-AJY, was deployed to operate flight AK-128 later that same day. The replacement service reached Shenzhen with an overall delay of approximately six hours.
AirAsia provided passengers with refreshments and assistance during the disruption. No passengers reported medical issues, and the airline is cooperating with Malaysian aviation authorities regarding the incident.
Technical Insight: Pneumatic Duct Failures in CFM56-powered A320s
The CFM56-5B engine is widely regarded as a reliable powerplant for short- to medium-haul operations. However, pneumatic duct failures—although rare—can occur due to:
• Material fatigue or corrosion within the high-pressure air ducts
• Improper installation or torqueing of duct clamps during prior maintenance
• Excessive thermal cycling, especially in tropical and high-humidity operating environments
Such failures can lead to extremely hot bleed air escaping and triggering fire detection loops, even in the absence of actual combustion. These events are typically contained by the aircraft’s fire suppression system and are more a systems failure than a combustion fire.
Safety and Preventative Measures
Following such incidents, operators usually carry out:
• Detailed borescope inspections of the engine internal components
• Leak checks and pressure tests on bleed air ducting
• Review of maintenance logs to identify prior duct repairs or anomalies
• Replacement of damaged ducts and insulation materials
If duct separation or leaks are confirmed, the airline is required to inform the OEM (CFM International and Airbus) and notify aviation authorities for incident tracking and trend analysis.
Conclusion
On 26 March 2025, AirAsia flight AK-128 (9M-AQG) experienced a left engine fire indication shortly after departure from Kuala Lumpur International Airport. The crew took swift and appropriate action by halting the climb, activating the onboard fire suppression system, and returning for a safe landing. The likely cause is attributed to a ruptured pneumatic duct. No injuries were reported, and the incident was resolved without further complication.
The aircraft remains grounded for further inspection, and regulatory authorities continue to assess the situation. AirAsia resumed the service using a replacement aircraft, ensuring minimal disruption to its passengers.
Disclaimer
This report is based on publicly available information and verified aviation sources as of 27 March 2025. While every effort has been made to ensure accuracy, we cannot guarantee the completeness of the information provided. If you are the rightful owner of any referenced material and wish it to be removed, please email takedown@cockpitking.com.
