History of the Flight
On 13 February 2024, a Boeing 737-800, registration 9M-LCM, operated by Batik Air Malaysia, conducted scheduled passenger flight MXD 1904 from Kuala Lumpur International Airport to Sibu Airport. The aircraft had last operated in May 2023 and underwent maintenance at the Batam Aero Technic hangar before being ferried to Kuala Lumpur on 30 November 2023. It remained grounded for additional inspections and de-registration procedures until the day of the incident, which was its first revenue flight after the maintenance grounding.
During pre-flight checks, discrepancies in onboard emergency equipment were noted, and the cockpit placard displayed the previous registration, PK-LZP. The cabin and flight deck were warm, and passengers expressed discomfort. Recycling the trim air switch during taxi provided some improvement. The aircraft departed at 1925 LT.
Incident Details
During climb, at approximately 5,000 feet, the BLEED TRIP OFF No. 2 light illuminated. The crew performed the associated Non-Normal Checklist, switching off Pack No. 2. They contacted the Maintenance Control Centre via satellite communication and were advised to continue to Sibu, as single-pack operation was permissible if icing conditions were avoided.
At FL290, the Total Air Temperature gauge indicated temperatures within the icing range, prompting activation of the engine anti-ice switches. Shortly after, the Thermal Anti-Ice annunciator for Engine No. 1 illuminated amber. The crew consulted the ENGINE COWL VALVE OPEN OR TAI INDICATION checklist, determining the No. 1 TAI valve was stuck open. To avoid icing, the crew climbed to FL350, where temperatures were below -40°C.
Emergency Descent and Diversion
Upon entering Kuching airspace, the situation escalated with uncontrolled cabin pressurisation. The crew initiated an emergency descent and deployed passenger oxygen masks. The aircraft stabilised at approximately FL100, and the distress signal was cancelled. The aircraft diverted to Kuching International Airport, landing safely at 2153 LT without any casualties.
Aftermath
The operator submitted a Mandatory Occurrence Report to the Civil Aviation Authority of Malaysia and the Air Accident Investigation Bureau. The AAIB investigation classified the event as a serious incident (SI 04/24).