What happened
On 6 March 2012, a SilkAir Airbus A319, registration 9V-SBH, arrived at Adi Soemarmo International Airport in Solo, Indonesia, from Singapore. During the landing roll, air traffic controllers observed smoke near the left main landing gear. Due to significant language barriers, the communication between the tower and the flight crew was unintellig and required the assistance of a nearby Lion Air pilot to translate between English and Indonesian.
As the aircraft taxied, the controller's reports became increasingly confusing. While the pilot repeatedly sought clarification regarding whether the issue was merely smoke or actual flames, the tower eventually reported the presence of moderate fire. Faced with this information, the pilot made the decision to halt the aircraft and initiate an emergency evacuation. The 124 passengers and crew exited via emergency slides, resulting in one minor injury to a passenger.
The investigation
The investigation focused on the source of the smoke and the breakdown in communication. Investigators examined the left main landing gear and found no evidence of actual fire or structural damage. However, they discovered approximately 8 cm³ of grease residue on the heat sink. It was determined that during a brake assembly replacement performed during a previous night stop, excessive grease had been applied, which migrated to the heat sink and produced smoke when heated by the brakes during landing.
Furthermore, the investigation scrutinized the qualifications of the air traffic controllers. It was established that the controllers in duty were not properly certified to perform their roles, as their medical and professional certificates had expired.
Findings
- The primary cause of the emergency evacuation was ineffective communication and uncertain identification of the hazard by the controller.
- Excessive grease applied during the recent replacement of brake assembly number 2 caused smoke when subjected to landing temperatures.
- The air traffic controllers lacked the necessary English language proficiency to communicate clearly during non-routine events, effectively operating at an ICAO Level 3 capability.
- The controllers were not eligible to perform their duties due to expired medical and professional certifications.
- Background noise from non-operational conversations was present in the control tower during the incident.
Safety action
The NTSC issued recommendations to PT Angkasa Pura I and Air Navigation Indonesia to ensure all personnel hold valid certifications and possess sufficient English proficiency for non-standard communications. Additionally, a recommendation was made to enforce a sterile control tower environment.