What happened
On 5 September 2005, a scheduled Mandala Airlines flight, operating as MDL 091, was preparing for departure from Polonia Airport in Medan, North Sumatra, destined for Jakarta. The aircraft, a Boeing 737-200 with registration PK-RIM, had completed its previous leg from Jakarta earlier that day. Following standard procedures, the crew received pushback and engine start clearance at approximately 02:52 UTC and was subsequently cleared to taxi to runway 23.
During the takeoff roll, witnesses observed that the aircraft required a longer distance than usual to accelerate. The nose of the plane lifted only a few meters before the end of the runway. After rotation, air traffic controllers noted that the aircraft began veering left and right across the airfield. During the subsequent loss of control, the left wing of the plane struck a building before the aircraft crashed into a heavily populated roadway. The impact was followed by large explosions and intense flames.
The accident resulted in 100 fatalities on board (comprising 95 passengers and 5 crew members), while 49 people on the ground were killed. In addition to the deaths, 15 passengers sustained serious injuries, 26 individuals on the ground were seriously injured, and two passengers survived the crash without injury.
Findings
Investigations by the National Transportation Safety Committee concluded that the primary reason for the accident was that the aircraft was operated with an improper takeoff configuration, specifically with the flaps and slats in a retracted position. This configuration prevented the aircraft from achieving sufficient lift to depart safely.
Contributing factors included:
- A failure to follow proper checklist procedures, which meant the crew did not identify that the flaps remained retracted.
- The possibility that the takeoff configuration warning horn was not audible on the cockpit audio recording, as it was not detected on the cockpit area microphone channel.