What happened
On September 30, 1996, a DC-9-83 (registration TC-INC), operated by Intersun Sunways, experienced a significant engine malfunction during a flight from Dalaman, Turkey, to Cologne/Bonn, Germany. Shortly after reaching cruise altitude, a loud bang was heard in the cockpit, indicating damage to the left engine. Although the engine continued to run, parameters such as Exhaust Gas Temperature (EGT), N2 rotation speed, and fuel flow stabilized at higher-than-normal levels. The aircraft landed safely in Cologne/Bonn.
Following the incident, the aircraft flew from Cologne/Bonn to Kajaani, Finland. While on the ground in Kajaani, the crew did not perform a proper technical verification of the left engine's condition. During the subsequent takeoff attempt for a flight to Dalaman, the crew increased power, causing loud bangs to be heard both inside the aircraft and near the terminal building. The left engine failed to accelerate normally, experiencing severe EGT fluctuations and repeated surges. After approximately 40 seconds of attempting to wait for the engine to stabilize, the crew aborted the takeoff and returned to the apron.
The investigation
The investigation examined the sequence of events, the technical state of the left engine, and the operational standards of Inters and the Turkish civil aviation authority. Investigators reviewed borescope inspections, maintenance records, and cockpit voice recorder data. The probe also looked into the training adequacy of the crew, the quality of the operator's documentation, and the oversight provided by the Turkish aviation authorities.
Findings
- The primary cause of the danger was the crew's unprofessional attitude and inadequate skills in troubleshooting the engine malfunction. The pilots attempted a takeoff without first verifying the operational status of the left engine.
- There was a significant failure in the operator's maintenance management, as technical anomalies observed during previous flights were not properly recorded in the aircraft's logs.
- The crew's training was insufficient; the First Officer had not completed the required number of simulator sessions, and the crew's English language proficiency was inadequate for managing non-normal situations.
- The Turkish civil aviation authority failed to provide adequate oversight of the new charter operator, Intersun Sunways.
- The crew's takeoff procedure in Kajaani was highly dangerous, as the engine failure would have likely resulted in a significant loss of safety margins had the takeoff continued.