What happened
On 28th November 2010, an Ilyushin IL-76TD, registration 4L-GNI, operated by Sunway Air Carrier (Georgia), crashed approximately 2 NM from Jinnah International Airport in Karachi, Pakistan. The aircraft was performing a cargo flight destined for Khartoum, Sudan, carrying humanitarian aid.
After taking off at 2048 UTC, the aircraft climbed to 600 feet before entering a descent and disappearing from radar. The impact occurred in a residential area, causing significant damage to several buildings under construction. The accident resulted in six fatalities among the crew and three fatalities among ground workers.
The investigation
The investigation was conducted by the Safety Investigation Board (SIB), Pakistan, with technical support from the aircraft and engine manufacturers. Investigators analyzed flight data recorder (FDR) information, wreckage, and metallurgical samples.
Data analysis revealed that the aircraft had departed with a total mass of 195 tons, which exceeded the maximum takeoff mass limit of 190 tons specified in the Flight Crew Operating Manual. The FDR also indicated that Engine #4 had experienced starting issues on at least two occasions prior to the accident flight.
Findings
Investigators established that the primary cause of the accident was an uncontained failure of the second-stage disk of the Low Pressure (LP) compressor in Engine #4. This failure was attributed to a fatigue fracture caused by fretting corrosion within the holes designed for the compressor blade pin bushings.
Following the initial failure, the LP turbine disk also disintegrated due to overspeeding. The resulting debris damaged the right wing, fuel system, and flaps. This damage led to an in-flight fire in the right wing area, which caused a loss of lateral control that the crew could not counteract through flight control inputs. A significant contributing factor was the use of the engine beyond its manufacturer-assigned life without proper assessment or life enhancement.