What happened
On the morning of 7 January 1974, an Antonov AN-12, registration BL740, was performing a takeoff roll from Chennai-Meenambhakam Airport. The flight had experienced an initial delay due to radio communication issues prior to departure. As the aircraft reached a speed of 160 km/h, the pilot was transitioning control from nose steering to the control column.
During this transition, the aircraft experienced a violent lateral oscillation, swinging heavily to both the left and right sides, eventually settling at a 45-degree angle relative to the runway. The crew identified an engine failure almost immediately. In an attempt to manage the situation, the pilot reduced all four throttles to idle. However, the aircraft drifted into a large ditch located ahead of runway 07 before it could be stopped. The impact caused the airframe to break into two pieces.
Despite the structural damage, there was no fire following the collision. There were no fatalities reported among the crew or passengers, though there were 2 injuries involving crew members. One crew member sustained a broken arm while attempting to exit through a side window, and a gunner also sustained injuries during the event.
Findings
The primary cause of the accident was the failure of the number four engine, which led to significant asymmetric thrust. This specific engine is noted for its critical role in the handling of the Antonov AN-12 due to the anti-clockwise rotation of the propeller blades. Subsequent simulations by experienced personnel suggested that an uncommanded auto-feathering event on this engine would make the aircraft extremely difficult to maintain on the runway centerline during takeoff.