On July 29, 1950, an Il-12 suffered no. 1 engine problems during a test flight at Alma Ata. The crew did not report the issues, and the airplane was returned to service. The next flight was a regular service to Moscow with refueling stops. The aircraft landed at Karaganda Airport at 04:50, took off after refueling at 05:36, and ascended to 150 meters. After takeoff, the crew radioed that the no. 1 engine had failed and they were returning to the airport. Permission was granted for a 30ø straight approach and landing. During maneuvering, a 67 m building blocked the extended centerline, causing the aircraft to overshoot and turn left, resulting in loss of control and a spiral descent.On July 29, 1950, an Il-12 suffered no. 1 engine problems during a test flight at Alma Ata. The crew did not report the issues, and the airplane was returned to service. The next flight was a regular service to Moscow with refueling stops. The aircraft landed at Karaganda Airport at 04:50, took off after refueling at 05:36, and ascended to 150 meters. After takeoff, the crew radioed that the no. 1 engine had failed and they were returning to the airport. Permission was granted for a 30ø straight approach and landing. During maneuvering, a 67 m building blocked the extended centerline, causing the aircraft to overshoot and turn left, resulting in loss of control and a spiral descent.