Investigation Summary
The investigation into Flight 3739 revealed a combination of technical imbalance and human factors. The aircraft was significantly overloaded and improperly balanced, carrying 104 passengers on a plane configured for 85. This passenger total included five unmanifested individuals: the radio operator's son who sat in the cockpit, two people in the restrooms, and two in the front of the aircraft. With a crew of 10, the total number of souls on board reached 114. The primary physical cause was the asymmetric fuel load, which created a rolling moment the pilots could not overcome with aileron input alone at low speeds. Flight testing later showed that the Tu-104 was particularly sensitive to side winds and roll imbalances during the transition from ground to air. The commission found that the crew failed to respond to the automatic angle of attack and vertical overload alarms for eight seconds. Crucially, flight testing determined that the proper response to counteract the roll sensitivity in a side wind would have been to sharply pull back on the throttles, a technique the crew did not utilize.
Final Conclusions
The Ministry of Aviation Industry of the USSR concluded the crash was caused by the asymmetric refueling of the aircraft (1,300 to 1,500 kg excess on the right side), which induced a roll that could not be corrected by ailerons alone. Contributing factors included the crew's inadequate response to the emergency and their failure to heed cockpit warnings for eight seconds following liftoff.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Fuel System
The aircraft was refueled asymmetrically, leading to a weight imbalance of over 1,300 kg on the right side.
Angle of Attack Alarm
An automated system designed to warn the crew of an impending stall or excessive pitch, which was ignored for eight seconds during the short flight.
Interesting Facts
- 01The aircraft was carrying 114 people despite being configured for only 85 passengers.
- 02Five unmanifested passengers were on board, including two in the restrooms and one in the cockpit.
- 03The right fuel tanks held 1,300 to 1,500 kg more fuel than the left tanks.
- 04The crashing aircraft struck a parked Chosonminhang (Air Koryo) Tupolev Tu-154, registration P-551.
- 05The crew ignored automatic angle of attack and vertical overload alarms for eight seconds.
Safety Actions & Advisories
Flight Manual Compliance
The investigation emphasized the necessity of adhering to the aircraft flight manual's recommended 2-3 degree angle of takeoff to prevent stall conditions in sensitive aircraft like the Tu-104.