Aeroflot Flight 3739 (1976)

Investigation

Investigators initially suspected the right wing had been modified during maintenance in such a way that it resulted in an aerodynamic imbalance. To confirm this hypothesis, the remains of the right wing were sent to the Central Aerohydrodynamic Institute, where engineers concluded the right wing was fully functional until impact. Investigators recreated the flight path until impact on another Tupolev Tu-104, and published their findings. Flight testing showed that the Tupolev Tu-104 was prone to banking in a side wind. In the low altitude situation, the pilot's response of adjusting the ailerons was not sufficient; the proper response would have been to sharply pull back on the throttles. They concluded that as soon as the aircraft separated from the runway, the aircraft exceeding the aircraft flight manual recommended 2-3° angle of takeoff, although still 3-4° from a stall angle; the wind was believed to have pushed the right wing into the roll. Calculations showed the right fuel tanks held an estimated 1300-1500 kg more fuel than the left, contributing to the roll.

Causes

The commission of the Ministry of Aviation Industry of the USSR tasked with investigating the crash concluded the causes of the accident were as follows;

The aircraft was refueled asymmetrically, calculations showed the right fuel tanks held an estimated 1300-1500 kilos more fuel than the left, causing the aircraft to roll to the right;

Inadequate pilot response to the emergency, ignoring the automatic angle of attack and (vertical) overload alarm for eight seconds before responding;

Increased right bank upon separation from the runway that could not be corrected with ailerons alone.