Of the (rather numerous) accidents involving the Tu-104, several were either caused or aggravated by major electrical failures, which disabled the aircraft's navballs, which caused the pilots to become spatially disoriented, which caused (or contributed to) a loss of control, which caused the aircraft to crash:
- SU4 (15 August 1958) - en route from Khabarovsk to Irkutsk, the aircraft climbed too high while attempting to avoid storms ahead; recovery from the resulting stall was rendered impossible by "...disorientation of the crew, from accompanied failure of the artificial horizons".
- SU3932 (30 September 1973) - shortly after takeoff from Sverdlovsk-Koltsovo, "[t]he aircraft crashed due to incorrect indications by the main artificial horizon and the compass system, caused by a failure of the electrical supply, resulting in spatial disorientation of the pilots."
- SU964 (13 October 1973) - while on approach to Moscow-Domodedovo, the aircraft banked excessively far to the left, entered a spin, and crashed; "[t]he investigation concluded that after the first right turn executed by the aircraft (in which the bank exceeded 40°), multiple navigation instruments including the compass and artificial horizon failed. Combined with the poor visibility at the airport, the crew lost spatial orientation and were unable to see any landmarks to determine their position. When the plane banked slightly to the right, the pilots corrected the right bank only to put the plane into a sharp left bank that reached 70°, causing the crash."1
- SU2415 (28 November 1976) - when making a right turn during climbout from Moscow-Sheremetyevo, the aircraft continued to turn past the assigned heading, rolled onto its side, and dove into the ground; "...among the causes of the crash included failure of the artificial horizon, poor visibility from the cockpit, and lack of warnings indicating the failure of the artificial horizon."
What made the Tu-104 so prone to these catastrophic electrical failures?
1: With 122 fatalities, this is still the worst Tu-104 crash to date.