Boeing 737 Safety Record

The captain's failure to stop the aircraft when given a stop signal by the ground marshaller and his failure to turn the aircraft when given a turn signal by the ground marshaller as he taxied into the gate resulting in the aircraft's left wing colliding with ground equipment.

The failure of the flight crew to provide a recommended landing traffic advisory, and the failure of flight service station personnel to provide a flight advisory to the arriving airplane concerning men and equipment operating on the runway. Factors in the incident were operations at an airport when the control tower was closed, and the failure of the snow plow driver to verify the eminent arrival of the airplane.

The lavatory service driver's failure to follow established company procedures and directives. A factor in the accident was the airline's use of a one person pushback procedure.

A discharged battery due to a loss of electrolyte, and the latent shorted failures of the No. 1 and 2 generator control unit (GCU) blocking diodes (CR910) for undetermined reasons. These failures resulted in an excessive current drawn from both GCUs, during the flight crew's attempt to start the auxiliary power unit, that caused the immediate overload (opening) of the AC power supply input fuses (POR fuses) internal to each GCU, and subsequent loss of the No.1 and 2 generators; complete discharge of the battery, and subsequent total loss of electrical power. Contributing to the incident was the incorrect reading of the cockpit DC voltmeter (read higher than actual reading) allowing the flight crew to depart with an unreliable (discharged) battery.

The Cessna pilot's incorrect visual identification of the Boeing 737's altitude, and decision to take evasive action that was not required, which resulted in the two airplanes coming within 500 feet horizontally, and 0 feet vertically of one another.

A loss of torque on the apex nut of the shimmy damper for undetermined reason(s), which resulted in a failure of the shimmy damper, and the subsequent failure of the lower torsion link of the right main landing gear.

The improper electronic control unit software logic that permitted the electronic control unit to lock on a failed hydromechanical resolver, which failed due to damage to a wire that was incurred during the manufacturing process, resulting in an uncommanded and sudden increase in fuel flow to the engine that damaged the turbine and caused the engine to lose power.

The dynamic imbalance in the yaw rate gyro, which provided input to the yaw damper and rudder. A factor was the deteriorated grease in the gyro bearings.

Separation of the ABSB-4 aileron bus cable, resulting in reduced lateral controllability of the aircraft. Related factors were wear in the cable and inadequate inspection of the cable by company maintenance personnel.