Page:CAB Accident Report, Pacific Air Lines Flight 773.pdf/7

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from Stockton. At this time, the recorder traces indicate the aircraft was cruising at 5,000 feet indicated altitude on a magnetic heading of approxi-- mately 230 degrees and at an airspeed of approximately 213 knots. The first erratic indications on the tape appear commensurate with the high-pitched transmission by the copilot which occurred at 06h8:15. At this point on the flight recorder tape, the four traces for altitude, airspeed, heading, and acCeleration begin to make sharp positive excursions. The altitude trace begins a sharp excursion indicating a descent from 5,300 to 2,100 feet within 22.5 seconds or at a descent rate of approximately 9,000 feet-per—minute. During the same time interval, the airspeed trace indicates an increase to 335 knots and the heading trace indicates a change to appromately 265 degrees occurred. The vertical acceleration trace indicates a decrease first to approximately minus 0.1: g, and then an increase to plus 2-1/2 g during this same period.

The altitude trace then indicates a climb to approximately 3,200 feet in 15 seconds or at a rate of 14,1100 feet-perminute, during which the airspeed trace indicates a decrease to approximately 265 knots. The heading trace continued a change to approximately 285 degrees. Vertical acceleration continued to vary from plus 2—1/2 3 to minus 0.1: g. From this point to the end of the recorded tracings, all traces were abnormal.

Anaksis

Investigation revealed that the crew was properly qualified for the flight and that the aircraft was properly dispatched. Examination of records and the investigation disclosed that the aircraft and powerplants were maintained in accordance with existing Pacific Air Lines and Federal Aviation Agency approved directives and procedures, and that the aircraft and poweiplants were in an ail-worthy condition prior to the occurrence of this accident.

As indicated above, there was no substantive evidence developed during the investigation to indicate that power failure was a causal factor in the accident. The evidenced asymmetric power condition is not deemed unusual when the condi- tions in the cockpit prior to impact are taken into consideration. A likely explanation would be acCidental left engine control novenent by at least one of the cockpit occupants immediately before impact, resulting in loss of power gutpu: and consequent propeller auto-feathering action in process at moment of

mpac.

The flight recorder tape indicated normal flight until 06118 when a steep descent began. Fifteen seconds later, the first officer broadcast his last high-pitched transmission. That transmission and the flight recorder record of a momentary interruption in the dive 22 seconds after it began, were the only indications of the flight crew's actions during the final minute of flight. This evidence does not furnish sufficient parameters to determine the specific time point at which both pilots became completely incapacitated. Such a measurenent is not essential to the determination of the cause of this

acciggnt. This evidence does, however, indicate the improbability of pilot sue a.