Accident Overview
The accident airplane, a Cessna, was destroyed by impact forces and no evidence of fire was found. Wreckage examinations revealed no preexisting powerplant, system, or structural failures, and the engine was producing power at impact. The wreckage was scattered over an area of about 600 feet, with crushing and bending consistent with a moderate angle of descent and a moderate right-wing-down attitude at impact.
Radar and Flight Path Analysis
Radar data indicated the airplane initiated a descent from 3,000 feet immediately after the pilot received a second traffic advisory from air traffic control. The pilot reported the traffic was above him and stated he needed to deviate. Data showed the airplane was in or entering an uncontrolled descent at that time. The closest identified aircraft was a DC-10 at about 4,000 feet, with horizontal and vertical distances of 1.1 nautical miles and 1,600 feet, respectively. Wake turbulence was determined not to be a factor due to the relative positions. The DC-10 was left of the position given to the pilot, but air traffic controllers do not have strict angular limits for traffic guidance.
Pilot Actions and Environmental Conditions
A simulated airplane performance analysis showed that, about 15 seconds before the pilot's last transmission, his view of the DC-10 moved diagonally across the windscreen while tripling in size. Shortly after stating "I needed to deviate," the airplane experienced high bank and pitch angles, rolling through 90° and peaking at about 150° before nearly recovering at impact. The airplane appeared structurally and aerodynamically intact to reach the ground. The meaning of the pilot's statement could not be determined. No evidence of pilot impairment or incapacitation was found before the descent.
Weather at the time of the accident included night conditions, with the moon obscured by low clouds. Instrument meteorological conditions prevailed, with visual conditions reported between cloud layers. The terminal aerodrome forecast indicated a possible cloud layer at 3,000 feet. The DC-10 pilot observed the accident airplane flying about 100 to 500 feet above a cloud layer and then entering clouds. Several conditions conducive to spatial disorientation were present: no visible horizon references between cloud layers, eye and head movements during visual search, and the DC-10 appearing as a moving light against a featureless background.
Wreckage Examination
Wreckage examinations found red transfer marks on many pieces, concentrated on the lower airframe skin forward of the main and nose landing gear. These marks were determined to be from parts of the airplane, cargo, and items encountered during recovery, with no evidence of an in-flight collision. A small piece of black anodized aluminum embedded in the left wing was identified as a fragment from a cockpit lighting dimmer. Sound spectrum analysis found no loud noises during the pilot's last three transmissions, but background noise increased, indicating an intact cockpit and increasing airspeed; the overspeed warning had activated. Radar transponder signals were lost below 2,400 feet, likely due to unusual attitudes masking the antenna.