A plane crash into an East Palo Alto neighborhood on Feb. 17, 2010, was most probably caused by the pilot's failure to follow departure instructions and failure to attain sufficient altitude to avoid striking power lines during takeoff in foggy conditions, the National Transportation Safety Board (NTSB) has determined.
Pilot Douglas Bourn and two fellow Tesla Motors employees, Brian Finn and Andrew Ingram, were killed after the Cessna 310 R they were traveling in crashed into high-power lines in the baylands and smashed into homes on Beech Street in East Palo Alto. The accident blacked out power to Palo Alto for hours.
Bourn was warned by the Palo Alto Airport traffic controller that morning that he would be flying at his own risk if he took off in heavy fog. The three men were traveling to Hawthorne Airport in southern California for a work assignment.
Fog was a contributing factor in the crash, according to the NTSB report, which was released on Tuesday (Nov. 22).
Investigators identified a series of errors by the pilot that were considered causes:
"Task performance: Use of equipment/info; use of equipment/system
"Personnel issues: Action/decision -- Action - Incorrect action sequence
"Aircraft, Aircraft operation/performance/capability: Performance/control parameters -- Altitude - Not attained/maintained
"Environmental issues: Conditions/weather/phenomena -- ceiling/visibility/precipitation. Low visibility contributed to the outcome."
The accident was probably caused by "the pilot's failure to follow the standard instrument departure as instructed, and his failure to attain a sufficient altitude to maintain clearance from power lines during takeoff in instrument meteorological conditions," the investigators concluded.
According to the report, Bourn departed the airport in near-zero visibility "instrument meteorological conditions," meaning that he would have to rely on instrumentation to guide him through the heavy fog.
Shortly after takeoff, the plane struck a power tower and power lines before impacting with homes and the ground.
Review of recorded air-traffic control tower transmissions revealed the pilot was initially given his instrument-flight-rules clearance to turn right to a heading of 60 degrees and climb to 3,000 feet.
Shortly after verifying his flight rule clearance, Bourn received a release from the air-traffic controller, but he was told the runway was not visible to the controller, according to the report.
The controller further informed Bourn that takeoff was at his own risk.
Bourn told the controller that he did not hear a "cleared for takeoff" instruction from the tower. The controller said he could not clear the pilot for takeoff because the runway was not in sight.
"The release is all yours, and it's at your own risk, sir," the controller could be heard telling Bourn in a recording.
Bourn acknowledged the transmission and took off. A witness who was adjacent to the accident site reported seeing the airplane "suddenly appear from the fog" to the left of her position. The witness said the airplane continued to fly in a level or slightly nose-up attitude until it hit the power lines.
Evidence indicated the plane struck the power tower at about 50 feet above ground level and at a high rate of speed, according to the report.
Examination of the airframe, engines and propellers disclosed no evidence of any mechanical anomaly, according to the report.
But weather conditions reported five minutes prior to the accident noted wind was variable at 5 knots and visibility was 1/8th mile. There was fog and vertical visibility of 100 feet at ground level. Weather conditions recorded by the control tower 11 minutes after the time of the accident showed worsening conditions: a visibility of 1/16th mile, fog, and a vertical visibility of 100 feet at ground level.
Recordings from East Palo Alto Police Department's ShotSpotter system, which captured the accident sequence, were coupled with airport surveillance radar readings that indicated that rather than making a right turn to a heading of 60 degrees, Bourn made an approximately 45-degree left turn shortly after departure to the area of initial impact with the power pole and lines. A sound-spectrum study determined both engines were operating near full power, according to the report.
Bourn's family could not immediately be contacted for comment. Four lawsuits have been filed against his estate by the victims' families and by East Palo Alto residents whose homes and property were severely damaged in the accident. A home day care center was destroyed by the crash and fire and has not been habitable since.