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NTSB analyses passenger’s iPhone video to determine the trajectory and speed of fatal DHC-3T accident
17 September 2014
(a) Camera Orientation Estimation - Airplane Reference Points Aligned with Image  (b) Airplane Location and Orientation Estimation - Ground Reference Points  Aligned with Image (NTSB)

(a) Camera Orientation Estimation – Airplane Reference Points Aligned with Image
(b) Airplane Location and Orientation Estimation – Ground Reference Points
Aligned with Image (NTSB)

Investigators of the NTSB have analysed video footage of a fatal aircraft accident to determine the trajectory and speed. The video was taken by a passenger on board the plane.

On July 7, 2013, a de Havilland Canada DHC-3T Texas Turbine Otter was destroyed after a collision with terrain shortly after takeoff from Soldotna Airport, Alaska. All ten occupants were killed.
The NTSB found that a passenger had recorded a video on an iPhone 5 camera that was retrieved from the wreckage. Since there were no eyewitnesses to the entire accident sequence and since the airplane was not equipped with a flight data recorder, the video contained valuable data for the investigators.
The camera was hand-held by a passenger on the airplane who recorded the scene south of the runway through the fourth window on the left side of the airplane. The video included the taxiing, takeoff roll, takeoff and flight phases. The useful segment of the video ended when, shortly after takeoff, the airborne airplane rolled to the right and started losing altitude. After that time, the video no longer showed any ground reference features, making the estimation of its location and orientation impossible.
The analysis of this video posed unique challenges, the NTSB revealed, because the camera was hand-held as opposed to being fixed to the airplane. Consequently, it became necessary to first estimate the time-varying orientation of the camera with respect to the airplane and then, with the camera fixed to the airplane with that orientation, to estimate the location and orientation of the airplane with respect to the ground.

The analysis revealed that shortly after takeoff, flight speed started decreasing rapidly and angle of attack started increasing rapidly. Approximately 11 seconds after takeoff, flight speed and angle of attack reached levels corresponding to stall. The airplane developed a large right-wing-down roll angle and impacted ground several seconds later.

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Estimated Speed, Altitude and Pitch Angle (NTSB)

Estimated Speed, Altitude and Pitch Angle (NTSB)