Photo: VR-BLN (previous registration) at London Heathrow, Matt Birch http://visualapproachimages.com
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This was a case of a highly experienced pilot flying a fully functional airplane into a lake short of the runway. The visibility was a factor but not causal. The cause was the pilot's incorrect view of the impact of glide path on landing distance. For more about this, see: Landing.
Everything here is from the references shown below, with a few comments in an alternate color.
Figure: Trajectory in the Vertical Plane, from Bureau d'Enquetes et d'Analyses, Annex 3.
11 H 20, the aircraft departed Geneva (Switzerland), from Chambéry under IFR flight plan. Upon arrival, the driver intercepts the localizer for a landing on runway 18. 11 H 31, he is allowed to descend to 6,500 feet and moved to Chambéry APP. A minute later, this station confirmed radar contact, asks him to perform an ILS 18 approach, and gives him the elements weather: "wind calm, visibility 2,500 meters, mist, sky clear, Temperature 2, Dew Point -2, QNH 1024, QFE 996".
At 11:37, the driver looks at 4 NM DME. The controller cleared for landing indicating a calm wind.
The aircraft then takes a greater vertical speed and passes below the normal plan of approach. It violently struck the surface of the water to about 0.6 NM from the beginning of track.
Thanks to a mobile phone, a fisherman, who was in the landing zone, gave the alert. Occupants evacuated the aircraft that was taking on water quickly. They did not have time to carry life jackets and used cushions as floats. Another fisherman, who was not far from there, recovered them in his boat to lead them into a nearby port. In a State of hypothermia, they received first aid before be taken to a hospital for medical examinations. The hostess was suffering, in addition, a fracture of the left arm.
The captain had already used the facilities of Chambéry the previous week by good weather conditions. The day of the accident, he was pilot. A few nautical miles from the threshold, while he had the runway in sight, he had decided to descend under the glide with the aim of achieving a "flatter" approach, to pass the threshold to 125 kt and avoid braking on the runway. During its descent under the normal plan of approach, he was dazzled by the Sun and lost the track of views. He tried to find external visual references but it distinguished over the surface of the water. He wore no sun glasses but only the corrective lenses from view. At no time, he considered a missed approach procedure.
"The impact with the water was the result of a loss of visual references during final approach during which the crew voluntarily brought the plane beneath the ILS glide slope, in an area affected by mist, on one hand and on the other hand due the failure to decide to execute a missed approach."
Bureau d'Enquetes et d'Analyses, Accident on February 6, 1998 at the Lac du Bourget (73) the aircraft Gulfstream G III registered VP-BLN, March 29, 1999.
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