[D6] DE CHEVILLY (45) VERS SOUGY (45) 21.10.2021

On 21 October 2021, at about 8:30 p.m., the witness is in his vehicle and he is driving on the D6 from Chevilly (45) towards Sougy (45). His attention is drawn by a small green light on the left, rather low, moving slowly, and which then suddenly gained speed. The witness stopped immediately, came out of his vehicle, to photograph and film the device with his phone. He then observed the phenomenon passing through the sky. Only one testimony will be collected: only the photograph is attached to the official witness-interview report. The evidential quality is good: one witness, one photo. The investigation concluded that the witness very probably saw an A400M military aircraft from Air Base 123 at Orléans-Bricy, on a very-low-altitude (TBA) exercise south of Air Base 132 at Colmar, as stated in the source (see investigation notes). This conclusion is based on the following: - Lights whose colours are typically those used in aviation. - Confirmed presence of the aircraft near the base, on approach. - Slow apparent displacement: the A400M moving relatively slowly in TBA flight. The actual speed remains difficult for the witness to judge, on the one hand because he himself was moving during the first phase, and on the other hand because the aircraft may not have been moving across the witness’s line of sight. The periods when it appeared to accelerate were those when it took a more transverse position after turning. The latter point is one of the 3 unusual features identified by the witness, the other two being the form and absence of noise. For the latter point, even though the A400M is a very noisy aircraft, the perception of the noise it emits depends on other factors, and in particular on the distance separating it from the witness, as well as the direction of wind, whether or not it carried sound toward the witness. We have seen that it was likely that the aircraft was about 3600 m away, and not 30 m as initially evaluated by the witness, who, under unfavourable observation conditions (at night and while on the move, at least for the first observation phase) could not properly estimate it. We have also found that the wind was blowing from the north, or opposite to the direction of observation; it therefore did not carry the sound toward him. These two elements may suffice to explain that the witness, particularly in the second observation phase during which he stopped, did not perceive noise. As for the perceived triangular shape, the aircraft was low on the horizon and was observed at a low angle. At night, with the aircraft’s dark coloring, these details (propellers, tail surfaces...) could not be perceived by the witness. The simplest form deduced by the brain under these conditions is that of the triangle. This angle of observation can also explain the lack of visibility of the other lights at the beginning, masked by the body of the aircraft itself. The angle of observation changing as the aircraft and the witness moved, the other lights eventually became visible and are visible on the photograph. GEIPAN classifies the case A: observation of a military transport aircraft A400M.