NavList:

Some random points regarding this story and the responses:

The pilot initially mistook Venus for the approaching aircraft, and seeing it was above his flight path, believed it was no threat. Then he sees the real aircraft, and in relation Venus, it probably looked to be much closer in altitude. His reaction on the controls was not in response to seeing Venus but to seeing the oncoming aircraft.

At night, most flight crews will turn on overhead lighting inside the cockpit once at cruise altitude, or even sooner. The reflections off the windshields make it impossible to see anything outside except the moon. Imagine driving on a country road in a rural area, then turn off your headlights and turn on your dome light; that's what it's like flying at night.

Most air traffic across the North Atlantic is unidirectional at certain times of day; eastbound to Europe at night, westbound to North America during the day. Air traffic control constructs a series of airways across the ocean for each time period, and to fly against the oncoming flock means you usually have to fly above, below, or around the route structure. To see an aircraft passing in the opposite direction is rare.

The traffic collision warning system displayed the oncoming aircraft but never produced any alerts since they weren't on a collision course.

The cockpit voice recorder is on a continuous loop and only records the last two hours of conversation. By the time the flight reached Zurich the incident had been recorded over, so there is no accurate record of what really happened other than the flight data recorder (with a 25 hour recording time) and the pilots' testimony.

A link to the investigative report:

http://www.bst-tsb.gc.ca/eng/rapports-reports/aviation/2011/a11f0012/a11f0012.asp

Some excerpts from the report:

"The FO initially mistook the planet Venus for an aircraft but the captain advised again that the target was at the 12 o'clock position and 1000 feet below. The captain of ACA878 and the oncoming aircraft crew flashed their landing lights. The FO continued to scan visually for the aircraft. When the FO saw the oncoming aircraft, the FO interpreted its position as being above and descending towards them. The FO reacted to the perceived imminent collision by pushing forward on the control column. The captain, who was monitoring TCAS target on the ND, observed the control column moving forward and the altimeter beginning to show a decrease in altitude. The captain immediately disconnected the autopilot and pulled back on the control column to regain altitude. It was at this time the oncoming aircraft passed beneath ACA878. The TCAS did not produce a traffic or resolution advisory."

"The assessment of relative position at night is difficult: there are few external cues by which the position and motion of objects can be assessed. Visual cues are further reduced if the cockpit lights are turned on full. In the case of assessing whether an oncoming aircraft at similar altitude will pass above or below, there is no horizon by which to assess the relative motion. When the aircraft is distant it appears as a single point of light with no motion relative to the observer. Based on tests conducted in an Air Canada B767 simulator, no distinct motion up or down the field of view of an oncoming aircraft was detectable until the aircraft was 15 seconds apart at a closure speed of 900 knots. An oncoming higher aircraft then moves up the visual field and an oncoming lower aircraft moves down the visual field. There are no known illusions where a person can perceive an oncoming object as moving contrary to the actual path.

"The first officer slept for approximately 75 minutes which likely placed the first officer into slow–wave sleep and induced longer and more severe sleep inertia."

"The first officer was experiencing a circadian low due to the time of day and fatigue due to interrupted sleep which increased the propensity for sleep and subsequently worsened the sleep inertia."

"The captain followed standard procedure after the identification of the oncoming aircraft as a TCAS target on the ND. The captain sought the aircraft visually—which, at this point, appeared as a single point of light approximately straight ahead of the aircraft—and verified the target. This task was made more difficult by the cockpit lights being on full, causing reflections in the cockpit glass and hindering the view outside the aircraft. At about this time the FO awoke. To avoid the FO being startled, the captain twice pointed out the relative position of the oncoming aircraft to the FO. This occurred approximately 1 minute after the FO had woken and was most likely suffering from the strong effects of sleep inertia. The FO was not in a state to effectively assimilate the information from both the instruments and from outside the aircraft or effectively provide an appropriate response. Despite having been trained to interpret TCAS targets and react to them, the FO was drawn to rely on immediate perceptual information. Under the effects of sleep inertia, the FO was likely confused and disoriented and perceived the aircraft on an imminent collision course. Consequently, the FO pushed forward on the control column to avoid the collision. The FO quickly realized the error because the traffic appeared to be moving down in the visual field, which did not make sense.By that time, the captain had reversed the control movement to return the aircraft to the previous altitude.

"By identifying the oncoming aircraft, the captain engaged the FO before the effects of sleep inertia had worn off. As a consequence, the FO did not form an effective response to the situation."

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