Before reading tonight’s story you must firstly look at photo 1 below, at first it looks like a photo of a naked lady in a window, when in fact it’s a total illusion, and there is no lady at all when you look again, knowing this fact, and know knowing what tricks an illusion can play with your brain, tonight’s story is about an illusion and how it was unfortunately deadly for an airliner in 1978.
December 23rd, 1978 was a busy day at Rome’s Leonard De Vinci Airport, lots of people were flying through Rome on their way home for the Christmas Holidays, all flights from Rome to Palermo in Sicily were full that day, and Alitalia, the national Italian Airline put on an extra flight to try and get rid of the backlog of passengers waiting to go to Palermo. The extra flight was operated by a Douglas DC-9 aircraft, and took off from Rome at 11:30pm as Alitalia flight 4128 to Palermo, with 129 on board. The flight was un-eventful, but on its final approach, one hour later, at half past midnight, the DC-9 crashed into the sea just 1.5 miles from the Airport, only 21 of the 129 onboard survived. The accident was attributed to the flight deck crew suffering from an extreme illusion, dangerous to pilots called – “The Black-hole approach illusion”.
A black-hole approach illusion can happen during a final approach of an aircraft at night (when there are no stars or moonlight) over water, or unlit terrain on to a lighted runway, beyond which the horizon is not visible or lit up. The pilot can therefore only see the runway lights in-front of him, nothing else, and If the pilot has no peripheral visual cues of exactly where the horizon is, or where the ground is in relation to their position, they may be tricked into the illusion of the aircraft being too high on its final approach, resulting in pitching the aircraft nose down to decrease to the perceived approach angle. Or that the aircraft is in level flight, and the runway appears to be tilted or sloping.
On that fateful night, flight 4128 was directed by air traffic control towards Palermo Airport, the intention was that air traffic control would talk the aircraft down to 2 miles from touch down, at this point, if the crew could see the runway, they would switch off the autopilot and visually land the aircraft. If they could not see the runway, the aircraft would apply full power and overshoot to go around for another try. Visibility was greater than 5 miles, but it was a windy night with full cloud cover and rain showers. The radar controller brought the DC-9 aircraft down to 1,500 feet, and when he was 4 miles from touchdown, the first offer, who was flying the aircraft, reported that they had the runway in sight, and was given landing permission. This is when the “black-hole approach illusion” kicked in – What happened next was the crew, believing they were nearer to the runway that they actually were, started to make a premature descent towards the runway, the wind was quite strong, and causing quite a bit of turbulence for the DC-9. The initial part of the approach was on autopilot until 2 miles from touch down when the crew turned off the autopilot, and stopped their decent at what they thought was 400 feet, as they were still thinking they were closer to the runway because of the illusion that the airport lights were giving to them. They were in fact not flying level but descending towards the sea. In the final nine seconds of the flight, traveling at a speed of 150 knots (173 mph), because of a sudden gust of wind, they lost enough altitude to impact the sea, which the crew had no idea was, at that time, only 30 feet below them, the aircraft’s right wing hit first, then the aircraft broke apart, and sank. 21 passengers survived and were rescued by nearby fishing boats. The cockpit voice recorder, when recovered, showed that the crew, who thought they were in level flight at 400 feet above the water, were confused as to how far away the runway was, they heard the “Too Low” warning, and if they checked their instruments, they would have seen that they were descending and not in level flight, but because of the illusion, they ignored the warning and instruments, and continued to fly the aircraft visually towards the runway, with a fatal ending. The accident was attributed to pilot error.
Photo 2 shows the aircraft in better times, one year before, and photo 3 shows the aircraft after it was salvaged from the sea, and upon the conclusion of the investigation, was sold as scrap metal to a local scrap merchant in Sicily.