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On February 6, 1996, Flight 301 of the Turkish airline Birgenair crashed into the Atlantic near the Dominican Republic shortly after takeoff. There were 176 passengers and 13 crew members on the plane, which was flying from Puerto Plata to Frankfurt, none of whom survived the accident. The airline was founded in 1988 to transport Turkish guest workers to Germany, but later the company also transported tourists to the Caribbean. Most of the passengers on Flight 301 were German citizens returning home from vacation.
Later, the experts investigating the incident determined that the plane had crashed based on the recorded data from the black boxes. Flight 301 was a Boeing 757-225, and for an aircraft of this size, tipping is a particularly dangerous phenomenon that usually occurs when the aircraft is flying too slowly. The crash resulted in a rapid loss of altitude and the pilots were unable to get the aircraft out of this fall. They probably didn’t react well to the situation, but aside from human error, a surprising reason was found: wasps.
Namely scratch wasps, one type of them is also called black stem wasp. Some scratch wasps build nests out of mud and small stones and are attracted to cylindrical cavities with a series of man-made holes. For example, for the pitot tubes of airplanes, which are named after their inventor Henri Pitot. The instrument is simply a tube in which the air flowing through creates a pressure difference that is measured by sensors. The size of the difference can be used to determine the speed of the tube, which is why the pitot tube is still one of the most important instruments for measuring speed in aircraft today. Although the pitot tubes of Flight 301 were not found, the official investigation suggested that the wasps had built a nest in the tube closest to the captain’s seat and that an instrument in the cockpit was therefore displaying incorrect speed data.
The house wasps quickly became suspicious as they live in large numbers around the Puerto Plata airport and constantly provide work for aircraft maintenance workers. The pitot tubes are partially obscured because of the wasps, which was not the case on Flight 301. The plane sat at the airport with its pitot tubes open for weeks before takeoff, and this time would have given the wasps plenty of time to nest. One of the ill-fated aircraft’s three pitot tubes malfunctioned, causing exactly the kind of malfunction caused by blockages.
House wasp – Photo: Didier Descouens / Wikipedia
However, the tragedy also required human error. During takeoff, the captain noticed that his speedometer was not working properly – at which point he should have turned back, but decided to continue the journey anyway. When he later transferred control to the autopilot, the autopilot began to slow the aircraft because the autopilot was receiving data from the captain’s speedometer, but the instrument detected excessive speed due to a clogged pitot tube. Even then, the captain made the wrong decision: he interpreted the difference in the speedometers to mean that they were all broken, even though the co-pilot’s showed correct values all the time. Soon the rudders began to shake, warning me of an impending stall, but at the same time an error message about excessive speed came up. The plane had already slowed dangerously, but the captain decided to slow down even further. Flight 301 overturned and crashed into the sea.
It later emerged that Birgenair had not properly trained its pilots and its practice of emergency simulations was incomplete. This was noticeable in the panicked reactions of the crew, as it was also possible to extract cockpit conversations from the black boxes. Birgenair also did not survive the disaster; the company initially canceled all flights and then filed for bankruptcy.
The circumstances of the disaster were later recreated in a simulator with experienced pilots. They also couldn’t get the plane out of the crash and found it confusing that the rudder rudder shake and the speed warning message were signals with opposite meanings. Boeing subsequently changed these warnings on its aircraft, and after the accident several airlines expanded their pilot training to include errors caused by clogged pitot tubes.
Even though Flight 301 is an extreme example, mud-brooding wasp species still cause problems with air traffic in almost all countries (such species are also found in Hungary). Newsweek cites an American aviation safety report that says risky species of wasps have proliferated around airports as airlines try to become more environmentally friendly and planes have become quieter and cleaner in recent decades, and their spread in many places is also due to climate change and has been also supported by forced flight breaks due to the Covid epidemic.
In the summer of 2021, an investigation at London’s Heathrow Airport found eight aircraft whose pitot tubes were contaminated by insects. And in 2013, a species of wasp called Pachodynerus nasidens caused a problem at Brisbane Airport in Australia when an Airbus A330 was forced to turn back after experiencing problems similar to those experienced during Flight 301’s takeoff. After landing, it turned out that wasps had blocked the pitot tubes.
The Pachodynerus nasidens, native to the Pacific region, is also very invasive and, as its English name – keyhole wasp – shows, is particularly interested in narrow openings. The connection between insects and pitot tubes has already been scientifically researched by setting up replicas of pitot tubes at airports. The three-year investigation finally concluded in 2020 that the wasp species “poses a significant risk to aviation safety.”
Curious keyhole wasp – Photo: Wikipedia /gailhampshire@Flickr
Fortunately, there are several ways to make your flight wasp-proof. The easiest option is to cover the pitot tubes after landing, which presents the problem of adding the possibility of human error. In Brisbane in 2018, an Airbus carrying 229 people had to turn back because it took off with its pitot tubes covered and the speedometers were not working properly. Another option is to redesign the pitot tubes into a less vulnerable shape or replace them with laser speedometers, which is of course a more expensive solution. But Australia is also experimenting with using insecticides to eradicate the caterpillars that are necessary for the reproduction of wasps in the area around airports and thus prevent the spread of wasps.
However, to avoid trouble, well-trained pilots who understand the situation are essential. The crew operating the aircraft must make good decisions even in unusual situations and must be aware of the possible causes of various instrument malfunctions. Unfortunately, this knowledge was not present in the cockpit of Birgenair Flight 301.
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