The clogged pitot tube is likely the cause of the Birgenair Flight 301 crash into the Atlantic Ocean, which resulted in the deaths of 189 people.
“Don’t pull back, please don’t pull back… Oh, what’s happening?” Twelve seconds later, the recording went silent. These were the last recorded words of the pilot on Birgenair Flight 301 on February 6, 1996, which was en route from Puerto Plata, Dominican Republic, to Frankfurt, Germany. However, the plane crashed into the Atlantic Ocean. All 189 people on board, including 176 passengers and 13 crew members, perished. So what happened?
Boeing 757 – the aircraft that crashed after taking off from Puerto Plata, Dominican Republic, on February 6, 1996. (Photo: Aero Icarus)
As the aircraft began its takeoff, the captain of the Boeing 757 noticed that the airspeed indicator was not functioning but continued with the scheduled flight. This was the first error made by the crew, according to Geoff Dell, a professor at the University of Technology Ostrava, who specializes in system safety, risk management, and ergonomics. “They should have aborted the takeoff and investigated the reason for the erroneous airspeed indication,” Dell told Newsweek on May 21.
Shortly after takeoff, the “stick shaker” was activated, shaking the pilot’s control yoke to warn that the aircraft was flying too slowly and dangerously. The autopilot disengaged, and the plane started to veer off course and plunge downward.
An investigation later concluded that one of the aircraft’s three pitot tubes – the pressure sensors protruding from the aircraft’s fuselage that measure airspeed – was clogged. This could have led to the crew receiving inaccurate airspeed information. Though it cannot be confirmed with 100% certainty, it is highly likely that a wasp nest was responsible for blocking the pitot tube.
Yellow-black mud dauber wasps (Sceliphron caementarium) are a species “famous” among pilots in the Dominican Republic. They tend to build nests in cylindrical artificial structures like pitot tubes. Experts were unable to recover any pitot tubes from the Birgenair Flight 301 accident. However, the aircraft used for the flight had not taken off for about 20 days prior to the incident, which is ample time for wasps to build a nest.
The issue of clogged pitot tubes is not uncommon. In June and July 2021, eight aircraft at Heathrow Airport in London had pitot tubes blocked by insects, eggs, or nesting materials. “The trend of ‘greening’ urban environments and the aviation industry will make aircraft quieter, cleaner, and airports less polluting, providing a more attractive environment for insects like wasps,” the UK Air Accidents Investigation Branch (AAIB) reported.
Brisbane Airport in Australia also faced similar issues when it was discovered that Pachodynerus nasidens wasps were clogging the pitot tubes. In 2013, an Airbus A330 had to return shortly after takeoff due to a malfunction in the airspeed indicator.
Yellow-black mud dauber wasp, the creature that could have caused the Birgenair Flight 301 accident. (Photo: Jean Landry/iStock/Getty).
Research conducted by consulting firms Ecosure and Eco Logical Australia, published in the journal PLOS One in 2020, examined this issue. The research team placed probes in simulated pitot tubes at the airport from February 2016 to April 2019. As a result, 93 tubes were found to be blocked, all due to Pachodynerus nasidens wasps. The study indicated that this species poses a significant risk to aviation safety.
Experts have proposed two solutions to the wasp problem. The first is to cover the pitot tubes when aircraft arrive at Brisbane Airport. However, this method also carries risks. On July 18, 2018, an Airbus carrying 229 people took off while the pitot tubes were still covered. The aircraft reached an altitude of 3,350 meters before needing to return.
Brisbane Airport has also implemented another precautionary measure. They are using insecticides derived from a plant in South America to eliminate caterpillars – the prey of wasps. After locating a suitable nesting site, female wasps paralyze the caterpillars, place them in the nest, and then seal them with mud. Once hatched, the young wasps will feed on them. The airport reported that this measure has helped reduce the number of wasp nests by 64%.
Additionally, experts are also researching redesigning pitot tubes to reduce the likelihood of freezing and blockage by wasps, or replacing pitot tubes with laser sensors for measuring airspeed. The first prototype of such a sensor was developed by BAE Systems in 2016.
