The Surprising Way Keyhole Wasps Can Take Down an Aeroplane

The Surprising Way Keyhole Wasps Can Take Down an Aeroplane
Don't you dare: A keyhole wasp at the opening of a pitot probe. (Image: House et al., 2020/PLOS ONE)

Keyhole wasps like to build their nests in tiny holes, including the openings of devices used to measure the speed of aircraft. A recent investigation shows the problem is worse than we realised.

On November 21, 2013, an Airbus A330-200 prepared to take off from Brisbane Airport in Australia, but the pilot turned back after noticing some odd airspeed readings. The plane was eventually allowed to take off some two hours later, but the anomalous speed readings returned just as the A330 was about to become airborne. Unable to stop, the pilots had no choice but to continue takeoff. Once in the air, the airspeed discrepancies returned, so the pilots issued a mayday distress call, turned the plane around, and performed a flawless, but fully loaded, landing.

“On inspection, the remains of what looked like a wasp were found in one of the plane’s pitot probes,” Alan House, a biologist with Eco Logical Australia and the lead author of a new PLOS ONE study, explained in an email. “Pitot probes are the instruments that tell the pilots how fast they are going whilst in the air, so are critical for safe flight.”

That an insect could take down an entire plane seems highly improbable, but such a thing may have happened before, in February 1996, when a Boeing 757 crashed shortly after takeoff from the Dominican Republic, killing all 189 people onboard. The pilots had misjudged the plane’s speed, the result of anomalous airspeed readings from the pitot probe. The malfunction was blamed on a wasp, but the probe was never recovered, so the theory was never officially proven.

As House’s new study points out, this problem, in which wasps build nests inside of pitot probes, is shockingly common. Of particular concern is the invasive keyhole wasp (Pachodynerus nasidens) — an insect native to South and Central America and the Caribbean. These wasps construct their nests in cavities, including window crevices, electrical sockets, and, you guessed it, keyholes.

Keyhole wasps have spread “presumably through shipping and/or air transport to the southern United States and all the way across the Pacific to eastern Australia,” said House. These solitary insects live in tropical and subtropical environments and measure about 10 to 12 millimetres long, he said.

The incident at Brisbane Airport in 2013 is hardly an isolated occurrence. From November 2013 to April 2019, officials at this airport reported 26 wasp-related incidents, some of them resulting in “emergency procedures,” as the new paper points out. But while airport officials have a reasonably good handle on the risks posed by larger wildlife, such as birds, they still don’t fully understand this invasive threat. The new paper seeks to fill this gap.

To quantify the danger of the keyhole wasp, House and his colleagues 3D-printed several replica pitot probes, which were placed in four strategic locations around Brisbane Airport. Over the course of a 39-month monitoring period, the team chronicled 93 instances in which the bugs blocked the replica probes.

The lengthy monitoring period also allowed the team to study the conditions under which these insects preferred to build their nests.

“We found that only the keyhole wasp used probes for nesting, and all replica pitot probes except the smallest aperture [3 mm] were used,” said House. “Nesting occurred in almost every month of the year, and most nesting was concentrated in one part of the airport,” namely an area filled with grass.

That said, the wasps did build more nests during the summer months, at temperatures between 24 – 31 degrees Celsius.

In terms of how airport and airline officials should deal with the problem, House said simple aircraft management, such as covering probes when planes are idle at the gates, and wasp population reduction measures, like traps, could “reduce the risk of an incident.”

In addition, he’d like to see “all airlines adopt a pitot probe cover policy” at Brisbane Airport and other airports along the eastern seaboard of Australia start to monitor for this wasp, as it’s a “seasoned traveller, and there is every reason to expect it to disperse to other locations from Brisbane.”

Eradicating keyhole wasps in Australia isn’t currently an option, and it’s no guarantee the insect won’t return in the future.

Wow, what a serious pain in the arse. House’s prescriptions make sense, but it’s an added hassle for the industry, and yet another potential reason for increased fares. With climate change being what it is, the keyhole wasp aviation problem could spread to other areas, including the United States. Hate to say it, but this story won’t be ending any time soon.

This article has been updated since its original publication.