Last month, Claire Ryder had a connecting flight through Dubai International Airport. She remembers looking out the window as her plane touched down. “It did look quite dusty,” said Ryder, a meteorologist at the University of Reading in the United Kingdom.
The long-haul aircraft that propel our intercontinental journeys are enormous, but delicate, machines—airborne dust can abrade the interiors of jet engines, for example, reducing their efficiency and necessitating maintenance.
The experience was fitting for Ryder—she and her colleagues recently took a census of the dust ingested by aircraft engines during takeoff and landing at airports, such as Dubai International, that are regularly affected by dust. They found pronounced geographic differences, in addition to daily and seasonal trends. Shifting flight times and holding altitudes could substantially reduce the amount of dust entering jet engines, the team concluded.
“You can go backwards in time and create a long, consistent data set.”
The researchers focused on mineral dust, which originates from arid regions such as Africa’s Sahara Desert and Asia’s Gobi and Taklamakan Deserts and also anthropogenic activities such as farming, construction, and mining. It can readily travel long distances from its source, Ryder said. “It can be transported intercontinentally.” Mineral dust is typically made of quartz, clays, and silicates, and its components are hundreds to thousands of times smaller than the sand grains found on most beaches.
The team mined so-called reanalysis data—measurements output from a hindcast. A reanalysis uses past data from various locations to interpolate past conditions over an entire region or the globe and up into the atmosphere. That hindcast allows researchers to pull information from locations and elevations that did not have records.
The power of reanalysis data is that they’re consistent with one another, said Helen Dacre, a meteorologist at the University of Reading and a member of the research team. “You can go backwards in time and create a long, consistent data set.”
The reanalysis data set the researchers used provided spatially resolved dust concentrations at various levels in the atmosphere every 3 hours. Ryder and her collaborators considered the airspace between 2003 and 2019 around five major airports—Beijing Capital International Airport in China; Diori Hamani International Airport in Niger; Dubai International Airport in the United Arab Emirates; Indira Gandhi International Airport in New Delhi, India; and Marrakesh Menara Airport in Morocco—and the airspace encompassing all eight of the airports on the Canary Islands. (They also looked at data from airports in Bangkok, Thailand; Hong Kong; Phoenix, Ariz.; and Sydney, Australia, but dust levels were low and not considered in the rest of the analysis.)
Big Gulps of Dust
The team then combined monthly mean dust profiles with flight information such as aircraft altitude and engine power. They calculated how much air—and therefore how much dust—flowed through an engine during different phases of takeoff and landing.
The team assumed that aircraft in holding patterns flew at an altitude of 1,000 meters (3,200 feet). That’s lower than average, Ryder and her colleagues acknowledged, but examining that case is useful for illustrating extreme cases of dust exposure because lower levels of the atmosphere tend to be dustier than higher levels. “It was chosen as an extreme value to illustrate the worst-possible scenario,” Ryder said.
“This is not a risk that’s going to cause airplanes to fall out of the sky.”
Dust doses averaged several grams over the course of a typical takeoff and landing cycle, the team showed. The largest dose—6.6 grams (0.23 ounce), or about the weight of two U.S. pennies—was recorded above Indira Gandhi International Airport.
It’s important to emphasize that the effects of mineral dust on jet engines, though cumulative, aren’t likely to cause accidents, Ryder said. “This is not a risk that’s going to cause airplanes to fall out of the sky.”
But dust does wear down jet engines over time, said Thomas Gill, an Earth scientist at the University of Texas at El Paso not involved in the research. “It’s literally like sandblasting something.”
Ryder and her team found the highest dust concentrations generally in the spring and summer. That makes sense because convective currents in the atmosphere, which loft dust plumes upward, are driven by solar heating in certain parts of the world, Ryder explained.
Airports far from sources of dust, such as Beijing Capital International Airport, tended to be characterized by high-elevation dust layers that peaked at altitudes around 2,000 meters (6,500 feet). But airports that are exposed to nearby sources of dust, such as Dubai International, exhibited peaks in concentration at altitudes of about 300 meters (1,000 feet).
Fly at Night
Low-lying dust dissipates out of the atmosphere quite rapidly after sundown, however, the team found. Changing flight schedules at airports close to dust sources is therefore one way to reduce the amount of dust ingested by jet engines, the researchers suggest. Shifting takeoff and landing from daytime to nighttime would reduce dust doses by about 30%. “For somewhere that is dusty all the time, like the Middle East, shifting to evening or night takeoffs could make quite a big difference,” Ryder said.
Such a change might be beneficial to jet engines, but passengers might not be keen to fly when they’d normally be sleeping, Gill said. “I think there will be a lot of customer resistance to that.”
When the team compared their data with dust concentration measurements made by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, which collected data from 2006 to 2023, they found that the reanalysis data tended to be low, however. That discrepancy might be due to the model failing to capture individual dust storms, Ryder said. “Dust storms tend to be small scale, so they can be hard for the model to capture.”
The study results were published in Natural Hazards and Earth System Sciences.
Installing instruments at airports capable of lidar could provide nearly real time measurements of vertical dust distributions, the team suggested. Such data could be used to help aircraft avoid dust plumes. Instruments known as ceilometers at airports routinely detect clouds, but such instruments aren’t as sensitive to dust, Ryder said. And though lidar-based instruments can be a significant investment, the relative expenditure for a large airport would be minimal, she said.
—Katherine Kornei (@KatherineKornei), Science Writer
Citation: Kornei, K. (2024), Lots of dust gets sucked up by jet engines, Eos, 105, https://doi.org/10.1029/2024EO240409. Published on 12 September 2024.
Text © 2024. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.
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