Early morning travelers are accustomed to the fog that covers the roads in the winter, but those in the aviation game know of something more insidious.
Key points:
- Freezing fog occurs at sub-zero temperatures and causes ice to build up on metal objects.
- Planes can get stuck on the tarmac as ice builds up in unprotected areas and instruments
- Northern Hemisphere countries can wash planes with defrost chemicals before takeoff
“Freezing fog” occurs when the microscopic water vapor that forms regular fog meets sub-zero temperatures.
Meteorologist Michael Conway said “super-cooled water droplets” don’t turn to ice while they’re in the air, but that changes if they collide with something solid.
“It needs a nucleation point. It needs something that the crystalline ice solid can start to form,” he said.
“So if a wing of an airplane moves or something, like the metal fender of a car moving through the air of frozen fog, the little super-cooled liquid hits the metal and makes him fall into the solid ice.
“For aviation, they don’t want the rotors of the helicopter, the wings of an airplane or other parts of the plane to become clogged with ice and start to fail.”
It was an ice start near the Country Club in Launceston. (ABC News: Lucy Macdonald)
Glued to the asphalt
Freezing fog is an uncommon “but not unheard of” phenomenon affecting flights to and from the city of Launceston, north of Tasmania.
Conway said patches were observed Monday morning amid temperatures as low as -3.8 degrees Celsius.
“It is necessary that these days of July with very clear skies, light winds and preferably after the rain during the last week or so, that the soil is already quite moist,” he said.
Shannon Wells, who runs the Par Avion charter airline, said the planes generally had ice protection equipment to prevent ice buildup in mid-flight.
However, Mr Wells said the protection was usually limited to surfaces exposed during flight, such as the propeller or the front edge of the wing, in a manner similar to how a car has a defogger for windshield, but little to protect the door handle.
“So if the plane doesn’t move, the whole plane can be covered in ice, because those surfaces that wouldn’t be exposed during the flight don’t have that protection,” Wells said.
“These surfaces will have ice, become heavy and cause aerodynamic problems.”
Horses with their winter coats in Launceston on Monday. (ABC News: Lucy Macdonald)
Wells said that in American and European countries that regularly experience sub-zero winters, aircraft were often bathed in thawing chemicals before takeoff.
“But we don’t have that in Australia because we’re not that cold,” he said.
“So when you have icy fog or other phenomena, you can’t do much other than take out the teapot.”
Ice crystals on the windshield of a car on a Monday morning ice in Launceston. (ABC News: Lachlan Bennett)
Security, a primary concern
Some light aircraft pilots have licenses that prevent them from flying without a high level of visibility, which means they are usually landed whether the fog freezes or not.
However, those with licenses that allow for greater reliance on an aircraft’s instruments may still have problems with icy fog.
The leader of the Civil Aviation Safety Authority’s aviation safety advisory team, Michael White, said the aircraft may have difficulty providing “the necessary power and lift” due to of increasing ice weight.
He said most riders facing ice fog simply had to “wait”.
“Generally speaking, as the morning progresses, it will burn with the sun,” he said.
“Pilots should use all the resources at their disposal to make that decision.”
Launceston was covered in frost Monday morning. (ABC News: Lachlan Bennett)
Another challenge for aviation
Fog is just one of many challenges that have disrupted the normal flow of flights this weekend.
At Launceston Airport, passengers waited for the flights as airlines struggled with fog, technical problems and severe storms along the east coast of Australia.
Airport executive director Shane O’Hare told ABC Radio that all of these factors had been aggravated “to create a rather messy situation.”
“Jetstar canceled a couple of flights on Saturday afternoon in anticipation of the fog the next morning,” he said.
Frost also hit Mount Roland in northwestern Tasmania on Sunday. (Provided by: Simon Kemp)
The fog continued to linger at the airfield Monday morning. However, Mr O’Hare said, most flights “turned out pretty well on time”.
“So we are operating right now, but we are holding our breath to see [whether] we can keep it running normally, ”he said.
Fog and frost can often go hand in hand. (ABC News: Daniel Miller)
As winter progresses, Conway said Tasmania could experience more icy fog in the coming months.
“It looks like things won’t be so resolved after Thursday,” he said.
“It’s another couple of cold days on the weekend but other than that, it’s a little hard to know when the next big day will be.”
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Posted 11 hours, 11 hours ago, Monday, July 4, 2022 at 5:56 AM, updated 7 hours, 7 hours ago, Monday, July 4, 2022 at 9:53 AM