Saturday, February 09, 2019

Deicing As We Leave Seattle's Snow For San Francisco's Rain

There was about 6 or 7 inches of snow this morning when we headed to Seatac.  Someone had plowed a snowy/icy path along the sidewalk and the walk back to the airport wasn't too bad.

A lot of flights had been cancelled, but our was scheduled to leave on time.  But then they had to deice.  I had a pretty good view.  So here's a minimally edited video of part of the process happening outside my window.  (As I was editing, I realized that often my purpose is not to just cut to the most dramatic few seconds here and there.  Rather I figure someone who knows a lot more than I about deicing (that would be anyone who knows anything at all about deicing) might get more out of my leaving most of the footage in.)

From Wikipedia:
On the ground, when there are freezing conditions and precipitation, de-icing an aircraft is crucial. Frozen contaminants cause critical control surfaces to be rough and uneven, disrupting smooth air flow and greatly degrading the ability of the wing to generate lift, and increasing drag. This situation can cause a crash. If large pieces of ice separate when the aircraft is in motion, they can be ingested in engines or hit propellers and cause catastrophic failure. Frozen contaminants can jam control surfaces, preventing them from moving properly. Because of this potentially severe consequence, de-icing is performed at airports where temperatures are likely to be around 0 °C (32 °F). 
In flight, droplets of supercooled water often exist in stratiform and cumulus clouds. They form into ice when they are struck by the wings of passing airplanes and abruptly crystallize. This disrupts airflow over the wing, reducing lift, so aircraft that are expected to fly in such conditions are equipped with a de-icing system.
De-icing techniques are also employed to ensure that engine inlets and various sensors on the outside of the aircraft are clear of ice or snow. 
Chemical de-icing[edit]
De-icing fluids consisting of propylene glycol (PG) and additives are widely used by airlines for de-icing aircraft.[2]:43 Ethylene glycol (EG) fluids are still in use for aircraft de-icing in some parts of the world because it has a lower operational use temperature (LOUT) than PG. However, PG is more common because it is less toxic than ethylene glycol.[3]:2–29

Alaska Airlines' blog also has a post on deicing.  

When we took off, the wing was green.  It was its normal color when we landed in San Francisco where the sun was out as we landed.  But when we got out the BART station downtown, it was raining.  But when i'm with my grandkids, the sun is always shining.

I'd also like to point to an article in the Alaska Airlines Magazine for February 2019.  It was about how CEO Brad Tilden spent a week shadowing employees in Alaska.  Yes, putting it in the magazine is hype, but the fact that he was on the ground (and in the air) with employees doing their jobs with them says good things about him and the airline.  He wasn't just in Anchorage, he also flew out to Dutch Harbor on PenAir.  And in Anchorage he did a night shift.  You can see the piece here.


  1. I've always thought that the way airlines de-ice is extremely inefficient and wasteful of both time and money. Each airline has its own deicing trucks, which do the job while the plane stands just off the gate, then the deiced plane has to get in line for takeoff. When the airport is jammed with traffic I have often been in planes that had to pull out of line and go back to get deiced all over again because it had been too long. What a pain.

    Instead, why doesn't the airport build a single deicing shed near the end of the runway. Every plane that got near the front of the line would pull into the shed and get worked on, in order, then it could immediately go out and take off before the chemicals are washed off.

    But I guess that would cause !@@** TAXES **@@! to go up. And cause airlines to have to cooperate with one another. So it won't happen.

  2. At the Alaska Airline link in the post it says,
    " Alaska is now testing a remote deicing location at Sea-Tac for use when weather and Air Traffic Control (ATC) conditions allow. Planes can be deiced away from the gates and closer to the runway prior to takeoff. With a spot for remote deicing, two aircraft at a time can be sprayed, freeing up badly needed gate space and maintaining a better flow for aircraft."

  3. That's great, if air traffic control lets them keep their place in line. (I've had this idea for 25 years -- how come they're just now testing it?). I hope it works.


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