Flying in smoke

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gcampbe2
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Flying in smoke

Post by gcampbe2 »

Here in Ontario we are blanketed in some pretty thick smoke from wildfires in Quebec. Yesterday I departed my home airport of Ottawa for a roundtrip flight to St. Catherines, about two hours each way. To give you some idea of the density of the smoke, visibilities were about 2 SM when I departed, and stayed at that level or a bit worse for most of the flight.

On the return flight, I started to notice some usual coloration on the wings of the aircraft. To my surprise, upon landing in Ottawa, I found that the plane was coated in a fine layer of black soot. It was difficult to get good photos, but here are a couple, the first showing what I saw in flight (you can clearly see how the airflows over the wing), and the second of the landing/taxi light assembly, where it was most easy to see the soot layer:
soot_inflight.jpeg
soot_onground.jpeg
I was surprised that the soot had stuck given that I had, immediately prior to departure, cleaned the wings with Aero Wash Wax All. I would have expected that the speed of the airflow would have prevented any soot from adhering.

Anyways, my question is: To what extent does one need to be considered about fouling air filters etc. when flying in smoke with this volume of particulate? Is this to be avoided, or is it a not a problem?
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Rich
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Re: Flying in smoke

Post by Rich »

I'm not surprised that the soot didn't blow off. There's such a thing as the boundary layer. I once took off on a flight from Idaho Falls to North Las Vegas. Right before takeoff we chomped on some tacos plane-side. As I climbed into the Cherokee I noticed a wee spot of lettuce had come to sit on the wing. I decided to leave it there to see what would happen. When we landed several hours later it was still there.

It's hard to be sure whether this stuff is harmful beyond cosmetics. When Mt. St. Helens blew up in 1980, the particulates were acidic enough that the FAA warned NOT to wash it off with water. It was recommended that we brush it off. Such ash has been know to clog air filters and damage engines if it gets though. These are thought to be really fine particles so clogging might not be an issue, and that you you can deal with, using alternate air. But whether it would be harmful to an engine is unclear. I haven't seen alert to this effect so maybe not.
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Soareyes
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Re: Flying in smoke

Post by Soareyes »

It looks like the soot sticks anywhere the laminar flow is disrupted, even by the decals next to the fuel caps.

Speaking of air filters, did you wear a mask in the plane?
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Boatguy
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Re: Flying in smoke

Post by Boatguy »

gcampbe2 wrote: Wed Jun 07, 2023 12:14 pm Anyways, my question is: To what extent does one need to be considered about fouling air filters etc. when flying in smoke with this volume of particulate? Is this to be avoided, or is it a not a problem?
I spent about 3hrs in similar smoke last summer between Seattle, WA and Santa Rosa, CA. IFR conditions in what was otherwise VFR. And in the previous year a few hours between LA and Grass Valley, CA. In my case the experience was sufficiently bad for the humans inside the plane who were also breathing that air that I avoided flying in it whenever possible.

PM2.5 is smaller than a typical automotive air filter which is rated to trap 99.5% of the particles 8x that size, so that stuff may be ending up in your cylinders and oil instead of the filters. I'm sure at some point it would be bad for the engine if not the filters. But I suspect that it's even worse for the humans.
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gcampbe2
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Re: Flying in smoke

Post by gcampbe2 »

It's a point well taken. I was much more concerned about the impact to the aircraft than to my own health. No mask was worn and I definitely felt abnormally fatigued by the end of the second flight. Unfortunately things on the ground in Ottawa were not much better that day, though winds have now shifted and we are breathing clean air again.

Russ's point about the particles being sufficiently small to elude the air filter and thus wind up fouling the oil is, I think, my main mechanical concern. It's sufficient enough of a concern that I will avoid flying in these conditions in the future. I also don't enjoy the mess it made of my shiny airplane! But, as Dan says, it was interesting to see such an obvious indication of where laminar airflow is compromised on a DA40NG wing.
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