Smoke Is a Bear

If you learn to fly in the Seattle area, then you learn to deal with low clouds and fog. As a CFI in the area, I have long warned my learners about how quickly fog can creep on you. However, it wasn't until a particular summer day that smoke became an issue.

I was flying a dual cross-country flight with a private pilot candidate. The weather was clear, with no ceiling, and visibility was greater than five miles. Our destination was Bowerman Field, Hoquiam (KHQM), a non-towered airport on the coast of Washington. 

The flight went well on the way out, but on the way back, we encountered a wall of reduced visibility rising from the ground between us and our home airport.

"Is that fog?" the learner asked.

"Don't think so," I replied, looking at the outside air temperature gauge, which read 24° C. 

Fog is formed when the temperature and dew point converge. A quick check of the nearest automated weather stations indicated the dew point was in single digits. As we drew closer, we could see an orange glow emanating from the obscuration. The smell of burning wood wafted into the cockpit.

Smoke, like fog, reduces visibility and obscures the horizon. If there is fire below, you'll encounter thermals and turbulence as well, so don't intentionally fly into or over smoke—turn around. I didn't even have to say this, as the learner turned us back to the west, where the air was clear.  

The learner pulled up the AWOS at our destination, Pierce County Airport - Thun Field (KPLU). It reported variable winds, visibility of six miles, and a ceiling of 4,000. We were both skeptical based on what we were seeing out of the windscreen. 

For safety’s sake, we decided to ask for the RNAV 35 approach into the airport. I knew that I could fly it if needed, and it was an opportunity for the learner to get some hood time.

We could see the airport (somewhat), but knew that could change. The learner glanced out the window and muttered that this was not the weather the AWOS was advertising, because unless we looked straight down, we couldn't see the ground, and the horizon was shadowy at best.

Wx Briefing Smoke

The good news is that a check of TAFs and METARs might let you know if you could encounter FU (smoke) or HZ (haze) during a flight. Of course, smoke probably won’t appear in Wx products until it appears in the real world first. Not counting prescribed burns, the initiation of a wildfire isn’t predictable like weather systems. 

As for the dissipation of smoke and haze, that’s easier to forecast. The only things that remove smoke and haze are shifting winds or rain.

While smoke can be unhealthy for humans and engines, haze isn’t, and it can be a valuable teaching tool. Haze is a combination of particulate matter, such as salt from the ocean and pollutants that bond with water molecules. It is very common on warm, humid days for this reason. Haze degrades depth perception, making it difficult to see landmarks on the ground. 

Add flying in accidental smoke-induced MVFR/IFR to the list of emergency procedures you practice in a sim. While you would never intentionally fly into smoke, if it happens due to nature's whims, you'll be glad you practiced it.

Know Before You Go