By mid-July, massive wildfires surged across Ontario, British Columbia, and the Northwest Territories of Canada, driven by severe heat, thunderstorms, and drought. As AirVenture approached, over 900 active fires burned simultaneously, sending record plumes of smoke southward, deep into the northern United States, including our flight path across Michigan. The airspace was eerily quiet for a typical pre-AirVenture Friday. The impact was so severe that it altered the plans for hundreds of pilots, delaying the typical swarm of aircraft crowding the airwaves and arrivals.

As we carefully watched the changing conditions for our route, we realized that range planning for alternate airports had to account for safe landing locations that could be up to an hour or more away from our planned fuel stops. We brought masks designed to filter smoke particles, kept the air vents closed, and chose altitudes that kept us out of the thickest smoke. However, dense smoke and low visibility could not be avoided during takeoff and landing. Contrary to the typical low-ceiling IFR breakout into a clear final approach, the smoke and low visibility translated into a gray-brown haze from which the runway appeared gradually, just prior to reaching minimums. With my son Jake (also a pilot) and me up front, we worked as a team to complete the trip safely, arriving at the show on time as planned.

Performing the postflight on the airplane, Jake (also an A&P) and I discussed the impact that flying in all of that smoke could have had on the aircraft itself. We decided to remove the air filter and examine it. The filter media was much grayer than I recalled at the most recent annual inspection and had visible specs of ash in it. Although it appeared to have largely done its job of filtering the induction air, even the backside of the filter media had become gray in color.

We removed the filter and brought it to my friend Vince Bechtel, vice president of marketing and distribution for Victor Sierra Aviation Holdings and the Tempest Aero brand. Bechtel was very interested in seeing the striking comparison of our used filter versus Tempest’s new air filters that were available at the show. This type of air filter can be cleaned with soap and water, but considering the challenges of cleaning it on site, as well as the total hours and condition of the media, replacement made a lot more sense.

Following the filter replacement, we also inspected the alternate air door on the induction intake to make sure it was sealing properly, preventing unfiltered air from entering the engine as long as the filter was clear. We then cleaned the windows inside and out, and wiped down all other parts of the interior and exterior. Ash from smoke can be very corrosive and, if not removed quickly, can cause damage to just about every unprotected surface on an aircraft.

Our last step was to go to our friends at the Phillips 66 lubricants booth, to discuss the impact that flying in smoke and ash can have on engine oil and the oil filter. They explained that the company’s ashless dispersant oils, such as the Phillips X/C 20W50 that we use, are designed to encapsulate contaminants and preserve the lubricating properties of the oil, protecting the engine.

The challenge to both air and oil filters lies in the size of the particles. According to the U.S. Forest Service, many of the particles in forest fire smoke tend to be less than 1 micron in diameter. Since most induction air filters are designed to filter out 99 percent of particles greater than 5 microns in size and oil filters are measured against a 40-micron rating, neither are very effective against the much smaller particles produced by forest fires. The good news is that particles of the size found in smoke, as well as the makeup of those particles, are unlikely to affect engine wear. That said, extensive exposure to these contaminants can saturate the oil’s built-in ability to encapsulate and protect against contaminants. Therefore, it makes logical sense to perform oil changes at shorter intervals under these conditions.

Although smoke was the issue on this flight, these guidelines apply similarly to any flights in areas with contaminated air. High dust, blowing sand, or volcanic ash can pose even more risk to an aircraft because of the high silicon content in the air, the effects of which can be similar to exposing the aircraft and engine to fine sandblasting. The bottom line is that you should tailor your maintenance to the environmental conditions in which you are flying. Whether you’ve flown through dark plumes of smoke on the way to AirVenture, or just spent a week of seaside flying at the beach, it pays to be safe and treat your airplane with the care it deserves. Until next time, I hope you and your families remain safe and healthy, and I wish you blue skies.