The NTSB’s Michelle Watters recently posted a blog on the agency’s Safety Compass newsletter advising general aviation pilots to watch out for the “silent killer in the sky” — carbon monoxide.
It begins: “As the weather gets colder and using your aircraft’s cabin heater becomes more of a necessity than a luxury, there’s no better time to start thinking about a plan for handling carbon monoxide. Commonly called the ‘silent killer,’ carbon monoxide is best known as the cause of household poisonings from oil or gas furnaces, stoves, water heaters, or portable generators or fireplaces. For general aviation pilots, carbon monoxide exposure poses a particularly concerning threat because impairing levels can build quickly in an enclosed cabin, and even nonfatal levels can lead to tragic consequences in flight.”
For example, in 2017, a private pilot was flying his newly purchased Varga 2150A airplane on a visual flight rules cross-country flight. After flying for about 80 minutes, the airplane suddenly entered a spiraling descent from cruise flight. Witnesses observed the airplane flying erratically at low altitude before it hit an open field near Bowling Green, Ohio. They stated that the engine was running until impact. Toxicological testing of the pilot’s blood found 55% carbon monoxide saturation (toxic level is 20%).
Read the entire post, where she delves into the dangers of carbon monoxide, maintenance and inspection issues, and how to prevent carbon monoxide exposure.
Over a number of years, I have been close to several fatalities CO has caused including friends and children of friends, both in and outside of aviation. Like almost all aviation components, in the interest of weight savings, exhaust components aren’t any stronger than they need to be, and must be rigorously maintained. Exhaust heaters are an efficient, cost effective, and lightweight method of providing cabin heat. Since becoming available, I have always carried electronic CO detectors, and am amazed how often they have given me and other associates who carry them, rapid warning of exhaust system deterioration when it was least expected. Before these became available, I was probably many times exposed to excessive CO exposure without knowing it. Sometimes I also had a “patch” which showed no sign of CO. While not a substitute for good maintenance and a reliable low-level CO detector, I have learned that lean-of-peak operation, besides its many other benefits, also greatly reduces the chance of CO exposure. I have actually experimented with lean-of-peak vs. rich of peak mixture settings while experiencing abnormal CO levels as witnessed by my CO detector, and while proceeding to an airport for an unscheduled landing. It is quite impressive to see how much the CO levels change, sometimes from very high and potentially dangerous readings all the way to zero. CO is indeed a insidious and dangerous gas, and with low-level detectors it will be seen to exist much more frequently than is often believed.