The Heat Is On! The Importance of Staying Warm
By Dr. Leo Hattrup, FAA Medical Officer
We are fortunate that for most of the time, staying warm is a matter just about comfort. We easily control it by how we dress and adjust the thermostat. Nonetheless, we operate in a narrow range of acceptable body temperatures; moving out of this range can imperil both our performance and even our survival. We will focus on a low body temperature (hypothermia) in this article. After all, winter is coming — and soon.
Humans are endothermic (commonly referred to as “warm-blooded”) meaning that we actively control our body temperature through metabolic processes. Regardless of the ambient temperature, we keep our body temperature between 97 and 99 degrees Fahrenheit or 36.6 to 37.2 centigrade (in adults). Like other mammals and birds, which are endothermic as well, we are able to function in a wide range of operating environments. In contrast, the body temperature of ectothermic (“cold-blooded”) animals such as insects, fish, amphibians, and reptiles reflects the surrounding environment; their advantage is that they need much less energy (food), pound for pound than endothermic species. However, there are limits to your body’s ability to deal with extremes before we become either too hot (hyperthermia) or too cold (hypothermia).
Trying to Turn up the Heat
We produce heat from metabolic processes and muscle activity. When this and the use of protective clothing is inadequate, you begin to feel cold and your body starts to generate more heat. As you know, if this is inadequate, you will shiver to generate additional heat followed by redirection of blood away from extremities in order to conserve heat for your vital organs. If allowed to progress, one can feel numbness or a “pins and needles” sensation in your fingers and toes. Your fine motor skills become degraded. There is a decline in judgement, memory, and thinking. Hypothermia also compromises your ability to recognize these impairments, so be alert for even minor changes. Warm up before you fly if needed. Obviously, even early symptoms of hypothermia are dangerous in an aviation environment.
An Ounce of Prevention
Being prepared for cold is essential. Begin with preflight planning. Know what conditions to expect. What is the forecast? Are there any conditions that would exacerbate the effect of low temperatures (i.e., wind, snow, rain, etc.)? Consider your origin airport, route (terrain and elevation), and destination. Make sure that you perform an adequate preflight no matter how tempting it might be to rush and shorten or even skip this step. Dressing in layers enables you to adjust your insulation needs before, during, and after a flight. Outer gloves with separate liners provide both insulation for most of the pre-flight and dexterity when needed. Military style flight gloves also work well for short exposures to cold. Pre-heating the engine is common, but the cabin should also be preheated if possible. This is better for the avionics and it allows you to remain comfortable without wearing a heavy coat prior to cabin heat. Removing a jacket in a small GA aircraft is challenging at best and, at times, dangerous. Do not count on jumping right into the airplane as an adequate mitigation strategy against the cold.
During flight, do not let concern regarding carbon monoxide (CO) poisoning stop you from using cabin heat. The risk is low and further mitigated by using either panel-mounted or portable active CO detectors. Modern devices are affordable and effective at detecting this odorless and potentially deadly gas. Be sure to keep your aircraft maintained and carefully preflight the exhaust and heating system. While not all cracks are visible on preflight, many are visible on preflight inspection … if you look. Stay safe and fly warm!