Excessive heat “kills” integrated electrical circuits, the kind found in modern avionics. Unlike many other electronic devices, avionics also may be exposed to sunlight filtered only slightly by a transparency. Combining the two sources—as when on the ground on a hot, sunny day, engine running and with all the electrical equipment active—is fairly common. While extreme cold temperatures can play havoc with avionics—for example, display screens may not work correctly—heat is the more pernicious threat. The bar graph at the top of the opposite page, adapted from the August 2017 issue of sister publication Kitplanes magazine, offers an estimate of life expectancy for modern avionics.
Not convinced? Consider the following statement from FAA Advisory Circular AC 23.1311-1C, “Installation of Electronic Display in Part 23 Airplanes”: “Electronic systems reliability is strongly related to the temperature of the solid-state components in the system. Component temperatures are dependent on internal thermal design and external cooling. In evaluating the temperature environment, consider the additional heat generated by the equipment, especially in a location where airflow is restricted.” In fact, cooling fans may be required equipment.
