Page 21 - Volume 15 Number 9

tradition. Wrong? No way! Maybe it’s because I have resided in Arizona for the last 34 years, but I just don’t see the need for running the Hot Five when it’s warm and clear, so typical of the United States’ southwestern states. My technique isn’t more “right” than running the Hot Five always, it’s just my habit/preference.
As we continue counting the switches on the right side of the pilot’s control wheel, we come to the ones that use significantly more electric power than all of the Hot Five combined: Windshield Heat, Prop Heat and Lip Boot Heat (if applicable). In fact, for the C90-, E90-, F90- and 100-series, these switches constitute the “lock- out” items. Since the electric heater is only a comfort item – not a safety-of-flight item like ice protection – the designers never wanted the less-important components to rob power from the more-important components. Whenever any one of these lock-out item switches are on, all grids of electric heat become inoperative. Let’s discuss each of these anti-ice items individually.
First, Windshield Heat. Until the 200 model appeared, all previous King Airs had a single Windshield Heat switch with three positions: Up, labeled “Both,” to heat both pilot and copilot windshields; Center, the Off
position; and Down, to heat only the pilot’s side. The down position is virtually never used. It would only be considered when one generator were inoperative causing total electric capacity to be half of what it normally would be. Be careful when moving the switch to Off from the Both position. Push down too hard and you will put it in Pilot Only. That increases the chance of blowing a current limiter during your next start.
For the 200-, F90-, C90A- and 300-series, there are separate switches for left and right windshields. Again, three positions exist: Up for Normal heat; Center for Off; and Down for High heat. Unlike the windshield on the other earlier King Airs, now nearly the entire windshield’s surface is heated, not just a horizontal strip across the lower third. Additionally, the heating elements embedded in the inner windshield layer run vertically, not horizontally as before. Surprisingly, when high heat is selected, the windshield’s thermostat control does not reset to a higher value. It still tries to keep the windshield’s middle ply at about 100°F. What changes is that about a 6-inch piece closest to the cockpit center post no longer receives any heat at all. By concentrating the available heat energy in a
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SEPTEMBER 2021
KING AIR MAGAZINE • 19