Page 26 - Feb 23

King Air 350 copilot’s left subpanel
needs to be unlocked to move in the up or down position, not for both?
The answer: windshield heat. I will wager that over 50% of King Air pilots don’t know this unusual fact. Back in the pre-C90A days – before 1984 – only the 200-series and the 300-series had separate switches for pilot and copilot windshield heat. The other models, instead, used only one switch and one windshield temperature regulation system to control both sides. Also, the heating element was a horizontal portion that covered only about one-third of the windshield, starting downward from near the center.
There were no “Normal” or “High” heat choices like the newer models have. The switch, however, still had three positions: “Both” at the top, “Off” in the center and “Pilot Only” at the bottom. This was a simple, three-position toggle with no locking action, no need to pull. About the only time the “Pilot Only” bottom position would be used was in the event of a generator failure.
The newer windshields very seldom require the use of high heat. Keep in mind – as you pilots of these models should already know – the windshield temperature that the thermostat circuit is trying to maintain does not increase when “High” is selected. Instead, the heat is concentrated in a smaller area. The innermost five inches or so of both windshields, closest to the center post, receive no heat so that the available energy is concentrated more directly in each pilot’s line- of-sight.
The only time either the pilot or copilot windshield heat switch must be pulled is to move it to the seldom-used high heat position! Stop pulling that switch every time you grasp it! There’s no need to do that! By doing so, you make it much more likely that you will accidentally move it down to the “High” position when you meant
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to just turn the “Normal” heat off. Use only your index finger on that switch and reserve the thumb/index combination for the rare times you truly want high heat. Realize that if high heat is accidentally on during engine starting, the chance of blowing a current limiter in a model 200 is greatly increased.
Another switch that started as a simple toggle but then became a lever lock in later years is the inverter selector switch. (Which now has been removed as the new airplanes no longer require alternating current.) This switch, again on the pilot’s left subpanel, has always been located next to the “Avionics Master” switch and the inverter switch, before it was changed to the lever lock type and had the exact same appearance as the avionics master switch ... a simple toggle. I have watched many a trainee deal with the failure of the No. 1 inverter I gave them by turning off the avionics! Oops! They hastily grabbed the wrong switch! Changing to the lever lock type makes this error highly unlikely.
The optional brake deice system’s control switch is also a standard, two-position lever lock type that
must be pulled to activate or deactivate. Although located on the pilot’s right subpanel along with eight or so other anti-ice and de-ice switches, the chance of activating it unintentionally while turning on the other items is nearly impossible.
The most important takeaway from this article? Stop pulling the windshield heat switches ... except when you actually want to select high heat! KA
King Air expert Tom Clements has been flying and instructing in King Airs for over 50 years and is the author of “The King Air Book” and “The King Air Book II.” He is a Gold Seal CFI and has over 23,000 total hours with more than 15,000 in King Airs. For information on ordering his books, contact Tom direct at twcaz@msn.com. Tom is actively mentoring the instructors at King Air Academy in Phoenix.
If you have a question you’d like Tom to answer, please send it to Editor Kim Blonigen at editor@blonigen.net.
FEBRUARY 2023