Page 17 - Volume 14 Number 9

ASK THE EXPERT
Manual Environmental Control Modes
If your King Air is a senior citizen built before the late 1970s, I am betting that you are quite familiar with the use of the “Man Cool” and “Man Heat” modes of operation of your environmental mode selector. Why? Because the kinks associated with the Auto mode of environmental control had not yet been worked out and hence the Auto mode was so erratic in its operation that few pilots used that mode. But, by the late ’70s, the Auto mode had been quite well-perfected and therefore it was rarely necessary to use the manual modes. But there will come
SEPTEMBER 2020
by Tom Clements
the inevitable day when the Auto mode fails and you must revert to the manual modes. This article’s intent is to review and remind you of how to best do that.
For the Auto mode to work properly – giving you the desired cabin temperature – it must know three things: (1) the desired cabin temperature; (2) the current cabin temperature; and (3) the temperature of the air flowing into the cabin. Let’s say you are filling the bathtub before the kids get in to bathe. Those same three parameters (but now dealing with the bath water temperature instead
of the cabin air temperature) are being checked by you. (1) you know from past experience what the desired water temperature is; (2) you swish your hand in the tub to see what it currently is; and (3) you place your wrist under the faucet to gauge the temperature of the new water flowing in. Right?
In the King Air, the desired cabin temperature (1) is set by the position of the Cabin Temp rotary knob. It is quite common to find that placing the pointer on the knob between the 6 o’clock and 8 o’clock positions will give a comfortable, 72-degree-like, cabin temperature.
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