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Realize this: If you want heat, turn on the flow packs right after starting. For those of us living in climates that are generally warm, it becomes standard practice that the bleed air switches remain off until runway lineup. But when faced with cold weather operation that is no longer optimal. Instead, as soon as the engines are running, the bleed air switches are moved to the up, open position. Granted, at idle compressor speed, the air is not as compressed and the bleed air is therefore not as hot as when lots of power and compressor speed are experienced. However, the bleed air entering the cabin, even at idle, will be warmer than the trapped, frigid, cabin air, so allow it to enter and start providing warmth right away.
It is exactly because the PT6 does not produce an overabundance of hot bleed air at idle that King Airs contain a supplemental electric heater. The electric heat system varies quite a bit depending upon the King Air model being discussed. I will start my discussion with the electric heat system that is contained in C90s, E90s, F90s, 100s, A100s and B100s. This includes all later C90 variants: the C90A, C90B, C90SE, C90GT, C90GTi and C90GTx.
For these models, the first thing to do is to ensure the engine speed is high enough to support the very large electrical demand that the heater system requires. This means we must have a minimum of 57% N1. Since Low Idle for the standard three-blade propeller models in this group is about 50%, you will need to adjust both condition levers forward to attain about 60% N1. On the other hand, the four-blade propeller models already idle near 60% – to avoid the “reactionless vibration” mode that can be harmful to these props – so further tweaking of the condition levers may not be required.
Make sure the N1 speed is near 60% and now select auto or man heat with the mode selector. Next, reach over and position the electric heat switch to the up, “Grd Max” position ... and standby for heat! Running all eight electric heat grids – four for the normal heater and an identical four for the ground maximum system – really puts out the BTUs!
Three important comments need to be made here. First, with that much electrical load – about 300 amps total heater demand – it is common to see that the Fuel Control Unit (FCU) has permitted some sag in N1 speed. This may be great enough that the four-blade prop models
NOVEMBER 2023
KING AIR MAGAZINE • 21