Page 19 - Volume 12, Number 3

heater from operating. The heater “Lock Out” systems are (1) windshield heat, (2) propeller heat, and, if so equipped, (3) lip boot heat.
The heater is rarely needed in flight due to bleed air heat. In fact, if you find that the cabin is chilly in cruise and you need to operate the supplemental electric heat to stay warm, the reason is virtually always two weak bleed air flow packs or a single totally dead pack. If you are in cold clouds and need the heater in flight, tough. You’re going to be chilly. On the other hand, when you break out on top you can get the heater to join in once
your turn off all two or three of your Lock Out items. Remember to get them back on before penetrating clouds in the descent.
Here is how it should go on your next icy winter flight: After starting, make sure your idle speeds are near 60 percent N1 and then reach for the environmental controls on the copilot’s left subpanel. The order is not critical, but here’s what we need to do: Bleed Air switches – OPEN, Vent Blower switch – HIGH, Cabin Temp Mode Selector – AUTO; Electric Heat switch – GND MAX.
Immediately the Ground Max heater elements should activate. You will observe a large increase in generator load and, in a few moments, you may notice a rather disconcerting smell of burning material. Relax, it is just the accumulated carpet lint and dirt getting burned off the heater elements that haven’t been used in a long time. You will also likely observe in a short time a click sound from another relay and the loadmeters increasing even more. What happened? The Normal heat grids just got added to the Ground Max ones. You see, the Normal heater, in Auto mode, never gets a command to operate until the bleed air has already gotten fully hot. So, it will not come on until the bleed air bypass valves have traveled to the full-hot position. This could take as long as 60 seconds, but it is likely that the bypass valves were probably in a fairly hot position at the end of the last flight (unless a massive cold front passed during the
MARCH 2018
KING AIR MAGAZINE • 17