Cabin Heat
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If using the piston Duke, you may need to raise the pressurization air temp a bit if it's too cold outside - pull the handles marked "pressurization air temp" out a bit, just above the two red handles on copilot's side. DON'T pull the red handles though, you'd limit air inflow for pressurization.
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I suspect this is one of the most common operational oversights that users will be making with the Dukes. Here's the relevant reading in the manual. The tablet can also be used to better understand the situation:
Since the Piston Duke has a service ceiling of 30,000 ft, outside ambient air temperatures can
be as low as -80°F (-60°C) in the extreme latitudes. This 150°F (80°C) temperature differential
between the intake air and a comfortable cabin temperature is more than the combustion heater
can supply alone. For this reason, the Piston Duke has two pull handles (one for each engine),
labeled “PRESSURIZATION AIR TEMP PULL TO INCREASE” above the red pressurization air
shutoff handles. When these handles are pulled away from the panel, air heated by passing
over the turbocharger intercoolers that is normally exhausted outboard is redirected into the
cabin. Use of the intercooler air should be minimized, as it is an additional source of potential
carbon monoxide intrusion into the cabin. When operating at very low outside air temperatures
(10°F (-12°C) or below), the intercooler air handles should be progressively pulled away from
the panel to achieve the desired cabin temperature.
