Diamond DA 42 NG, Maintenance Manual

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AIRCRAFT
DA 42 NG AMM Heating and Ventilation
Doc # 7.02.15
Rev. 4
21-40-00
Page 3
15 Mar 2018
2. Description and Operation
The heated air from the left engine is used for windscreen defrosting and the heated air from the right
engine is used for cabin heating. Both the left and right engine air heating systems are similar. The left
engine system is used in this description.
With the engine running, or when the airplane is in flight, ambient air is forced into a duct on the lower
right side of the engine cowling. The duct connects to a carbon fiber composite (CFC) shroud which
houses a heat exchanger. Hot coolant from the engine liquid cooling system flows through the core
of the heat exchanger. The coolant is taken from upstream of the engine cooling system thermostatic
valve. The temperature of the ambient air is raised as it flows through the matrix of the heat exchanger.
A flexible hose connects the outlet of the CFC shroud to the heater valve.
The heater valve is mounted on the engine firewall and has one air inlet and two air outlets. An internal
flap divides the air flow from the inlet between the two outlets. In the OFF or bypass position, the flap
covers the outlet to the airplane heating system and provides the firewall seal. In the this position all
the air from the heat exchanger is vented into the engine nacelle and then overboard with the normal
flow of air through the engine nacelle. As the flap moves from the OFF or bypass position some air can
flow through the heater valve into the airplane heating system. When the flap is in the fully ON or open
position the flap seals the outlet into the engine nacelle and all the air flows into the airplane heating
system.