QUOTE(jim_hoyland @ Sep 1 2008, 09:02 PM)
QUOTE(Bartlett 914 @ Sep 1 2008, 08:28 PM)
When the engine is idling, there is less air available for the cabin. The electric fan is used to boost the airfllow. The flappers act as check valves so the electric fan can provide more air.
So they are closed at idle, or does the flow from the fan close them ?
Jim,
The flappers close off the fan housing when engine speed is low. This prevents air from the electric fan from escaping into the fan housing. As engine speed climbs, the higher pressure in the fan housing forces the flaps open.