REFLECTOR:Alternate Air
Jack Sheehan
reflector@tvbf.org
Thu Jun 3 15:52:50 CDT 2004
Scott,
You need to look at the system on the gallery. The filter is not a
typical aircraft filter system. It is a conical K&N located under the
engine in the heated area and is not exposed to any weather. The
purpose of the filter is to provide filtered air for ground
operations. Normal induction air comes through the ram air scoop in
flight. If for some reason such as ice or a seagull stuck in the ram
air scoop I can switch back to filtered air from with in the engine
compartment. I made the system actually backwards from a typical
aircraft system which always operates on filtered air unless it is
clogged then a little door opens and it receives alternate air. The
advantage of using unfiltered Ram air is about a .7 inch increase in
manifold pressure at about 10,00 feet.
So The concept of alternate air is somewhat reversed. I have not yet
experienced any reason in flight, either rain or ice, that has
prompted me to close the Ram air and switch to filtered air but it is
an option On runways where I am concerned about dust or dirt I take
off on the filtered air and there is no degradation in performance. I
usually open the ram scoop at the same time I raise the gear.
I hope that is a little clearer.
Jack
N55XL
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