If you are interested in low "observer" noise, one thing to consider is
that the 914's turbo removes a lot of energy, and therefore noise, from
the engine exhaust. Noise isn't much of a concern in the US - yet - but
it's a big deal in Europe and has spawned some interesting designs.
I'm thinking of the HB207 Alfa, the prototype of which used a 5-blade CS
prop of scimitar shape turning at 1800RPM to reduce observer noise to
57dBA, about the level of normal conversation. The engine was a 110HP
2:1 geared Porsche, which, as you might expect, enjoyed such wide
acceptance that it was replaced by a Rotax 912/914.
Andy's comments about the Jabiru 3300 installation are very interesting
and informative. John Lawton's comments about the quietness of the Jabiru
installation are provocative, given the 3000RPM takeoff RPM. Andy, would
you happen to have any ideas as to why this is so, and what Jabiru does
to address the observer noise issue?
SS
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