Aerodynamic question for Peter Garrison and/or Paul--On the configuration/design of the new
Lancair Evolution turbine cowling--- what's the deal with the sharp edges to the rectangular
inlet scoop and sharp leading edge vertical center splitter?  Surely there is a good reason
but don't know what it is unless possibly a compromise to use a sharp inlet radius done
strictly in order to get adequate square inches of inlet in space available?  We ran into
this issue when doing a similar type scoop in 1995 on the second gen cowling on the rotary
powered RV-4 with the prototype Mazda conversion engine/internal spur reduction gear....and
to juggle everything in space alloted, I had to compromised the boundry layer offset and
blend radii from scoop to cowling slighly to the tight side to keep the bottom of the scoop
from extending below the bottom line of the fuselage.  Possibly they had same type of issue,
along possibly with downstream diffuser considerations?  But the latter issue unlikely as
this P/W is a rear inlet engine. Whenever we tried an inadequate inlet radius on a boundry
layer scoop, or on an annular inlet, we always had separation and increased drag when the
lip inlet was too tight.  Something different at work here?

Steve Beckham.


Good question. Sharp lips are used on supersonic
airplanes so maybe it is a styling thing :) Maybe it is sucking more
air than the ram effect can provide but I doubt it. I think they
just got lazy.

BTW that airplane used to be called the Lancair Tigress and it had
an Orenda big block Chevy V8 based engine. It had a sharp lipped
P51 type cooling scoop as well.

http://www.aircraftworlddirectory.com/civil/l/lancairtigress.htm


Peter?

Paul Lamar