[f-AA] Fuel Burn and MPH (Tom Roush)(cfjss@telus.blackberry.net)

[Mtn...@aol.com]

 

Just a couple of thoughts on this that may confuse the issue further.  First, my limited experience is that you cannot expect to compare props, pitches, and lengths from different manufactures to one another.  They use different airfoils, I think. Second, prop re-pitching is not an exact procedure and once you start doing so, the pitch will never again will be exactly what is stamped on the prop hub.  Third, I use a McCaulley A series, '74-45 prop on my C-85 11BC.  Yes. I know it is NOT an approved prop, but back when Field Approvals were easier to get...I. got one for my 11AC during the modification from 11AC to 11BC. My Chief likes to cruise at 100 MPH at 2300 RPM, and, depending on weight and weather, will top out around 115 MPH at 2,600.  I've never run her at 2,600 RPM long enough to measure fuel burn, but it has to be 6+ GPH. Additionally, at 115, the controls get 'heavy', and I really have to be in a hurry (or showing off to someone) to fly her much above 100MPH... why would anyone really want to anyway?  I have always thought that the extra 10 MPH I seem to have over most other Chiefs has to do with the LENGTH of my prop more than the PITCH of the prop.  While my McCaulley prop is factory stamped as a 74 inch prop, it actually measures 75 inches in length. I have never understood why you would want to chop the length of an otherwise OK prop as long as you are getting the RPM you need or want.  Just my thoughts.  Regards to all, Tom Roush, 11BC, OF #092740.