MaxNr(at)aol.com
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 Posted: Mon Oct 15, 2007 10:10 am Post subject: O-235 Prop |
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A starting point and one way to a deal with it is to plagiarize and use what the competion (type certified A/C) are using and develop from there. They test an engine/prop combination that will in turn cut down some development time on your part. Some examples:
Last weekend, I flew a Piper PA-38 Tomahawk with a O-235 L2C. It had a Sensenich 72CK-O-56. Type Cert. Data Sheet for the PA38 (TCDS #A18SO) says that it can be cut down to no less than 70 in. PA 38 is a 1670 LB GW bird that climbs at maxGW on a 20 dg C day at 500 fpm and cruises about 100KT at 2400 rpm. Plan on about 6.5 gal per HR at 3000'. I have an engine/prop combo from a Grumman American/Tiger LLC AA-1. It is a O-235C2C with a McCauly 71/54. TCDS #A11EA for the AA1 also approves the 71/53 and 71/57 props. Never flew a Yankee, but its a 1560 # GW and goes over 100KT. It has 3' less span and about 10Sq ft less wing area than a 601XL. To see a AA1 with a cruise prop take off on a hot day at GW is painful to watch. More Diameter for a given pitch gives more low speed "dig", noise and climb.(seaplanes) Less diameter gives more speed. 71" diameter is about the most I will use for the 601XL because of ground clearance. Could cut down to 70". Also could re-pitch another inch or two later. Another thing about both of these certified birds is that the airframe mfgr limits max RPM at 2600 RPM. They had to meet a noise certification standard. I have the latest O-235 Operators Manual and it says that "Rated Power" is at 2800 RPM all day long. My plan is to list my limits as 2800 for 5 minutes and Max Continuos Power (MCP) as 2600. Climb performance is important to me too. TBO is 2400 hrs. The only max operating time limits for the engine are for CHT and oil temp. FAA TCDS for certified A/C have a lot of data re: engines for us builders. Go to FAA home page, Clk on Aircraft, scroll down to Tech Info and select the TCDS. I also downloaded an Excel spreadsheet from Sport Aviation for prop selection. Its neat.
Bob, Pace,FL
XL/Lyc (tail feathers)
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