FlyingScot Posted September 12, 2020 Report Share Posted September 12, 2020 (edited) Greetings All -- My plane is in the shop for some panel work, so no flying. When it is flying, my engine monitor doesn't report %HP, so that got me to wondering how those that do calculate it for each engine type, since obviously RoP %HP is dependent upon a number of factors, some external and others tied to the specific engine. Not many manufacturers reveal much about their algorithm, and many seem to rely on fairly simple treatments, which I assume do not produce consistent results over all power settings. After some reading and research, I was able to assemble a model from several sources, though, and put together a spreadsheet to do the calculations. The guts of the parameterization comes from a nice analysis done by Calle Hedberg and John Smith at MGL. I have attached the spreadsheet; as constructed it is specific for the 310 HP NA IO-550. it could be tailored for other engines with the use of appropriate parameters. Seems to produce reasonable results, consistent with experience and within a few percent at worst of the published tables where they overlap. It does both LoP and RoP (the interesting case) and plots out a variety of data, including for grins the lean offsets required to keep out of the yellow zone of the redfin for a given set of inputs. Thought this might be interesting to someone here, so if it is, it's yours. If you do use it, I would welcome feedback on if it produces results that are consistent with your engine monitors, etc. Enjoy! Cheers - Bob P.S.> The sheet is protected, but can be unprotected without a password. IO-550N Performance Calculator.xlsx Edited September 12, 2020 by FlyingScot Upgraded Download Version w/improvements Quote Link to comment Share on other sites More sharing options...
carusoam Posted September 12, 2020 Report Share Posted September 12, 2020 Interesting spreadsheet FS! There is an app discussed around here for turning a spreadsheet into a usable app, for the I device crowd... I pushed the download button... no idea where it downloaded to... I’ll check the excel app see if it ported over there... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
jlunseth Posted September 12, 2020 Report Share Posted September 12, 2020 Anthony, if you are on a PC look in the lower left hand corner of the screen for a file. If you are on an iPad like me, you will see a circle with an arrow appear in the menu bar at the top, just to the right of the line that you would type an address into. Click on that circle with the arrow. 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted September 12, 2020 Report Share Posted September 12, 2020 Oh fancy that! It was so good, I downloaded it twice... thanks JL! Best regards, -a- Quote Link to comment Share on other sites More sharing options...
jlunseth Posted September 12, 2020 Report Share Posted September 12, 2020 You can straighten out the next picture I try to post. Best regards to you too. 1 Quote Link to comment Share on other sites More sharing options...
StevenL757 Posted September 12, 2020 Report Share Posted September 12, 2020 2 hours ago, FlyingScot said: Greetings All -- My plane is in the shop for some panel work, so no flying. When it is flying, my engine monitor doesn't report %HP, so that got me to wondering how those that do calculate it for each engine type, since obviously RoP %HP is dependent upon a number of factors, some external and others tied to the specific engine. Not many manufacturers reveal much about their algorithm, and many seem to rely on fairly simple treatments, which I assume do not produce consistent results over all power settings. After some reading and research, I was able to assemble a model from several sources, though, and put together a spreadsheet to do the calculations. The guts of the parameterization comes from a nice analysis done by Calle Hedberg and John Smith at MGL. I have attached the spreadsheet; as constructed it is specific for the 310 HP NA IO-550. it could be tailored for other engines with the use of appropriate parameters. Seems to produce reasonable results, consistent with experience and within a few percent at worst of the published tables where they overlap. It does both LoP and RoP (the interesting case) and plots out a variety of data, including for grins the lean offsets required to keep out of the yellow zone of the redfin for a given set of inputs. Thought this might be interesting to someone here, so if it is, it's yours. If you do use it, I would welcome feedback on if it produces results that are consistent with your engine monitors, etc. Enjoy! Cheers - Bob P.S.> The sheet is protected, but can be unprotected without a password. IO-550N Performance Calculator.xlsm 2.33 MB · 15 downloads Bob, great sheet...thanks for providing. One note - suggest adding a column for 2550RPM, which is the optimal, suggested climb, cruise, and descent RPM recommended by Bob Minnis...the original STC developer and owner of the 310HP conversion. Steve 4 Quote Link to comment Share on other sites More sharing options...
FlyingScot Posted September 12, 2020 Author Report Share Posted September 12, 2020 7 hours ago, StevenL757 said: Bob, great sheet...thanks for providing. One note - suggest adding a column for 2550RPM, which is the optimal, suggested climb, cruise, and descent RPM recommended by Bob Minnis...the original STC developer and owner of the 310HP conversion. Steve You can! The rpm for each column can be changed by the user. You may have to unlock the sheet, but once you do, you can put whatever Prop speeds you wish in each column and the graph will update accordingly - 1 Quote Link to comment Share on other sites More sharing options...
FlyingScot Posted September 12, 2020 Author Report Share Posted September 12, 2020 Improved version attached - same model, better ergonomics - macro-free, so much smaller size IO-550N Performance Calculator.xlsx 2 Quote Link to comment Share on other sites More sharing options...
Little Dipper Posted September 13, 2020 Report Share Posted September 13, 2020 This is pretty cool. Thanks. N995K Quote Link to comment Share on other sites More sharing options...
FlyingScot Posted September 15, 2020 Author Report Share Posted September 15, 2020 Here's an updated version of the excel spreadsheet, formatted for the screen size of a mobile device. I have also converted it via Openasapp, and have attached a QR code to access that version, which can be run as an app on iOS/Android. The excel version is better, b/c it produces a HP table (MP vs RPM) for a given set of environmental conditions, and you can change the fit parameters. It will run with iOS or Android versions of excel. Enjoy - Direct URL for App version: https://oaa.app.link/launch-app-8c4beb57-e1d5-47fc-83f0-e266fa232a62 IO-550N Performance Calculator - iOS.xlsx 1 Quote Link to comment Share on other sites More sharing options...
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