FlyingScot

As others have amply described - I have no hard comfort limits - too many variables - but anything approaching 3K or less - extra scrutiny considering all factors. For example, Ocracoke at 3K’ at sea level - no issues (love that airport). Put that same runway in NM at a density altitude of 9000’ with pax and fuel - no way. Obstructions? 280HP 2-blade vs 310 HP 3-top prop - huge difference in T/O performance. Good energy management and a stabilized approach - always, or go around.

Just did this - but it required (in my case) swapping out the Vacuum AI and DC HSI for dual GI275’s. If you do that, then you can drive the KFC 225 (I have one of these too) and eliminate primary and backup vac systems (and some tubing and a whole bunch of white wire). As for it being an inexpensive way...well...

Mine always seemed accurate. Then I had some fuel tank work done (the tanks had to be drained) I used the opportunity to check when I refilled - and they were pretty much spot on to dispensed usable fuel (my tanks are 95 gal / 89 usable). I confidently use them for flight planning. Measured on the ground, of course. I think they are more accurate than the panel gauges are in flight - in flight I crosscheck the panel tank readings with the preflight sight gauge levels + integrated fuel flow based usage - they never agree (off by as much as 5 gal total over a long flight). I use whichever is less when figuring out when to land for fuel

Thank you @Baker Avionics - that is exactly what I needed - many thanks!

You are absolutely right - They are not relying on me to calculate it - quite the contrary. This was as much a personal interest of mine to verify how the original consolidated W&B entry was computed and how it would be modified by the change. That will give me some personal confidence in the empirically derived number calculated in the way you suggest. I always like to understand how the numbers are derived and sourced. May have something to do with being a physicist... It may be common, but I haven't seen a system that spans the airplane (instruments on the panel, servos in the wings, gyros in the tail, etc.) recorded in the Equipment list/W&B as a single consolidated entry before.

Thats it! - might you be able to post the W&B page in section 2 with the equipment breakdown? That would be very helpful - many thanks - Bob Looks like:

Thanks - that is where I went first, in fact - and where I found the consolidated (handwritten) entry for the 225. Unfortunately the preprinted list part of the W&B section does not include this or the components of it. I think the preprinted section was a holdover from the 90's Ovations with a standard KFC150 install, and the 2000 O2 was the first year to have the 225 as an option. My page 6-23 looks just like yours (Rev F). Just a guess.

That would be great if you have it - thanks. You are right about what’s coming out + kmt112. The 102 is in the rear, however, but the station should be straightforward to figure out. But that still leaves the servos & brackets, etc. if you have a breakdown that would be really helpful - mine is a 2000 O2 as well, so we should be similar. Thank you - Bob

Greetings all - I am in the process of replacing my ki525 and ki256 with GI275’s and I have come across an interesting problem. In my equipment list there is a single entry for the KFC225 System but no breakdown of individual components - it aggregates the component weights and arms into a single entry. This includes the servos, the KG102A, etc. The issue is this - I am keeping the autopilot, so I am therefore removing parts of the total system but not all, so to recompute the weights and arms correctly of what remains, I need the component W&B breakdown. This is found in the Installation and Service Manual - I know this b/c I have found one for the TB20 and it has all this info in a table in the manual. The component weights are probably intercomparable, but not the arms. So far I have had no joy for the I&S manual for the M20R. Any of the wise folk on MS have an idea where to find one of these? Thanks! - Bob —— An example for the TB20:

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

Thanks for the great posts ~ you and I are in parallel, my O2 went under the knife last week. I went through a similar evaluation, and came up with pretty much the same conclusions. The reason I went with the third 275 as an MFD is a little different – in my install, AI failover will go to the MFD, not the HSI. This allows you have a fully functional and independent AI plus a separate HSI in the event that there’s a primary AI failure, rather than using a combined instrument. With this arrangement the HSI can be just a base unit; it does not need AHARS. The two full blown boxes are the AI and MFD. The MFD is going where my old backup electric AI was in my panel. i’m happy with my engine monitor, all of that may change if my Moritz gauges fail, however. Making the third an MFD will allow for simultaneous display of Sirius and ADS-B weather ~ I find myself doing a lot of flipping back-and-forth between these two on the 750 a lot in the soup when navigating around the cells in the southeast. I hope This works to alleviate some of that. Dodging convective cells is something I know you’re very familiar with. And having lived through at least a dozen hurricanes on the ground, I have no desire to chase one in the air ! I look forward to your next installments and I will post pics when I get some. I agree with you on one other thing – when they tear into a panel, the result is a frightening sight. Cheers – Bob

Improved version attached - same model, better ergonomics - macro-free, so much smaller size IO-550N Performance Calculator.xlsx

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 -

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

It's gone in for the install, so pireps to come. 3 GI275s: AI, HSI, and MFD - the AI & MFD are full AHARS, the HSI a Base Unit. Failover to the MFD. No AP functionality in the failover, however - we were able to sort that one out, but lots of interesting config options with 3 + Sirius + WX500 + ADS-B + Syn Vis, etc...) Lots of potential in this combo, so we'll see. Keeping most other redundant primaries, still not comfortable with giving them up for reading tapes just yet. Thanks everyone for the input and suggestions - Bob

I did, and then some - what a great group - thanks to all who helped me out - special thanks to @StevenL757 and @Deb (Deb and David) - you were all super! Thank you - Bob

@StevenL757 Steve - Thank you! This is obviously a newer version of the manual than I have - do you have any suggestions on how one comes about getting a copy (and the right schematic)? You have been very helpful - Thank you - Bob

Thanks Steve. 29-0248 - I am having a lot of panel work done in the next couple of weeks and the Avionics Shop asked if I had a copy of the Schematics - and that started the hunt - any help would be appreciated! Cheers - Bob

Greetings all - I need a copy of the electrical schematics for my O2. I have the pdf of the service manual and on the last page it refers to the schematics and to the fact that they are included in pouches in the book. (@carusoam - I did search MS for references to these and where to get them, and there are a lot of postings - but none apply to this particular problem. ) My AP/IA has a copy of them for the J, but not for any of the later models. Have any of you Ovation drivers out there solved this one? Do some of the MSC's have copies, or are they in the same boat? Specifically, I am looking for 800383 (R5). Thank you in advance for any help/suggestions - all the best - Cheers - Bob

>>> II thought this might be the case - thanks I have a Stormscope and Shadin, etc. Does this mean the SS will no longer track to the heading? This is really helpful - thank you. Nice looking panel BTW!

We have been working with Garmin on this - my current understanding is that, as you say, the AP is INOP in failover to the HSI, but if you have a redundant AI+ADAHRS, then dedicated failover to it can preserve AP function. I am not convinced of this, however, and am still working it - not an AP, but I don't know that it passes the smell test given how I know the KFC225 interfaces to the KI256. I suspect at a minimum there needs to be additional HW in the loop, eg the GAD43e.They don't have a lot of examples to point to of this type of configuration, as obviously most people opt for two units as primaries in the standard stack. I'll post when I have an answer that satisfies.

That sounds reasonable and makes it worth OH rather than replace -

I have no idea what a servo overhaul costs on the 225. Any thoughts?

I understood there was an issue with the G3X driving the KFC225 - but maybe that's wrong?

Greetings - I hope everyone is well and healthy - I am contemplating replacing my KI256/KI525A combo with GI275's (a GI275 ADAHRS+AP and a GI275 Base HSI). I would also add a third 275 ( GI275 + ADAHRS) to act as an additional functional display, but could also be used as a failover from the primary AI GI275 (I know the HSI will do this, but this way, you don't compromise the HSI by cluttering it in an emergency, and can retain AP functionality in the failover). I have a low-time 02 with the KFC225 and an upgraded stack including 750&650 Nav's. It seems like this is a good solution to eliminating the Vac system, digital-izing the primaries, and integrating with the rest of the Garmin stuff in the panel, w/o taking the full bite needed to install a G500Txi - that option is at least twice the price and also starts to move the amount I have put into the plane well past what I think it's reasonable to expect to get out of it - I love the aircraft, really love it, but think someday I will want to move into a turbo, so I can't yet justify investing like it's my forever plane. Anyone have any experience with this type of replacement or with the GI275's in general? I did a search for this before posting, but didn't see much in the way of a discussion on this - Thanks in advance for any feedback/insights - Bob