C-75 Install

[Gary Blevins]

I recently looked at Dick Ranks Mite he has for sale and am very interested in buying it. The problem is he has a C-75 but no paperwork approving the installation, and I would really like to keep the C-75 on it. The STC's listed on the web site don't apply to his installation....wrong prop.

I need an example of similar installation to help convince the FAA to approve his C-75 install. Any information anyone may have would be greatly appreciated.

Gary Blevins

[Glenn]

Does it have a C-75 or an A-75? If it's a C-75 you could convert it to a C-85 and use the STC for that installation except you'd want to use a different prop. If it's an A-75 the easiest thing to do is convert it back to an A-65. Same engine. All you need to do is use a stock Mite prop and put a red line on the tach at 2300 rpm. If you use the rated prop for the 75 0r 85 engine your Mite will cruise at 90 and burn 6 gph. There are service bulletins available from Continental on how to perform these conversions.

[Gary Blevins]

Thanks for the reply Glen. I apologize, I meant to say a A-75. It does have the stock prop on it and Dick says it runs great. Ideally I would like to keep both, but after a little research the only solution I can come up with is to convert it back to a A-65.

[Glenn]

Well, for all practical purposes you have a 65 hp engine with that prop and you rarely ever get 65 hp from the engine anyway. The engine gets full power at redline, sea level on a standard day. When do you ever want to see that? At takeoff, right. How often have you seen that unless yer swinging a Beech Roby, never. What's the redline on the tach? My bet it's still at 2300. If it's not, change the redline and ask Continental for a new data plate.

You could, however, find a prop with less picth to get more rpm for takeoff. It would shorten your roll and increase your climb and slow your cruise. The picth of the prop is the theoretical distance your aircraft would be 'screwed ' forward in one revolution. 64 pitch = 64" forward. In theory. I don't know what a 75 hp pitch is but my guess it would be about 10" less pitch. Now an A-75 can turn faster so you can run it against the redline in cruise to go faster but 5things will happen: 1) the cockpit makes a lot more noise 2) your fuel burn goes up dramatically 3) your range goes down 4) the airpeed is lower 5) the engine runs hotter & wear increases

Is it worth it? An A-75 adds no value to a Mite. Only headache when trying to get it licensed. I don't think the Mite was ever approved for a 75. McCually does make a prop which is certified under an stc for a 75 hp Mite. My old Mite has one on it now. Don't ask your local prop shop. Doesn't show up in their books. Go to the factory. My guess is that owners got field approvals for the upgrades. Try finding a fed to do that for you today. Not likely.

The Mite flies great with a 65. A 75 doesn't give you any more bragging rights.

ps: The A-75 had subtle changes to a 65. A venturi change if you were running a Stromberg carb. Waffled pistons for better cooling. And an oil hole drilled in each rod end that would squirt extra oil into the opposing cylinder for better lube and cooling. Good stuff. However, every 65 I've ever had apart included these mods. I think the factory just put them in all the engines after the 75 came out.

ps/ps:

If you really need to get off faster and cruise better there is one thing you can do. It's kinda a gray area. The Mite TC shows what props are certified for the Mite. Then it ads " or any wooden prop that meets the static rpm limits' or something to that effect. What that is saying is that you can use an experimental prop as long as it meets the static limits. There are some fine prop makers out there. May want to talk to a few.


g

[Joelj]

Glenn - If I understand you correctly, you are saying that the simple "fix" to make an A-75 legal on a Mite is simply to limit it to 65hp by keeping the tach red line at 2300 RPM, which seems like a sensible solution. Would a simple log book entry suffice to make this legal? Is there anyone who can confirm that this will suffice and offer written proof that might convince and FAA official?

I examined the 337's that are posted here on the forum and there are two that address an installation of a 75hp Continental on the Mite. One is for a C75-12 with a 65A66 Flottrop prop (replacing an original A65-12 that the aircraft was certified with) and includes a flight manual supplement that cites an STC #SA2-1506 which my mechanic can't find anywhere in the FAA registry (Can anyone help with this?!?!). This STC limits the C-75 to 65hp by red lining the tach at 2160RPM.
The other 337 cites an A75-8 with a McCauley prop installed as per STC #SA1044WE and this STC red lines the tach at 2300RPM to derate the engine to 65hp.
My Mite currently has an A75-8 with the Flottrop so neither of these 337's or STC's directly apply. If there is anyone out there who currently is flying this combination and has the paperwork to back it up - or knows that their airplane was configured this way sometime in the past and might have had a 337 or STC submitted to the FAA on it - please contact me!!!

As for the prop issue - is there any way I can get the TC list of props that were certified on the airplane as well as the statement that cites "or any wooden prop that meets the static rpm limits"??

Joel

[Keith Mackey]

As for the prop issue - is there any way I can get the TC list of props that were certified on the airplane as well as the statement that cites "or any wooden prop that meets the static rpm limits"??

Down load the TCDS (Type Certificate Data Sheet) A-803 from the Mite Site or from:
http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/2D37206BEF82BAF18525673C006045CA?OpenDocument&Highlight=a-803

The statement is on page 4.

Keith

[Glenn]

Joel:

You may be able to get a field approval on a 337 from the Fed's to "de-rate" the engine. Get copies of the type certificate data sheets for the engines. You can download them from the FAA.gov website. Hope you can find an old timer in the FAA. They don't like doing field approvals for anything anymore. However, this is so simple a squirrel could do it. If that doesn't work search the Continental website for service bulletins. I may have a set buried in the garage. They have all sorts of bulletins on how to change from one model to another. That can be done with a log book sign off. May be useful to have that bulletin if you go the field approval route. You can make an 0-200 out of a C-75 if you want. I'll see if I can't dig up that SB and send it to Dave for the site.

[Joelj]

I think I hit the jackpot - Mike McCrath in Seattle sent me a pdf of his $10 FAA CD for N283DE which has field approval documents for converting an A65-8 to an A75-8 with a Flottorp prop on M-18C. This should help some of us who are flying behind A75's that have never been properly documented. I e-mailed the file to Dave Rutherford and hopefully he will post a link to it.
This brings up an interesting point - if all us proud Mite owners would spend the $10 for a disk of the paperwork history of our airplanes and forward a copy of that to Dave for posting, we could all share data at our leisure.
The funny thing about Mike's airplane is - if you check the FAA Registration for his airplane on the FAA website and look under the Airworthiness heading where they cite what engine it has - it says he's still flying a C-65/A-65 Series engine, even tho the disk from OK City shows the docs approving the A75-8.
Joel

[Keith Mackey]

Joel:
The 337 form you gave Dave to post still relies on our infamous STC SA1044WE for the installation of the engine as the basis for the "previously approved data" I'm not certain that this form will solve your problem. I would recommend asking a local friendly ASI for his opinion on how to get around this point. While the form is "Field Approved" by an ASI, I'm not sure exactly what was approved, as the installation was done per the STC. I suspect this field approval is only for the "Instructions for Continued Airworthiness" (ICA) page, which is now required for such installations, but was not back in 1961 when the STC was approved and possibly the Flight Manual Supplement page which may not have been a requirement when the STC was approved, but now is also.

Keith

[Rick Lewis]

Keith & All,
I am a new guy to the Mite world & the new owner of N4117 w/A65-8 and TC approved prop. My problem is that I own a C-75-12 which I would like to use. I've searched the documents and don't find any that show conversion to a lesser hp version.
Has anyone gone any further with the "derated" approach and a field approval?
Rick

[Glenn]

I think it would be easier to convert your C-75 to a C-85 and do the inatallation in accordance with the C-85 STC. Both engines weigh the same, You may find a sympathetic Fed (is that a contridiction?) who will allow the 75 under the same STC. Somewhere on this site David has posted the Continental SB on how to convert your engine.

[Joelj]

Rick - it appears that Dave may have already posted the documents you need as I see a 337 and a FMS posted for the A75-12 on the Mite. I will e-mail Dave the 337 I received after my last annual for the A75-8 on my Mite with the Flottorp prop. This 337 references the Aero-Spec STC SA1044WE which cited the conversion using a McCauley prop. To approve the Flottorp we simply had to do a static run of the engine on the ground at full throttle and have the tach reading fall in the envelope readings given by the factory in the TC for that engine/prop combination.
Joel

[Rick Lewis]

Glenn - The way I read the C-85 STC fuel must be downloaded and a max pilot weight of #155 is imposed. Both of those restrictions don't meet my requirements. RICK

[Rick Lewis]

Joelj - I am not sure the A75-12 documentation will meet my C75-12 requirements. It's logical to me but what about the Feds.

[Joelj]

Hey Rick - I doubt if my A75-8 documentation will help you directly, but it might serve as a reference. I don't know of any current Mites with a C75-12. We own a second Mite N335M that came from the factory with either an A65-12 or C65-12, I'm not sure which and am also unsure of the difference between the two, but this would give me hope if I were you because my M18C (N4124) that was factory TC'd with an A65-8 has been field approved for the A75-8. It seems that it would stand to reason that if the factory TC'd a C65-12 from production, you'd have a good chance of getting a similar upgrade approved to the C75-12 on the same basis that my -8 model was approved. What prop are you planning to use?
Joel