Porterfield Airplane Club

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Fellow club members: I have engaged a vintage DAR. To assist with the engineering analysis for a C85 conversion for the 65 Porterfield. I need the fuselage drawings to help get the analysis going.  My DAR has contacted the Rankins and they will try to help, but their drawings are still boxed up and things are difficult to find. If anyone has the drawings I would be very interested in getting a copy.  Please help if you can. I am certainly willing to pay for copies.  The analysis will not be cheap but should benefit any owners wishing to go down this route. I do have the engine mount drawing already which I picked up from this site. Thank You!

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Comment by john elliott on July 29, 2019 at 12:13pm

Fellow club members

As an update, I have engaged the DAR and he is mostly done with the engineering work to get my approval for the conversion to C85.  Once he is done, the approval is complete; no need to get any FAA further approval.  Thanks to the efforts of some for the great members on this forum, I was able to obtain the appropriate drawings to have him review the fuse structure. 

I have a mechanic welding up an engine mount and should start the process of engine change this fall.  I was able to get copies of two field approvals from aircraft that had existing c85 conversions, but my FSDO indicated that since the horsepower change was over a certain threshold I could not use the existing field approvals as technical data to support the change.  So it is good that I went to the DAR.  Once he has the work done on mine anyone wishing to do the conversion can go to him and get the approval for a fee (not sure what he would charge)  

Comment by Andy Gelston on July 29, 2019 at 11:12am

How have you made out with your DAR/contacting Brad Rankin for your C85 conversion?

Comment by Chris Forte on May 27, 2019 at 12:08pm

Hi Andy, Hope all is well with you. Sorry, I’ve been “off the air” for a while. I’m planning a trip to N. H. this spring/ summer. Sure would finally like to see 41 VT! Let me know what day of the week is least busy for you and I will plan accordingly! Chris Forte

Comment by kevin feauto on April 18, 2019 at 4:39pm

My old aircraft n25563 had a c85-8 on it that I had field approved out of the Fort worth FSDO somewhere around 1995. Id be happy to speak with you about it. Kevin clearprop75r@hotmail.com

Comment by john elliott on March 26, 2019 at 11:42am


Yes, please send me any drawings you have even if they are a bit muddy.  Do you have any paperwork on the franklin 90 change that you can share?  My DER may be able to also use that to substantiate the change.

Comment by Andy Gelston on March 26, 2019 at 7:30am

In the mid-50’s, Angelo Forte replaced my old girl’s Franklin 65 with a Franklin 90, using the accessory case from the 65 so it would be lighter (no starter & generator) and fit the same engine mount. The only mod required was to feed carb heat from both muffs in order to get enough hot air for the bigger carburetor.  The structure was deemed sufficient.  

Joe Rankin put a C85 on his Collegiate.  It’s a shame he didn’t get this installation incorporated into the Type Certificate.  Too many unscrupulous Porterfield owners screwed him over in the past: I got the feeling from speaking with him that he’d all but given up on supporting the Type. I have the fuselage drawing, though it’s a bit muddy, in a pdf that I can email you.

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