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On Jan 5, 2005, at 4:19 PM, Skyport Services wrote: > At 05:02 PM 1/5/2005, Skyport Services wrote: >> The McCauley 1A/B90 prop is certified for use on the C85 for lengths >> from 70" - 78" and RPMs up to 2600. As long as you respect those >> limits and don't have an O200 crank, you're likely safe, > > Wolf! Wolf! Wolf! Wolf! > > I take it all back. McCauley explicitly limits the C85-1A/B90 combo > to lengths between 68.5" and 71". Where? > No one in the FAA in their right mind would issue a field approval, > much less an STC, that doesn't meet those limits. I'm not sure I want to go there...but keep in mind that refer to members of an unelected agency comprised of career bureaucrats that has already achieved every politician's dream...unlimited (personal) authority without meaningful (personal) responsibility! > Like I said before, get it cut down or replace it. I've seen too many > C85's with broken center main bearing webs and/or broken crankshafts > to risk chancing it. How many have you seen and, of those, would you attribute all to propeller-induced stress or could other factors have initiated said failure(s)? Most of us lack such personal experience to draw from. > > My own, uneducated opinion is that the lower limit is of more concern > than the upper limit... Of what-static rpm, cruise rpm, allowable length? If the latter, how does that relate to our thread exploring the difference between a 71" prop or a 72" prop on a C-85? > > John Cooper > Skyport Services Hi John, Forgive me, but I'm totally confused by your pronouncements here. That may result from the lack of source information to cross check. A cursory check of a Univair catalog, No. 198, p. 202 (McCauley Installation List) shows a Taylorcraft 19 landplane fitted with a C-85-12 or 12-F (same as in the Ercoupes) had a CM7251 "Standard" prop and a CM7248 as a "Take-off Climb" prop recommended with a max. diameter of 72" and a min. diameter of 69.5". This references notes 1 and 2, which essentially confirms no rpm restrictions (from McCauley), and explaining that the 1A90/CF (elliptical tip) and the 1B90/CM (square tip) models of the same diameter and pitch are directly interchangable. My point here is that, IF the FAA actually had to explain to someone exactly why they would not issue a one-time STC or 337 for a 7246CM on a Continental C-85-12 or 12-F, what would a logical reason be? Regards, William R. Bayne <____|-(o)-|____> (Copyright 2004) ========================================================================== ==== To leave this forum go to: http://ercoupers.com/lists.htm Search the archives on http://escribe.com/aviation/coupers-tech/
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