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---------- From: William R. Bayne <[EMAIL PROTECTED]> Date: Thu, 20 Feb 2003 23:35:19 -0600 To: COUPERS - TECH <[email protected]> Subject: Re: [COUPERS-TECH] 0 200 engine part STC. on 2/20/03 7:17 PM, [EMAIL PROTECTED] at [EMAIL PROTECTED] wrote: > ...the prop TCDS sets limits on which model props are permitted to be > installed on which engines and what the dimension limits are for such > installations. Further more, the aircraft TCDS further restricts > the choices and dimensions and takes precedence over the prop TC. You're talking "official" heirarchy legaleze...arbitrary (and in some cases clearly outdated) parameters as opposed to common sense and genuine safety considerations. There is often a huge difference between what is "approved" and what is safe. The approval process incorporates safety factors that, in some cases, poison the viability of the product being tested; one specific example being the 415-D elevator limit. A prop knows no paperwork, which "trumps" another, or even dates thereon; but only vibration and stress. McCauley's earlier plaquards warning of "Continuous operation" in certain ranges and applications were confirmed as unjustified when rescinded by McCauley. An rpm is an rpm, so any genuine vibration-related hazard to operation of the STC engine would also logically relate to CONTINUED operation at a vibration frequency known to be a problem with opposed-four powerplants of similar design and identical firing order. > TCDS states that the installation on the 85 horse engine is limited to 2575 > RPM. They do not specify that they refer to a continental C85, so I suppose > there may be another 85 horse engine out there, and it may be certified for > more than 2575 RPM. McCauley is simply stating that that installation would > be limited to 2575 RPM. In reality, however, they are saying that the > airframe manufacturer should not include that engine/prop combination. > I think we've agreed that the STC engine is capable of putting out 93-94hp. Revisiting the MaCauley Installation List, I see that the 415 85-hp series and Forneys, Alons, and M-10s all use the CF or CM 7150 as "standard" on both the C-85 and C-90, each with reference to Notes 1 & 2 (as earlier referred). So what rpm limits are on your TCDS for this prop on a C-90? > What concerns me is that McCauley has specifically said that when installing > the prop on an O200, which operates above 2575, for the purpose of > maintaining an adequate vibration profile, the MINIMUM diameter is 71". The > coupe TCDS stateds that on the C85 installation, the MAXIMUM diameter is 71" It may also be that McCauley knows it unlikely or impossible for an 0-200 to develop sufficient rpms to reach rated horsepower for the desired service life (logically a number of overhauls) unless it starts at a certain maximum diameter FOR THAT ENGINE and has sufficient "meat" to lose 2" before a replacement should be installed. Many a 73" (C-75) prop has been reworked (chopped/repitched) into a 71" (C-85 and C-90) one and keeps on going. The STC engine has much more in common with the C-90 than the 0-200. Is there specific McCauley data to support your stated concern that the "vibration profile" likely in operating this STC engine (functionally a C-90) is somehow "inadequate" or dangerous? The certified 0-200 prop is commonly the ACM, DCM or SCM (another TCDS?). Per Note 9, on one aircraft does require the plaquard "Avoid continuous operation between 2650 and 2750 rpm." Different prop, and our STC engine/prop can't wind up near that. > So, if you have your prop reworked while the O200 crank STC is being > installed in your C85, and put the two together and decide to fly at greater > than 2575 RPM, you are operating in a range that McCauley specifically > prohibits, as does Continental and ERCO. The only one of us that recommended "reworking" the prop on our STC example was you. As a separate point, McCauley, Continental and ERCO have never addressed our STC engine/prop combination. It is "specifically approved" by the FAA. Lack of specific approval does not equal a "specific disapproval" or "specific prohibition". These are merely implied in the absence of data. > > Why bother anyhow? If you want to go fast, buy a [real] Mooney. > I think many of us want the coupe to "be all it can (reasonably) be"! You and I had great fun speculating, but Mr. Fowler is the man with the facts on his STC engine. He knows (or presumably will) what his full-throttle static rpm is, and what "just-off-extra-rich" full throttle cruise rpm is reached (presumably below 2575 rpm!). I hope he has an accurate tach, and will (privately) let some of us know. Maybe he would even hook in a temporary manifold pressure gauge! Cordially, WRB ========================================================================== ==== 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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