----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----
on 1/29/03 6:39 AM, Greg Bullough at [EMAIL PROTECTED] wrote: > At 07:09 PM 1/28/2003 -0600, William R. Bayne wrote: >> If a C-85 is "prop-challenged", does the prop turn up book rpm on the >> ground? > > A lot of people did the C85 conversion (re-jetting the carb) when they > did a 415C to D update. But they didn't change the prop. So they don't > get the RPM improvement. Per TC 787, p. 6: Note 1 (Sensenich wood prop, D, E and G with 85hp)-Static r.p.m. at maximum permissable throttle setting: "not over 2100, not under 1900. No additional tolerance permitted." Note 4 (McCauley metal prop, D, E and G with 85hp)-Static r.p.m. at maximum permissable throttle setting: "not over 2225, not under 2025. No additional tolerance permitted." TC 718, pages 2 & 3 similar, except 1850 rpm lower limit for wood prop. You then choose as follows: 1. An optimum "cruise" prop that allows the engine to make maximum power (2575 r.p.m. for the 85hp) flat out (when leaned from built-in full-throttle automatic cooling enrichment...another reason to retain this control!). 2. An optimum "climb" prop that turns the maximum allowable r.p.m. on the ground that is r.p.m. limited in cruise (and therefore cruises slower). 3. Something in between My intended point was that if the (converted) prop/engine combination doesn't conform to the preceding, they won't perform as intended; nor does the airplane properly conform to its type certificate. (when all else fails, read the instructions!) > >> If not, maybe the engine or the prop needs attention! At full rich >> and high altitude a Stromberg is being asked to do something no carburetor >> can do...deliver best power with a non-optimum fuel mixture, to say nothing >> of the fuel waste. > > True...a lot of the Strombergs never made it up high so the full-rich wiring > was well-advised. Or at least a reasonable practice. > All properly-functioning Strombergs will "make it up high". Should a pilot choose not to use that portion of the aircraft's available operating "envelope", the full-rich wiring of his carburetor's mixture control would seem about as "well-advised" and/or "reasonable" as painting over altitudes above 4000' on the altimeter; all issues of airworthiness aside. >> As a separate consideration, has anybody seen a 337 to remove (or disable) >> the mixture control? Is your insurance good without it if your >> airworthiness isn't? > > Interesting point, but if it's the case then there are sure a lot of illegal > J3s, C120s, C140s, Ercoupes... And has there ever been a test > case. Why stir up the can of worms? > Every pilot chooses a "level of risk" in operating aircraft, whether consciously or unconsciously. Is it not better for each of us to be aware of potential problems, and to thereby exercise an informed choice? A flock of ostriches is not safe if all heads are in the sand. > >> Now I'll have to admit on that coupe the "automatic" mixture enrichment had >> been removed (same questions apply) or this might not have happened. I've >> yet to "be aware" of this actually functional on a coupe...maybe most are >> removed? > > Sure... ...along with the automatic carb heat. GOOD POINT! > > What it comes down to is that a well-turned-out O200 conversion with a Marvel > carb makes for a really nice improvement. It seems to take the plane from > under-powered to 'just right.' At the same time, the C90 seems also to > provide a good (some say the best) balance of airframe, engine, and available >props. Well-turned-out Alons really scoot in many cases. > > Greg Agree wholeartedly. WRB ========================================================================== ==== To leave this forum go to: http://ercoupers.com/lists.htm
<<attachment: winmail.dat>>
