Hi list, All of the interest in speeds and performance has peaked my curiosity and I went diving into the type certificates for Ercoupes, C-85 engines and McCauley props. What I found is only representative of a 415C with a C-85 and a 1A90 prop (mine).
First, you can find you own type certificate at www.faa.gov/avr/air/airhome.htm. Under "available documents" select TCDS, then type certificates by category. The engine TC does not list allowable propellers, that's called out by the airframe TC. Under the airframe TC, each engine/prop combination has it's own static rpm limits. Not over, not under. Also , each prop has it's own min and max diameters. The pitch min/max is found under the McCauley TC. For example, the 1A90 prop on a 85hp engine has a min pitch of 38" and a max pitch of 68". Static rpm, while running up on the ground will tell you the relative health of your engine if you have the right prop and arent in a hot/high situation. If you cant make min stat on a good cool day then you dont take off legally---. In the air the engine and prop unload and depending upon your engine's health and type of prop (cruise/climb) you may or may not hit redline in level cruise. Several things will affect your engine's ability to achieve min stat on the ground or redline while in the air. They can be: timing incorrectly set (including point gap), dirty air filter, improper carb, leaking induction pipes (clamps loose or split rubber hose), bad rings/valves, carb airbox leaking hot air into carb (improperly adjusted) and lastly, an exhaust system that is falling apart inside and causing back pressure. Any one, or combination of these spells out poor performance. If you happen to have a cruise prop you will notice these symptoms on runup. If you have a climb prop with low pitch it may mask the symptom on static runup, but in the air you will notice lower top speed with the throttle jammed all the way in. Hopefully this sheds a little light for us. Jan Zanutto IA N87204 __________________________________________________________________________ ______ To unsubscribe from this list please send mail to [EMAIL PROTECTED] _____________________________________________________________ Get your favorite topic delivered daily. http://www.topica.com/t/11
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