I have an 85HP engine with 168 hours since major. My GPS and airspeed indicator are about right on when there is basically no wind. I also have used a Prop TAC to insure my actual RPM's are the same as what is indicated on the RPM instrument and they are.
I also have a wooden climb prop. I started to use 75 MPH indicated for my climb and it was pretty low and flat. But I was at 1320 lbs ( light sport) and it was in the 80's. But when I tried 70MPH the climb was much better and the aircraft flew well in the climb. With the climb prop my indicated cruise speed at 2400RPM, 2,000ft is about 100 MPH. Figuring the old mans way of computing indicated airspeed to true airspeed ( 2% per thousand) equals to 4% of 100 MPH or 104 MPH TAS. Hope my figures are correct. Never was real good at math. Jim N3439H 415C FDK ----- Original Message ----- From: Caliendo Dan To: Percy Cc: [email protected] Sent: Saturday, August 30, 2008 1:19 PM Subject: Re: [ercoupe-tech] Re: How to get the most out of your fuel More and more pilots are getting GPS units that can give you airspeed. Or borrow one and see what your airspeed indicator error is. (Don't forget to allow for wind). I checked mine and actually it is right on target. Now the problem is just what is the best rate of climb speed for your Ercoupe. I think mine is pretty close to 65 mph. Dan C (the dummy who can't figure out which Yahoo group to use) On Aug 30, 2008, at 12:11 PM, Percy wrote: Dave Hirschman wrote: "According to Jack Norris, an aerospace engineer and technical director for the 1986 Voyager around-the-world flight, a simple, mechanical ASI (and an nderstanding of the aerodynamic drag chart and an airplanes best rate of climb speed) is all we need to maximize speed vs. drag. Minimizing drag is the key to reducing fuel burn and extending range." I purchased the book. The proposition is quite simple; Total Drag = Parasite Drag + Induced Drag. Total Drag is what you pay for. Parasite Drag comes from pushing the plane through the air AND GOES UP WITH THE SQUARE OF THE AIRSPEED. Induced Drag comes from lifting the weight of plane, pilot(s), et al, up into the air AND GOES DOWN WITH THE SPEED. By plotting airspeed vs. the two drags, one sees that they cross at some point (PD = ID). This point is the "bottom of the Drag Bucket;" a low area where drag is almost constant over a range of airspeeds. At the upper end is where you run; a little more drag for the best speed. And this is only the first trick. The rest of the story involves flying at the highest usable altitude (10,000 ft MSL for Sport Pilots) with the openest throttle and leaned the best. So flying slower saves money! The final trick uses the first two to avoid fuel stops. Not only do you "keep on truckin'" while the fasties are on the ground, but you are spared the descent/climb cycle. You get to the "hundred-dollar hamberger" before they do! As a final note. All this wisdom is only diectly available with an accurate airspeed indicator. Many `coupes don't have that. So read that piece when Ed gets it transfered from "fly-in." Percy in NM, USA
