Bob Stearns asked: > Is there such a thing as "Best Glide Speed" > for the Ercoupe - 415D? I find quite a bit on > "Glide Ratio" but nothing on speed.
Glide Ratio is key to define best glide speed. The speed at which you get the best glide ratio, power off, engine windmilling, is normally your best glide speed. The Ercoupe shares the short, thick wing type with planes like the Tripacer and several other planes supported by the "Short Wing Piper" club as well as the original Cherokee and some other planes. Like those other planes, the Coupe's wing is quite efficient at higher airspeeds but at low airspeeds these planes all develop extreme "sink" rates. (The sink rate of a Tripacer gliding at very low airspeeds feels like it's approaching helicopter autorotation sink! Coupes can approach this, too, at minimum flying speed.) The glide ratio curve for the Coupes (and those other planes) is very steep on the low speed side, has a nicely rounded, fairly wide peak around 75-85 mph and has a more gently sloping tail off on the high speed side. I've found that the Coupe's best glide speed / best glide ratio is about 1.3 to 1.5 times the minimum flying speed as indicated on YOUR airspeed indicator. See the articles on airspeed indicator errors. http://edburkhead.com/Ercoupe/airspeed_indicator_errors.htm This gives a decent glide ratios even with the all too common aberrant airspeed indicators. I strongly recommend you test your ASI and get it repaired/replaced if it's faulty. (See the testing/calibration method at the bottom of that article.) I'd recommend that you start by going up high - on your next flight, before your next landing - and find out the indicated airspeed on YOUR ASI at minimum flying speed, power off, yoke all the way back. Multiply that times 1.4 and use that as your approach speed till you can test your ASI. With a good ASI, that 1.4 times minimum may give you a number as low as 70 mph. (A lot of Coupe owners fly approach 5 mph faster than that.) As I said, the top of the glide ratio curve is fairly wide. If you are gliding toward a target at the best glide speed you determine and find yourself coming down short of the target DO NOT EVER pull back on the yoke - that'll guarantee that you'll be short. If there's a moderate to strong headwind, you might extend the glide by dropping the nose (big grin as this is not easy when you're gliding and already short of your target) and pick up 5-10 mph. If you are still coming down short of your target you'll have to change your target. (I remember guidance when I was taking lessons 30+ years ago that you should only change your emergency landing spot once - don't dither and keep changing it.) Slightly increasing your glide speed will allow you to penetrate a headwind better while not losing much in the way of still-air-glide-ratio. So, the correct answer to your question is for you to go out and do glide ratio testing at a range of airspeeds (after calibrating your ASI). The results of this testing will tell you the best glide speed for your aircraft with your ASI. (Please report your results as we need exact, measured data for several aircraft to create charts that otherwise don't exist.) Well, that's the short answer. <grin> If that doesn't explain it well, or if I messed up the explanation, please ask further. Here's a bit more information: http://edburkhead.com/Ercoupe/performance_information.htm Ed Ed Burkhead http://edburkhead/Ercoupe/index.htm ed -at- edburkh???ead . com (change -at- to @ and remove ??? and spaces)
