Thank you very much Ed ! Your answer is very clear, and I agree with you in that if the runway is so short that having a tail low Coupe instead of a correctly rigged Coupe makes a significant difference in safety, there is no margin left to operate out of that airfield and some change has to be made in the plane, as you said, or move to another airfield. Best regards Daniel Arditi
________________________________ From: Ed Burkhead <[email protected]> To: [email protected] Sent: Fri, April 30, 2010 7:57:05 PM Subject: RE: [ercoupe-tech] Raising the tail: Two more questions Daniel Arditi wrote: > For those who got accustomed in taking off and landing > with a "low tail" (especially during take off): Did you have > any problem or something to tell about the difference? > >I once heard that after rising the tail, and on a short grass > field the pilot had to abort a take off because he felt > uncomfortable as it was a bit hard to rotate in that same > field as he used to operate ? Daniel, Tail dragger aircraft drag their tails on the ground largely because that angle of attack is about right for absolute minimum speed liftoff. In other words, according to Wolfgang Langewiesche, author of “Stick and Rudder,” a tail dragger gear (called the “conventional” gear in antique days) is really a “takeoff” gear. A Coupe with a tail low condition is rolling down the runway part-way to being a taildragger and could, conceivably, lift off sooner than a properly rigged Coupe – as long as the crosswind is mild, otherwise the plane is in danger. When you lift off at that minimum airspeed, you have little reserve lift and a lull in the wind could drop you back to the runway in a bad way. Over many years, I was able to operate comfortably out of 1800 ft. grass runways (with no obstacles) and would sometimes accept a 1600 ft. grass runway if conditions were right. I found this in the worst configuration, 1400 pounds gross weight and tail at the normal height on a plane rigged with the 9˚ elevator up travel.: 1. The plane will pick up speed faster when it is level on the ground as the wings are at a low angle of attack presenting their lowest parasitic and induced drag. 2. When you are on a very short runway, as you get close to liftoff speed, you can use the elevator to raise the nose, lift off a couple of feet, lower the nose a bit and let the plane pick up speed in low ground effect. In low ground effect, you have no rolling friction from the ground or grass AND you have almost no induced drag as you are in close ground effect. So, you quickly pick up the extra few mph you need for a safe climb out at best angle or best rate of climb airspeed, your choice. This technique is especially important on long grass, muddy or rough air fields. 3. If the runway is so short that having a tail low Coupe instead of a correctly rigged Coupe makes a significant difference in safety, you do NOT have enough safety margin to be operating out of that airfield. Get an aggressive climb prop and/or a bigger engine and/or lighten you load considerably so you can change to a different airfield. Ed Ed Burkhead http://edburkhead/ Ercoupe/index. htm ed -at- edburkh???ead. com (change -at- to @ and remove ??? and spaces) _
