----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]---- In air, as in water, the offending vehicle must get beyond the inefficiencies of trying to climb (or plane) at too low a speed. I agree that trying to pull the Coupe off the ground, in ground effect, is going to cost you in terms of climb. You'll stay 10 ft. above the ground until you gain speed and lower the nose. Yes, the added drag will most likely cost you altitude, and you won't make it over that tree. On the other hand, lifting off at the speed of best rate of climb, with a normal nose low ground roll, should result in your best chance of clearing an obstacle. On the other hand, I've been wrong before......
Larry Greg Bullough wrote: > ----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]---- > At 05:21 PM 10/15/00 -0700, Larry Wilkins wrote: > >----[Please read http://ercoupers.com/disclaimer.htm before following any > >advice in this forum.]---- > >Ok, I've gotta jump in here with both feet. There is no way the drag is > >less with all three wheels on > >the ground. Not only do you have the friction with the air, but you've > >got the friction of the bearings > >and brake drag. > > What about the difference in induced drag with the wing at or near zero angle > of attack, vs. when it's trying to lift the airplane? > > Having tried it both ways a) early lift off into ground effect and b) hold > it on > the ground for about 1000 feet of runway, (b) seems to result in having more > E in the airplane upon givng a haul on the old yoke. > > > Yes, I suspect the initial climb out at 85 mph would look good, but, if > > there are trees > >at the end of that thar runway, you'd best bring her off at 70-75, and > >look for that best rate (or > >angle) of climb speed. Additionally, after you've climbed a hundred feet > >or so, all that forward > >velocity will have disappeared and you'll be climbing out like the rest of > >us, only we'll be in front > >of you and higher up. > > I read an interesting discussion on this question of obstacle clearance > techniques a while back. Now I can't recall if it was a Ron Machado or > Howard Fried piece. Anyway, the point made was that the conventional, > accelerate to Vy, rotate, and hold Vy, until clearance, then establish > Vx is a BOOK technique. In other words, it may or may not be the > most effective in a given plane. The author made a rather good argument > that, in most cases, the zoom technique may actually get you over the > obstacle at a higher altitude. His reasoning for why it wasn't taught is > that, as a technique, it is harder and demands that a student pilot have > too fine a feeling for the airplane... ...if you don't end that zoom, you WILL > do a departure stall! > > I tried a standard soft-field takeoff in the 'Coupe the other day, too. You > know, full back elevator, hold the nose off, get into ground effect ASAP, > and establish Vx before departing. Doing that resulted in a rather dismal > altitude over the far end of the runway in comparison to a conventional > takeoff. > > We know that the Ercoupe wing readily builds up drag at low speeds and > high angles of attack. We see it when we get slow on final. The behavior > of my plane on a soft field departure suggests to me that the act of holding > the nosewheel off, lifting early, then running along in ground effect is > consuming a whole lot of E along the way. Also, I've noticed that the > practical best rate of climb speed deteriorates very quickly with increased > AoA. There's about 5MPH difference between climbing like crazy according > to the VSI (i.e. better than 500FPM at around 1200 pounds) and only about > 200FPM. Again, that suggests to me that the wing REALLY starts getting > draggy when asked to lift at lower airspeeds. > > So I'm not convinced that there isn't something to be gained from leaving the > wing 'turned off' (i.e., keeping the angle of attack and thus induced drag > low) > until building up a good chunk of speed isn't going to result in ending up > higher > than getting to a lower V-speed and flying off right away. > > It may also be that with the luxury of the extra room to accelerate, the > picture > is different than if I were trying to clear that 50 foot standard tree (how > does > the FAA manage to persuade trees to be exactly 50 feet high?) from a > paltry 1100 feet of asphalt. > > Greg > > Please start using [EMAIL PROTECTED] to get in touch with me. It is > my PERMANENT e-mail address! > > __________________________________________________ > To unsubscribe from this list please send mailto:[EMAIL PROTECTED] > ___________________________________________________________ > T O P I C A The Email You Want. http://www.topica.com/t/16 > Newsletters, Tips and Discussions on Your Favorite Topics __________________________________________________ To unsubscribe from this list please send mailto:[EMAIL PROTECTED] ___________________________________________________________ T O P I C A The Email You Want. http://www.topica.com/t/16 Newsletters, Tips and Discussions on Your Favorite Topics
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