----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]---- Very interesting! But what about soft grass runways. There's one near me where acceleration is very sluggish until I get the nosewheel light. Does that mean I should be very glad there are no obstacles?
David N6359V 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
<<attachment: winmail.dat>>
