Colin Hales wrote: > I haven't got flaps or a speed brake. You don't need > them. People keep saying that "They float!" How? Its got tiny wings! > The problem mostly seems to be that people need a high throttle > position to keep their poorly idling engines going on the ground at > say, 700 rpm. This unfortunately turns into about 1,400 rpm in the > air. No wonder it floats, thats still about 1/4 throttle. If you > remove the idle stop for your engine all together, if you close the > throttle completely, it now acts like a exhaust brake. The engine > will never stop in the air, it just windmills at 500 rpm causing > massive drag and the aircraft stops and falls out the sky. When you > land and the idle gets lower as they airspeed decreases, just crack a > little throttle back on.
I have several problems with the above paragraph. One is that even if your engine is switched off and the prop stopped (I've never seen mine windmill, either the Corvair or the VW), a drag brake is useful. If nothing else, the brake acts as another control system to provide more flexibility in landing, whether "deadstick" or normal. It's another tool in the box, just like slipping. Another benefit is added drag behind the CG, which helps to stabilize the airplane while landing. Nothing like a drag chute, but a small step in the right direction. As for "poor idling at 700 rpm", most aircraft makers, and indeed auto makers, probably wish they could make their engines idle reliably and smoothly at 700 rpm under all temperature conditions. Most everything I've driven is stabilized from the factory at something like 950 rpm. The best I can do with N891JF's engine is idling at about 800 RPM, and the Corvair is similar. This puts me at about 1050 to 1100 RPM on short final. I've never seen a carburetor that would run 700 rpm while open at 25% throttle. Most carburetors (or what passes for a carburetor in the case of the POSA) either have a dedicated idle circuit and require no throttle opening at all, or have a slight opening that might be 5%, rather than 25% open, when running at idle. 25% throttle might be 1800 rpm, but not 700 rpm, at least not on a "normal" engine. You have far bigger gonads than I do if you fly with no throttle stop and routinely let the engine almost die on every landing. Fiddling with the throttle to keep it running on rollout seems another distraction that I don't need. I pull the throttle back to idle when I'm abeam the numbers and leave it there unless I need power to make the runway (which is rare...although I may slip it to kill extra altitude). I guess I can't argue with your success, but it's contrary to everything I know about how to drive cars or fly airplanes. It's one less thing to fool around with while landing. That cure seems worse than the disease. I guess I can't say I've tried it, but I have tried belly boards (both before and after), and I do highly recommend them... -- Mark Langford ML at N56ML.com http://www.n56ml.com
