Bill, Your article here is long over due. It is the best and most concise that I have ever read. I would print it off in big letters, frame it and mount it on my wall here. It applies to all aircraft types,such as the Piper Short Wing types. Ron Hynes
--- On Sun, 3/14/10, William R. Bayne <[email protected]> wrote: From: William R. Bayne <[email protected]> Subject: Re: [ercoupe-tech] "Falling Out Of The Sky" at 72 mph To: "ety" <[email protected]> Received: Sunday, March 14, 2010, 11:43 PM Jerry, Your G model has (or should have) the "split elevator". If the air speed indicator is accurate and if the plane is rigged correctly it WILL NOT "fall out of the sky about 72 mph". That's well above the "high sink rate" range. As a first step, I suggest you take a GPS aloft, slow the bird to 73 mph indicated, and compare the two readings. The Approved Flight Manual for Models 'E' & 'G' on p. 11 showed a "true airspeed" of 60 mph when 56 mph was indicated, 70 mph when 67 was indicated and 80 when 78 was indicated. Landing the various coupe models at the speeds Ed stated is not rocket science, but it does presume an accurate air speed indicator and proficiency in accomplishing an appropriate sequence of events. In my own case, I had absolute confidence in the Ercoupe Instruction Manual and "just did it"; but some are more comfortable having these things demonstrated before they can proceed. As a rule of thumb, the indicated airspeed is higher that the truth below 100 mph and lower than the truth above. For all values above "minimum speed" the error is 3 mph or less. That's not enough to get anyone in trouble that has any "feel" whatsoever for the aircraft in flight. The "stall" in an Ercoupe should be a gentle drop of the nose to pick up a few miles an hour and altitude loss should be minimal. If the yoke is moved back too rapidly near the minimum speed, the resulting "whip stall" is much more abrupt and more altitude is lost. This is something best worked out at altitude and not just above the runway. Should a low time pilot "balloon" (suddenly climb and find themselves 5-10 feet off the runway with little forward speed), immediate application of full power restores lift to the wings with minimum loss of altitude. Hesitation, however, will likely result in a hard landing with possible damage. Most of us have a WW II training base with long runways within flying distance that is now municipally owned and operated. Go there and make any necessary arrangements to practice slow flight and touch and goes with plenty of hard surface available. With a 5,000' runway, practice slow flight...holding the bird one foot off the pavement at the slowest speed possible. Before the coupe can "stall", it will sink. So long as you can keep the bird from touching the runway surface with the yoke at a constant speed you absolutely cannot stall while in "ground effect" at that speed. Keep reducing that speed in two mph increments and eventually you will be able to fly an approach arresting descent one foot off the runway and fly the length of it without touching down. Next time around, at that same constant speed move the yoke back a bit. If the plane goes up, you weren't flying slow enough. If it sinks to the runway surface, it will be your slowest, smoothest landing ever. At the moment of touchdown, THAT is YOUR plane's "minimum speed" occurring just when you want it to...at touchdown. Jot it down for future reference. If you go back up to pattern altitude and establish that "minimum speed" you will probably find that you are sinking like a stone. That's why the landing approach is not flown at that speed in an Ercoupe. The G model has a power off stall speed of 56 mph. The low speed warning cushion (spring) is supposed to be felt at 60 mph. The 415-D Approved Flight Manual on p. 10 suggests an approach speed of 75 mph and its power off stall speed is 58 mph. The manual for the E & G models refers you to the Ercoupe instruction Manual, and it suggests approaches be flown between 60 and 70 mph. At or near 1400# the higher value is more appropriate. Remember that 70 mph (true) is your "Best Rate of Climb" (see Climb Data, p. 10 of the Approved Flight Manual for Models 'E' & 'G'). At that speed, anytime you move the yoke back gently the energy of the "excess speed" is converted into altitude and the plane's altitude increases even as the forward speed decreases. Your speed for "Best Angle of Climb" is even slower at full throttle. This is simply NOT a speed range where you are tempting fate so long as you understand how to trade speed for altitude and altitude for speed. This is a fundamental skill all should practice, but If you are more comfortable flying the approach at 80 mph, do so. The speed of the approach is relatively unrelated to the speed at which touchdown takes place. Most find it easier to establish a "stabilized approach" (constant airspeed and engine rpm while maintaining a relatively constant rate of descent with the yoke) until just before touchdown. When you cross the runway threshold at 5-10' up reduce power and SLOWLY move the yoke back only as fast as does NOT make the bird climb. The idea is to slowly increase drag with higher and higher angle of attack holding the plane one foot off the pavement and when ALL the "excess speed" is thus scrubbed off the plane will gently sink to a very smooth landing. Unfortunately you may be using 4000'+ of runway to do it. Now do this again, establishing the one-foot-off slow flight. Simultaneously close the throttle and move the yoke back to keep the plane "balanced" at that one foot off. Once THAT coordination is worked out, reduce engine rpm on final (if necessary) to cross the "fence" at 70 mph. This should make it possible, with practice, to land and make most second turnoffs WITHOUT BRAKES! Minimum speed at the moment of touchdown is desirable because (1) the plane can't lift off the runway again without power, (2) the wear on the tires (the "chirp" at touchdown) is less because they have to "spin up" only to the lower speed, and (3) brake puck and disk wear is reduced so much that once the technique becomes "standard operating procedure" for you there will likely be the need to land fast and hot about once a month in order that the puck remove the accumulated rust from disuse. Operating a properly rigged Ercoupe in this manner is "stall proof" except in high, gusty crosswinds. For high, gusty crosswinds, add 5-10 mph to your approach speed, but chop the power over the runway threshhold at 5-10' up and do everything in the preceding paragraph exactly the same from that point on. Having extra speed at or after touchdown is a PROBLEM, not "insurance". Should a gust suddenly lift the plane off the runway, immediate throttle restores lift to the wings and returns to the pilot the option of go-around or a smooth landing (remaining runway permitting). Until this level of proficiency is developed (and more than a few that will "instruct" in a coupe don't have it to pass on), your are not master of the Ercoupe. Until you are master there is risk. Maximum safety depends on owners or operators reducing that risk to zero with appropriate priority. Your metal wings reduce your useful load, but they have no meaningful effect whatsoever on your approach speed or minimum (touchdown) speed. Hope this helps. William R. Bayne .____|-(o)-|____. (Copyright 2010) On Mar 14, 2010, at 22:43, Jerry Ward wrote: > > > You guys all keep talking about landing your coupe at such slow speeds - I > have a metal wing G-model and I have trouble getting it to land under 75mph. > I sure am jealous of all of you that can land slow. If I were to try that I > would break my landing gear off. It starts to fall out of the sky about > 72mph.. And I do mean fall fast. Jerry in the Great Northwest. > > >> ----- Original Message ----- >> From: Ed Burkhead >> To: ety >> Sent: Sunday, March 14, 2010 7:45 PM >> Subject: FW: [ercoupe-tech] Kim's Ercoupe >> >> >> >> >> Maybe this is more readable: >> >> >> >> As I said a couple of days ago, this gave these results: >> >> >> >> 13˚ up travel 48-52 mph landing speed >> >> 415-C and 415-CD >> >> >> >> >> >> 9˚ up travel 55-60 mph landing speed >> >> >> >> 415-D and on earlier models >> >> with 9˚ elevator limitation due >> >> to using the 1320 pound STC >> >> >> >> >> >> 20˚ up travel 48-52 mph landing speed >> >> >> >> 415-E and all later models AND >> >> earlier models with split elevator >> >> installed via STC or field approval >> >> on a form 337 >> >> >> >> __________________________________________________________________ Be smarter than spam. 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