I have a little different take on all this. One of the first things I do with a new plane is determine what spot on the wing is where I will land with no power. (On my Cherokee 6 it was a line of rivets about half way out on the wing). On my Ercoupe it is under the tip of the wing. I do this by practicing engine out landings at a local airport doing touch and goes. I have a small airport nearby with 5,000 ft runway and not much traffic so I pick about midway on the runway as my touchdown spot. That allows me to end up short or long until I determine the answer. The advantage to this method is it doesn't change with altitude, instrument variation or others factors that may be difficult to remember when the engine quits. (My experience is that I lose a lot of memory without the engine running.) Use the same airspeed for your ASI on all landings (after you have determined "best glide speed" for your plane during these practice T & Go's.) As with any landing, the spot straight ahead that isn't moving up or down on the windshield is the spot you will end up with if you continue straight ahead. Once I have determined the above I also determine how much I can lose by slowing the plane, doing S turns, or slipping the plane if you have rudder pedals. I like to be long on my engine out landings and lose some extra when I have the spot "made"....I haven't had as much luck getting more distance as I have at losing extra! One other advantage to this method is you get to experience just what ground effect will do that you don't get practicing at 4,000 feet.
Dan Caliendo Ercoupe Mach 0.14 3658H On Jan 2, 2010, at 4:27 AM, William R. Bayne wrote: > > Hi Daniel, > > Your interest is appreciated. > > You're absolutely right that people who try to fly an Ercoupe like other > aircraft always blame the design when things go badly. While only the > uninformed will believe them, this include those (a majority?) in the pilot > "community" that presume all criticism of the Ercoupe valid without proof. > Consider the source. > > I can't give you actual "high sink rate" numbers because it's been so long > since I checked it...1,000+ FPM comes to mind. If the opportunity presents > in the next week or so, I'll get back to you on this. The "best glide to > land without power" sink rate is the opposite extreme of the overall range > available. > > The "glide to land" option in an Ercoupe is what it is. If the engine quits > and you have no "real" information, assume a 10"1 glide ratio at which the > plane will travel 10,000' forward with every thousand feet of altitude lost. > Do you REALLY want to wait until your engine quits to check out this > assumption? > > Monitor a 70 MPH glide on a straight course from 4,000' to 2,000' with a > traffic observer, your altimeter and a watch (or stopwatch). Don't forget to > "blip" the throttle every 30 seconds or so to verify the engine is running > and not just windmilling. NEVER go below 2,000 AGL when practicing! The > only difference in the final 2,000' is "ground effect" and the strength with > which one's sphincter progressively grips the upholstery when landing without > power off-airport. > > If it takes you 3 minutes 15 seconds (3.25 minutes) to lose that 2,000' and > your airspeed indicator is accurate, at 70 MPH ground speed on a calm day and > "standard day conditions" you would travel 6,160' in one minute (70 MPH x > 5280' feet per mile divided by 60 for FPM traveled horizontally). If 70 MPH > IS your "best glide speed" for maximum range and it doesn't take you MORE > than 3.25 minutes to lose that 2,000' of altitude, what does this mean? > > It means in 3.25 minutes you would travel 3.8 miles (20,020' divided by > 5,280') while descending at an average rate of 615 FPM! (2,000' divided by > 3.25) It means that if you slow that plane down below 70 MPH without power, > the rate of descent will INCREASE, so don't even think about doing that. It > means you MUST sustain that 70 MPH trimmed glide all the way down, flaring to > slow just only before touchdown (trading excess speed in the flare to reduce > excessive sink). Touchdown off-airport at a rate of descent of about 300 FPM > with immediate brake application (unless ground is soft) should minimize > ground roll-out and potential damage. > > Check your Airspeed indicator against your GPS for accuracy at 70 MPH. Vary > the trimmed speed up and down seeking the least sink rate and then see how > much the sink rate increases to gain another 5 MPH forward speed. You need > to cover ground at a good rate as well as stay aloft. If the 3.25 minutes is > not optimum for your plane, redo the calculation(s). > > While I have a prewar Ercoupe brochure that claims a landing "ground run" of > 200' possible on pavement, you will need no less than 500' so as to clear a > 5' fence, flare and stop before hitting something; 1,000' or 1,500' if > possible. Pace off 1,000' at your airport and mark it. Make an overhead > pass at 2,000' AGL and mark your windshield with tape either side such that > you know what that 1,000' looks like from that height. You will want to > evaluate a potential landing site while above 2,000' AGL without livestock, > power lines, ponds, gullies, crops, furrows, trees, fences, gates, signs and > vehicles. Learn and stay familiar with what these things look like from that > high. Learn the clues of wind direction at ground level from that height. > No clues = light winds and longer ground roll. Strong wind lowers touchdown > speed and ground roll the more directly you can land into it. > > Go up again on a calm day having picked two landmarks 3.8 miles (or whatever) > apart. Set up a glide to commence at 4,000' AGL from above one towards the > other (GPS is the best way to judge this). Once the 70 MPH glide at idle is > established toward the second landmark, put a piece of tape on the windshield > such that the tape is "on the landmark" when you resume your "normal" sitting > position. A 12" wide line either side of the windshield centerpost marking > this "line of sight"line inside your windscreen will reveal to you in a slow > 360ยบ turn the limit of your glide range (if the wind were calm) FROM ANY > ALTITUDE within which to pick a landing site while trimmed for a steady 70 > MPH with the throttle at idle. If other directions do not look more > promising, gliding downwind will allow you slightly increased range within > which to select a landing site. > > As to numbers, which of your instruments is more reliable? Trick question. > A VSI indication is a momentary "snapshot" of what is happening at a given > moment. The Altimeter is slow, but remarkably accurate representation of what > is happening over a longer period of time. So let the airspeed and trim > control the rate of descent until just before touchdown, then using Airspeed, > eyes and seat of the pants govern your final control inputs (in that > priority). > > Best regards, > > William R. Bayne > .____|-(o)-|____. > (Copyright 2010) > > -- > > On Jan 1, 2010, at 22:04, Daniel Arditi wrote: > >> >> >> William, >> I carefully read your mail about the Coupe 'glide ratio', >> and found it very interesting. I consider this topic really important >> because it is related with security. >> >> There is one thing I would like to know, and is the sink rate in numbers >> (for example in feet/minute), when the Coupe is gliding like a refrigerator >> as all pilots say (you referred as 'alarming' rate of descent). >> >> I heared several times this comparison with a refrigerator, but this is the >> first time I hear it the way you expressed, and it sounds marvelous (I am >> referring to the phrase "In computer lingo, this isn't a bug, it's a >> feature! Learn to use it."). >> >> I think it has to do with something basic, but important, as to know the >> plane we are flying. Just that. The plane is, as it is. It is in our hands >> and mind the capacity of understanding it, how it behaves in different >> conditions, configurations, and that is not free. We have to invest some >> time to know how 'the machine' works and fully understand it. >> >> Thank you very much in advance for all your help. >> >> Happy 2010 to all of you ! >> >> Daniel Arditi >> Ercoupe Argentina.
