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ZTGT + CAFE BV Jack \orris and Andy Bauer

Last month we described the development of Zero Thrust Glide Testing (ZTGT), the first practical, easily accessible, flight test method - to get real drag data and "drag curves," and, as a result, "propulsion efficiency," on actual flying propeller airplanes, design flaws, leaks, imperfections and all! Concisely, the method is based on measuring gliding sink rate, s, knowing Gross Weight, and True Airspeed - while maintaining "zero thrust" - based on sensing the crankshaft transition from thrust to drag - in the engines thrust bearing clearance. D# = GW# x (s/TAS), (both s and TAS in ft/sec.). This month we'll explore CAFE's (Comparative Aircraft Flight Efficiency, Inc.) integration of the method with modern air data instrumentation, in quest of FACTS, look at some of the opportunities and problems, what it all means. , • . ... , , All science, the whole modern world that has exploded around us in our century, to our great benefit, has happened simply because, starting in the 16th century, "philosophers," really the prototype scientists and engineers, started to get serious about a specific detailed grasp of exactly how the physical world around us worked. There was a gestation period, slow at first, as knowledge grew and spread, then an 1800's quickening. The 1900's effect of defining the specifics has been breathtaking. We were on the moon 66 years after the Wrights' first, flimsy, homebuilt leap of 120 feet. We are now in the midst of a homebuilt "leap forward," a revolution in performance and efficiency. With our newfound ability to establish real facts, we are all going to appreciate and understand it all much better. Soon we're all going to understand the specifics of how our flying machines work and perform, and the CAFE organization, with EAA sponsorship, has taken on the challenges of "turning on the lights" for knowledge and progress. There is a beautiful integrated simplicity to the n a t u r a l laws. The challenge is in their vast scope, all the unwanted complications that will get in the way if you dare try to conquer them, pin them down. Brien Seeley invited me to join the CAFE Foundation and at first I said no because I had been trying to break free to build my RV-6, and after a lifetime in aerospace engineering, I clearly understood Nor-

ris' First and Second laws: 1. Nothing is ever really simple! 2. If you thought it was simple, you were too uninformed, too dumb to understand everything that was really

going on!

44 APRIL 1995

Those words were not conceived as a put down of the u n i n i t i a t e d , but rather to "retweak" the awareness of my professional aerospace team for challenges like rushed fixed price bids on not yet invented spacecraft controls. Ultimately, Brien's offer was too good a challenge to turn down. We clearly had the opportunity to define all the aerodynamic facts, on the whole homebuilt and private aviation fleet. The team was exceptional, the task was clearly doable. All we had to do was accomplish in a weekend or a week what Edwards Air Force Base would do in six months or more, per plane, for several million. That sounded like a worthy challenge, a lot of fun - but, of course, there would be plenty of sweat equity, in accordance with the laws above, by a unique group of volunteers. The first CAFE advantage that Brien Seeley's creative insight envisioned was replacing the normal rat's nest of instrumentation, calibration, correction and analysis, with a modern "strap on," precalibrated, sensor/integrated circuit, almost automated air data system for the aerodynamic data. Team members Steve W i l l i a m s (Hewlett Packard) and Frank Braal (Braal Micro Instruments) had already developed the basic Air Data, Barograph Boom for the CAFE TriAviathon competition. They'd do a larger, next generation model and calibrate it in the NASA Ames wind tunnel for unquestioned accuracy. Ed Vetter (MCI) would take on the newly envisioned engine instrumentation, an inflight laptop computer, integrated output, working with Brien and Steve. The objective was "close to automated" data correction, selection, analysis, and generation of actual

drag, power and propulsion efficiency curves. Potentially really slick, compared to the misery and drudgery that used to be the rule, with Ed, Brien, Steve, and everyone integrating. Would there be plenty of trouble, growing pains, e q u i p m e n t failures with obscure causes, pooped out computer and b a r o g r a p h batteries on crucial tests, computer crashes, destroyed data, when you hit the mic button? You bet. . . tons of it, much more than a year's worth of development tests, still up at 3 a.m. on ice cold winter nights at the CAFE hangar, lift off before dawn in search of "dead air." It's always the same game, getting the Apollo to the moon, getting the Voyager through 67 dawn, O-darkt h i r t y test flights, finding, fixing, polishing. That's what Norris' laws accurately predict. As a guy who watched his space craft customers overrun 600%, as a norm, while figuring out how to manage that on fixed price contracts, I knew at least five things. 1. It was going to be the predictable, wild uphill fight; 2. The caliber of guys involved were not about to be licked; 3. Tom Poberezny bought himself one hell of a bargain; 4. Most folks would never have a clue of how much had to be accomplished; 5. There'll be a long remembered party at the goal line with this great group of guys laughing about how dumb and naive they were at first when, of course, they're all ace guys, the real fun of a challenge like this. The CAFE team would fully pay their dues, as happens in every effort like this. That's always how the next step is bought, what makes the final victory so sweet, creates the fond memories, another notch in the 2001 world that surrounds us already in our lifetime.

But, that's getting way ahead of the story. There's always the day of potential panic when the really fundamental challenge occurs, that Mother Nature pops on you, only after you're fully committed! Brien Seeley, M.D., like all the CAFE people in the Santa Rosa area, is a very special guy. A leading eye surgeon, he could just as well have been a space age engineer because he has both that special leadership spark, and the technical vision to see past the predictable problems. He's a very unique individual, extremely valuable to the homebuilt movement. CAFE Director Otis Holt is another of the special guys. A math graduate, he's a deep thinker and deep digger, a real craftsman in wood, or just about anything, any mechanism you might need. He's building a gentleman's estate: land, wine grapes, a view, a shop in a crafted barn with hardwood floors and cabinetry you wouldn't find in a rich man's home, a proper guest house, a main house as he gets to it. Otis is a careful and independent thinker. R a t h e r t h a n j u s t use my simple 1/16" model airplane music wire Zero Thrust Switch, laughably simple, guaranteed vibration proof, based on a graduate course in Dynamics and Vibrations and 40 years experience, Otis insisted on making a craftsman's project out of it, being able to set the wire to .001" inch. I kid you not. "Come on, Otis," I said, trying to help. "It just goes klunk, just set it in the middle like I did on the Luscombe." Otis kept setting it off center, sometimes way off center, to see if he could find a bias. I'm not sure that I ever got him to just put it on center. Experienced in the ways of intelligent people, I quit talking early and listened. You can't steer smart, independent people . . . shouldn't try. Competent people will find their own way to the truth, usually shedding new light in the process. Panic! He did find a bias off center. He even found a moving target, a varying gap, a moving center, varying cold to hot, a fundamental challenge to the dead simple zero t h r u s t concept described last month. That's potentially bad news, because you must be sure you have real zero thrust. It was not hard to understand the findings. The Lycoming in CAFE's Cessna 152 test mule was pumping twice the oil volume at twice the pressure as my old early WW-II design 85 hp Continental, creating a predictably bigger thrust bearing face pressure

gradient at each end of the axial stroke. The later design also had a front bearing twice as long, the hot steel shaft expanding half as much as the aluminum crankcase, moving the axial gap and center, turning an easy sensor problem into a fundamental challenge. It was all perfectly logical, Norris' Laws at work. Mother Nature just never lets anything stay simple, and always springs the complications on you in the heat of the battle. Panic? Naw! Just the CAFE team earning their part of the next step. We've got a great team. Otis and Ed Vetter got together, applying some of Ed's special electronic creativity. So now we have a new digital proximity sensor with a resolution of .0001", yes, one ten thousandth. In the air, Otis can now instantly run the prop

"You can't steer smart, independent people . . .

shouldn't try. Competent people will find

their own way to the truth . . . " forward, then back, accurately nail the t r u e center, zero thrust, bias free. You'll soon see that we now do somet h i n g much slicker than the "level flight, zero thrust RPM/TAS calibration" described last month. The final laugher, you can't hold the prop in the center. Happily, it just goes klunk klunk, back and forth in the free center, bias free, just like the Luscombe. BUT, the big difference is, now we can handle tighter thrust bearings with assurance and super inflight adaptability. My only challenge will be in restraining the guys from going for planes with too tight a thrust bearing, trying to work a too tight null between two end pressure gradients. In good science, good engineering, there is always a BIG need for good judgment, good horse sense. You already have enough to handle to get it

right. That just prepares you to understand and fully appreciate the next really nifty invention. Three years

ago, to do a valid Luscombe test, I'd be way out to sea at dawn, furiously

working my calculator to do a proper calibration of my mickey mouse Luscombe instrumentation, calculating a

precisely corrected TAS at 2500', halfway through my 1,000' test glide, for the morning's temperature and pressure - multiplying that TAS by 14.94 RPM/TAS to get a valid Zero Thrust rpm for the test glides - then all over again for each test speed. Got the picture of a very busy guy - ONLY willing to do it because a flyable test had never been accomplished before in nine decades of flight? So some combination of Steve Williams, Ed Vetter, Otis Holt and Brien Seeley mutually challenging and prodding each other, comes up with the incisive insight that RPM/TAS x 60 equals REVS PER MILE. Do you recognize what that means? At any speed, any altitude, for zero thrusts the propeller always turns the same revolutions per mile. Progress is built one step at a time, the next guy standing on the previous guy's shoulders, producing the next step. Andy Bauer, ace professional aero, can calculate for you a plus or minus, half to 1% correction, high wing vs. low wing, to account for wing circulation changes, slow to fast, high to low angle of attack, for precise Zero Thrust, but the REV/MILE insight is the huge new grasp. We throw in a circulation correction, but the challenge, naturally, is getting test data as good as 1%. So, now Ed Vetter feeds his digital tach into Steve and Frank Braal's automatically corrected boom TAS, and comes up with a big, REV/Mile digital readout. 842 is the magic number calibrated level by Otis on CAFE's C-152 test mule, using a new digital level. Now, compared to my prehistoric development method to do a drag test, C. J. Stephens, CAFE test pilot, concentrates on nailing IAS in a glide (recognize drag is constant at constant IAS, any altitude, constant GW). Otis, playing flight engineer, nails any plane's calibrated REV/Mile with the throttle. That's instrumentation and methods anyone at Edwards or NASA would be proud to conceive. Tach, level, crank position, auto corrected TAS, REV/Mile - they're all digital. The beauty but challenge of the natural laws is that starting simple, there is soon gross complexity, as the whole SPORT AVIATION 45

DRAG CURVES -1400# GW Luscombe BE - RV6A

240-r

D R A G

20

40

60 8E-Dp RV-Di

D - Total Drag 46 APRIL 1995

80 100 120 TRUE IAS-CAS MPH -*-e-

RV-Dp 8E-D

Dp - Parasite Drag

140

160

180

8E-Di RV-D Di - Induced Drag

200

Great Insight - DRAG

Avid Owners

Luscombe vs. RV-6A This graph looks complicated, but, trust me, dive in . . . we'll help you and you can gain a ton of insight. It's not hard. The three standard type drag curves on the left, define the Luscombe 8E; the three on the right define the RV-6A, all for the same 1400 pound gross weight of the Luscombe, 200 pounds below the RV's max weight. The two top curves are the classic, leaning "lazy J" total drag curves for each plane that result when you add the two drag curves below each together - the induced (due to lift) drag curve that swoops down as you go faster, and the parasite drag curve (due to surfaces hanging out in the airstream) that swoops up as you go faster. Got that? Read on. Any of the curves could be higher or lower, depending on the designer (and builder), but the same two basic drag curves, always with the same characteristic shape (but not height, or drag), add together to create the plane's J curve it's total drag. Many pilots will understand that parasite drag is a V 2 curve twice the speed, four times the drag, 3, 9, etc. Far fewer will realize that the drag coefficient of a slow, high angle of attack wing increases so rapidly (proportional to Ci 2 ) that it overpowers the effect of speed, (V 2 ), becomes a 1/V 2 curve, twice the IAS, 1/4 the induced drag, dropping like a sinker with increasing speed, but rising rapidly if you slow down. You do not have to grasp all the math. Simply, induced

high aspect ratio (span/chord) Luscombe has an induced (lift drag) curve only about half the RV's stubby wing curve. But that compact, super clean RV has only about half the flat plate parasite drag of the Luscombe, 2.25 ft. 2 vs. 4.55. The result is that the RV easily scoots out to high speed, its induced lift drag drops like a sinker and the RV's induced drag - and total drag - come out lower at a much faster, mathematically o p t i m u m cruise speed, 130 mph IAS, at comparable weight, vs. 95 on the Luscombe. At the RV's 1600 pound gross weight the optimum t h i n k i n g man's IAS is 140, 170 TAS at 12,500 ft. With much better propulsion efficiency, you get even better MPG on a heavier RV-6A, going much faster, 170 TAS at altitude vs. 100 or so on the Luscombe, a calculated 1000 mile range, LA to Seattle. The mathematically optimum cruise speed is where you get the most IAS vs. pounds of drag. You find that by drawing a tangent line from the 0,0 origin of the graph, tangent to the drag curve. Try it, you'll find the 95 and 130 IAS speeds above. Notice every other point on the drag curve is above that sloping line, that ratios drag to IAS, more drag in proportion to speed. The RV will go 200, something the Luscombe won't do straight down, but the drag is almost twice, half the MPG, if you force it to 200 IAS, about 240 pounds vs.

up, they add together, the J always the same shape. Get that and you've grasped the basics. There is a classic comparison here. The classic, long wing,

Wait until you see The Logic of Flight . . . with more room to explain, teach, impart more insight than you ever thought possible.

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technical spectrum comes to bear,

fighting you, challenging those who

would dare try to advance. But to those who t r a i n , learn, dare and , frankly, work their fannys off, the clouds part, the magnificent, technically elegant simple clarifications crystallize as their own private inventions, their contribution to the next step. After nine decades with no real basic drag data, now to get an honest drag answer, you just measure sink rate in dead air at zero thrust, constant revs per mile, knowing gross weight and true airspeed. A lot of people who are afraid of technology think engineers are a little weird. What an unfortunate, unknowing viewpoint t h a t is. At the first launch of the all up, unmanned Apollo stack, Apollo 5, I stood next to the second stage Rocketdyne J2 engine project engineer. Ten days before that his creation would not pass the withering "white noise" vibration test requirement. Guts . . . show me a test pilot, a guy on the front line with the guts or the stamina, or the brights, to stand up to the awesome responsibility of thinking your way out of that one - a 15 billion dollar program, the whole nation's prestige squarely on your shoulders. Understand, appreciate engineering and engineers. They

are how and why you got to fly and live as you do in modern comfort with ever unfolding progress, productivity. Unbent, he solved his vibration problems in time. But was there sweat about the launch? You bet, you can answer that one, about 8 tons! I almost forgot about my own control products in there, their problems and vulnerabilities. Weird? Can you imagine his exhilaration and sense of accomplishment seeing that 36 story, 6-1/2 million pound behemoth lift off, 7-1/2 million pounds of thrust, a fire plume the size of the Empire State Building, the eighth wonder of the world on its way to the moon and back. Those unknowing folks don't have the first clue of the real guts and thrills involved. Engineering is exciting. So we've got this great group of volunteers, all this neat science. Is it real, are all the problems solved, is it accurate, is ZTGT drag really equivalent to a propless glide? Where are the still hidden problems and challenges? What will all this new insight mean? The first thing to understand is that this is a unique group of volunteers, willing to work on their own time just to get to the real truth. No one has any axes to grind, no pet theories to 48 APRIL 1995

protect. No one is out to find anyone's

plane good or bad, better or worse than another. Like Joe Friday, the game is "just the facts, ma'am" - and we're after three types of information: 1. The basic aerodynamic facts, never before available, through ZTGT; 2. Real performance numbers; 3. Professional handling qualities evaluation. (Are the control forces matched or unmatched, is there inadequate stick force per G? - the things few pilots realize they should question.) Now, to the problems of truth. Good engineers learn it's really dumb to not tell it like it is and substitute a wish, an opinion. Time goes by, and the truth comes out. You get cut off at the knees if you push opinions. But, a very prevalent situation in engineering is that the first answer is often not the truth. A fool rushes forward with the

"... for (he first time in nine decades, we're going to have real aerodynamic facts." truth, only to find he's been both dead wrong and dumb. It's much harder and that's where both a pro's accurate insight and integrity are needed. So, now we're ready to more carefully talk about truth. Brian Hobbs from Edwards, my great young Assistant Technical Director on the Voyager, gave me a valuable insight. "There's a lot of 5% data at Edwards" . . . you can do a lot of good work and be that far off. The whole physics book proves to be a wily enemy. So, let's look at whether ZTGT gives you the same drag answer as a propless glide. In our Luscombe tests we found poor propulsion efficiency, reasonably good at minimum power, but quite logically degrading as power input is substantially increased,

increasing flow and extra drag over the fuselage, possibly separation, even

reattachment, a "lumpy" power curve.

Raspet found the same characteristics in his breakthrough free glide tests in the '50s. Each case is a little different, but if you extrapolate back to zero thrust, about 2 hp calculated turns my prop at max L/D IAS, it looks like no drag difference, or any unmeasurable difference. The thing to realize is that we're not dealing with laminar flow front ends on powered planes, but turbulent flow, not all that vulnerable to being upset. At first I thought that perhaps the prop ticking over at zero thrust might cause separation on a critical case. But then, looking at the Cessna 152, which has terrible separation on that too steep rear window, I realized separation happens when the air gets all the way to stagnating, actually reversing flow. If it was that bad, our minuscule input was not in the ballpark of causing the problem. As above, we're always looking for the real truth, and if there's a difference we'll find it and report it, but the best insight to date is you can't find a drag difference. Some, not believing thelow drag and poor propulsion efficiency we found on the Luscombe and not realizing we had simply confirmed what Raspet found years ago, said, "Ah ha, your drag is too low, a flawed method." They hadn't thought it through, didn't know of Raspet. ZTGT is conservative. If there were any difference, it would show a tad more drag. Their argument was backwards, and we found a big propulsive efficiency loss, not a tad. We crossed checked everything versus Raspet's free glides, got very close sensible checks, did seven years prior analysis before testing, and only then published. We did a dawn, propless, towed, free glide over Santa Rosa Airport, and found a 5% difference versus some over the ocean ZTGT drag tests, which looked like we had found a difference. We went to Mendicino, which has a

coastal airport, where we could do free glides out over the ocean, and clearly established that we got data that straddled the data for both previous drag tests with the same propless method, the same morning, clearly establishing what I already knew. It's the quality of the air that controls the accuracy. What we f o u n d was bad a i r , "lift, sinkers," where we didn't think they should be. Good science finds truth! Now to the real central truth. In a corruption of the Democrats

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'92 slogan, "It's the Atmosphere, Stupid," is the watchword, the real key to good or bad data, that the whole team now understands. If you find a 600 ft./min. sink rate at max L/D, minimum drag, that's only 10 ft./sec. - so, logically, only 1/2 ft./sec. lift or sink will give you a 5% error. That almost sounds too tough. Of course, you don't try testing on a hot, thermal packed, desert afternoon. The truth is this: Dick Johnson finds the subtle bumps, knees of laminar separation on a really demanding 60:1 sailplane by picking appropriate air masses on

dead winter days. I got Luscombe data to plot to 1 pound, yes, 1 pound, and that's really good, averaging multiple runs (except for unchecked quick run, extreme end points), once I got smart enough to get four miles out to sea at dawn over the stable ocean off Ventura in the protected "quasi bay" south of Point Conception, CA. Zero Thrust Glide Testing is potentially a very accurate test and analytical method simply because the plane tends to sink only as much as it really needs to. Sensitive, accurate, it takes good piloting skill, professional instrumentation work and double checking to hope to go for 1 to 2% professional data, but as you can see, the end game is going for good stable air. Now, this is where you can see and appreciate the huge advantage of ZTGT - you can go test where the good air is. You don't do multiple propless glides three miles out to sea you'd drown. ZTGT isn't less pure than propless; it's how you have the capability to get good double checked data. Consistency proves

accuracy. That's the real central truth of the matter. Our problem is nowhere near as tough as Dick Johnson's, finding laminar separation knees at 60:1. We tend to do minimum drags at 10, 12:1, 15:1 at the outside, max speeds in controlled dives at much lower ratios, so the air is substantially less critical than the sailplane case. It still is all important to the very best data, and you don't find perfect air every dawn. If you're stuck with a 5% day, ZTGT can again save your bacon by allowing you to do multiple glides, find and separate out the clearly biased test points that don't plot, average the good data and make data that's credible to a couple of percent real. CAFE's Santa Rosa site is proving to be a tougher case than I had out to sea from Camarillo, Pt. Mugu, the Pacific Missile Test Range. The good SPORT AVIATION 49

news is Santa Rosa also has access to the more stable ocean. The bad news

is the ocean is very cold there, tending

toward a stronger shore - sea circulation with more and stronger sink/lift to dodge. Mendicino showed me bad dawn air existed above the inversion

CAFE Cafe. A bottom line star of the show is, of course, the modern electronics and instrumentation that makes it all possible - sometimes even

on a weekend. The book that I'm writing, The Logic of Flight, to be completed in where the best meteorological data I mid '95, will make never before incould get from Voyager's great weather sights on the thinking man's way to fly director, Len Snellman, said it should- really easy to understand and use. It n't be. We're checking stability now, even easily teaches a fundamental grasp with Len's help; another part of earn- of aerodynamics and its integration ing the next step. with engines, insights everyone can We've also looked into doing a full grasp and use, insights that are not scale wind tunnel test at NASA Ames now understood. It cuts through all on the Cessna 152 to double check, to the complexity like a hot knife through correlate it to our glide tests. The tun- butter. It even has cartoons, because nel test is not the iron clad accurate the objective is to make a better than test you might at first think. It's not necessarily more accurate. Their force transducers for heavy planes only re6 solve 5 pounds. We're closer than that averaging our data on less than great days. They'd need a mounting and transducer upgrade, a significant effort. Then when you look at mounting the plane, you can see errors on how big the drag is, depending on where its true center is. Depending on the tunnel selected, the plane can be flying in ground effect, so the answer may not be as good as glide testing. You can't use a tunnel as a check method if there are errors as large or larger than the method you'd like to check. Mother Nature is a wily opponent; nothing is ever really simple, per the basic laws at the start, and incisive work is a fundamental requirement. The bottom line is, we're right there at the goal line, resolving the final nitty gritty, the last few percent, the expert grasp a laugher, fun to learn. last few few pounds. A great job is It's almost like everyone left me this being done by CAFE, with EAA spon- great opportunity to write the definisorship. The lights are being turned tive book on really understanding flight on, and as the testing output builds that never got written. I can't wait to and is refined, for the first time in get it out there. Don't write. We'll annine decades, we're going to have nounce it when it's ready; work, not real aerodynamic facts. Once the talk, until then. So, what are we going to see from facts are available, everyone will come to understand them - what they mean, all this testing? First, we're going to how these planes really work, the real see that the homebuilt airplane movedifferences between them, with spe- ment has become a new leading edge of flight. The best new designs are cific, quantitative answers. There's so much more I could tell not just better, but a whole lot better you about the CAFE people and their than their m a n u f a c t u r e d cousins. work. Great ideas, experimental ma- For example, Van's sport planes chine work by Gris Hawkins, for all aerobatic, stronger, travelers with those test parts you need to do all this; half the drag of their manufactured fantastic scales, good to .1 pound by cousins, faster, lower fuel b u r n , Granden Elmer and Dwane Green; an longer range, STOL's, slower landinflight calculating fuel flowmeter by ings and takeoffs, a whole lot more Ed Vetter, .3 lbs. off after a full test fun - flat better, all around. In the hidden technical areas, we'll run, fantastic gross weight accuracy. VP Larry Ford demands a class opera- see far better propulsion efficiency, tion and sometimes feeds us in the closer to the numbers that were al-

. . . we re going to see that the homebuilt airplane movement has become a new

leading edge of night."

50 APRIL 1995

ways assumed but just not there on

many old, small planes. A funny, simplistic sounding but technically incisive insight exists - Norris' Fourth

Law, "If it goes really fast, it has good propulsion efficiency; if it doesn't, it doesn't." If it goes 200, it has to have pretty good propulsive efficiency, eta sub p. At 200, even with low drag, reasonable horsepower just doesn't get you there unless propulsion efficiency is also quite good. High drag and good propulsive efficiency are not easy partners, unless a fluke case where energy heals a separation is found. The 152 may have some of that when we get to checking power. The Bellanca Cruisair, a great old plane, just didn't go as fast as a modern h o m e b u i l t . Raspet found an airspeed system t h a t lied, a 58%

propulsive efficiency. I found the same on the great old classic Luscombe I bought in college. Mine does 116.6 mph, flat out with calibrated instruments, propulsive efficiency below

60% considering cooling. Special work gets you over 120. We're going to get a lot smarter on what's really there, the specifics that control the differences. Every time you get better factual insight, you get deeper smarts, ever better products. Remember, understand CAFE's object is to also give you real performance data, and the handling quality insight that you tend not to think about until you catch on too late that it's important, that it detracts from the joy of flying unless the designer got it right. The CAFE tests can be the most comprehensive test program in history. It's all happening, guys, and CAFE, the EAA and the homebuilt movement are right there at the leading edge turning on the lights, making real advances, refining, improving the breed. It's really great, but the central point I intended to make is that the progress is only earned with a lot of hard demanding work. We're really lucky to live in such an exciting time, as progress accelerates, where our life and satisfaction can improve, where we're able to work on getting smarter, maybe even wiser, if we're really thinking. Life can be very good these days we can even fly! The sidebar example has more insight than we have space to explain totally here, but notice the great insight it can give you, and with the book you'll be amazed how much more you can grasp - even easily, with all the help that's possible. *