The original 1981 CAFE 250 flight efficiency race was inspired by Nick Jones' Oshkosh Lowers-Baker-Falck 500, a race on limited fuel. For the CAFE 250, I wanted to create an aircraft competition in which the basic laws of physics determined the winner. To this end, Lyle Powell and Jim Horn helped me derive a mathematical formula for a "Fuel Efficiency Factor," (see SPORT AVIATION, March 1981). This formula multiplied the aircraft's speed times its miles per gallon times the square root of its cabin payload. It was proportional to the square root of the quantity L/D ratio divided by the flat plate drag area. Though it gave undue advantage to the smaller aircraft, this CAFE 250 formula launched the idea that overall aircraft efficiency could be expressed in a single number. The event was a success because it clearly illustrated how speed, mileage and payload were interactive capabilities limited by the laws of physics. This really got people thinking about how their aircraft stacked up against all the rest. Roy LoPresti, Chief Engineer at Mooney at that time, was so impressed with the significance of the event that he designed a beautiful trophy for its winners.

The True Formula

For the 1982 CAFE 400, I derived a new formula which was simply:

Speed x MPG x Payload = Score.

This formula is equivalent to the speed times the lift to drag ratio of the aircraft. It measures a "universal truth" about any vehicle's fuel efficiency because it optimizes speed per dollar of fuel burned. Professor B. H. Carson showed the validity of this formula in his excellent paper, "Fuel Efficiency of Small Aircraft," AIAA-80-1847. He drew upon the earlier work of Gabrielli and von Karman, which had predicted that the laws of physics imposed an absolute barrier or limit to any vehicle's score by this formula. That limit is due to such fundamental factors as the viscosity of air, the force of gravity, the energy density of hydrocarbon fuels and the laws of aerodynamics. This means that the quest to reach this limit is a timeless challenge. It can only be approached by the brilliant application of advanced technologies of the future.

Fine Tuning

The CAFE 400 formula exponents were reluctantly modified in 1985 when experience showed that they encouraged the race aircraft to use only 50-55% power and that the larger aircraft were dominating the event. The new formula was:

Speed 1.25 x MPG x Payload.75 = Score

Fortunately, this formula retains the characteristic of having a physical barrier or limit. After 10 years of CAFE racing in Santa Rosa, with nearly 600 aircraft scores on record, we are still nowhere near that limit. The all-time high CAFE 400 score was set by Mike Melvill in the 5 seat Rutan Catbird in 1988. The burning question remained: How much better can aircraft efficiency get in the future?

The Triaviathon

In 1986, we began the CAFE Triaviathon competition to measure the extremes of aircraft performance. This was made possible by the self-contained CAFE barograph designed and built by Board members Steve Williams and Frank Braal.

In this event, the wingtip-mounted barograph was used to measure each aircraft's topspeed, rate of climb and stall speed. The score was computed as the rate of climb times the ratio of top speed to stall speed. In 1987, the late Jim Ewing set the all-time high Triaviathon score in his Harmon Rocket, an aircraft designed expressly for the Triaviathon. Again the question was: How much better can aircraft get?

The Triaviathon was such a success that we felt it, too, deserved its own special trophy. By this time, CAFE trophy fabrication resided with my friend and volunteer machinist Cris Hawkins. He helped me design a new, solid aluminum trophy for the Triaviathon and an Outstanding New Design Award. Using programs which he wrote and ran on Randy Easterling's CNC mill, Cris machined all of our CAFE trophies for 1990. Aircraft Spruce donated the aluminum and Ken Brock Manufacturing volunteered to polish them.

EAA Supports CAFE

The 10 years of CAFE events were made possible by member volunteers from EAA Chapters 124, 427, 393, 20 and 62. EAA Headquarters in Oshkosh was the major sponsor. Aircraft Spruce & Specialty Company, Chevron and AOPA also provided sponsorship.

In 1991, Tom Poberezny proposed that EAA sponsor the building of a new CAFE Aircraft Performance Evaluation Center in Santa Rosa, and support an ongoing program of Aircraft Performance Reports. This renewed my hope that the CAFE formulae would continue to offer their basic challenge to personal aircraft design.

In the spring of 1993, Bill Massey, President of EAA Chapter 124, invited the CAFE Foundation to take part in their First Annual Air Fair by staging an Open House at our new facility, which is located at Chapter 124's headquarters. This seemed like the perfect occasion to renew the CAFE competitions.

We decided to invite the all-time high scorers in the CAFE 400 and CAFE Triaviathon to compete again at the Open House. This time they would compete to set the all-time high scores as targets for new and future competitors. I suggested that a single, grand, perpetual trophy be created for each event, and that there be only one weight class, i.e., personal experimental aircraft of under 4,000 pounds gross weight. To win a place on the trophy, a pilot and designer would need to exceed the all-time high score.

When I told Tom Poberezny about the new contests and trophies, he was immediately enthusiastic. He called a few days later to offer SPORT AVIATION Editor Jack Cox's idea for the name of the new cruise efficiency event: The CAFE CHALLENGE. The CAFE Board felt it was a perfect name.

The CAFE Challenge

Reviewing the top CAFE scores for aircraft of different sizes, I set out to further refine the CAFE 400 formula. The payload exponent needed to be slightly reduced to afford a "level playing field" for single and 2-seat aircraft, alongside those with 7 or 8 seats for payload. The speed exponent needed to be raised to place a higher premium on speed, and push the "Challengers" to use near-70% power. The CAFE Challenge formula became:

Speed1.3 x MPG x Payload.6 = Score

Table I shows the amazing similarity of the relative scores of top CAFE 400 aircraft computed with this new formula.

The CAFE 400 race course also needed revision to create a last, generic contest "for the ages." We wanted to take advantage of GPS to track the aircraft's flight and avoid the necessity of pylon spotting crews. As he drove home after a late night CAFE Board meeting, Otis Holt devised an ingenious new 500 mile race course. It consisted of flying outbound in a prescribed range of altitudes from Sonoma County Airport to any point on a 250 mile radius circle, and then returning. A GPS receiver and notebook computer would record speed, position and altitude throughout the flight.

A climb gradient requirement to reach a certain altitude within a short radius after takeoff was needed. We decided to require the aircraft to reach 10,000' MSL prior to reaching a 25 mile radius from the point of brake release. We chose a required enroute altitude range from 7,500' to 12,500'. This would stay below the altitude at which oxygen is required and yet be high enough for realistic cross country travel.

Upon return, a final descent from these cruise altitudes is allowed beginning 50 miles out from the starting point.

Trimble Navigation and Mentor Plus Software graciously provided the GPS receiver, Apple Powerbook and modified FlightMap software necessary to stage the CAFE Challenge. Matt Trask at Trimble and Steve Splonskowski at Mentor Plus were a great help in creating this system. Note that this system allows the staging of a simulated CAFE Challenge from nearly any airport and can thus provide a yardstick for any aircraft's efficiency.

Table II shows a variety of scores necessary to equal the record score in the CAFE Challenge, 1,315,396, which was set by Dick Rutan and Mike Melvill with the Rutan Catbird on May 8, 1993. Their outstanding score included a speed of 210.73 mph, mpg of 20.15 and payload of 976.63 pounds. A New Triaviathon The Triaviathon formula, like the CAFE 400 formula, also needed reworking for use in a contest "for the ages." The old formula would allow an infinite score by any aircraft which could hover, and yet did not provide an intense enough penalty for high stall speeds. I tried numerous formulae to fix this until CAFE Board member Steve Williams came to the rescue. Using curve fitting software, he created the new CAFE Triaviathon formula. It provides for a marked reduction in score for stall speeds above 70 mph and minimal additional score for stall speeds below 30 mph. These limits recognize the FAA single engine stall speed requirement and the fact that off airport landings at below 30 mph are generally survivable. A very steep score increase occurs as an aircraft's stall speed drops from 70 to 35 mph. This complex formula accomplished our goal:

         28110625 x [Vmax x ROC]2
Score = --------------------------
          [4100625 + Vso4] x 109

The 3 elements in the score are Vmax at 6,000' indicated altitude, rate of climb (ROC) from 2,500' through 3,500' on a STD day, and Vso, or power off stall speed. The Triaviathon score ignores fuel consumption and serves as an index of the aircraft's "exhilaration factor." It requires a designer to simultaneously optimize power to weight ratio and the lift and drag coefficients. It is open to propeller driven non-turbine experimental aircraft of under 4,000 lbs. gross weight.

Table III shows the scores necessary to equal the CAFE Triaviathon record score of 1316.45, which was set by John Harmon in the Harmon Rocket II on May 8, 1993. He scored an awesome Vmax of 244.79 mph, stall of 56.36 mph and ROC of 3330.21 feet per minute.

Trophy Artistry

"You're going to be dead a long time." - popular axiom

When Tom Poberezny offered to display the new CAFE trophies in the EAA Air Adventure Museum, we were awestruck at the prospect of leaving our mark on aviation history. These were now going to have to be very special trophies! I found myself constantly thinking about ways to artistically symbolize our epic aircraft performance contests in the new trophies.

One day while working out on a treadmill at the health club, I saw the words "Speed-Power-Elevation" above the control buttons for the machine. It suddenly occurred to me that the 3 fundamental physical elements in aircraft design - lift, thrust and drag - were the natural themes for the new trophies. I presented this idea to the CAFE Board and they generally concurred.

Board member Cris Hawkins, the best machinist in the land, again volunteered to help design and build the trophies. His great talent for programming CNC milling machines and using AutoCad would make the whole endeavor possible.

Cris and I reviewed the extensive Laserdisc photo archives of the Smithsonian's National Air and Space Museum to see what essence had made the Bendix Trophy, Thompson Trophy and many others so famous. We knew that we would be unable to create their same artistic castings of heroic female figures. Yet, we wanted our trophies to succeed in becoming famous someday as well.

Borrowing from Roy LoPresti's CAFE 400 trophy design, we chose to use three separate but converging aluminum arms in each trophy. In the Challenge, they would be delicate ribbons of metal, but in the more brutish Triaviathon, they would be massive rigid arms. We spent numerous evenings making AutoCad drawings on Cris' computer. We wracked our brains for ways to artistically symbolize lift, thrust and drag in sculpted icons on the upper end of each respective metal arm. We finally adopted the lift, thrust and drag symbols as shown in Figure 1.

CAFE Board member Otis Holt, a superbly talented craftsman and woodworker, was asked to create the wooden bases and he then joined the trophy effort. This provided even more impetus to do our best, since Cris and Otis both knew each other to be perfectionists. We chose California redwood for the bases as symbolic of the CAFE's origins in the Redwood Empire.

We were thrilled when Otis presented his model for the base. Beautifully made from clear heart, fine grained, kiln dried redwood, it was an elegant shape and fit perfectly.

I purchased several large slabs of aluminum from Bataeff Salvage. Cris then devoted untold hours writing the complex CNC mill software programs and producing the aluminum parts needed for the CAFE Challenge trophy. Randy Easterling again donated use of his CNC mill for the project. Otis and Cris then spent 48 hours of wrenching, backbreaking effort to symmetrically bend the Challenge trophy ribbons. An all-night work party in Otis' shop finished the trophy just in time for the May 8 event.

Otis and Cris first unveiled the Challenge trophy just after SPORT AVIATION Editor Jack Cox performed the ribbon cutting ceremonies at the CAFE Aircraft Performance Evaluation Center.

Then began the task of finishing the Triaviathon trophy. After several hundred manhours, it was completed in time for the award ceremony held June 3 at the EAA Chapter 124 Headquarters. Dick Rutan and John Harmon flew in to receive their award certificates for setting the all-time records.

The Perfect Finish

A few days later, a jeweler was invited to see the trophies. He was pleased by the design but said that the satin finish was atrocious and would need fine polishing with diamond paste.

The trophies were disassembled and, on marathon polishing sessions, we attacked every square inch of the trophies, meticulously sanding with successively finer grits of MicroMesh abrasive. Beginning with 400 grit wet or dry sandpaper, we prepared them with, in succession, 800, 1200, 1800, 2400, 3200, 3600, 4000, 6000, 8000, and 12000 grit MicroMesh. The final 1 micron diamond paste made the finish on the trophies reach a true mirror quality. These work parties consumed over 1500 manhours and enlisted the late night elbow grease of Larry Ford, Anne Seeley, Crandon Elmer, Frank Braal and Steve Williams. Lorin Leith, Otis' wife, served wonderful meals to the hard working crew at Otis' workshop. Meanwhile, we were thrilled when Tom Poberezny invited us to design and send drawings for trophy displays as we envisioned them in the museum. Otis designed these as handsome hexagonal pedestals offering views of the trophy from any angle. We sent Cris' AutoCad drawing of the displays to Gordy Selke at the museum, whose expert team of Jim Faris, Ken Schucknect, Andy Cox and Lee Ann Abrams did a great job of building them.

With the polishing completed barely in time for Oshkosh, Otis and Cris carefully packed most of the trophy parts into a custom plywood crate and had them shipped to the museum. We hand-carried the Triaviathon arms onto our airline flight, and I spent several late nights finishing one in my Oshkosh dorm room. On August 2, Otis, Cris and Larry Ford spent the entire day in the EAA museum restoration shop assembling the trophies for the presentation that night at the Theater in the Woods. The next day, we lovingly placed them in their new permanent home in the museum's main lobby.