280kt, 4,200fpm… on four cylinders!

When residents of the Northern Hemisphere think about Brazil, mental images of the Amazon and beautiful people on the beaches of Rio typically come to mind before flying machines. But Brazil has a strong aviation tradition, going back to pre-Great War days when Brazilian aviation pioneer Santos-Dumont flew his dirigible to his favourite café in Paris for coffee (he was living in France at the time). In the 20th century’s next big war, a squadron of Brazilian fighter pilots campaigned P-47 Thunderbolts across the Med and Italy for two dangerous years.

Today, millions of people are transported in comfort and speed by Embraer aircraft – just one company in a growing Brazilian aviation industry. To support that industry, Brazilian universities educate and train young people in engineering, materials and mathematics. At the Federal University of Minas Gerais (UFMG by its Portuguese initials) in Belo Horizonte, Brazil, Professor Paulo Iscold has spent years training and inspiring aviation students using the most straightforward of methods… he has them design and build aircraft. Not just average aircraft, but aircraft that set records, by definition doing what no other aircraft have done.

Paulo conceived an ambitious project… to design and build the fastest four-cylinder aeroplane in the world. The CEA-311 would be designed, fabricated and built by university students under his supervision. Paulo was eminently qualified to mastermind the project. He was raised in an aviation family (his father was an aeronautical engineer) and at just 39 years of age he holds a PhD and a professorship at UFMG, where he has taught aerostructures for years. His understanding of how air behaves has made him the go-to-guy for race pilots trying to get the absolute best from their aeroplanes. On a practical level, he has become deeply involved in Red Bull racing (contributing to the success of Paul Bonhomme) and competitive aerobatic aircraft, and has designed an aircraft that holds several world records. The irony is that, although a pilot himself, he’ll never get to fly any of the aircraft he designs; at 6ft 6in he simply can’t fit in one.

Building an aircraft under the guidance of a youthful, charismatic leader with huge practical experience and a deeply intuitive understanding of aerodynamics is a special opportunity. The UFMG students recognized that, so Paulo had no trouble assembling a talented team with a voracious capacity for work. They needed it. There have been some pretty fast four-cylinder aircraft.

Dennis Polen showed up at Oshkosh in his Polen Special in 1976 and caused ripples in the homebuilt aviation community that haven’t finished yet. The compact, but very sophisticated, single-seater was designed to cruise well above 20,000ft and achieved true airspeeds of over 300mph on a Lycoming IO-360. Later developments, including turbocharging, resulted in speeds approaching 350mph.

Jon Sharp’s Nemesis racer, first flown in 1991, managed 290mph, using a Continental O-200. Obviously it was a far cry from the little dog on the nose of a C150, but still only 200 cubic inches.

Paulo had a dog in the hunt as well. A previous design built by his students, the CEA-308, set records in 2010. It achieved 223mph on a Jabiru 2200 (134 cubic inches ) with two leaky cylinders.

So the bar was already high, but the arithmetic was fundamental: to make an aircraft that was the ‘fastest’ would require an airframe with as little drag as possible, an engine that could provide as much power as possible and a propeller that could turn that power into usable thrust over a very wide range of speeds.

Designed for the pilot… and speed

They started with basic decisions. The engine would be the venerable four-cylinder O-360 Lycoming. Other, potentially more sophisticated powerplants might be out
there, but with a brand-new airframe pushing the envelope, Paulo decided that a well-proven engine would avoid yet more risk. His UFMG mentor, Professor Claudio Barros, had taught Paulo the mantra, ‘New aeroplane, old engine; old aeroplane, new engine.’ Which is to say, ‘Don’t put an untested engine in an untested aircraft.’

He also decided on a tractor arrangement, building on the 308 experience. Choosing a specific individual as the pilot might seem odd, but in this case it makes sense. Gúnar Armin Halboth was the man for the job. He was an experienced, professional pilot, a former aerobatic champion and, best of all, a man of modest size who barely comes up to Paulo’s shoulder. His slight build enabled an airframe that would virtually hide the man behind the engine. Anequim was quite literally wrapped around Gúnar… a good thing because as a sponsor of the project, he’s now the aircraft’s owner!

With the basic parameters established, Paulo and his students dived into a year’s worth of intense design work. Using sophisticated computer tools, many of which they’d fine-tuned themselves, they developed the shape of the all-composite airframe. The resulting aircraft is an exquisite combination of flowing curves designed to slip through the atmosphere in a way the air barely notices. It evolved as a mid-wing monoplane with an ovoid fuselage housing a tiny canopy just behind the trailing-edge of the wing. A long canopy comes forward from just behind the pilot’s head to the centre of the engine cowl.

The slim fuselage and swept tail look very shark-like, hence the name Anequim, the Portuguese word for the mako shark.

The cowl itself looks huge, sporting bulbous cheeks that remind one more of a chipmunk preparing for winter than a shark, but that’s only because the Lycoming engine is so outsized for the tiny airframe it powers. It is actually formed of carefully considered curves that direct air both inside and out.

The wing has a continuously-curving leading-edge, similar to the blade shape of a ‘scimitar’ propeller. The straight trailing-edge consists of small, high-aspect-ratio ailerons and large, split flaps. Flaps might seem odd on a wing designed solely for speed, but without them the aircraft would be very difficult to land on anything short of an airline-sized runway. There is so little drag that losing speed may be a more difficult piloting problem than gaining it; by some estimates Anequim may have the smallest flat-plate area of any man-carrying aircraft yet built.

The flowing shape demanded composite construction; it would be too difficult to create the curves and exquisitely smooth surfaces in metal. The computers fed the data to large CNC machine tools which carved moulds
from MDF;  Paulo had discovered Brazil is one of the few places in the world that produces medium density fibre (MDF) sheets in eucalyptus wood, which is more stable and less hygroscopic than the pine version, that is common in most other places around the world, resulting in a precise and relatively inexpensive (nothing that uses carbon fibre is truly cheap) way to produce an airframe in a very short amount of time. After a year of design work and another year of building, the airframe was ready for the engine.

Normally, a Lycoming, parallel-valve IO-360 is rated at 180hp, but to reach record speeds even Anequim was going to need far more than that. The Brazilian team turned to the American firm of Sky Dynamics, recognizing its work on Red Bull aircraft and other racers. The result had the familiar size and shape of the Lycoming, but Sky Dynamics had worked over virtually every part of the engine. The compression jumped from 8.5:1 to 11:1. The cylinders were ported and equipped with special rocker arms. Magnetos were replaced with a pair of electronic ignitions and further magic was worked upon the induction and exhaust systems. The finished engine then spent a week on the dynamometer being tweaked, before heading to Brazil. Demonstrated power is close
to 280hp.

In the 1990s, circular cooling inlets became all the rage, promising low drag and good flow over the cylinders. You won’t find them on Anequim – instead there’s a tiny horizontal slit on each side of the spinner that feeds a carefully-designed plenum wrapped over the top of the engine. The plenum, a result of much testing and computer modelling, allows just enough air to pass over the cylinders at just the right speed to optimise heat transfer. Given the horsepower that the engine develops, that’s a lot of heat to carry away. You’d think a tiny, extremely efficient aircraft like Anequim would get by on a small fuel tank, but that’s not the case. All that horsepower doesn’t really come from the engine. It comes from the fuel. Quite a lot of fuel which, being a liquid, cannot be condensed. The answer was six fuel tanks within the wings and fuselage, giving a capacity of 100 litres.

The prop probably dips deepest into the well of magic. It’s a composite unit from American prop guru Craig Catto, a man who’s probably propped more really fast small aircraft than anyone else. Consider the requirements: a prop that has to absorb almost 280hp, turn it into enough thrust to go about 350mph, be efficient at rpms well over the usual 2,700 Lycoming redline and accelerate the aircraft into the air from a dead stop. And do all this without changing pitch. It’s a little like riding the same single-speed bicycle for every stage of the Tour de France.

Riding the shark

In a little over two years of intense effort by Paulo’s students, Anequim was ready to fly. Iscold himself, always the hands-on teacher, had participated in every phase… welding, laying up composites, programming CNC machines, but he seems proudest of the young men and women who dedicated thousands of hours and overcome many difficult problems in design and fabrication to produce the lovely sculptural shape, gleaming like polished marble, that was about ready to leave the ground.

Gúnar slipped into the cockpit as if he was putting on a handmade shoe. He faced a relatively simple instrument panel with a small Dynon EFIS, enhanced with some extra telemetry/data gathering functions, a Becker radio and transponder and a Garmin nav unit. His right hand rested on the side-stick controller; there just wasn’t room for a traditional centre stick. His left hand was on the throttle. His feet rested on tiny rudder pedals with (believe it or not) heel-brakes.

The aircraft weighed just over 700lb; when you realise that the engine as installed weighs about 350lb, you realise how impressive the engineering of the airframe is. Its skin was smooth to a couple-of-thousandths of an inch, the product of days of detailed finishing and polishing by composite expert Fernando Zancani.

The first take-off was from Brigadeiro Cabral Airport, serving Divinópolis, Brazil, on November 14, 2014; see https://vimeo.com/112598730 for a video. The take-off was a bit long in coming, the product of Gúnar being cautious with the power, a density altitude of about 3,000ft and the effects of a prop pitched for about 300mph more than rotation speed. But once Anequim reaches flying speed, it leaps into the air and literally soars for altitude.

Fifteen minutes later, Gúnar’s professional flying skills were put to the test. There was a snapping sound as the flaps started down, and a bang as they went back up and stayed there. He was now riding an aircraft designed to go fast, but now had no flaps, no speed brakes, no retractable gear to lower, no variable speed prop to push into fine pitch and the flat plate area of a large moth. If he could have stuck his hand out the window it probably would have doubled the drag.

All of a sudden the 1,500m of the airport’s longest runway didn’t seem any too much. It took three approaches, the last in a hard slip, and Gúnar stopping the engine to get the aircraft down and stopped. After the broken rod-end bearing was repaired, the flaps operated normally and Gúnar’s life became much easier.

Test flying has proceeded sporadically, broken up by Paulo’s travel schedule, Gúnar’s need to make a living as a commercial pilot and the weather. The engine has proved reliable and the Anequim has exhibited few quirks other than its extreme slipperiness. Iscold is being a bit coy about the actual performance numbers, but several flights have reportedly exceeded 300mph by a significant margin. Somewhere Wilbur and Orville are smiling… “We told you four cylinders were enough!”

No matter how fast it ultimately goes, Anequim has already fulfilled one mission. Paulo reminds everyone, “The main reason to build this aircraft was to teach and to motivate young people with aviation and engineering. It is only the second reason, I call it the ‘playful reason’, to set speed world records.”