CubCrafters' new flagship

The turbine engine whines as it spools up and ticking igniters light off the jet fuel streaming into its combustion chamber. The feathering, multi-blade propeller spins slowly at first, then becomes a blur as it shifts into low pitch.

The Turbotech TP-R90 engine’s dual full authority digital engine control (FADEC) systems monitor internal temperatures and pressures as they step through an automated, six-step start sequence. The crescendo lasts about 30 seconds, then a message on the graphical engine display confirms the engine is ready to fly—and that’s the pilot’s cue to release the green button. The turbine sounds, smells, and sensations are a clear break from the thousands of piston Super Cubs and clones that have popularized adventure flying since Piper created the first PA–18 in 1949.

I move the single power lever forward and all the way aft to confirm the position sensor is working properly. CubCrafters Vice President Brad Damm coaches me from the back seat and tells me what to expect.

“It’s a tailwheel airplane so keep your feet lively during the takeoff roll,” he says. “The left-turning tendency will be very manageable, even at full power. And you’ll need to give it some forward stick to get the tailwheel off the ground.”

Holding short of Runway 27 at Washington’s Yakima Air Terminal Airport (YKM), I set one notch of flaps (15 degrees) and I’m soon cleared for takeoff.

There’s no way to exceed the FADEC-controlled torque or temperature limits, so I push the power lever full forward. Acceleration is moderate, and it takes about three seconds for the engine and prop to reach full power. A nudge on the control stick raises the tailwheel and I hold a tail-low attitude as the prop digs into the dry air.

The heavily loaded Carbon Cub ULT lifts off on its own after a five-second, 300-foot takeoff roll and accelerates to 70 mph as I pitch the nose up 12 degrees for the initial climb. After raising the flaps, the airplane settles into an 800-fpm climb at 75 mph.

The numbers don’t begin to describe the nature of the airplane, however.

The ULT is uncannily smooth and remarkably quiet with the prop turning about 2,200 rpm.

The ULT is uncannily smooth and remarkably quiet with the prop turning about 2,200 rpm. Fuel consumption is 10 gph at 100 percent power, about one-third as much as a similar-sized auxiliary power unit would burn on the ground.

It’s something of a cliché to describe a piston engine as “turbine smooth.” But only a turbine is turbine smooth, and the “regenerative” nature of the TP-R90 is unique (see “Turbine Conversion”).

This developmental airplane, N90UL, is still in testing and CubCrafters expects even higher performance from more engine power, a larger air inlet, and a five-blade composite prop optimized for backcountry operations in future iterations.

I level off at 4,000 feet, let the airplane accelerate to 110 mph indicated (120 mph true), and power back to 75 percent power. Fuel consumption drops to 7 gph. With a fuel capacity of 44 gallons (40 useable), that’s enough for five hours with VFR reserves. Range and endurance increase even more at higher altitude.

Steep turns reveal a lively roll rate, minimal adverse yaw, and the pushrod-actuated, balanced ailerons have a pleasing centering tendency. Lazy 8s show delightful control harmony as the airplane moves gracefully throughout its full speed range—just like the Carbon Cub UL on which the ULT is based (the T stands for turbine).

Slow flight is especially precise as the engine and prop seem to settle into a groove. Adjust flaps via the bar in the upper left corner of the cockpit: one, two, or three notches (15, 30, or 50 degrees), then use the electric switch atop the control stick to set elevator trim. (There’s no manual elevator trim wheel.)

Power-off stalls are benign regardless of flap setting, and stall breaks range from extremely gentle with flaps up to a mild at full flaps. The airplane feels heavier and more substantial than its actual weight, and visibility over the slightly elongated nose is excellent.

The graphical engine monitor is easy to interpret since everything’s in the normal green range. But the units are different: Power settings are shown in kilowatts, torque is in Newton meters, and fuel flow is in liters per hour. The U.S. version will show more familiar horsepower, foot pounds, and gallons.

Full flaps and 30- to 35-percent power nets 60 mph and a 500-foot-per-minute descent, and I take note of that combination because it’ll provide a useful starting point for the approaches and landings to come.

Unlike traditional turboprops in which the pilot manually selects either “flight” or “ground” idle, adjusts propeller rpm, and can shift the prop into flat pitch or even reverse for additional stopping power, the TP-R90 engine avoids these areas. The engine’s dual FADEC system automatically adjusts between ground and flight idle based on the airplane’s speed (not weight on wheels). The computer also sets prop rpm, and flat pitch is available on the ground but not in the air.

The FADEC logic is meant to avoid harmful hot starts, or expensive pilot blunders such as inadvertently cutting off the fuel flow, then reintroducing it before the engine has completely shut down.

Moving the prop into flat pitch (beta) has long been an effective technique for turboprop pilots to decelerate rapidly. But in the ULT, pulling the power lever all the way aft in flight doesn’t produce extreme aerodynamic braking as it would on a Beechcraft King Air, Daher TBM, or Cessna Caravan.

“We want to make the transition to the ULT as straightforward as possible for pilots new to turboprops,” Damm said. “Beta and reverse simply aren’t necessary and would bring needless complexity with little if any benefit.”

Backcountry innovation

CubCrafters has been making waves in its backcountry niche since its founding in 1980. The company’s first leader, the late Jim Richmond, was a master at reading FAA regulations yet interpreting them differently than anyone else.

When the FAA approved a highly restrictive light sport aircraft category in 2004, Richmond developed the Carbon Cub SS, a high-performing, 180-horsepower STOL aircraft that became both the most expensive and best-selling LSA.

When the FAA spelled out the tasks an amateur builder had to accomplish to meet its “51 percent” rule for experimental-category aircraft, CubCrafters created a program in which amateur builders come to the company’s Yakima factory twice. They accomplish a set of tasks overseen by CubCrafters staff on their first visit, then go away for about six weeks while factory experts perform laborious but high-skill work such as fabric covering and painting. Then the builders return for a week at the end of the process to finish their airplanes and get their airworthiness certificates.

CubCrafters was the first company to install the Garmin G3X avionics display in an FAA-certified aircraft. And the company took the heretical step of introducing the nosewheel NXCub in 2019, a radical departure from the backcountry community’s tailwheel origins. That move expanded the adventure flying market, however, and today nosewheel models account for roughly half of the XCubs the company produces each year.

CubCrafters also raised eyebrows when it launched its Rotax 916-powered Carbon Cub UL in 2024. The turbocharged, liquid-cooled engine made in Austria can run on mogas and was aimed at the international market where leaded avgas is hard to find, punishingly expensive, or both—but the minimalist airplane with exceptional high-altitude capability has been a domestic hit, too.

Once in a great while aviation produces something so novel that you almost see it shaping the future.

“We don’t innovate for the sake of innovation,” says Pat Horgan, CubCrafters president and chief executive. “We do it when we see a clear path to meaningful improvements—and that’s in keeping with everything Jim Richmond, was about.”

Horgan said CubCrafters and Turbotech have been working together behind the scenes since 2018, quietly testing and refining an airframe/engine combination they anticipate will create a new standard for high-end, adventure aircraft.

Horgan and Damm have visited the Turbotech factory near Paris, France, and Turbotech engineers have made multiple trips to Yakima to take part in the first installation in N90UL—an airframe otherwise identical to CubCrafters’ current UL line from firewall aft.

“We’ve managed to keep all this under wraps for a long time,” Horgan said. “But now we have a real product that offers some exciting new capabilities.”

From the outset, the ULT design faced fewer technical obstacles than other turboprop conversions because the Turbotech engine is so much more fuel efficient than traditional turbines. As a result, CubCrafters didn’t have to add fuel capacity to its existing UL design, a major consideration in most turbine conversions.

Also, the cylindrical heat exchanger that produces that fuel efficiency weighs about 80 pounds, so the total weight of the Turbotech engine isn’t radically different from a piston engine.

CubCrafters has purchased six Turbotech engines and anticipates buying many more. Customer deliveries of Carbon Cub ULT are scheduled to begin in the second half of 2027.

The first Carbon Cub ULTs will be licensed in the experimental/amateur-built category. CubCrafters plans to eventually get ASTM approval to build finished ULTs under MOSAIC regulations—which could make it the first U.S. company to do so with a turbine engine. Turbotech also is seeking European and FAA approval to install its engines in standard-category aircraft.

In the pattern

A five-knot breeze is well aligned with Runway 27 as I’m cleared for a straight-in approach for my first ULT landing.

This airplane is equipped with 29-inch tires and Acme Aero titanium shock absorbers, and I aim to be gentle with the soft rubber tires and use the hydraulic Beringer brakes sparingly.

Damm recommends 60 mph and full flaps on final and I follow his guidance. He’s the world’s highest time ULT pilot with about 30 flight test hours logged so far in the young program.

“Shoot for 60 on final and you’ll touch down between 40 and 50,” he said.

I slow to flap speed about one mile from the threshold and follow the PAPI lights on the visual glideslope. Thirty-five percent power seems about right for keeping the lights red over white.

I flare slightly high, pull the power lever to idle, and drop in with the tailwheel touching the pavement an instant before the mains. Thankfully, the forgiving shock absorbers and marshmallow tires cushion the blow.

I recalibrate during a lap around the traffic pattern and wait to flare until I just can’t stand it. This time I touch down just beyond the numbers and exit on the first taxiway turnoff about 500 feet from the runway threshold. The ULT has yet to be publicly unveiled so CubCrafters keeps it in an out-of-the-way private hangar to avoid attention.

The future

Once in a great while, aviation produces something so novel that you can almost see it shaping the future.

I felt that way the first time I saw a handheld GPS lock onto a constellation of orbiting satellites and show my exact position on the planet. It was obvious that GPS would change everything about aerial navigation—and that we were just at the beginning of its worldwide impact.

To a lesser extent, ForeFlight, the iPad, and the ADS-B system with its graphical weather, traffic, and terrain depictions, and Garmin’s one-button Autoland system seemed almost magical.

Now, after an introductory flight in the Carbon Cub ULT—a highly refined backcountry airplane powered by a regenerative turboprop engine—I’m left with that rare combination of wonder, disbelief, and excitement I felt the first time I held a GPS receiver.

The significance of a regenerative turbine engine that delivers operational simplicity and reliability while sipping the same amount of fuel as a similar-sized piston model is hard to overstate. The engine might not look nor sound revolutionary at first blush, but it’s easy to imagine a family of similar engines being retrofitted to existing training aircraft, legacy airframes, and a wide range of new ones.

Instead of flying behind ancient carburetors and magnetos, future flight students will be able to log hundreds of hours of turbine time during primary and commercial training. Hazards such as carburetor ice, magneto, and exhaust valve failures will be relegated to history, shock cooling will become a thing of the past, and skills such as leaning the fuel/air mixture will become parlor tricks.

There are major obstacles and pitfalls, of course, and getting to a turbine future won’t be quick or easy. The most obvious hurdle is cost: these engines are expensive and will require high utilization to pay their way. Perhaps that will make more economic sense for clubs and partnerships than individual owners.

CubCrafters doesn’t expect the ULT to be its top seller. It’s a $700,000 flagship that raises the bar for backcountry flying in terms of flying qualities, engine technology, and sticker price.

Also, getting these new engines into the legacy fleet will require supplemental type certificates that are cumbersome and costly to obtain. And there’s no guarantee that Turbotech or any other firm will be able to produce them in large enough quantities to influence the course of aviation in the near term.

The unspoken bottom line in any pilot report is whether the reviewer steps away from an airplane scheming about ways they might be able to rearrange their life in order to fly such an airplane again. I felt that way after first flights in a de Havilland DHC–2 Beaver, the Cessna Citation CJ3+, a Socata TB 30 Epsilon, and a Waco YMF–5. All very different airplanes that somehow exude quality and exceed even the highest expectations.

Add the Carbon Cub ULT to that short and distinguished list.

It’s that good.

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