When Audrey Hepburn went careening with Gregory Peck on a scooter through the cobbled streets of Rome in “Roman Holiday,” the Vespa she drove was simple enough that she could just jump on, twist the throttle and get to her destination — even if her execution was slightly inelegant for a princess.
Italian aerospace engineer and aviator Simone Castellani is working to similarly simplify the experience for pilots, albeit after they obtain a proper license. He is part of a GE team developing a digital brain for turboprop planes that will make flying them so easy “my mom could do it,” he says. “Everything is done automatically. In a way, it is just like flying a scooter.”
The idea for the digital brain came from Brad Mottier, who runs GE Aviation’s Business and General Aviation unit. The technology, officially called Full Authority Digital Engine and Propeller Control, or FADEPC, is common in jets, but it has never been used in commercial turboprop planes. That’s because most Cessnas, Beechcrafts, Air Tractors and other aircraft in this category use engines based on designs that are several decades old. Using FADEPC on them wouldn’t be practical without other major changes. “The turboprop market has not gone through a major redesign in a long time,” Castellani says. “Using FADEPC on those engines would be like putting the most modern fuel controller on a car from 30 years ago.”
But things changed two years ago when Mottier asked his engineers to design a brand-new engine called the Advanced Turboprop, or ATP. The engine uses components originally developed for supersonic jet engines, 3D-printed parts, and, for the first time, FADEPC. “Everything is new on the ATP,” Castellani says. “Since we have designed this new engine from scratch, we felt this was the right engine for the technology.”
Castellani has spent the last two decades working in China, the Czech Republic and elsewhere for Avio Aero, the Italian aviation powerhouse GE Aviation acquired in 2013. Today, he is based at the company’s headquarters just outside of Turin, the northern Italian industrial town steeped in engineering and the birthplace of Fiat cars. He loves to fly during his time off, and the technology he’s building could make his hobby more enjoyable.
Today, when Castellani flies a turboprop plane, he controls the power of the engine with one lever and the pitch of the propeller blades with another. He uses a manual that tells him the right settings for engine and propeller speeds, depending on altitude, temperature, efficiency and other conditions. To manage thrust, he has to set the engine power and the propeller speed independently, taking care not to exceed any of the engine limits. “I am a pilot, and I can tell you that flying a modern turboprop plane requires a lot of effort,” he says. “Most of the time, you are really watching the gauges in the cockpit instead of looking out.”
But the team’s FADEPC can do the same thing with just a single lever, just like twisting a scooter throttle. It’s a neat trick, but one that’s difficult to pull off. The system first ingests data from sensors monitoring parameters such as temperature, turbine speed, torque and pressure inside the engine. It combines that with external information about the ambient temperature, altitude and aircraft speed. It then uses smart algorithms to analyze the data and come up with the sweet spot allowing the engine to run in the most optimal way. “It’s simpler than driving an automatic car,” Castellani says. “You push the throttle, and the controller will tell the engine and propeller the best way to go.” Paul Corkery, the general manager for GE’s turboprop business, says that FADEPC “can make flying as simple as pushing a lever, and pilots love it. They have more time to fly the plane, look out of the window and take in the experience, instead of monitoring and adjusting the engine all the time.”
The engine not only excites pilots like Castellani, but also plane builders like Textron Aviation, whose new Cessna Denali will be the first plane to use the ATP. That’s because the technology helps reduce the ATP’s fuel burn by as much as 20 percent and gives the engine 10 percent more power compared with engines in its class. “It sounds simple, but it’s really disruptive,” says Cristian Lai, Castellani’s counterpart who helped write the code for the system.
The FADEPC team is spread out between Turin and the southern Italian town of Bari, where Avio Aero partnered with a local university and opened digital and additive manufacturing labs. They have filed for a dozen patents as a result of their work.
Lai’s and Castellani’s boss, Suzana Chakrokh, started pulling together the team that developed the system two years ago. Because the system involves software as well as hardware — the algorithms control the pitch of the propeller, the position of the fuel valves and other physical variables — she needed engineers with aerospace, electronics and mechanical engineering backgrounds. “But most of all, I wanted to have people with passion for the job,” she says. “I wanted people who really wanted to be working on it,” she says.
Castellani, Lai, and two dozen or so others that fit the description quickly plunged in. They watched the sun set behind the snowcapped Alps outside of their windows during many long days at their office. “Starting from zero is not easy,” Chakrokh says.
The team first ordered a blank electronic box built by the French aerospace company Safran to host the system. Next, they got to work writing software for controlling the ATP engine. The team used a model-based programming language for aerospace engineers that allowed them to convert the program to C, C+, Python “or whatever other language” we needed, Lai says. “The designers didn’t need to learn a specific language.”
Next, they uploaded the code and applications that control the engine into the box, kind of like loading a program into a new computer. “The box holds the operating system,” Chakrokh says. “We were writing the apps that will control the engine and the pitch of the blades.” The design is “double-redundant” and can quickly reconfigure itself if it detects a problem. “If this would happen, the pilots would see it on the dashboard, but otherwise they wouldn’t notice a thing,” Lai says.
The finished product, which is attached to the engine, weighs about 12 pounds and looks like a large laptop. GE successfully tested the full engine for the first time in December in Prague, the home of the company’s turboprop headquarters.
Castellani was there to see it run. “It’s a piece of art,” he says.