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Saturday, March 25, 2023

A Better Motor Is the First Step Towards Electric Planes

In a white and grey laboratory, where neat runs of orange cables on the walls provide a relief of color, a three-bladed propeller spins on the front of a Cessna “Iron Bird” test frame. It’s eerily quiet, free of the buzz you expect from a propeller-propelled aircraft. Just the whoosh of air, like a ceiling fan spinning at full speed. It’s slow at first, then faster, to the point that the blades blur out of vision, and only the bright chrome center cone is visible, as engineers at the Magnix Systems Integration Laboratory on Australia’s Gold Coast push the rig, before powering it down to a silent stop.

This is the start of airframe tests for a new motor, designed for the coming era of electric aviation. It’s a 350-horsepower machine that weighs just 110 pounds. But Magnix's engineers focus on a different metric. “We were able to achieve 5 kW per kilogram,” says CEO Roei Ganzarski, about double the power to weight ratio of a Tesla motor. In a car, that balance is less important. At worst, a few extra pounds will add a bit of time to a 0 to 60 mph sprint or knock a few miles off the car's range. But in a plane, the ongoing fight with gravity demands low weight coupled with high power. “If a plane doesn’t have the power to weight ratio that it needs, it simply won’t take off ,” Ganzarski says. "It becomes a safety issue."

And just as automakers are coming around to the idea of electric drivetrains being more efficient, quieter, and more flexible, the aerospace industry is doing the same. Companies like Zunum, Eviation, and even NASA with the new X-57, are all exploring the idea of replacing engines, and eventually jets, with electric motors. Aviation is a significant, and growing, global contributor to climate change. Flying accounts for 12 percent of US transportation greenhouse gas emissions. Electric planes could run much more cleanly, using energy from renewable sources. They could also cut down on airline's jet fuel bills, which can run up from 10 to 50 percent of their operating costs.

Magnix was founded in 2009 as an R&D firm working on all electrical motors, and has headquarters and another engineering facility in Redmond, Washington to go with its Australian outpost. It recruited talent from Airbus, Boeing, Tesla, and Pratt and Whitney, and quickly decided that it didn’t need to be limited to research—it could build what it takes to make these flying visions a reality.

That meant tackling the bit that puts the plane in the air, which involves challenges beyond the power to weight issue. In a car, engineers can rely on air for at least some cooling effect, but that doesn't work at thousands of feet up, where the air is thin. So Magnix had to design and integrate an oil-based liquid cooling system into its motor, to get rid of excess heat. It’s also had to design its machine to be able to meet the rigorous requirements that getting safety approved for flight entails, with a close eye on materials and structural integrity. Failing in midair is a lot more serious than breaking down by the side of the road.

“We haven’t invented any materials, nor how an electric motor can work, but we’ve put together the combination of what materials to use, in what configuration of coils, magnets, and liquid cooling to allow us to provide that power-to-weight ratio,” Ganzarski says.

The airframe tests, where the motor has been bolted into the place a fuel-belching engine would usually sit, in the chopped-off front of a Cessna, will run for over 1,000 hours. Engineers are taking readings of the way the motor behaves, the torque it develops, and the temperature it runs at, starting with gentle runs from 100 to 500 rpm. Next come endurance tests and runs that mirror how the motor would be used on a flight, with high power demand at takeoff, some climbing, cruising, and descent.

Ganzarski expects to move from the lab to real flight tests in about a year. At the same time, his team is working on a range of motors for other applications. Planes of the future might not have just one propeller at the front, they might have rows of motors and fans along the wings, or one pushing at the rear.

Siemens, which is working with Airbus on the development of electric planes and electric vertical and takeoff machines, makes similar power to weight claims for its electric motors, and has already started demonstration flights, in a small aerobatic airplane. But otherwise, Ganzarski says he doesn’t see many competitors, at least in the sky. The company is already working on a larger, 750-horsepower motor, which could be a bolt-in replacement for a Pratt and Whitney PT6 turboprop engine, used on small planes like the Beech Queen Air.

By figuring out the detailed engineering needed to make a motor for flight now, stands Magnix in a good position to capitalize on a growing industry, and provide a very real demonstration of at least one aspect of electric flight—a technology that still sounds just a little bit crazy.

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