: 11 min

Taxi! Follow that plane!

Safran is investing heavily in aircraft electrification, with a particular focus on propulsion systems, to make air transport more environmentally-friendly.
VTOL multi-rotors

Taxi! Follow that plane!

Safran is investing heavily in aircraft electrification, with a particular focus on propulsion systems, to make air transport more environmentally-friendly. While all-electric commercial airliners are not going to be flying any time soon, smaller aircraft of this type could shortly make their appearance, especially multi-rotor vertical takeoff and landing (VTOL) machines.

FASTER AND GREENER

March 6, 2030, 8:23 am. Thomas, an engineer at Safran, has just landed at Paris-Charles de Gaulle airport after an assignment in the United States. He keeps checking his watch, because he has to be at his office at 9 sharp for an important meeting. The widgets in his smartphone show traffic jams all around and pollution in the danger zone.

 

I better take an air taxi he decides, opening the AirTaxi app to order the vehicle.. That'll get me to the office in just 15 minutes and it's also better for the planet!" He quickly heads toward the elevator taking him to the "vertiport" on the roof of the terminal.

 

 

Several people are already ahead of him in line. While waiting, Thomas takes a closer look at the autonomous air taxis landing vertically one after the other, unloading and loading their passengers and taking off again, straight up! His taxi turns out to be the latest 8-rotor model. He's already seen the ads, vaunting the VTOL's energy efficiency and silent operation. Three other passengers join him in the cabin, a couple and their ten year-old son, who watches the ground quickly recede into the distance from a large bay window.

 

It's the first time I've ever taken an air taxi" he says proudly to Thomas.

 

A COMPREHENSIVE AND PRAGMATIC STRATEGY

"Good for you!" smiles Thomas. "Did you know that, up to five years ago, the only taxis around were cars on four wheels? At the time, I had just joined Safran to work on aircraft electrification. Everything seemed so futuristic!"

The boy looks at him with a puzzled air: "Electrification? But the airplane we just flew on wasn't electric."

"That's only normal," answers Thomas. "We don't yet have the technology needed to electrify the propulsion on such a big plane. But it should be possible in a few dozen years. In the meantime, we started by electrifying smaller aircraft flying shorter distances, like this air taxi.

 

And our technologies will gradually improve to the point where we can store and deliver the energy needed to power an all-electric airliner."

 

The boy perks up, asking, "So this taxi is all-electric?"

"Not this model, because it's a fairly heavy one that can carry four passengers, explains Thomas. "It's got what we call a hybrid propulsion system, combining a regular gas turbine engine and a set of batteries. The aircraft calls on these two energy sources together or separately, depending on where it is in the flight, whether takeoff, climb, landing or cruise, to manage energy as efficiently as possible."

The boy nods his head. "And how about that one?" he asks, indicating a smaller aircraft he can see through the window, a two-passenger model which just overtook them.

"Yep," says Thomas, "that's a lighter aircraft with all-electric propulsion, thanks to its high-performance battery."

 

In fact, within a couple years we'll probably see some aircraft using a fuel cell, an energy source that operates on stored hydrogen and oxygen from the air, and that only releases water vapor!"

 

A HOST OF CHALLENGES

The boy's parents are listening to the conversation with more than casual interest, as the air taxi continues its flight. It is now flying at about 75 mph (120 km/h) according to the info screen in the cabin. Scheduled arrival at the "vertiport" on the roof of the Triangle building, near Safran headquarters, is only a few minutes away. From there, Thomas can use an electric bike to finish his trip.

 

At this point, the boy's father starts talking to Thomas. "I'm an engineer in the auto industry, and I also experienced the start of the ‘electric revolution'. I imagine that you have even tougher requirements in aviation…"

"Of course," nods Thomas. "One of the main roadblocks to developing this kind of VTOL was flight safety. That's why all designs today are based on multiple rotors. It wasn't easy to get them certified, because they had to meet draconian regulatory requirements."

 

In fact, the first few aircraft of this type always flew with a pilot. Today, however, these aircraft are safe enough to fly on their own. Technically speaking, we had to work on the propulsion system, of course, but above all on the energy system as a whole, including power generation, distribution and management. We still have a long way to go to develop an all-electric airliner, because its power needs are much higher, which means we have to address the daunting problems of battery weight and high-voltage operation."

 

ALL-ELECTRIC AIRLINERS

At that point, they all hear the signal for landing. The air taxi touches down, the door opens and Thomas says goodbye to his fellow passengers, who will be getting off at the next stop. Another passenger quickly takes his place. The boy waves goodbye to Thomas, then turns to his parents and, with the determination of youth, says: "When I grow up I'm going to be an engineer and I'm going to invent the first all-electric airliner!"

 

 

> Credits
© Airbus
© Bell Helicopter Textron Inc.
© L'Oeil du Chat / Safran
© L'Oeil du Chat / Safran
© Alex Marc / Safran
© Alex Marc / Safran
© L'Oeil du Chat / Safran
© Alex Marc / Safran
© Alex Marc / Safran
© Bell Helicopter Textron Inc.
© Alex Marc / Safran
© Benoit Vallet / Safran
© L'Oeil du Chat / Safran
© L'Oeil du Chat / Safran
© Bell Helicopter Textron Inc.
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