World’s most efficient passenger plane gets hydrogen powertrain

The entire shape is designed for extreme efficiency, and as a result Otto says the Celera uses an astonishing 80% less fuel than a comparably sized jet.  Otto Aviation

Otto claims the Celera 500L in standard fossil fuel-propelled form is “the most fuel-efficient, commercially viable business aircraft in the world.” Its “flying suppository” shape might not win it any fashion awards, but if true beauty lies in perfect function, then this thing could be a bulbous supermodel.

The whole thing is designed to maximize laminar flow – smooth layers of airflow with little to no mixing of adjacent layers moving at different speeds. This avoids the swirls and eddies that lead to air turbulence at speed, causing aerodynamic drag and wasted energy. Laminar flow is by no means a new concept, but Otto says it’s pushed the idea so far forward with the Celera design that it uses 80 percent less fuel than a traditional design. No, that’s not a typo.

Otto Aviation's Celera 500L prototype in flight: the world's most efficient passenger aircraft design by a country mile

Otto Aviation’s Celera 500L prototype in flight: the world’s most efficient passenger aircraft design by a country mile.  Otto Aviation

Running on an efficient 550-horsepower combustion engine, Otto claims this thing will fly six passengers up to 4,500 nautical miles (8,334 km) at cruise speeds over 460 mph (740 km/h), challenging small business jets for top speed while more than doubling their range. An impressive glide ratio of 22:1 allows pilots to switch off the engine altogether and glide for up to 12 miles (200 km) completely unpowered. This monster efficiency factor, says Otto, should make the Celera some 5-7 times cheaper to run than a comparable jet.

Mind you, it wont scale up to full-size airliner size, since the low-drag laminar flow model relies on a width-to-length ratio that’d be impractical in a bigger bird. But Otto says it’ll scale up to take 19 passengers, and there are plenty of markets that could make use of an efficient airframe in the 6-19 passenger space.

It’s not a pie-in-the-sky render, either. Otto has built a full-scale prototype, and by November last year the company announced it had completed some 55 successful test flights, reaching speeds over 250 mph (400 km/h) and altitudes up to 15,000 ft, and that “all test flights have validated the aircraft’s operating performance goals.” You can see the thing flying in a video below.

Now clearly, an 80 percent reduction in fossil fuel use is an environmental win in and of itself. But if there’s one sector in aviation that’s crying out for brain-busting efficiency figures like the Celera promises, it’s the emerging zero-emissions sector, which is currently struggling against poor range figures thanks to the low energy density of lithium batteries.

Indeed, when we first wrote about the Celera 500L back in 2020, many questioned why the heck this thing wasn’t electric from the get go. And it seems Otto is on board with the idea, as it’s now announced a collaboration with hydrogen aviation pioneers ZeroAvia to develop a fuel cell-electric powertrain specific to the Celera’s requirements.

This airframe’s bulbous shape works well with a hydrogen concept – hydrogen powertrains can weigh much less than battery-electric ones, but they tend to take up a bit of space. Still, ZeroAvia is being relatively humble with its ambitions to begin with, aiming for a range of just 1,000 nautical miles (1,852 km) of zero-emissions range for a hydrogen-fueled Celera. Still, that’s a very useful distance, and pretty extraordinary for a clean electric passenger plane.

The Celera flies on a single pusher prop

The Celera flies on a single pusher prop.  Otto Aviation

ZeroAvia is champing at the bit; this could be the company’s first chance to work on a brand-new aircraft design. “The majority of our commercial deals to date,” says founder and CEO Val Miftakhov in a press release, “have focused on retrofit and line-fit for existing airframes, which is essential to deliver zero-emission flight to market as quickly as possible. However, efficiency gains from new airframe design can expand the impact of zero-emission aviation. We are pleased to collaborate with innovators, like Otto Aviation, bringing cutting-edge clean sheet designs to market as we can optimize the hydrogen-electric propulsion system for those designs.”

Of course, there’s a downside to working on brand-new airframes too. It’s one thing to build a prototype and do flight testing, and another altogether to get an aircraft certified and ready for volume production – particularly one that deviates from the norm.

Otto has made remarkable progress thus far, and if the company’s efficiency claims are true – which will remain a hotly debated topic on aviation forums until Otto puts extraordinary proof beside its extraordinary claims – this does feel like an important aircraft that the world needs right now. Even the fossil-fueled version could be exceptionally useful for passenger and cargo operations, and could make a significant contribution to decarbonization.

But the next steps will be a huge challenge, requiring a ton of long-horizon investment. We hope Otto’s team is fortified and ready for the grind ahead, and all jokes aside, we wish them all the best. We’d hate to see this flying suppository get shelved.

Source: ZeroAvia / Otto Aviation

It can be scaled up to bigger planes if it will be built as a two and even t[h]ree decker.

There seem to be a lot of unrealistic claims around this airplane –;dr: L/D of the airframe and specific fuel consumption of the engines are credible but that doesn’t add up to the claims made regarding fuel consumption and speed relative to jets. Laminar flow seems to be used as the snake oil to sell this to gullible customers.

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