Ser konseptet Blended Wing Body endelig dagens lys? - AW&ST

 

Den første skalamodellen til Boeing, X48B, fløy første gang i 2007. Airbus har fulgt opp, og ikke overraskende Kina slik jeg skrev her på bloggen for tre måneder siden. Personlig tror jeg at konseptet har mye for seg og at konseptet vil materialisere seg snart. (Red.)

JetZero Unveils Midmarket Airliner And Air Force Tanker BWB Plan

Guy Norris Graham Warwick April 21, 2023

 

Partnering with Northrop Grumman, JetZero has proposed the Z-5 for the U.S. Air Force’s program to build a large-scale advanced tanker-transport demonstrator.

Credit: JetZero

Has the time for the blended wing body finally arrived? JetZero thinks so, and the California startup has emerged from stealth mode to unveil a multimission design targeting the midsize commercial and military tanker-transport markets.

First appearing as a concept in the late 1980s and studied on and off ever since, the blended wing body (BWB) has failed to gain traction despite promising performance projections. Now, JetZero says, a yawning market gap for a sustainable midsize airliner and the U.S. Air Force’s simultaneous quest for a similarly sized advanced tanker-transport means the stars are aligned for a BWB as never before.

·         JetZero emerges to challenge Boeing and Airbus

·         Scaled Z-5 demonstrator is set for flight tests

·         Pivot gear concept is key to new blended wing body

The BWB concept blends the airframe structure and aerodynamics to reduce weight and drag while enabling the fuselage to contribute to lift. Also known as a hybrid wing body, the configuration is usually tailless and more efficient than a conventional tube-and-wing design because of its reduced wetted area, friction drag and lower form drag. BWBs are also inherently quieter than current airliners because the airframe shields most of the noise from engines mounted on the upper surface.

JetZero’s Z-5 design, the first in a proposed family of Z-series aircraft, is optimized for a range of at least 5,000 nm and up to 250 passengers. The all-composite aircraft has a wide single deck and high-aspect-ratio wing. Although this extends the wingspan to close to 200 ft., similar to an Airbus A330, the body length is shorter than a Boeing 767. Despite the overall size, JetZero says the midmarket aircraft “will be about half the weight and require half the power of aircraft it replaces, such as the 767.”

The Z-5 is shorter than a Boeing 767 and has a wingspan close to the Airbus A330’s. Credit: JetZero

Importantly for JetZero’s business plan, which targets entry into service in the 2030s, the reduced weight and power requirements are designed to enable the Z-5 to use derivatives of existing single-aisle engines such as the CFM Leap 1 or Pratt & Whitney PW1100G. The aircraft is equipped with mostly conventional systems, simplifying development and reducing cost and risk, the company adds.

The Z-5 is aimed at the heart of the market for the new midmarket airplane (NMA) that was studied by Boeing until the project was shelved in 2020. Although Boeing has since revived low-level studies of a conventionally configured NMA-class aircraft for possible service entry in the mid-2030s, the manufacturer is, by its own admission, still years away from any new product launch.

Airbus also is years away from developing an all-new aircraft in the NMA category, although a 200-seat BWB is one of three mid-2030s hydrogen-fueled concepts being studied under its ZEROe initiative. The European manufacturer is focusing instead on developing the A321XLR, a long-range variant of the A321neo designed to carry as many as 220 passengers on routes up to 4,700 nm. The aircraft is due to enter service in 2024.

But the program that could provide a near-term springboard for development of the Z-5 is the U.S. Defense Department’s plan for a BWB demonstrator that is to be evaluated as a future tanker and airlifter. The initial goal is to develop the digital design of a prototype, as well as perform initial airworthiness and test planning for a demonstrator, culminating in the “manufacture of a prototype large-scale aircraft for certification and testing,” the Air Force says.

JetZero submitted its proposal for the $245 million cost-sharing program at the end of March, and with flight tests of a NASA-supported subscale demonstrator planned for this year, the company decided the time was right to go public with its concept.

“The milestone is that, having completed the conceptual design, we have to move out of the incubation phase and into the demonstration phase,” says JetZero co-founder Tom O’Leary. “That conceptual design has led to the development of a blended wing body that would fill the middle-of-the-market gap with existing single-aisle engines and a 50% reduction in fuel burn and emissions—and be a viable tanker.

“The goal of the Air Force is to demonstrate the capability of a commercial BWB that can be converted [into a tanker],” O’Leary continues. “We have letters of support from across all the supply base that we submitted with our Air Force proposal—including fabrication and mission systems.”

Because of its fuel efficiency, the Z-5 can carry up to twice the fuel of the Boeing KC-46 tanker on a maximum-range mission, JetZero says. The aircraft also is designed to use current airport infrastructure. The Air Force is due to select a winning proposal by midyear and plans to begin demonstrator flights in 2027.

The Air Force released its initial solicitation last year, stating that the BWB “is one of the single most impactful technology opportunities for future U.S. Air Force aircraft, both in terms of capability improvement and greenhouse gas emissions reduction.” Converting the cargo, tanker and bomber fleets to a BWB design would reduce annual fuel costs by $1 billion compared with kerosene at current prices, it added.

The Z-5 emerges at a serendipitous time for the industry, says Barry Eccleston, former Airbus Americas and International Aero Engines CEO and a member of JetZero’s advisory board. “You have all these tailwinds from the environment, the Air Force and NASA, plus you have the technology tailwind, which makes it viable when it wasn’t before,” he says. “Then you set that against the fact that Boeing and Airbus are doing nothing new in this space and you say, ‘We can’t sit here and do nothing.’ The industry deserves it, and the industry needs it. If you’ve got something you know will be 30-50% better than today’s products, why would you not do it?”

JetZero, meanwhile, is preparing to flight-test its subscale BWB demonstrator, a 23-ft.-wingspan, 12.5%-scale vehicle funded under a 2021 contract awarded during an earlier round of NASA’s Sustainable Flight Demonstrator (SFD) program. The aircraft will be used to evaluate the Z-series configuration, a key feature of which is a novel landing gear design that maximizes internal volume and assists the aircraft in rotation. The main SFD contract went to Boeing in January for development of a 737-size demonstrator of the Transonic Truss-Braced Wing concept.

Developed by Mark Page, a BWB veteran from the McDonnell Douglas days and the co-founder and chief technology officer of JetZero, the “pivot gear” concept improves low-speed pitch control and lift capability—two key challenges faced by BWB designs. First designed for the Ascent 1000 BWB airliner proposed by California-based Dzyne Technologies, a forerunner of JetZero, the design moves the nose landing gear forward and the main gear rearward into unused internal volume aft of the cabin.

For takeoff, the nose gear extends by several feet to increase angle of attack by about 6 deg., allowing the BWB’s body to produce lift to “amplify the effect of the aircraft’s elevons,” JetZero says. The design, which is passively controlled without needing pumps or actuators, enables the Z-5 to reach pitch attitude faster. This allows liftoff speed to be slower and reduces demand for high takeoff thrust. It also eliminates the requirement for leading-edge high-lift slats and reduces the size of the trailing-edge flaps.

In addition to the high-aspect-ratio wing and embedded top-mounted engines, the midmarket Z-5 features side exits and skylight windows. Credit: JetZero

To counter concerns about passenger egress, ride quality and the lack of windows in sections of the cabin—all criticisms of earlier BWB concepts—the Z-5 has side windows in the forward section and skylight windows in the main and aft cabin. Although no internal dimensions have been released, the aircraft is expected to have a cabin width and ride quality similar to the Airbus A380. For emergency egress, the Z-5 is expected to follow principles outlined for the Ascent 1000, which offered quicker access to exits forward and aft than a comparable conventional cabin layout.

The wide single-deck main and aft cabin has three aisles, skylight windows and digital outside view display screens. The forward cabin has side windows. Credit: JetZero

JetZero says advances in composites for primary structures, added to the single-deck configuration of the Z-5, eliminate the design challenges of constructing pressure vessels in a noncircular fuselage. While the initial design is based around conventional tanks for sustainable aviation fuel, the company says the BWB configuration provides ample internal volume for liquid-hydrogen fuel tanks in the future.

As part of its industrial development plan, JetZero says it is “simultaneously launching an outreach to private sources of funding and engaging with potential program partners.” For the tanker demonstrator proposal, this includes Northrop Grumman, the only major airframe-maker with design and manufacturing experience of flying-wing aircraft similar to the BWB configuration.

“We think we’re in a real good spot with the Air Force to win this BWB demonstrator program award,” says O’Leary, who was formerly chief operating officer of electric vertical-takeoff-and-landing aircraft startup Beta Technologies. “To build it, we’ve got a host of industry partners. In order to come up with a conceptual design, we had to work with the entire supply base. So you name it, we’ve talked to them. There’s nobody who said, ‘Oh, that’s crazy—we won’t work with you.’ And that’s everybody, from top to bottom of the supply base.”

“One of the biggest battles is, of course, that Boeing and Airbus are going to work really hard to make sure it doesn’t happen,” Eccleston points out about the competitive aspect. “I’m not saying we’re smart enough to outsmart Boeing and Airbus, but we’re getting a bunch of partners that are going to give us real credibility,” he adds. “So when the first question you get in the marketplace is, ‘How are you going to do all that?’—we have a plan, and we have the strength of partners to do it.”