Airbus A350 forward fuselage section assembly. Photo Credit: Airbus
Teal Group Air Transport Market by Segment outlook. Photo Credit: Teal Group
The result has been devastating to the global commercial air travel market. Initially, passenger air travel dropped about 90% around the world, grounding thousands of aircraft. Eventually, some travelers comfortable being on an airplane returned to the air, leading a small resurgence for the market. By late October 2020, when this article was written, global passenger air travel was down about 63% compared to 2019, according to aerospace industry analyst Teal Group. As a result, airlines throughout the world grounded aircraft, furloughed employees and canceled or delayed orders of new aircraft. Some smaller airlines have gone out of business.
Airbus and Boeing
In response, Boeing (Chicago, Ill., U.S.) and Airbus (Toulouse, France) reduced the production rates for all of the aircraft made by each company. Boeing, which had stopped manufacturing the 737 MAX in 2019 because of two crashes of that plane, actually restarted 737 production in May 2020 (at a very low rate) in anticipation that the plane would be re-certified for flight. The company says it hopes to increase that number to 31 by 2022. The 777/777X was reduced to five aircraft per month, the 767 to six and the composites-intensive 787 to 10 (and possibly six by 2021).
Airbus, for its part, reduced A320 production to 40 per month, down from an average of 53 per month in 2019. The A330 and the composites-intensive A350 were reduced to a rate of two and six per month, respectively. Further, Boeing announced in early October 2020 that in 2021 it would close all 787 assembly operations in Seattle, Wash., U.S., and consolidate them into the company’s North Charleston, S.C., U.S., facility. Some employees at Boeing and Airbus have been furloughed or laid off.
Assuming that a COVID-19 vaccine is developed and deployed globally by mid to late 2021 — as seems likely — it is a given that global commercial air travel will return to some level of pre-pandemic normalcy, but when and how that recovery occurs can only be speculated about. China, which was hit by the coronavirus first and implemented the strictest virus mitigation measures, has seen its passenger air travel begin a recovery. According to Gardner Intelligence, year-to-date through October 2020 Chinese passenger air travel was down 25% compared to the same period in 2019.
For the rest of the world, the outlook is much less certain. Most analysts predict that single-aisle aircraft (737, A220, A320) serving domestic and regional routes will return to service first and could help production and delivery of that aircraft type return to 2019 levels by 2024. However, international long-haul routes served by large twin-aisle aircraft are expected to recover more slowly. The Teal Group forecasts that production and delivery of these aircraft —787, 777X, A350, A330 — may not return to 2019 levels until after 2030.
Parked aircraft. Photo Credit: Getty Images
If this scenario holds, Airbus and Boeing are in distinctly different competitive positions. Airbus’ portfolio of aircraft gives it product options to meet any airline need, ranging from the smaller single-aisle, 150-seat A220 to the long-haul, twin-aisle, 400-seat A350-1000. In between is Airbus’ most profitable and successful plane, the single-aisle A320, which now includes the A321XLR, a long-range (4,700 nautical miles) single-aisle aircraft that seats up to 244 passengers. The A321XLR, introduced at the 2019 Paris Air Show, is expected to enter service in 2023, although that may change depending on how the coronavirus pandemic plays out. In any case, Airbus seems well-positioned to meet the needs of customers as passenger air travel recovers. Airbus CEO Guillaume Faury, in public statements, has expressed interest in making sure that Airbus and its supply chain is stable and intact when aircraft production resumes. To that end, Airbus is reluctant to make disruptive changes to aircraft production rates, particularly as a hoped-for recovery begins in 2021. The Financial Times (FT) reported on Oct. 22, 2020 that Airbus hopes to see A320 Family production increase 18% in the second half of 2021. “We have asked the supply chain to protect up to rate 47 to be prepared for when the market recovers,” says Airbus in the FT report. “This decision aims to provide some visibility to our supply chain.”
Boeing, conversely, is at a disadvantage on four fronts. First, the 737 MAX, Boeing’s analog to the A320, was grounded in 2019 following two fatal crashes caused by the plane’s automated flight control system. Boeing spent all of 2019 and the vast majority of 2020 correcting the flight control system, testing it, training pilots to use it and earning re-certification from the U.S. Federal Aviation Administration (FAA) and the European Union Aviation Safety Agency (EASA). In the meantime, the pandemic hit, causing many 737 MAX customers to delay or cancel orders.
Boeing’s second challenge lies in the fact that it does not have an aircraft that competes with the Airbus A321XLR. Pre-pandemic, Boeing had on the drawing board a new aircraft dubbed NMA (New Midsize Aircraft), a twin-aisle, 200-270-seat, 4,000-5,000-nautical-mile plane that would fit between the 737 MAX 10 and the 787-8 in the company’s lineup. Such a plane, it was assumed, would have made significant use of composites. Ultimately, however, Boeing could not convince the market that the NMA was needed, plus the company had much of its resources committed to getting the 737 MAX back in the air.
Boeing’s third challenge is the 777X, the successor to the very successful 777. The 777X, a twin-aisle that seats up to 426 passengers and has a range of 7,285 nautical miles
Finally, Boeing’s fourth challenge, relative to Airbus, is its lack of a smaller single-aisle plane akin to the A220. In July 2018, Boeing announced a plan to form a strategic partnership with Brazilian aircraft manufacturer Embraer (São Paulo) that would have produced a smaller single-aisle plane in the 70-100-seat range to compete with the A220. The partnership required that Boeing invest $4.2 billion in an 80% share of Embraer’s commercial aerospace business. In April 2020, however, Boeing dissolved the agreement, claiming that Embraer had failed to meet certain obligations. Embraer disagreed with Boeing’s assertion and claimed that Boeing simply did not want to spend $4.2 billion in the midst of a pandemic. In any case, Boeing lost an opportunity to develop an aircraft type that its portfolio lacks.
Pre-pandemic, the aerocomposites supply chain had been gearing up and organizing itself for one and possibly two new aircraft programs — widely thought to be single-aisle replacements for the A320 and the 737, with in-service dates in around 2030. Such planes would have been manufactured at rates of 60-100 per month and certainly would have consumed significant amounts of composite materials.
The extent of composites use in a new single-aisle aircraft is up for debate, but it almost certainly would include the wings and wing box and tail structures, and likely the fuselage as well. Fabricating such large aerostructures at a rate of at least two shipsets per day would have necessitated migration to out-of-autoclave (OOA) materials and processes, including resin transfer molding (RTM), liquid resin infusion, compression molding and thermoplastic composites. Indeed, the entire composites supply chain, from resin and fibers producers to Tier 1 structures fabricators, had ben investing heavily in materials and processes (M&P) to meet this anticipated demand.
The coronavirus pandemic, however, has not only slowed production of current aircraft, but has pushed development of new aircraft out several years, throwing into disarray some of the M&P the supply chain had put in place. That said, although the need for high-rate, high-volume composites manufacturing may be less urgent, it is not less important, particularly given the long lead times required to qualify new materials and processes. In that light, there were, in 2020, several R&D programs pursuing high-rate, high-quality, OOA aerocomposites manufacturing solutions.
Clean Sky 2 MFFD
Multifunctional Fuselage Demonstrator rendering. Photo Credit: Clean Sky 2
Most of this R&D activity is taking place in Europe, where public funding provides greater visibility into the technologies being developed. The highest profile program in Europe is Clean Sky 2, and within that, one of the most notable subprograms is the Multifunctional Fueselage Demonstrator (MFFD). As detailed in CW’s report, “Moving forward on the Multifunctional Fuselage Demonstrator,” the main deliverable for this project, which is led by Airbus with partners from academia and the aviation industry, is an 8-meter-long, thermoplastic composite, single-aisle commercial aircraft fuselage barrel demonstrator, to be produced by 2022. The MFFD is one of three full-scale fuselage sections being produced within Clean Sky 2’s Large Passenger Aircraft (LPA) Innovative Aircraft Demonstrator Platform (IADP). Begun in 2014, the MFFD project’s goals include: Enable production rates of 60-100 aircraft per month; educe fuselage weight by 1,000 kilograms; reduce recurring costs by 20%. To achieve these goals, dozens of individual projects and work packages are being completed, with two main structures being produced: an upper fuselage shell and a lower fuselage shell, which will be welded together to form the final demonstrator.
The lower fuselage section of the MFFD is being produced through project STUNNING (SmarT mUlti-fuNctionNal and INtegrated thermoplastic fuselaGe) and will comprise the lower fuselage shell with welded stringers and frames, the cabin and cargo floor structure and relevant interior and system elements. STUNNING is led by GKN Fokker (Papendrecht, Netherlands) with key partners Diehl Aviation (Laupheim, Germany), (NLR, Amsterdam, Netherlands) and Delft University of Technology (TU Delft, Delft, Netherlands). The project aims to further mature automated assembly processes, thermoplastic manufacturing and welding technologies, integrated design and manufacturing development and advanced electrical systems architectures.
The consortium producing the 8-meter-long upper shell includes Airbus; Premium Aerotec (Augsburg, Germany), which is the industrial and structural design lead; DLR, in charge of the skin layup and welding technology development; and Aernnova (Vitoria-Gasteiz, Spain), which is producing the stringers. This consortium is developing novel advanced fiber placement (AFP) technology with, notably, in-situ consolidation for the carbon fiber/PAEK skin layup, as well as industrialization of continuous ultrasonic welding and resistance welding for integration of the stringers, frames and other components, improving safety and reducing cost. DLR is first building a 1-meter-long, pre-demonstrator test shell to validate the technologies before the full-scale demonstrator is built, and plans to have the skin for the pre-demonstrator shell fabricated by the end of 2020. Integration of the stringers is scheduled for early 2021. Full-scale versions of both fuselage halves are expected to be completed by the end of 2021. Once completed, they will be welded into the final demonstrator at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM (Stade, Germany).
17-meter tool for Airbus Wing of Tomorrow lower wing skin at Spirit AeroSystems (Europe) in Prestwick, Scotland. Photo Credit: Spirit AeroSystems (Europe)
Wing of Tomorrow
Another high-profile project being led by Airbus is Wing of Tomorrow (WOT), designed to assess the cost and rate viability of OOA processes for the manufacture of wing structures, including wing skins/stringers, spars and ribs. Participating companies and organizations include Spirit AeroSystems (Prestwick, U.K.), GKN Aerospace (Redditch, U.K.), Northrop Grumman (Clearfield, Utah, U.S.) and the National Composites Center (NCC, Bristol, U.K.).
As detailed by CW in “Update: Lower wing skin, Wing of Tomorrow,” Spirit AeroSystems is developing the liquid resin infusion process for fabrication of the lower wing skin for WOT and in 2020 shed some light on progress it has made. Pre-2020, Spirit had already fabricated a 7-meter wing skin demonstrator, and then in summer 2020 took delivery of a 17-meter full-scale tool so that the company can fabricate structures for testing and evaluation.
The 17-meter demonstrator will represent the approximate shape and size of a lower wing skin for what would be, notionally, a new single-aisle commercial aircraft — a replacement for the A320. The maximum chord of the skin measures 3.3 meters, and 1.1 meters wide at the tip. Thickness of the skin laminate measures 5 millimeters near the tip and 30 millimeters at the skin’s interface with the main landing gear fittings. The wing skin will be produced with a suite of technologies developed by Spirit AeroSystems called Intelligent Resin Infusion System (IRIS), comprised of specialized tooling, automated material deposition, integrated stringer forming and closely controlled process temperatures. At the heart of this system is an embedded tool-heating technology located close to the mold surface that uses low-voltage resistive heating located close to the mold surface to provide rapid and precise temperature control. The level of heating is achieved by controlling and moderating the power input. The carbon fiber tool includes an IML heated lid as well as a semi-flexible, reusable vacuum bag.
The dry reinforcements for the wing skin are supplied by Teijin Carbon Europe GmbH (Wuppertal, Germany), derived from that supplier’s line of intermediate modulus, 24k tow carbon fiber. Fiber formats include unidirectional (UD) fabrics as well as biaxial and triaxial noncrimp fabrics (NCF). Glass fiber patches are also included for drill breakout and to protect against galvanic corrosion. The same Teijin NCF reinforcement can be found in the stringers, which will be manufactured via a bespoke continuous stringer forming machine developed by automation specialist Broetje-Automation GmbH (Solvay Composite Materials, Rastede, Germany). The stringer forming machine will be capable of producing stringers with varying thickness, curvature and blade angles. The resin system chosen for the wing skin is a single-component epoxy system from ’ (Alpharetta, Ga., U.S.). Resin, Brown notes, will be delivered to the dry reinforcements via “multiple” injection points, carefully chosen to maximize injection speed and wetout. Injection equipment is being provided by Composite Integration Ltd. (Saltash, U.K.). As noted, the structure will be vacuum bagged with a semi-flexible, reusable bag, overtopped by a massive heated lid.
The use of specialized mold temperature control technology, combined with the one-part resin system, flow media (from Airtech International, Huntington Beach, Calif., U.S.) and a caul sheet are expected to expedite resin take-up and infusion into the dry fibers. Further, resin will infuse the skin first and the stringers last. How long that process will take remains to be seen, but Spirit AeroSystems says
Finished A320 spoiler manufactured via RTM by Spirit AeroSystems (Europe). Photo Credit: CW
More immediately applicable, but also developed with an eye toward future aircraft production, is another M&P effort led by Airbus and Spirit AeroSystems, as reported by CW in “High-rate, automated aerospace RTM line delivers next-gen spoilers,” this one focused on the development of a highly automated resin transfer molding production line for the fabrication of spoilers for A320. Since the A320 was launched, composite spoilers — of which there are five on each wing — have been made by hand. Airbus, looking to increase manufacturing throughput and product quality, worked with Spirit on the drop-in replacement spoilers that Spirit is now manufacturing at its Prestwick facility.
Each spoiler is about 1.8 meters long and 0.7 meter wide. It is about 50 millimeters thick at the leading end and tapers to about 5 millimeters at the trailing edge. Each spoiler also features, in the middle of its leading edge, a 200-by-100-millimeter metallic bracket to which the mechanical actuator attaches — in the case of the A320, a rod end actuator. At the corner of each leading edge are also smaller metallic attachment points.
The Spirit RTM line includes automated cutting and kitting of Teijin and Hexcel (Stamford, Conn., U.S.) carbon fiber fabrics on six Schmidt & Heinzmann (Bruchsal, Germany) cutting tables, preforming on Pinette Emidecau Industries (Chalon Sur Saone, France) preformers, manual loading of preforms into the RTM molds, and then molding with RTM 6 (Hexcel) epoxy resin on one of seven RTM presses, supplied by Coexpair (Namur, Belgium). Next to each press is a resin pump system, also supplied by Coexpair.
At full rate production, this line will produce spoilers at a pace — with quality and consistency — heretofore unseen in aerocomposites manufacturing. At a rate of 65 shipsets per month, which would include Airbus’s new A321XLR, the Spirit line will produce almost 6,500 spoilers a year. At a theoretical rate of 100 shipsets per month, that number jumps to 10,000. Spirit’s A320 spoiler is weight-neutral compared to the legacy product, and costs 30% less, the company says.
The hydrogen-fueled concept aircraft envisioned by Airbus as part of the company’s ZEROe program. Hydrogen would be stored in the aft fuselage section. Photo Credit: Airbus
Hydrogen in the aero-future
The prospect of development of commercial aircraft powered by combusted hydrogen became suddenly urgent in 2020 when, in June, France’s $17 billion pandemic relief program tied to goals from the “Hydrogen-powered aviation” report published by Clean Sky 2. Air France also said it will cut CO2 emissions in half for domestic flights by 2024. Then, in July, Airbus CEO Guillaume Faury, in an interview with Aviation Week, committed to the first decarbonized aircraft EIS by 2035; he forecasts program launch by 2027-28 and maturation of necessary technologies by 2025.
In September, Airbus announced the launch of its ZEROe program, which consists of three aircraft concepts, each powered by hydrogen:
- A turbofan design (120-200 passengers) with a range of 2,000+ nautical miles, capable of operating trans-continentally and powered by a modified gas-turbine engine running on hydrogen, rather than jet fuel, through combustion. The liquid hydrogen will be stored and distributed via tanks located behind the rear pressure bulkhead.
- A turboprop design (up to 100 passengers) using a turboprop engine instead of a turbofan and also powered by hydrogen combustion in modified gas-turbine engines, which would be capable of traveling more than 1,000 nautical miles, making it a perfect option for short-haul trips.
- A “blended-wing body” design (up to 200 passengers) concept in which the wings merge with the main body of the aircraft with a range similar to that of the turbofan concept. The exceptionally wide fuselage opens up multiple options for hydrogen storage and distribution, and for cabin layout.
However, as CW’s Ginger Gardiner reported, hydrogen’s viability as a fuel source — regardless of industry — depends on rapid development of a variety of transport, delivery and storage technologies that are young but fast-evolving. Commercializing these technologies will not be simple, but they are being addressed. In July, ZeroAvia (Hollister, Calif., U.S.) completed test flight of single-engine, six-seat Pipe aircraft modified to use compressed hydrogen (H2) gas and unveiled U.S.-based flight testing for a similarly modified twin-turboprop, 19-seat Dornier Do 228 per its roadmap to certify a 20-seat, H2-powered aircraft with 500-mile range by 2023. Then, in August 2020, Universal Hydrogen (Los Angeles, Calif., U.S.) announced twin tank modules for a 50-seat aircraft, plus refueling logistics and infrastructure for regional airlines/operators to be commercial by 2024.
If hydrogen-powered commercial air travel does come to fruition, it is likely to be implemented first in regional aircraft, like the Dornier referenced above. Next would be single-aisle aircraft like the A220 and the A320. The last aircraft type to be hydrogen-capable would be long-haul widebodies like the A350.
One of the biggest challenges of composites use in hydrogen storage systems will be managing the cryogenic temperature requirements for liquid hydrogen, which Airbus says is its preference for the ZEROe program. Another challenge will be to manage potential changes in hydrogen pressures as aircraft increase and decrease in elevation — and thus increase and decrease ambient pressure — during flight. In any case, significant technical hurdles will have to be cleared to make hydrogen-powered flight a reality by 2035.
As part of the DLR effort to study use of liquid resin infusion to fabricate a pressure bulkhead, a robot picks up and places a large carbon fiber fabric ply in the mold. Photo Credit: German Aerospace Center (DLR) Institute of Structures and Design
Thermoset vs. thermoplastic
Composites typically compete with metals, but in aerospace, composites also compete with themselves. Case in point are thermosets, which are well-qualified in aerospace, and thermoplastics, which, although not new to the industry, don’t enjoy a long history of use in large primary aerostructures. Some recent research attempted to do an apples-to-apples comparison of the two materials and related processes.
As detailed in CW’s report “Automated composites production: Liquid molding or welded thermoplastics?” the German Aerospace Center (DLR) Institute of Structures and Design operating the Center for Lightweight Production Technology (ZLP) in Augsburg, compared a liquid-molded thermoset rear pressure bulkhead (RPB) for the twin-aisle Airbus A350 with a thermoplastic RPB for the single-aisle Airbus A320 respectively. Both projects worked with the Tier 1 supplier of these structures, Premium Aerotec Group (PAG, Augsburg, Germany), and demonstrated automation while evaluating cycle time and cost.
The results of the work were mixed but promising. The thermoset infusion process showed great potential to reduce costs, but would require a level of automation in production that would incur upfront expense to implement. The thermoplastic composite manufacturing process reduced weight from 41 to 35 kilograms, process and assembly time by 75% and overall part cost by more than 10%, but the technology needs further maturation before it’s considered for production.
Wisk’s Cora UAM. Photo Credit: Wisk
Urban air mobility (UAM)
In its infancy but potentially extremely important to the aerocomposites industry is urban air mobility (UAM), which is rapidly emerging as a driver of automation and industrialization in composites fabrication. As CW reported in “Composite aerostructures in the emerging urban air mobility market,” UAM aircraft are small 2-6-passenger rotorcraft or airplanes that are battery powered, capable of vertical takeoff and landing, may be piloted or autonomous, and designed to carry passengers and/or cargo intercity or intercity as an air taxi service.
There are more than 100 companies today working on the development of UAM aircraft for air taxi or cargo transport services, but only a handful have been sufficiently funded to produce flying prototypes or demonstrators. They are: Beta Technologies (South Burlington, Vt., U.S.), EHang (Guangzhou, China), Joby Aviation (Santa Cruz, Calif., U.S.), Lilium (Munich, Germany), Pipistrel (Ajdovščina, Slovenia), Volocopter (Bruchsal, Germany) and Wisk (Mountain View, Calif., U.S.). All of these suppliers are using composites in their craft, but given that each is still in prototyping stage, manufacturing processes are primarily traditional hand layup. That will have to change, however.
One of the leaders of the air taxi service is, predictably, Uber, which has created Uber Elevate, an aerial ridesharing service. Uber Elevate has contracted with several UAM manufacturing partners who will build aircraft for the company. These include Aurora Flight Sciences, Bell, Embraer, Hyundai, Jaunt Air Mobility, Joby Aviation, Overair and Pipistrel Vertical Solutions.
Mischa Pollack, vehicle design and structures lead at Uber, said during a CAMX 2020 presentation that the company anticipates initial certification of its service in a few cities by 2023, followed by expansion in 2026 and then significant scale-up in 2028. By 2035, he said, Uber Elevate expects to have aerial ridesharing services in more than 50 markets with demand for 10,000 UAM aircraft per year. “This number,” he said, “is still closer to commercial aerospace manufacturing rates, but we still need composites manufacturing to evolve.”
What does such evolution look like? Pollack’s full-rate production wish list is basically a roadmap to the industrialization that the composites industry has anticipated for several years: Up to 4,500 metric tons per year of high-modulus/high-strength carbon fiber, increased automation via automated tape and fiber placement, expanded use of compression and pultrusion processes, strategic use of fiber-reinforced additive manufacturing, automated bonding and welding, real-time inline inspection, little or no waste, increased use of low-embodied-energy materials, substantial use of recycled materials and application of sustainable energy, material and process strategies. The composites industry, it appears, has about five years to get all of that done.
Boom Supersonic XB-1 one-third scale demonstrator of the company’s Overture supersonic airplane. Photo Credit: Boom Supersonic
Supersonic commercial travel
There are two companies pursuing development of all-new supersonic passenger jets. One is Boom Supersonic (Denver, Colo., U.S.) and the other is Aerion (Reno, Nev., U.S.). On Oct. 7, Boom Supersonic unveiled XB-1, the one-third-scale demonstrator of its Overture supersonic jet. The composites-intensive XB-1 will demonstrate key technologies for Overture, which the company has its own goals for, including a demonstrator build by 2022, rollout in 2025 and an aim to begin carrying passengers by 2029. During the rollout, it was announced that the XB-1 will complete its ongoing, extensive ground test program before heading to Mojave, Calif., U.S., in 2021 for the flight test. At the same time, the company says it will finalize Overture’s propulsion system and conduct wind tunnel tests to validate aircraft design. Overture is expected to have a maximum speed of Mach 2.2, a cruising altitude of 60,000 feet (19,354 meters) and will take passengers (55-75) from Sydney to Los Angeles in just 7 hours, or Washington D.C. to London in just 3.5 hours.
Aerion is developing the AS2 business jet, which will seat 8-10 passengers and have a supersonic cruising speed of Mach 1.4. It will be able to fly New York to London in 4 hours, and London to Beijing in just more than 7 hours. Aerion announced in late 2019 that GKN Aerospace will develop the empennage for the AS2 and that Safran will design the engine nacelles, braking system and landing gear. In July 2020, Aerion entered into a memorandum agreement to expand the role of Spirit AeroSystems (Wichita, Kan., U.S.) in the development of the AS2 to include production of the forward fuselage. As part of the agreement, Spirit has committed to additional investment in the AS2 program and has increased engineering resources working on the design of the AS2’s composite forward fuselage.
For all of the latest reporting from CW about composites in aerospace, please visit CW’s Aerospace Zone.
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