• 11 Jan 2023 10:08 AM
• 0

Archer’s Midnight Showing

By Mike Hirschberg
Vertiflite, Jan/Feb 2023

Santa Clara, California-based Archer Aviation unveiled a full-scale mockup of its five-seat Midnight electric vertical takeoff and landing (eVTOL) aircraft during an open house event in Palo Alto, California, on Nov. 16. Midnight is the evolution of Archer’s demonstrator eVTOL aircraft, Maker, which has been flying to validate its distributed electric propulsion approach and key enabling technologies.

Archer is designing Midnight to be safe, sustainable and quiet, with a payload of over 1,000 lb (450 kg): a pilot plus four passengers and their luggage. It is being optimized for back-to-back, short-distance trips of around 20 miles (32 km), with a charging time of approximately 10 minutes in between. Archer is working with the US Federal Aviation Administration (FAA) to certify Midnight in late 2024 to use in its urban air mobility (UAM) network, which it hopes to launch in 2025.

“From day one Archer’s strategy has always been about finding the most efficient path to commercializing eVTOL aircraft,” said Adam Goldstein, Archer’s Founder and CEO, in a press release. “We believe our strategy and team’s ability to execute on it has allowed us to establish our leadership position in the market and is why we are confident we will be the first company to certify an eVTOL aircraft in the US with the FAA.”

Archer said that its unique approach to designing Midnight focuses on “combining high function and high emotion, inspiring passengers to want to experience it, similar to the feeling that was evoked in this country during the Golden Age of aviation in the 1950s. Archer is confident that Midnight will lead the way in this new era of vertical flight.” Midnight’s approach marries cutting-edge distributed electric propulsion technology with state-of-the-art aircraft systems to deliver the key attributes of its eVTOL aircraft, as described by Archer:

• Safety: High redundancy and simplified propulsion systems with no critical single points of failure, meaning that should any single component fail, the aircraft can still safely complete its flight. In addition, electric motors have significantly fewer moving parts than those in a turbine or piston engine, allowing it to operate with less maintenance and lower overall risk.

• Low noise: Designed to cruise at approximately 2,000 ft (610 m), the noise that reaches the ground is expected to measure around 45 A-weighted decibels (dBA), almost 1,000 times quieter than a helicopter. During forward flight, the aircraft’s tilt propellers spin on axes that are aligned with the oncoming air flow, rather than edgewise like a helicopter’s, and at significantly lower tip speeds, resulting in much lower noise levels.

• Sustainable: Midnight is all electric, resulting in zero operating emissions. Archer is also utilizing sustainable materials. For example, Midnight uses seats constructed of “flax” fiber, a natural plant that requires little irrigation and is highly absorbent of CO2, and uses fabric made from recycled contents like plastic bottles.

Working Towards Midnight

The company announced in July that it had partnered with FACC in Austria to build elements of the fuselage and wing, and that Honeywell will provide the flight control actuation and thermal management technologies (see “eVTOL Leaders Continue Momentum,” Vertiflite, Sept/Oct 2022).

This is in addition to previous announcements of working with major industrial partners. Stellantis — the multinational automotive manufacturing corporation formed in 2021 through the merger of the Italian-American Fiat Chrysler Automobiles and the French PSA Group (formerly PSA Peugeot Citroën) — has provided engineering, supply chain and manufacturing expertise. Specifically, Stellantis advised on batteries; noise, vibration and harshness (NVH); and manufacturing.

Archer is also working with Hexcel, a leading supplier and manufacturer of carbon fiber and other advanced composite materials. Archer said that Hexcel is an ideal composites partner, supplying lightweight carbon fiber and highly toughened resin systems that provide both strength and durability while reducing overall aircraft weight and enhancing aircraft safety. Hexcel composite materials also exhibit repeatable manufacturing and performance.

On Aug. 10, Archer first announced the Midnight name with only a teaser image. The announcement followed the successful completion of the aircraft’s preliminary design review (PDR). The PDR was a meticulous review of the aircraft design to ensure the program is on track and the design is mature enough to proceed to the next development phase and begin production of long-lead-time hardware. The PDR covered all aspects of the aircraft’s specifications and manufacturing requirements, necessary preconditions to determine that the design is feasible for regulatory compliance and viable to bring to market.

The company has also been busy with additional partnerships and alliances to operate the aircraft once certificated.

Archer announced in August that it had received a $10M predelivery payment from United Airlines for 100 eVTOL aircraft. This was the deposit on Archer’s production aircraft that it had agreed to purchase in 2021.

United also formed a Joint eVTOL Advisory Committee with Archer, allowing the two companies to work more closely on eVTOL maintenance and operational matters. Committee members include Archer’s operations and maintenance leadership, as well as leadership from United’s maintenance, materials and engineering groups.

On Nov. 10, Archer and United Airlines announced what could be the first commercial electric air taxi route in the US — between the Downtown Manhattan Heliport and Newark Liberty International Airport (EWR). Archer estimates the journey will take less than 10 minutes by Midnight versus an hour or more by car during rush hour traffic.

Archer’s early launch routes will provide airport-to-city-center transportation service. Once these primary trunk routes have been established in 2025, Archer will begin building out branch routes to connect to surrounding communities.

The week of the Midnight unveiling, Nov. 14–17, Archer had four press releases related to its production plans.

First, the company announced plans to locate its manufacturing facility in Covington, Georgia, at a site adjacent to the Covington Municipal Airport. Archer plans to initially build out a 350,000-ft² (3,250-m²) facility on a 96-acre (39-hectare) site capable of producing up to 650 aircraft per year. The facility is eventually expected to create more than 1,000 jobs. Construction should be completed in the first half of 2024 with initial production beginning in the second half of the year. The facility will be capable of being expanded by an additional 550,000 ft² (51,100 m²), which would support production of up to 2,300 aircraft per year. Archer’s goal is to field 6,000 aircraft by 2030.

Key factors in choosing Covington Airport, 30 miles (50 km) southwest of Atlanta, included the availability of talent in the local labor market, utility availability, ability to conduct seamless flight test operations, construction costs, and logistics. Archer will receive an incentive package, which includes land conveyance, tax incentives and a Georgia Regional Economic Business Assistance (REBA) grant.

Archer also announced that it had entered into an agreement for Garmin to supply the G3000 integrated flight deck for Midnight. Archer noted that the Garmin G3000’s compact and lightweight system offers both an extensive certification pedigree and the configurability needed for Archer to bring its aircraft to market. The large-format displays and intuitive controls will provide pilots with the situational awareness needed to operate Midnight. The widespread use of Garmin avionics will also make the Midnight aircraft cockpit more familiar to many pilots.

Part of Archer’s commercialization strategy is to focus its inhouse development on only the key enabling technologies that cannot be sourced from the existing aerospace supply base. The Garmin relationship is a good example of Archer’s approach of establishing strategic relationships for the supply of components that are already being used on certified aircraft today, reducing Archer’s certification risk, as well as its development timelines and costs. Archer announced that, as of that time, it had selected more than 64% of the suppliers for Midnight’s bill-of-materials.

Finally, prior to the unveiling itself, Archer announced that it had selected E-One Moli Energy Corp. (Molicel), an industry-leading supplier of lithium-ion battery cells founded in 1998, to manufacture and supply the battery cells for Midnight.

Archer noted that the Taipei, Taiwan-based Molicel’s advanced battery technology and fast-growing production capacity made them an ideal partner. In 2021, Molicel announced plans to establish its first Gigafactory in Taiwan, which is scheduled to ramp up production in 2023. The facility will have the capacity to produce 1.8 gigawatt-hours (GWh) of battery capacity annually. Molicel’s high-performance cells also offer a significant cycle life when utilized in Archer’s battery pack and, as a result, reduce the long-term operating cost for its Midnight production aircraft.

Making Progress with Maker

Archer’s Maker demonstrator — sized for two-passengers but only flown uncrewed — made its first flight on Dec. 16, 2021 (see “Archer Hits Its Target,” Vertiflite, Jan/Feb 2022). The technology demonstrator has proven Archer’s approach for Midnight.

When unveiled, Maker was said to be a roughly 80%-scale demonstrator. “The fuselage cross-section probably won’t inflate when we go to a five-seater, but it’ll stretch and the wing and rotors will roughly scale,” Archer Chief Engineer Dr. Geoff Bower had told Vertiflite previously (see “Archer Advances eVTOL Commercialization,” Vertiflite, March/April 2021) — although the design for Maker may have grown larger than was planned at that time.

The basic configuration of the 3,325-lb (1,508-kg) Maker is identical to Midnight, with six propellers for lift only and six for lift and cruise. This is a classic “L+L/C” configuration (see “Coming to Terms,” Vertiflite, Jan/Feb 2023), which Archer refers to as its “proprietary 12-tilt-6 propeller configuration.”

The aircraft had been flown regularly, often daily, as it gradually expanded the flight envelope by incrementally increasing the airspeed in 10-kt (15.8-km/h) increments. Later, Archer gradually increased the propeller tilt angle, with the full wingborne flight announced on Nov. 10.

On Nov. 29, 2022, Archer completed Maker’s first full transition flight, with a 90° conversion to fully horizontal. “The aircraft took off vertically and climbed to an altitude of about 240 ft [73 m],” Bower wrote in a Dec. 1 blog post. Maker incrementally inclined the thrust angle of its tilt propellers to generate forward thrust and aerodynamic lift over the wings. “It then accelerated to an airspeed of 91 kt [169 km/h] while maintaining altitude, flew around a pattern, decelerated back to a hover, and completed a vertical landing.” He also noted “excellent correlation between our flight test data and analysis tools.”

According to Bower’s blog post, Maker demonstrated a nearly 65% reduction in power required from hover to this demonstrated cruise speed, showing the advantage of a winged eVTOL. “Flying the majority of a trip in wingborne flight is critical to maximizing aircraft efficiency; in other words, carrying a payload at a high speed for a useful range.”

Guests took a 75-minute bus trip to Salinas Municipal Airport (SNS) — 60 miles (100 km) southwest of Palo Alto — on the morning before or after the open house and were treated to a Maker flight test lasting nearly 10 minutes.

CEO Adam Goldstein gave an early history of the company from its founding in 2018, and its progress to date. This was followed by talks by Archer COO Tom Muniz and Chief Engineer Geoff Bower, and explanations during the flight demo. A Bell 206B (Sierra Bravo Aviation) was used as a chase aircraft for safety and the video feed for the audience; Maker could generally not be heard over the noise of the Jet Ranger. A “jumbotron” display screen showed the audience the video feed, a birds-eye map of the flight path, basic flight data, and the propeller tilt angles. The flights hit speeds up to 70 kt (130 km/h), propeller angles down to 25–30° above horizontal, and an altitude up to nearly 500 ft (150 m).

Although the audience was not able to get close to the test aircraft (N301AX), the back-up demonstrator, “Maker 2” (unregistered) was displayed at the open house for close examination.

Open House Presentations

Archer hosted around 150 guests at its open house in Paolo Alto, California, on the afternoon of Nov. 16, plus visits to see Maker fly on the morning of Nov. 16 and 17 (as mentioned above). Guests included more than 40 current and potential partners and vendors, journalists, government representatives and analysists.

The Midnight unveiling was held in a hangar at the Palo Alto Airport (PAO). The open house event itself was held at Archer’s facilities across the street from the airport. Archer has posted a two-hour video of presentations and the unveiling on its YouTube channel.

In addition to talks by CEO Goldstein, there were in-depth presentations on the company’s approach and team competencies regarding powertrain, certification and commercialization.

Archer’s Dr. Michael Schwekutsch, Senior Vice President Engineering for Propulsion/High Voltage/Battery Systems, highlighted the breadth and depth of Archer’s electric propulsion team. Nearly 100 employees at Archer are working on the powertrain (about 20% of the total employees) with more than 70 of them in engineering. Schwekutsch himself was previously the Senior Director of Engineering at Apple Special Projects Group and VP of Engineering at Tesla. The 16 members of the leadership team, with more than 200 years of combined powertrain engineering experience, has worked on electric vehicles at places like Bosch, General Motors, Joby, Kittyhawk, Lucid, NASA, Tesla, Wisk and Zee Aero.

Alex Clarabut, Archer’s Director of Battery Design, highlighted the propulsion systems electrical architecture, which it has been designed for low weight and to support the necessary aircraft performance capabilities at low states of charge.

The high-voltage power system features six independent battery packs of Molicel 2170 power cells, with each pack supporting a diametrically opposed pair of >800-Volt electric motors, using “intelligent battery paralleling.” Each battery pack is expected to last for more than 10,000 average flights of 20 miles (32 km), after which it can find a “second life” in a ground-based energy storage system.

The company sees its approach as having power requirements 20% lower when compared to a standard architecture, but has designed it to be fault tolerant to potential powertrain failures. Archer has already conducted thousands of hours of tests on the Molicel cells. It says it has been collaborating with the FAA on the design standards, which meets RTCA DO-311 (“Minimum Operational Performance Standards for Rechargeable Lithium Batteries and Battery Systems”). The company has developed a proprietary thermal runaway strategy with “robust propagation prevention.” Archer has leveraged Stellantis’s “automotive style” manufacturing input and designed the packs for high-volume manufacture “from day one.”

Alan Tepe, Archer’s Inverter Design Lead, explained the challenges of the electric propulsion system architecture. Archer has designed two “electric engines” — one for the six tilting propellers (each with five blades) for hover and cruise, and a variant for the six non-tilting propellers for VTOL-only flight (each with two, high-twist blades). Archer has been able to maintain design commonality between the two motors. About 95% of the parts are the same between the “tilter” and “lifter” motors. Only the housings and output shafts are different, which is important for economies of scale in production. The motors are dual-wound motors with dual inverters, so if one side fails, the other side can still produce the required torque.

Tepe compared the Archer electric engine to the Lycoming IO-360-L2A engine producing 181 shp (135 kW) used on the Cessna 172, which uses leaded Avgas. Archer’s motor produces 168 shp (125 kW) but at only 55 lb (25 kg), it is five times lighter, has only seven moving parts (compared to about 160 for the piston engine), wastes about 50 times less energy, has four times lower energy costs to operate and produces no emissions.

Archer designed a gearbox that allowed the motor to spin six times faster (at 12,000 rpm). Overall, the motor ended up about 50% smaller and lighter than a direct drive; this increased Midnight’s overall payload by more than 100 lb (220 kg). Tepe noted that the Archer engine has a power density of 5 kW/kg, compared to 2.3 kW/kg for a Tesla Model 3 drive unit and 3.2 kW/kg for an electric conventional takeoff and landing (eCTOL) aircraft motor — a 45% reduction in engine mass.

Archer Chief Operating Officer (COO) Tom Muniz explained the planned timeline to certification of the company’s Midnight concept. By the end of 2022, Archer expected to have its airworthiness criteria from its updated certification basis (which was published in the Federal Register on Dec. 19), with its means of compliance accepted by the FAA. The agency’s change to using FAR 21.17(b) for airworthiness certification in May (see “FAA Changes Course on eVTOL Certification,” Vertiflite, July/Aug 2022) reset the approvals for the leading eVTOL companies, leading to these administrative delays from the FAA. By the second half of 2023, Archer expected that its subject-specific certification plans would be accepted by the FAA. It will build its certification-conforming Midnight in 2023 and perform test and analysis for certification credit in 2023–2024. As mentioned above, the company expects to achieve its type certification by the end of 2024.

Midnight Reveal

After ample time for networking and inspecting Maker 2, attendees were invited to cross the street to the hangar at Palo Alto Airport. After Goldstein explained his vision, Archer VP of Design & Innovation, Julien Montousse, discussed the Midnight design approach. “We knew at Archer we had to strive for mathematical excellence,” said Montousse. “But at the same time, we’re creating a new way of living, and it has to inspire people. So, we developed a unique design expression to make air travel feel more personal,” with cabin features that welcome passengers and make them feel comfortable. Midnight has a partial divider between the seats that will display “your personal trip information such that when you’re approaching the aircraft you can see your name assigned to your seat but also your destination and your time to take off.”

In addition, the cabin was designed to be entered hands-free. “We designed a unique landing gear that will enable the aircraft to sit lower to the ground, similar to the height of midsize SUV. So, with Midnight, you can easily get in with a small bag, a phone and a cup of coffee in your hand.”

Although transparencies weigh more than carbon fiber, the aircraft was made powerful enough for more glass. Archer prioritized panoramic windows, so that at 2,000 ft (600 m) in the air, “you’re fully engaged with the city below.”

The nose of the aircraft features a line of light descending down towards the nose wheel, which Montousse said was “Archer’s first brand DNA signature so that everyone would identify our aircraft from a distance.” In addition, the designer “made the aircraft look confident. This is a breakthrough architecture in a brand new space, so confidence is key to establish trust with our customer.” The production design is believed to be at or near a maximum takeoff weight of 7,000 lb (3,175 kg).

The audience was then invited to explore the Midnight mockup up close, inside and out.

From Midnight to the Dawn of a New Era

The most challenging tasks for Archer lie ahead.

Over the next 24 months, Archer plans to complete the detailed design and build of its Midnight prototype and one or more conforming aircraft, fly them, expand the flight envelope, and then iterate and improve the design as necessary. Archer must prove that its design is robust, reliable and safe beyond a doubt. Midnight must finalize the certification plans, gain acceptance from the FAA, demonstrate its compliance with the requirements, and prove to the regulator its airworthiness and production repeatability. In addition, Archer has to deliver a Midnight that meets its promised performance and cost targets for its customers to operate the aircraft, and for their customers — the public — to find cost-effective utility from their services.

Archer’s unveiling of the Midnight design was ahead of its scheduled 2023 timeframe. Like many other milestones to date, Archer has exceeded expectations and its own publicly stated timelines. In just four years since its founding, the company has leapfrogged to the front of the pack with its certification plans.

Archer has set an extremely aggressive schedule. Time will tell the actual certification date, but with a world-class team of nearly 500 engineers and aviation professionals, a healthy bank account and a proven track record, Archer is poised to usher in a new age of electric aviation.