AFWERX Agility Prime partner Joby Aviation, a California-based company developing an all-electric vertical take-off and landing (eVTOL) aircraft, recently completed developmental testing with NASA to help understand Joby’s vehicle’s performance characteristics and acoustics profiles during normal operations of take-off, landing, and overflight. Since Joby intends their vehicle to be used as an air taxi for commercial use in urban areas, its acoustic signature is key for public acceptance. Critics of eVTOL technology argue that a vertical takeoff method of transportation that can operate in an urban environment already exists: the helicopter. However, helicopters are expensive in fuel and maintenance and have been the subject of noise complaints.
In September 2021, Joby became the first eVTOL company to fly in NASA’s Advanced Air Mobility (AAM) National Campaign, focusing on aircraft operations and acoustic measurements for two weeks of flight testing. NASA engineers deployed their Mobile Acoustics Facility and over 50 pressure ground-plate microphones arranged in a grid to measure Joby’s sound emissions from all directions. On May 10, Joby released a few initial results from that study: the company’s full-scale aircraft measured the equivalent of 45.2 A-weighted decibels (dBA) from a distance of 1,640 feet (500 meters) at 100 knots airspeed, a sound level which Joby is confident will barely be perceptible against the ambient environment of cities.
NASA engineers also measured the aircraft’s acoustic profile during take-off and landing operations representative of planned operations to be below 65 dBA at a distance of 330 feet (100 meters) from the flight path. NASA also released more information about how these measurements were collected and analyzed. Both Joby and NASA will release further details on procedures and measurements in technical papers to be presented at industry conferences this summer.
This testing demonstrates the potential of distributed electric propulsion aircraft – when designed with acoustics in mind – to achieve an acoustic footprint that is orders of magnitude smaller than most rotorcraft aircraft in service today. With six five-blade propellers and high-torque motors, the Joby aircraft is able to achieve the lift necessary for flight with low rotor blade tip speeds, reduced even further in cruise by transitioning to wing-borne flight.
Joby’s history of collaboration with NASA began in 2012, when the entities worked together on various electric flight initiatives such as the Leading Edge Asynchronous Propeller Technology (LEAPTech) project and later on with the design of NASA’s X-57 Maxwell’s motors and cruise motor controllers.
Additionally, Agility Prime and NASA maintain a strong partnership, sharing data between their organizations in order to encourage progress in the AAM sector.
Joby’s goal is to launch an aerial ridesharing service in congested cities around the world through partnering with rideshare services like Uber and constructing landing infrastructures near where people live, work, and want to go. After over ten years of development, Joby is currently conducting flight testing on what the company calls its full-scale pre-production prototype eVTOL, with six electric motors powering propellers placed around the airframe. It is a piloted, four-passenger aircraft that has a maximum range of over 150 miles powered fully by electricity, with a maximum speed of 200 miles per hour, zero operating emissions, and the ability to perform vertical take-off and landing.
Additionally, in December 2020, Joby completed an initial airworthiness assessment and received approval from the Air Force to support and operate their prototype test aircraft during U.S. Government-sponsored flight testing, becoming the first eVTOL company to do so. A year later, in December 2021, Joby received the same approval on their second prototype.
In the past year, Joby reached several milestones on their road to commercial operations. The company’s initial pre-production prototype made its first flight in conjunction with Agility Prime on March 26, 2021. A few months later, on July 14, 2021, the team proved the aircraft’s range with a record 154.6-mile flight. Then, in February 2022, Joby’s eVTOL achieved a new speed milestone, flying the aircraft in excess of 205 knots (235 miles per hour) and more than 11,000 feet above mean sea level – both believed to be records for eVTOL aircraft to date.
As part of the speed and altitude expansion campaign, Joby tested its aircraft’s performance at speeds significantly faster than its intended maximum and subsequently experienced a component failure during remotely piloted testing over uninhabited land. Following a pause on flight testing introduced by Joby’s internal safety review board, the company has since returned to flight testing with its second pre-production prototype aircraft and continues to work with the FAA and the National Transportation Safety Board to investigate the accident.
In parallel with these flight-testing accomplishments, Joby is also working with the Federal Aviation Administration (FAA) to certify its aircraft. Joby entered the implementation phase of the certification process for the first time in February and soon after announced the completion of its first Systems and Compliance Reviews with positive feedback. In May, the company announced its first area-specific certification plan was accepted by the agency.