Tier 1 Engineering, in collaboration with Lung Biotechnology PBC, successfully finished the first fully-electric cross-country helicopter flight along the scenic Coachella Valley of California on October 29, 2022, as per Vertical.
The third-generation battery-electric e-R44 conversion of the famous Robinson R44 helicopter was piloted by Ric Webb, CEO of part 135 charter operator OC Helicopters, and CEO of United Therapeutics, Dr Martine Rothblatt. The aircraft was outfitted with a 50 lbs (23 kg) payload to simulate a transplant organ care system in the rear cabin.
The helicopter took flight from Jacqueline Cochran Airport (KTRM) and landed at Palm Springs International Airport (KPSP) at 11:11 AM, covering the FAA-approved 24-mile (39 km) route in 20 minutes flight time.
The e-R44 was welcomed by many guests invited to Palm Springs Airport by Tier 1 Engineering and the project sponsor, United Therapeutics, to witness the historic event.
“This was the first ever electric helicopter flight between two cities and between two airports,” said Rothblatt, adding that it showed “it is practical to deliver transplantable organs by electric helicopters from hospital to hospital.”
President of Tier 1 Engineering, Glen Dromgoole, said the e-R44 could fly 20-minute trips “with a good reserve,” stating the battery cells had a 50% state of charge (SOC) on landing.
“We believe we’re developing a really practical solution for short duration rotorcraft flights such as organ deliveries, pilot training, scenic tours and other inner-city trips,” said Dromgoole.
In addition, Dromgoole noted that significant achievements in aviation often begin with flying short distances, like the first non-stop airplane flight across the English Channel in 1909 and the first commercial helicopter flight in 1947, covering a similar flying distance to this flight with the e-R44.
First generation e-R44
An accomplished fixed-wing and helicopter pilot, Rothblatt began looking into the feasibility of electric vertical flight around six years ago and shared the specifications of zero-emissions electric rotorcraft with some aerospace companies to set out a research project.
Dromgoole was the first to respond positively to Rothblatt’s line of inquiry. Tier 1 Engineering got a contract in early 2016 to produce and fly a proof-of-concept electric helicopter quickly.
UT subsidiary Lung Biotechnology bought a 2006 model R44 Raven II (registration N3115T) for around $300,000. Dromgoole’s team took off the aircraft’s bulky 260-hp Lycoming IO-540-AE1A5, weighing about 500 lb (225 kg), including accessories and a complete fuel system.
Then, the engine and fuel system were replaced with an electric propulsion system mainly sourced from the automotive industry, including two early YASA P400HC electric motors (stacked in parallel and powered by separate inverters), inverter/motor controllers made by Formula 1 hybrid-electric supplier Rinehart Motion Systems, lithium polymer batteries made for the Brammo electric motorcycle, and a reduction gearbox made by Autoflight.
The YASA motor was sufficiently light to install by hand. It could achieve the rated power necessary for the R44, producing 183 kW (245 hp) peak shaft power for five minutes and 153 kW (205 hp) continuous shaft power.
Webb made the first successful hover of the first-generation e-R44 at Los Alamitos Army Airfield (KSLI) on September 13, 2016, its first hover-taxi the next day, and a record five-minute cruise flight on September 21, which drained an estimated 20% of the battery energy.
On February 16, 2017, Tier 1 Engineering produced a series of world records for “altitude, duration, weight, payload and speed of battery-powered rotorcraft or helicopter flight” at Los Alamitos Army Airfield, six miles (9.6 km) east of Long Beach Airport.
The flight lasted 30 minutes and reached 800 feet (244 meters) and 80 knots (148 km/h) peak speed, with an 8% battery SOC remaining after a safe hover landing.
To claim the world’s first two-pilot electric helicopter flight, the battery capacity was reduced by 18% to let Rothblatt fly with Webb.
On December 7, 2018, Tier 1 Engineering set a Guinness World Record when Webb flew the farthest distance of an electric helicopter, covering 30.7 nautical miles (56.87 km) at an 80 knots (148 km/h) average speed over a circular course wholly within the confines of the Los Alamitos military base.
Aircraft optimization
After the record flights, Tier 1 rolled out to optimize the e-R44 design and replace the automotive systems with hardware that could be aviation certified.
By early 2020, the first improvement was cutting the battery pack’s weight from 1,100 lb (500 kg) to 800 lb (365 kg). This was achieved by utilizing higher energy-density cells and a streamlined structure to back them. It meant the e-R44 could fly with an organ transfer system, a pilot, and a co-pilot.
Furthermore, when the second electric motor and invertor didn’t perform as anticipated during ground tests, Tier 1 moved the YASA motor and Rinehart Motion Systems inverters to the second-generation e-R44.
The second iteration of the design included four independent onboard liquid cooling systems in the engine bay for the motors (packaged as a single unit), battery packs, inverters, and a reduction gearbox.
In the cockpit, the twist grip throttle on the collective was taken off, and rotor RPM is now wholly controlled by the electric motor controller.
“There is no need for pilot input into the throttle,” says Dromgoole in an earlier interview during the Vertical Flight Society’s 9th Annual eVTOL Symposium in San Jose in January this year.
The toggle switch on the end of the right seat collective used to switch the RPM governor on and off is now used to choose 100% RPM for normal operations or 90% RPM to let autorotation training. That allows the pilot during a practice autorotation to adjust the rotor speed using the cyclic and collective, and “if the rotor RPM was to drop to 90% or less, the motor will automatically pick up and apply torque, which is an added safety feature,” explained Dromgoole.
New magniX electric motor
In December last year, the e-R44 program acquired renewed momentum when Tier 1 Engineering picked the magniX magni250 electric motor.
“magniX was chosen as they are leading the industry in the development of aviation-specific electric propulsion, and we recognized that significant progress had been made towards obtaining FAA certification,” stated Dromgoole when the motor deal was announced.
“With magniX’s technology, we are now much closer to obtaining a supplemental type certificate [STC] approval of the e-R44 and transforming the delivery of life-saving human organs,”
Tier 1 took delivery of a prototype magni250 on December 6, 2021, to blend into its third-gen e-R44, which will be its FAA STC application’s basis. The airframe of the proof-of-concept e-R44 aircraft, N3115T, is reused as the new electric motor’s platform.
The Magni250 is twice the YASA motor’s diameter. However, it matches the original Lycoming IO-540-AEA5 engine’s speed and torque better.
This aided in simplifying the rotor drive system on the third-gen e-R44 by replacing the engine reduction gearbox (necessary for the 5,600 RPM YASA motor) and the R44’s original vee-belt drive and automatic tensioner with a synchronous belt drive. The changes simplified the pilot workload and resulted in extra weight savings.
The initial ground runs of the third-gen e-R44 began on March 31, 2022, with Rothblatt and Webb performing system checks to verify the cooling system and engine controls of the magni250. This was followed by the first flight at Los Alamitos on June 4, lasting three minutes, with Rothblatt Webb again at the controls.
Cross country flight
Tier 1 Engineering has been planning a cross-country e-R44 flight for some years, but the ground and air testing of the new propulsion system must mature before the FAA grants the required flight permit.
Since the first flight, the helicopter had finished 16 test flights totalling an estimated three hours and extensive testing at full power with the e-R44 anchored to the ground through the summer.
It was brought by trailer to Thermal Airport the week before the flight, alongside a ground charging unit.
On the morning of the record-setting flight, Rothblatt and Webb flew the approved route in a piston-engine Robinson R44 owned by Lung Biotechnology shortly before they took flight in the e-R44.
Webb said one of the novelties of the flight was that the e-R44 electric engine doesn’t emit a lot of heat in flight or on landing.
However, there are still gaps in the FAA regulations regarding addressing electric aircraft, even if it is an STC conversion rather than a clean sheet design.
One challenge for any electric aircraft developer will be to present the “means of compliance” with the new regulations to validate the electric propulsion systems.
That is why Tier 1 actively participates in industry committees interpreting airworthiness standards and explicitly developing consensus standards for electric propulsion systems.
Meanwhile, the e-R44 offers a zero-emissions means of performing traditional helicopter flights. Dromgoole believes that the business case for the aircraft will also include around a 20% noise reduction (from the engine) and a 20% operating cost reduction in contrast to a piston R44, as a result of lower energy costs and maintenance savings.
The exact cost saving will only be known once the battery cell’s cost and replacement life are known, which steadily changes over time.
Additionally, Tier 1 also sees a market opportunity for the e-R44 in places where aviation gasoline is unavailable or very expensive. This includes Catalina Island Airport, 34 miles (54 km) offshore from Los Alamitos Army Airfield.
The company believes that the best time to convert an R44 to electric propulsion is during the helicopter’s factory-mandated 2,200-hour or 12-year overhaul, which usually costs more than $230,000 and includes an engine exchange.
e-R44 conversion line in the Santa Ana facility
Notably, it plans to open an e-R44 conversion line at its Santa Ana facility to fill orders from Lung Biotechnology and Webb’s OC Helicopters, the first charter helicopter operator to set an order for the e-R44.
As Dromgoole left Palm Springs Airport after a momentous day, he paid tribute to Tier 1’s small team of multitalented staff.
“I’m really proud of the team today. They’ve done a lot of work. It’s taken a lot of time to get to this point.”
