• 07 Jun 2022 02:30 PM
• 1

Tier 1 Engineering Flies magniX-Powered e-R44 Electric Helicopter for First Time

By Kenneth I. Swartz

The electric helicopter revolution moved a big step closer to reality on June 4 with the first flight of Tier 1 Engineering’s third-generation e-R44 powered by a magniX magni250 "electric engine." [See also Tier 1 press release.]

The three-minute flight took place at Los Alamitos Army Airfield (KSLI), southeast of Los Angeles, California. The aircraft was flown by test pilot Ric Webb and co-pilot Dr. Martine Rothblatt, CEO of United Therapeutics, which is both the primary sponsor and launch customer for the battery-electric retrofit program.

“We are really excited to achieve a flight with a certifiable magniX electric engine. It’s an important step towards obtaining type certification,” said Tier 1 CEO Glen Dromgoole in an exclusive interview with VFS. 

Tier 1 Engineering’s e-R44 battery-electric retrofit was launched in 2016 as a result of Rothblatt’s quest to develop a fleet of zero emissions rotorcraft that could deliver transplant organs to hospitals in the next decade.

At the time, very few people were interested in electric vertical flight and the idea that manufactured organs would one day be available for lifesaving surgeries seemed a distant and unrealistic dream.

Tier 1 Engineering’s first project for Rothblatt was a three-month feasibility study completed in 2015 for electric rotorcraft configured to transport human organs, which became known as the Electrically-Powered Semi-Autonomous Rotorcraft for Organ Delivery (EPSAROD).

That led to the rapid development of a proof-of-concept electric helicopter in 2016. The first hover of the retrofitted 2006 Robinson R44 Raven II (registration N3115T) at Los Alamitos, California, was made on Sept. 13, 2016. The aircraft made its first hover-taxi the following day and a record five-minute flight on Sept. 21 (which drained approximately 20% of the battery energy).

Then on Feb. 16, 2017, Tier 1 Engineering raised the bar when it set out to establish a series of world records for “duration, altitude, payload, weight and speed of battery powered rotorcraft or helicopter flight.” The flight lasted 30 minutes, reached 800 ft (245 m) and at peak speed of 80 kt (148 km/h) with an 8% battery state-of-charge remaining after a normal landing. To claim the world’s first two-pilot electric helicopter flight, the battery capacity was reduced by 18% to allow Rothblatt to fly with Webb.

Since then, Rothblatt has actively participated as an investor and helicopter pilot in the development of the e-R44 and other eVTOL aircraft programs sponsored by United Therapeutics, primarily through its subsidiary, Lung Biotechnology, PBC.

In 2017, Tier 1 Engineering decided to pursue the full-scale development of a battery-electric supplemental type certificate (STC) retrofit program for the Robinson R44 family that would cut operating costs of the world’s most popular four-place helicopter.

Since the first e-R44 used off-the-shelf Yasa motors, Brammo batteries, Rinehart Motion Systems inverters/motor controllers developed by automotive industry suppliers, Tier 1’s main focus the past five years has been developing and flight testing a propulsion and energy storage system that could obtain certification from the US Federal Aviation Administration (FAA).

One of the major challenges was the development of a certifiable motor controller that met the needs of the helicopter in all phases of vertical and cruise flight.

On July 26, 2021, Ric Webb flew the second-generation e-R44 (N484AK) for the first time at Los Alamitos, with the new, lighter 800 lb (363 kg) battery pack providing the same power and endurance as the 1,100 lb (499 kg) battery pack on the original e-R44. Since the first flight, the cockpit instrumentation has also been refined and a new United Therapeutics interior installed with tie downs for an organ care system in place of the rear seats.

In late January 2022, Tier 1 trailered the second-generation e-R44 from Santa Ana, California, to the Hiller Aviation Museum at the San Carlos Airport for the first ever VFS eVTOL static aircraft display on the day following the 9th Annual eVTOL Symposium.

At the time, Dromgoole said he believed that future e-R44 operators would achieve about 20% reduction in operating costs compared to a conventional piston R44 Raven II. That was based on the early 2022 price of 100 octane low lead (100LL) fuel, which now costs a record $7.80 per gallon at some airports in the greater Los Angeles area.

The introduction of new generation turbofan engines like the Pratt & Whitney PW1000G Geared Turbo Fan (GTF) and CFM International LEAP high bypass turbofan have achieved a step change reduction in single aisle commercial jet operating costs, but the helicopter industry has yet to see such breakthrough technology.

The e-R44 program gained fresh momentum in December 2021 when Tier 1 Engineering selected the magniX magni350 electric engine for its fourth-generation e-R44 design targeted for STC certification.

This is the first time the Everett, Washington-based electric propulsion company wholly owned by the Clermont Group of Singapore was selected to provide an electric engine to a VTOL aircraft, with all of its previous applications for fixed-wing aircraft (all-electric Eviation Alice, Harbour Air DHC-2 Beaver seaplane and AeroTEC Cessna 208B Caravan).

In November 2020, the FAA issued its proposed special conditions for the Part 33 certification of the magni250 and magni500 engine models. After a year of public consultations, the special conditions went into effect on October 27, 2021, but have now been updated for the new magni350 and magni650 electric engine models.

Tier 1 Engineering took delivery of a prototype magni250 on Dec. 6 to integrate into its third-generation e-R44. The airframe of the proof of concept e-R44 aircraft, N3115T, is being reused as a platform for the new electric motor.

The initial ground runs of the third-generation e-R44 began behind the Tier 1 offices in Santa Ana on March 31 with Martine Rothblatt and Ric Webb performing system checks to validate the cooling system and engine controls of the magni250 electric engine in e-R44 N3115T.

Dromgoole said Tier 1 conducted more than 50 ground tests before the e-R44 was ready to make its first hover and flight around the traffic pattern. The tests included low and high-power runs with the aircraft anchored firmly to the ground.

Some of the tests simulated various engine fault scenarios and the pilot response. The magni250 engine has two motor segments which are powered by separate inverters. This means that the helicopter can keep flying if one inverter or motor segment fails.

Last year, Tier 1 conducted extensive flight tests using their piston-powered R44 Raven II to determine how much emergency power one motor segment would have to produce for the e-R44 to keep flying if one motor segment or inverter failed, which is one of the company’s design goals.

The tests were conducted with the R44 at a maximum gross weight of 2,500 lb (1,135 kg) at a 4,000-ft (1,200-m) density altitude. Each segment of the magni350 motor will be able to produce 65% of takeoff power to allow the aircraft to keep flying or gradually descent, depending on the density altitude.

The prototype magni250 and production magni350 are about twice the diameter of the Yasa motors, producing more torque at a lower RPM, which is similar to the R44's original Lycoming engine.

This has allowed Tier 1 to simplify the rotor drive system on the third-generation e-R44 by replacing the engine reduction gearbox (required for the 5,600 RPM Yasa motor) as well as the R44’s original vee-belt drive and automatic tensioner with a synchronous belt drive.

The internal configuration of the magni250 and magni350 are very similar, but the external interfaces are slightly different, with Tier 1 expecting to take delivery of a production magni350 engine at the end of the year, for what will be Tier 1's fourth generation e-R44. 

An in-depth look at Tier 1 Engineering and the e-R44 will appear in the July-August issue of VFS Vertiflite magazine, as well as in-depth videos posted to the VFS YouTube Channel.