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Tier 1 Engineering e-R44 2nd Generation

Tier 1 Engineering e-R44 2nd Generation electric helicopter flying, Tier 1 Engineering photo credit


e-R44 2nd Generation
Tier 1 Engineering
Santa Ana, California, USA

Founded in 2009 by Glen Dromgoole, Tier 1 Engineering is a provider of engineering and manufacturing services, specializing in the development of lightweight structures. The company offers engineering design, analysis, fabrication, material cutting, testing documentation, research and development and more, to the aerospace, energy, marine, medical and the consumer product sectors.

Dromgoole has been focused on the fastest and easiest path to certify an electric rotorcraft after concluding that the work and cost involved in certifying a clean sheet aircraft design would scale significantly if electric propulsion was added to the task list. Instead, Tier 1 Engineering is developing an electric propulsion system that can be easily installed in a proven airframe like the Robinson R44 Raven II by way of a Federal Aviation Administration (FAA) approved supplementary type certificate (STC). Aviation innovators have long used STCs to upgrade existing aircraft with new powerplants to enhance payload, speed, reliability and safety.

In 2018, the company decided to focus on in-house development of the battery pack, electric motor, motor controller and pilot interface, which are the key components of the electric-propulsion system.

The e-R44 2nd Generation is a one person/pilot electric experimental helicopter using a modified Robinson Helicopter R44 Raven II for the airframe. The e-R44 2nd Generation helicopter has one main rotorblade, one tail rotor, two electric motors, battery packs, control systems and has fixed skid landing gear.

This 2nd Generation model notably features a battery pack that was lighter than the previous design by 300 lb (135 kg) and performed with the same level of power and endurance as the e-R44 1st Generation electric helicopter. The weight reduction was achieved by using higher energy density battery cells, improving the battery pack design, and designing a new lightweight and streamlined structure to support the battery packs.

Despite delays caused by COVID-19 restrictions, Tier 1 Engineering flew its e-R44 2nd Generation electric helicopter (N484AK) for the first time at Los Alamitos (California, USA) on July 26, 2021. 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.

A new electric motor was also developed with a partner for the 2nd Generation helicopter but it did not perform as expected. To solve this problem, Tier 1 Engineering decided to work with a new supplier and announced on Dec. 7, 2021 that it had selected magniX’s electric-propulsion units. The e-R44 3rd Generation electric helicopter was flown using the magniX electric motors in June 2022.

Tier 1 Engineering e-R44 2nd Generation electric helicopter in a hangar, Tier 1 Engineering photo credit

Tier 1 Engineering e-R44 2nd Generation electric helicopter in a hangar, Tier 1 Engineering photo credit


  • Aircraft type: Electric helicopter demonstrator
  • Piloting: 1 pilot
  • Cruise speed: Unknown
  • Range: Unknown
  • Estimated flight time: Unknown
  • Cruise altitude: Unknown
  • Rotorblades: 1 main rotor blade, 1 tail rotor
  • Electric Motors: 2 electric motors
  • Power source: Lithium polymer batteries, 800 lb (360 kg)
  • Fuselage: Welded steel tubing and riveted aluminum sheet
  • Windows: Panoramic helicopter windows in the cockpit
  • Landing gear: Fixed skid helicopter landing gear
  • Safety features: The helicopter can autorotate in case of power failure

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