Wings: Battery-powered full-size helicopter flight accomplished

The battery-powered manned helicopter program put together by Tier 1 Engineering achieved a successful first hover on Tuesday, Sept. 13, a first hover taxi the next day, and a record 5-minute cruise flight to 400 ft altitude with a peak speed of 80 knots on Wednesday, Sept. 21. The helicopter was a modified Robinson R44 test piloted by Captain Ric Webb of OC Helicopters. Tier 1 Engineering is an aircraft design and development company with operations in Costa Mesa, CA, and Victoria, Australia.

All flights were accomplished at the Los Alamitos Army Airfield under a special airworthiness certificate in the experimental category issued by FAA's Los Angeles Manufacturing Inspection District Office (MIDO). Tier 1 Engineering accomplished the project under contract from Lung Biotechnology PBC (part of United Therapeutics) to produce a full-size Electrically Powered, Semi-Autonomous Rotorcraft for Organ Delivery (EPSAROD).

Glen Dromgoole, president of Tier 1 Engineering, called the project an "historic breakthrough in aviation."

"Never before has a conventional manned helicopter performed a vertical takeoff, cruise, and landing solely on battery power, and we are thrilled to have further achieved 400 feet altitude and 80 knots during our first full test flight," Dromgoole said.

The Tier 1 Engineering team designed and integrated all of the helicopter sub-systems, which included 1,100 lb of Brammo Lithium Polymer batteries, twin electric motors, and a control system from Rinehart Motion Systems. The historic 5-minute flight on Sept. 21 drained approximately 20 percent of the battery energy.

Lung Biotechnology PBC intends to apply the EPSAROD technology to distributing manufactured organs for transplantation to major hospitals using much less noise and carbon footprint than current technology.

Q&A: Tier 1 Engineering's battery-powered helicopter flight and EPSAROD program

What were the key specifications of the electric helicopter, such as its weights, power system and controls?
The helicopter had a gross weight of 2,500 lb and a basic empty weight (BEW) of 1,250 lb. A series of 11 Brammo battery modules weighing 1,100 lb completely powered the aircraft. The flight controls and drivetrain were unchanged from that of a Robinson R44, although a digital cockpit display was added for pilot management of torque and power, as well as for data logging.

What is the range of the electric helicopter?
The range of the proof-of-concept helicopter tested on Sept 21 is estimated at 20 minutes or approximately 30 nautical miles. We expect to improve the endurance using higher-energy-density batteries, a more efficient electrical drive system, and ultimately a more aerodynamic airframe.

What about the test pilot who flew the historic flight?
Ric Webb is a commercial helicopter pilot at OC Helicopters. He has 25+ years military service as a member of the Air Force, Navy, Army, and Coast Guard.

Who led the design, build, and installation effort?
Glen Dromgoole, President of Tier 1 Engineering.

What is the purpose of the electric helicopter and EPSAROD program?
The purpose is to demonstrate the feasibility of electric propulsion for this use case; identify key areas requiring further development; obtain performance data on battery, rotor, and motor system; and validate our performance predictions. It is the first phase in the development of the EPSAROD. Semi-autonomous avionics, navigation, and controls will be implemented later in the EPSAROD development program. The ultimate goal of the EPSAROD Program is to produce electric-powered semi-autonomous aircraft that are capable of distributing manufactured organs to hospitals for transplantation.

How many passengers can it carry?
The mission specification for the EPSAROD aircraft is to carry two people and three manufactured organs with a total payload weight of 600 lb for not less than 150 minutes, including a 30-minute reserve.

When and where do you expect the next test flight to be?
Tier 1 Engineering has an ongoing EPSAROD test program that will extend at least through 2017, during which time a more advanced prototype aircraft will be designed and built.

Was this project in partnership with Robinson Helicopters, or any other companies?
There was no involvement with Robinson Helicopters. We simply purchased a used R44. Design and development partners in the project include Rinehart Motion Systems and Brammo Power. Test pilot services were provided by OC Helicopters. Lung Biotechnology PBC sponsored the project.

Is the U.S. government or military involved in the program?
There is no U.S. government or military involvement in the program other than the permission for conducting test flights at JTB Los Alamitos.

What was the size of the design-and-build team?
Nine people.

How long did it take to design, build, and install the electric propulsion system?
Six months. The design effort started in January 2016. The installation was completed in July 2016.

What was the biggest challenge?
Finding a design solution within the certified takeoff weight of 2,500 lb.

What modifications were made to the helicopter?
We removed the Lycoming IO-540 internal combustion engine, installed a custom mount for the electric motors, and a reduction gearbox to interface with the existing drivetrain. No changes were made to the drivetrain or flight control system. The engine bay contains the motor controllers and cooling system for the electric drive components. The battery modules are supported by a lightweight composite panel and attached to the landing gear under the belly.

What about the electric motors?
There are two three-phase permanent magnet synchronous motors. The motors are stacked together and provide redundancy in the event of a motor failure. The motor assembly, which has a very high power-to-weight ratio, was installed by one person by hand.

Who manufactures the motor controllers?
Rinehart Motion Systems

What type of battery system is used?
Lithium polymer battery by Brammo, 700 volt, 100 amp-hour.

Why was a Robinson R44 helicopter chosen?
The R44 helicopter has a heavy, 500-lb Lycoming piston engine. The retrofit with electric motors, weighing in at 100 lb, provided a useful load size for batteries.