The Future of Advanced Air Mobility

Ampaire's Hybrid-Electric Eco Caravan Makes First Test Flight

The Eco Caravan made its first flight on Friday, marking a key waypoint in Ampaire’s efforts to bring the converted hybrid-electric aircraft to market. The 33-minute sortie from the Los Angeles-area Camarillo Airport marks the start of a flight-test program that the California-based startup aims to lead to an FAA supplemental type certificate for its modification kit in 2024.

With test pilot Elliot Seguin at the helm, the aircraft took off at 7:49 a.m. PST and climbed to an altitude of 3,500 feet at full power. The pilot then throttled the aircraft to a cruise setting, reducing the load on both the combustion engine and the electric engine, after which he spent about 20 minutes testing the aircraft’s various power settings and observing temperatures and other sensor readings before descending back toward the airport in a low-power setting, according to Ampaire. 

“The Eco Caravan propulsion system performed just as expected,” Seguin said after the flight. “It was smooth and quiet. All temperature and power output readings were normal.” 

Preparations for flight testing the first Eco Caravan prototype have been backed by extensive flight trials with Ampaire’s Electric EEL technology demonstrator. This aircraft has conducted exercises with airline partners in Hawaii and the UK to assess factors such as infrastructure requirements for hybrid-electric aircraft.

For Ampaire, the nine-passenger Eco Caravan will be its first market entrant in a longer-term plan to support the electrification of larger aircraft. Next in its sights is the 19-seat EcoOtter, a reworking of the DHC-6 Twin Otter, and beyond that Ampaire CEO Kevin Noertker sees potential for 30- or 50-seat hybrid electric regional airliners as the 2030s get underway.

Ampaire said it will help customers source Caravans for conversion and estimates that around 3,000 airframes are in service worldwide that could be available for upgrade. Noertker said  he’s spoken with airlines who have expressed interest in operating 1,000 or more of the reinvented green aircraft.

To install the modification kits, Ampaire will use its own facility at Hawthorne Airport near Los Angeles and also a network of independent service providers. These will include Air France Industries KLM Engineering & Maintenance, which in October signed a memorandum of understanding to partner with Ampaire.

At the heart of the Eco Caravan’s powertrain is the A03 compression ignition engine, which its manufacturer RED Aircraft said will be rated at 410 kW as part of Ampaire’s integrated parallel configuration with the 160-kW electric motors and battery packs. The German company, which was announced as a program partner during the EAA AirVenture show in July, said its engine will deliver twice the thermodynamic efficiency of a comparable turboprop engine. The net power rating of the overall powertrain is projected to be 570 kW, or 765 shp.

The electric motor will provide power as the aircraft takes off and climbs to cruise altitude, at which point the engine would generally take over. Depending on an operator’s mission requirements, the electric motors could be used for cruise flight or to recharge the batteries, which can otherwise be charged on the ground.

"In Ampaire's integrated parallel hybrid-electric drivetrain architecture, the motors can either add torque to the propeller shaft, resulting in increased propulsion power, or remove torque from the propeller shaft, resulting in recharging the batteries like a generator. They do not do both at the same time," Noertker explained. "In all phases of flight, the combustion half of Ampaire's hybrid system provides a base load of power. During takeoff and climb, the batteries provide electricity to the motors which increases the total propulsion power of the system. During cruise, the motors can optionally pull power from the propulsion system in order to recharge the batteries like a generator."

In September, Ampaire selected Electric Power Systems (EPS) to provide its Epic energy storage system for the Eco Caravan. According to EPS, its battery packs will provide an energy density of 200 Wh/kg and be able to operate for more than 2,000 fast-charge cycles before having to be replaced. The battery packs will be installed in a body fairing on the aircraft to conserve space available for passengers and cargo.

Noertker hopes to see airlines currently struggling to achieve profitability on some routes unlocking their potential with hybrid-electric aircraft, even to the extent of being able to restore some “atrophied” services that have had to be suspended. He also expects communities that have not previously benefited from air service now getting these connections. 

The Eco Caravan is expected to have a maximum range beyond 1,000 miles. The ubiquitous airframe is also well suited to air freight and multiple other missions, including emergency medical support.

Fundamentally, the hybrid-electric Eco Caravan promises a reduction in fuel burn of between 50 and 70 percent, with the greater savings being on short flights. The engine will be able to run on sustainable aviation fuels and other replacements for jet-A. 

Factoring in anticipated lighter maintenance requirements compared with the aircraft’s existing Pratt & Whitney Canada PT6 engine, Ampaire expects to give airlines savings in direct operating costs of between 25 and 40 percent. However, it has not yet released specific target flight-hour or seat-mile costs for the Eco Caravan.

Noertker acknowledged that the ongoing war in Ukraine following Russia’s invasion in late February and its impact on world fuel supplies has got the attention of aircraft operators who may have remained complacent about the need for new energy sources. “We have seen a rethink about fuel costs. I’ve tracked the price of jet-A against rates of airline bankruptcies and it’s a very scary correlation. I would love to break that cycle, and this is all about helping people and communities,” he told FutureFlight.

With expectations for further leaps forward in areas such as batteries, Ampaire has declared itself to be agnostic on available energy sources for future aircraft. Noertker said that by starting with a hybrid-electric approach, the company “has resolved the technology risk [compared with starting with all-electric propulsion] and mitigated it to upgrade existing aircraft.” The fact that hybrid models like the Eco Caravan can enter service using currently available fuel supplies, which increasingly could include SAF, also mitigates risks from complex recharging infrastructure needs.

“We’re taking a crawl, walk, run approach and that’s why we’re starting with [conversions of] existing fleets of aircraft, and will then work with OEMs to make the propulsion system standard on new-build aircraft,” Noertker said. “When we get 10, 20, and 30 years from now there will be multiple [electric-powered] clean-sheet airplanes.”

One of these could be the Tailwind concept design that Ampaire has teased on its website. The company has released no details about this design, which appears to feature an intriguing ducted fan powerplant enclosing the rear of the fuselage and some more ducted fans where the wing meets the top of the fuselage.

“Aviation is the hardest industry to decarbonize,” said Noertker. “Fully-electric aircraft are range limited because of the weight and energy capacity of current-generation batteries. Hybrid-electric aircraft, however, can preserve the range and utility of today’s aircraft. That is why we are focused on hybrid-electric propulsion for a series of increasingly capable regional aircraft. It’s a way for the airline industry to decarbonize more quickly and also to benefit from lower operating costs.”