The NRC announced in early 2021 that their Hybrid-Electric Aircraft Test-bed (HEAT) had successfully taken to the air!

The following picture is a presentation of their HEAT project.

Figure 1: HEAT being prepared for a test flight!

Source: NRC Canada

A critical decision for this program was to use a Cessna 337 due to its unique design. The Cessna 337 was first built in the ’60s and uses a two-engine, push-pull approach. One engine is found on the nose, and the other engine is situated at the back of the body. For a closer view of the propellers from these two engines, Figure 2 is provided.

Figure 2: A closer look at the front and back (push-pull) propellers of the Cessna 337

Source: Aero Corner

Dubbed the “Mixmaster,” the Cessna 337 provides an important nuance to this test-bed – in that using only one engine does not create a pilot challenge, such as when dealing with engines positioned on the wings. This plane is stable no matter whether or not only one engine or the other is working.

A team from the Aerospace Research Centre converted the Cessna 337 for a series of tests and then successfully flew the plane for 5 minutes in early February 2021. See Figure 4 for an in-plane tour during these tests. Additional tests were also made, and at test flight number five, the aircraft was tasked to fly for 32 minutes!

What made this project unique was that the rear engine was replaced with an electric motor, a battery and an electronics support system for the HEAT project. The hybrid component of this project comes when combining an electric motor in the rear with the conventional aviation engine at the front – which in this case was a typical 210 hp, fuel-injected, horizontally opposed, air-cooled engine. Using an electric motor at the rear, both space and weight savings were accomplished, which are desirable outcomes in aerospace design. Electric motors also produce a lot less noise, which can be appreciated by air travelers.

While green technologies, such as hydrogen and batteries, are being rapidly tested or deployed in the automotive industry, there are many challenges to these technologies being implemented in the aerospace sector. Some of these challenges involve ensuring that aircraft can operate safely and reliably in dealing with many and rapid temperature changes, absorbing considerable and constant aircraft vibration and regular cycling through high altitudes, which produces pressure changes.

Figure 3: Hybrid-Electric Aircraft pre-flight checks

Source: NRC Canada

As the HEAT research aircraft was built as a test-bed, it will never be flown commercially. Nevertheless, the NRC team of 40 engineers, technicians and test pilots took on this technical challenge to develop the expertise to help the Canadian aerospace industry design, test and validate a novel electric propulsion system.

Part of NRC’s Low-Emission Aviation Program is developing the know-how, and now data can be shared with other researchers and the aerospace industry to assist with certifying future electric and hybrid aircraft.

NRC thanks its partners Transport Canada and Environment and Climate Change Canada for being part of this adventure!

Go to the LinkedIn page for more about this story.

Figure 4: Hybrid-Electric Aircraft Test-Bed takes flight!

Source: NRC Canada

Elements of this story were retrieved from an NRC LinkedIn and from the NRC website.