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Abbreviations for Electric Aircraft Types
  • 16 Jul 2024 01:01 AM
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Abbreviations for Electric Aircraft Types

The Vertical Flight Society's Mike Hirschberg recently published a Forbes.com article on Abbreviations for Electric Aircraft Types (June 30, 2024). The article provided a breakdown of terms such as eSTOL, eCTOL, heVTOL, H2eVTOL, etc.  for different types of aircraft that use electric energy to drive motors to generate lift or thrust. VFS member Dan Newman subsequently proposed a graphical representation of some of the terms. Three versions of the graphic were generated, with differing layers of complexity.

The simplified version (shown above) depicts three general types of propulsive energy systems vs. three types of design categories for runway length. As in the original article, it defines the basic terms. Battery-electric aircraft are possible for vertical, short or conventional takeoff and landing aircraft. The hybrid-electric row is shaded, as it is not all-electric and it produces pollutants. Highlighted features of each propulsion category are as follows:

Battery-Electric

  • All-electric, using only batteries to drive the motors
  • Powerplant emissions: none
  • Akin to the automotive battery electric vehicle (BEV)

Hybrid-Electric

  • Internal combustion engine (piston or turbine) to drive generator to provide electricity (with or without a storage battery) for greater range and payload
  • Powerplant emissions: reduced CO2, NOx, heat, etc.
  • Akin to the automotive hybrid electric vehicle (HEV)

Hydrogen-Electric

  • All-electric, using a hydrogen fuel cell plus a buffer battery to drive the motors for greater range and payload
  • Powerplant emissions: water and heat
  • Akin to a the automotive hydrogen fuel cell electric vehicle (FCEV)

A more detailed version (below) highlights the operational applications available with the different propulsion schemes. The limitations of energy storage in battery electric VTOL (beVTOL) aircraft allows them to fulfill short-range, intra-city urban air mobility (UAM) applications, but not longer range missions. It's possible that hybrid-electric VTOL (heVTOL) aircraft could be designed for either UAM or longer-range regional air mobility (RAM) missions (e.g. inter-city or flights from rural-to-city or rural-to-rural), while hydrogen fuel cell electric VTOL (H2eVTOL) aircraft should be able to be designed with have enough range for RAM applications.

Similarly, eSTOL aircraft can be designed for UAM and/or they can also be designed for RAM missions, while eCTOL aircraft cannot perform UAM missions without major investment in downtown airports. 

 

Finally, the original chart depicts the more detailed version with additional information about the different categories embedded in the image. In addition, this version includes various nomenclature for electric aircraft:

  • US: Advanced Air Mobility (AAM)
  • European Union: Innovative Air Mobility (IAM)
  • Canada: Integrated Air Mobility (IAM)
  • Future Air Mobility (FAM) — an umbrella term to avoid implying any specific region's airworthiness authority

 

 

What do you think? Are these helpful? We are interested to hear your feedback! Leave us a comment below.

 

Comments

Chris May

The tables provide a useful distinction and comparison between the various sources of electricity for driving the electric propulsion of the aircraft.

However, it is insufficient to try to fit all aircraft into the three categories VTOL, STOL and CSTOL considering the diversity of designs that are capable of transitioning from vertical take-off to aerodynamic lift configurations in forward flight. A beVTOL or heVTOL with this flight transitioning capability could thus be suitable for RAM.

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