Trajectory Energy Management for eCTOL: Examination of Battery Discharge Under Two Flight Profiles
Date of Award
Master of Science (MS)
Aerospace, Physics, and Space Sciences
Ralph D. Kimberlin
The expanding industry of electric airplanes presents a significant regulatory challenge for aviation authorities worldwide. The first step towards achieving a precise Trajectory Energy Management (TEM) is to understand how the powertrain behaves during the operation. Therefore, this work examined the battery performance of an eCTOL, the Pipistrel Velis Electro, under two different prescribed flight profiles and take-off weights. Flight 1, a destination trip profile, was conducted with a gross weight of 1146 lbs and a constant power setting of 22 kW during the cruise segment, while Flight 2, a local training flight profile, was conducted with a gross weight of 1318 lbs and exhibited more pronounced variations in power setting. The test sorties were conducted at different outside air temperatures (OAT) and both of them were completed before SOC dropped below 40%. The analysis of motor power shows that the power generation was predictable, and the batteries’ ability to supply power was consistent throughout the discharge, with a mean value of approximately 3% in power loss. However, a growing discrepancy between the state of charge (SOC) of the batteries was observed during discharge due to the difference in the state of health (SOH), resulting in one battery storing more energy than the other. The energy required analysis shows that Flight 2 had more available energy at engine start than Flight 1 due to the higher OAT during battery charging. To climb to the same altitude of 1900 ft MSL, Flight 2 required approximately 18% more energy than Flight 1. In the cruise segment, Flight 1 exhibited a specific range of 3.5 NM/kWh and specific endurance of 2.6 min/kWh with 22 kW, while Flight 2 achieved 3.9 NM/kWh and 2.9 min/kWh with 21 kW, despite the higher weight. This counterintuitive outcome is attributed to the difference in OAT and reinforces the importance of understanding the impacts of temperature on battery performance while planning the flight. Additionally, sustained turns with 30° of bank angle were performed at a target airspeed of 85 knots, requiring approximately 0.52 kWh to complete the maneuver. This represents a 17% increase in energy required compared to the amount required to trim the aircraft at a steady flight with the same airspeed. The study also highlights that the aircraft is sensitive to external factors such as airmass, air quality, and the pilot’s handling techniques, where significant differences in energy required can be observed during maneuvers and flight conditions replicated in different sorties. These findings underscore the importance of considering maneuvering energy required when establishing safety margins for electric aircraft operations. This point deserves the attention of regulatory authorities, who play a critical role in ensuring safe and efficient operations.
Campos Cunha, Denner, "Trajectory Energy Management for eCTOL: Examination of Battery Discharge Under Two Flight Profiles" (2023). Theses and Dissertations. 1269.
Available for download on Monday, November 06, 2023