scope:

PURPOSE AND SCOPE

This document provides means of compliance with the EASA SC-VTOL requirement VTOL.2615 (a) regarding lift/thrust instruments related to the energy state.

It defines compliance methodologies for the energy level information that should be presented to the crew during the flight planning and execution phase for electrical Vertical Take-off and Landing (eVTOL) aircraft.

This document is focused on electrical propulsion, as this type of lift/thrust has specific challenges that require new strategies to be put in place to enable safe operations.

Energy Storage Systems (ESS) is recognised to be limited in capability to provide the same level of certainty of the available usable energy, as compared to conventional fuel-based systems.

Power that can be delivered from the ESS to the lift/thrust units is not constant and varies in relation to several parameters, that include the State of Function (SOF) and State of Health (SOH).

The energy required to complete a flight considering the applicable reserves will be dependent also on the planned power demand profile.

The margin between the amount of available energy and predicted energy at a given point during the flight, should be estimated, and clearly displayed as it is an important information to support decision making by the crew.

There should be clear indications of how this margin changes as the crew choose/change the destination/alternate vertiport, increase/decrease speed, change or are asked to change cruise altitude or encounter/update different external ambient conditions (winds, OAT).

Interpreting the observed available energy as well as predicting the surplus at the end of the flight given the mentioned above factors would require continuous complex calculations, which the flight crew most likely will not be able to perform, without additional supporting tools and indications.

Uncertainties in energy observation and prediction introduced with electrical propulsion can be managed by either increasing the safety margins when calculating the energy requirements for a flight, reducing considerably the range of eVTOLs, or increasing the accuracy of the prediction of the difference or margins between available and required energy (energy margin).