Originally Posted by
JimL
eVTOL is a technology-led product still looking for the killer application.
As wrench1 has said:
Joby has already shown that, with fuel-cell technology, liquid hydrogen can extend that range (currently at about 30 minutes) to several hours without adding dramatically to the take-off mass.
But to return to UAM, it is not quite as simple as it first appears; yes, eVTOLs with their many thrust units with modern geometry props/rotors are much quieter, and therefore acceptable, than the current crop of helicopters. But, they suffer from issues of downwash/outwash (some of them extreme) and, because of their certification basis (EASA - 'enhanced', and FAA 'increased performance'), will be subject to rules similar to Performance Class 1 (although for the FAA that is not yet clear).
EASA's enhanced certification requires that the safety target of 1 x 10-9 be achieved; depending on the reliability of the power-unit train, this might mean the loss of one or even several thrust units (and asymmetric power control might not be that easy).
However, for UAM it is the limitation of the take-off climb 'obstacle limitation surface' (OLS) in an obstacle-rich environment that might be the real issue. ICAO addressed this several years ago by permitting the elevation of the (origin of the) OLS sometimes by hundreds of feet - thus allowing it to be positioned above all obstacles. Helicopter manufacturers met that challenge (or might even have facilitated it) with the development of 'vertical procedures' - allowing the attainment of the OLS elevation by adding an all-engines-operating (AEO) steep/vertical (ascent/descent surface) element to the Category A profiles.
Elevation of the OLS remains the solution for vertiports in an urban environment. but the achievement of the steep/vertical ascent/descent requires an application of maximum power for a period that might wreck the previously designed flight profiles with the demand on battery power.
Yes, eVTOL development is moving at an impressive pace but still has to satisfy the population's (both those travelling and those over which operations are being performed) aspirations of safe flight.
Jim
just catching up on the thread as it was rekindled. Question on vertiports and the thinking on them being able to be used by all operators of a wide range of aircraft or specific? I think more than a couple of this type aircraft are Gyroplane based - such as Jaunt
https://jauntairmobility.com
Obviously that’s a very specific aircraft but backed by Uber and so one imagines maybe quite numerous if the concept gains traction. Not sure how that could ever be flown in an urban environment without accepting more risk that seems acceptable today.