Urban Air Mobility is fast becoming a reality and we all have seen some ideas about what transport could look like in our urban environment through mock-ups and videos.
EASA’s study on Urban Air Mobility has clearly indicated that use cases such as air taxis and deliveries for medical reasons have broad acceptance from EU citizens, and they will most likely be the first to be implemented.
Our article on ‘Vertical Take-Off and Landing (VTOL)’, explained the concept of aircraft taking off and landing in our urban areas. But where exactly will VTOLs and other aircraft take off from and land?
This article will set out some broad ideas, principles and designs to set the scene.
Vertiports – hubs for VTOLs such as air taxis and drones
Take a look at the technical description of a Vertiport:
‘an area of land, water, or structure used or intended to be used for the landing and take-off of VTOL aircraft.’
This means that vertiports are dedicated areas that supply the infrastructure needed for safe commercial air transport of passengers or goods that travel by VTOL. To realise fully the potential of Urban Air Mobility, vertiports need to be easily accessible, with good connecting services to streets, railway stations, buses, etc. They can be either at street level or on top of buildings.
Trajectories (flight paths during take-off and landing)
By definition, a VTOL can take off and land vertically, but the vertical part may be limited to the very initial part of take-off, with the rest of the flight path being more or less shallow.
It is therefore important to take into account the whole flight path the VTOL takes or, put another way, the trajectory of the flight.
The image on the left shows, a roof-top vertiport with a ‘clear’ green trajectory, meaning that a VTOL can take off from this vertiport without obstructions. On the right you can see a vertiport at ground level, indicating that the same VTOL would not be able take off from there, as its trajectory is too shallow and so there would be an obstruction in the way. This means that taking off here is not possible for this aircraft with lower performance.
Adaptable Urban Air Mobility
EASA wants to provide the broadest possible requirements to ensure Urban Air Mobility can be adapted to support all urban settings and types of VTOLs. Take a look at the three different take-off profiles.
Elevated conventional take-off:
VTOL takes off from an elevated point in a city (e.g. rooftop of tall building), even allowing for a possible dip in the trajectory in case of certain failures.
Here the VTOL takes off in an area without any obstacles close by. The vertiport could also have a small runway to accommodate a rolling start, raising the energy efficiency for some VTOL types and missions.
Again, there is an allowance for a possible dip in the trajectory which is important in case of certain failures.
This profile is specifically designed for vertical take-off in an obstacle-rich environment, with a large portion of the VTOL trajectory being performed vertically.
Also under these circumstances certain failures are manageable.
Ensuring safe take-off and landings
Apart from the above take-off profiles, there are broadly speaking two more sets of objectives that need to be taken into account when deciding on the location and kind of vertiports and VTOL trajectories.
- The aircraft can be certified in two categories: Basic or Enhanced.
- The highest safety objectives have been set for the category Enhanced, which is requested for flights in busy city / urban skies, or for Commercial Air Transport of passengers (Air Taxis).
- The Basic category has lower safety objectives that depend on the number of passengers (0-1, 2-6 or 7-9) transported with the VTOL, to provide proportionality. It can be used for non-commercial air transport of passengers, outside congested areas such as in the countryside.
- They describe for each category the capability that the VTOL must have for safe operation, in case of events such as an engine failure.
For VTOLs making use of the urban sky in congested areas such as cities, it is requested that the VTOL is fit to perform a ‘continued safe flight and landing’ as an immediate landing of the VTOL might not be possible in a city outside of a vertiport.
VTOLs that are flying in non-congested areas have more options to perform a controlled emergency landing. The landing can be outside a vertiport but must be controlled, similarly to what a helicopter or aeroplane can achieve in case of power-loss.
Funnel—shaped solution to obstacle free take-offs & landings
EASA’s prototype technical specifications that were published March 24, 2022, showcase an innovative concept to ensure obstacle free take-offs and landings.
A funnel-shaped area above the vertiport, called an “obstacle free volume”, ensures that VTOLs can perform take-offs and landings with a significant vertical segment and therefore take account of environmental and noise restrictions in an urban environment.
Comprehensive explanatory video – technical but very interesting
As part of our information package for the European Rotors event in November 2021, Lionel Tauszig (EASA’s Senior Project Certification manager for VTOLs and eVTOLs) put together a very comprehensive video presentation.
The video covers the main information summarised in this article and gives additional technical and detailed information about trajectories and vertiports.
Check out the video. If you just want to see the parts that we explained in this article, here are direct links to the respective points in the video: