eVTOL – John Vincent

This week, I watched an FAAs Advanced Air Mobility (AAM) webinar[1]. The subject was community engagement. AAM could be air taxies but it’s many uses of the new electric aircraft that are becoming a reality. The term eVTOL is used for those aircraft that have the capability of vertical flight. My reflection is that there are several aspects of AAM that need much more attention. Naturally, I’m taking the discussion of what’s going on in the US and thinking about it in relation to the UK.

Land Use Planning

Generally, National Aviation Authorities (NAAs) are consultees when it comes to land use planning. They do not determine planning applications. NAAs may well have set out policies and guidance on the subject but they will not be determining the site of vertiports.

It seems to me that there’s little chance that eVTOL aircraft routes will be established without sufficient community consent. Community engagement has been appropriately recognised as essential. The aspects in play are like those for existing aerodromes. Often for AAM applications proposals are for the use of new locations, hence a concern. Anytime there’s a serious proposal for a new aerodrome the opposition is up and running long before the proposers have got their act together.

The subject is complicated by the mix of public and private ownership of infrastructure. If the intention is to interconnect AAM with other transport services (bus/train/boat/road), then complicated agreements are going to be inevitable. It’s not just about buildings and tarmac but having a trained workforce available is a location dependent issue too.

Business Models

I’m about to sound as if I’m securitising the plans of a contestant on The Apprentice[2]. There are plenty of way of losing money in commercial aviation. It’s been a well-practiced art over the years. Great ideas fall by the wayside after huge amounts of money have been expended. Customers are key. People must want to fly the routes available, time and time again. And like London Black Cabs be prepared to pay the fare. Given the relatively small cabin sizes that are on offer these people are likely to be moderately prosperous groups or individuals.

Regular schedules air services can produce a reliable income. Airport-to-airport connections seem like a good bet. Problem there is the conveyancing of weighty luggage. Busy airspace could be a challenge too. That said, with tens of thousands of people at both ends of a route, no doubt some people will choose a comfortable, speedy direct connection.

There are good possibilities for major event driven transport services. Getting to and from a motor race or horse race event or a concert or festival can be hell when tens of thousands of people are all trying to get to and from a location or venue. The numbers may well stack-up to make eVTOL a premium way of dodging the crowds in an environmentally sound way.

Batteries, Batteries, Batteries

Everything in respect of aircraft performance depends on power density. How much oomph can you get out of a small, light weigh physical space. Recharge and go. Do it, again and again. It’s as simple as that. Not only that but aircraft battery packs must be affordable and available. Whizzy technology that cost a mountain of cash and can only be use for a few hundred cycles is no use at all.

Power distribution infrastructure must be up to the job too. Who will pay for this is up for grabs. There’s a good case for public funding given that there are multiple uses of enhanced electrical supply. Given the monopolistic nature of power generation and distribution this will not be easy or quick.

That’s only three issues that require a great deal of attention. Not the attention of researchers. Not the attention of academics, Not the attention of political policy wonks. Connecting entrepreneurs and public bodies needs practical stimulus. The possibilities are exciting.

[1] https://youtu.be/1sfVuJlPQoY

[2] https://www.independent.co.uk/arts-entertainment/tv/news/the-apprentice-2024-winner-pies-b2531331.html

What makes a bird strike different is that it’s an unpredictable collision. If we talk about aircraft collisions with terrain the outcome is predicable bad. All that kinetic energy must go somewhere. So, a high-speed vehicle hitting something that is immovable is not going to end well.

Now, it must be said that some hunting birds can dive at incredible speeds. More typically, a large bird in flight between feeding sites isn’t going to be traveling fast. In fact, it may as well be viewed as a static object relative to an aircraft in flight. A bird in-flight is unlikely to be able to take avoiding action. For a pilot the action of “see and avoid” may work in respect of other aircraft but a bird ahead is no more than a pinprick in the sky.

These factors make aircraft bird strikes inevitable. That said, the range of outcome because of impacts are rarely at the severe end of the scale. One reason for this is the effort made at design certification to ensure an aircraft is sufficiently robust. Damage can occur but if the aircraft design and test processes have been rigorous everyone should get home safely.

I remember paying particular attention to the zonal analysis done by several major manufacturers. In my experience the most difficult designs are for those of business jets and large helicopters. One of the design challenges in both cases is the limited physical real estate within the aircraft structure. Weight is another big consideration. This leads to cramming essential avionics and electrical systems and their interconnections into confined spaces.

Zonal analysis is about ensuring there’s segregation between different systems. Afterall what’s the point of having two Attitude & Heading Reference Systems (AHRSs)[1] and putting them next to each other in the nose cone of an aircraft. That’s not a good design strategy. One damaging impact must not take out two essential independent aircraft systems.

It’s just as important to ensure an aircraft’s wiring isn’t all bundled togther and taken through one connector. That may save money on electrical parts but it’s not going to work after being hit hard by a 5kg goose.

These issues will need particular care in the new electric vertical take-off and landing (eVTOL) aircraft that are on the drawing boards. Choosing a safe architecture, manufacturers must balance the use of creative design solutions, to produce a competitive product, with limited physical space.

A couple of key words in the certification requirements concern hazards that are anticipated. Bird Strike is hazardous and aircraft systems and equipment must “perform their intended function” should it occur. See EASA Special Condition for small-category VTOL aircraft, Subpart F[2].

POST: Good to see the bird strike criteria Joby’s airworthiness criteria: A blueprint for the nascent eVTOL industry – Vertical Mag

[1] https://helicoptermaintenancemagazine.com/article/layman%E2%80%99s-guide-attitude-heading-reference-systems-ahrs

[2] https://www.easa.europa.eu/sites/default/files/dfu/SC-VTOL-01.pdf