Feedback on the FAA’s UAM CONOPS v1.0

Integrating large volumes of small aircraft into US airspace.

Marc Ausman
August 19, 2020
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6 min read

I was planning to share feedback on the recent FAA UAM CONOPs v1.0 document when I saw that Anna Dietrich already posted a great writeup with her thoughts here. If you know Anna, you know that she’s very credible and knows her stuff. I agree with her assessment and very much appreciate that the FAA is starting the dialog in this area. Specifically, I like the FAA’s crawl, walk, run approach that outlines a pathway to high-volume operations. In this post, I’d like to provide additional feedback specifically around the FAA’s proposed idea of Urban Air Mobility (UAM) corridors to route and separate UAM traffic. Any upcoming rules need to integrate rather than segregate new aircraft.

FAA CONOPS v1.0

The FAA Concept of Operations v1.0 document outlines how next-gen aircraft operating in urban airspace could integrate into today’s existing airspace. The envisioned future state for UAM operations includes increasing levels of autonomy and operational tempo across a range of environments including major metropolitan areas and the surrounding suburbs.

Before we dig in, let’s review one of several good points that Anna makes about corridors in her writeup (edited for length): Once the designated UAM corridors are defined, it wasn’t immediately clear to me how the FAA intends to protect them from non-cooperative traffic. … Simply marking the corridors on sectional charts or treating them like TFRs (or similar) does not, in my opinion, provide the level of airspace protection that is needed.

In the original FAA document, the authors touch on the issue of separation from VFR traffic in section 4.3.9: Other NAS Airspace Users have the responsibility to know about and meet the relevant performance and participation requirements to operate in, or cross, active UAM Corridors or avoid the active UAM Corridors. UAM Corridor definitions and availability will be publicly available.

As I read the FAA paper, I couldn’t help but think how much easier it would be to incorporate UAM traffic if we had only IFR traffic in the air. IFR stands for “Instrument Flight Rules” and it means that air traffic controllers tell pilots where to fly and are responsible for aircraft separation. Most airlines and commercial traffic fly under IFR flight plans. IFR traffic could simply be routed away from UAM corridors, and UAM corridors could be placed where IFR traffic doesn’t usually fly.

But things are never that simple. Aviation provides many benefits to society and many of those benefits are realized with VFR aircraft. VFR means “Visual Flight Rules” and pilots can fly wherever they want (subject to certain restrictions) and are responsible for their own separation from other aircraft. Examples of typical VFR flights include crop dusting, recreational flying, primary flight training, tourism flights, medical evacuation, news helicopters, police oversight, fire fighting, power-line inspection & servicing, adventure travel, remote camping/backcountry flying, and search & rescue.

FAA diagram showing proposed corridors.

Getting back to corridors: the idea of corridors is bad because corridors create impractical and unsafe restrictions on VFR aircraft.

Why? Three reasons:

1. Corridors added to already complex metropolitan airspace will prove to be unmanageable by human pilots and human controllers.

Imagine a many-to-many relationship between multiple UAM aerodromes in a metropolitan environment and the hundreds of routes between them — it would look like a spiderweb. Even with precise location information provided by onboard moving maps, there’s no practical way for a human pilot to manage that environment. Pilots will spend time looking inside the cockpit at charts rather than looking outside the cockpit for conflicting aircraft. Additionally, asking controllers to route aircraft around the corridors would be very labor-intensive in areas where controllers are already very busy. Although it is envisioned that human controllers will direct aircraft above the corridors, there will be inevitable intermixing of aircraft that need to climb and descend through lower altitudes.

Early UAM network as proposed by FAA
Network map proposed by Uber

2. Corridors will likely increase the probability of mid-air collision.

Even before the point when the UAM route structure looks like a spiderweb, we should all expect that VFR pilots will regularly (and unintentionally) fly through the proposed corridors, which can range in altitude from a few hundred feet to a few thousand feet AGL. Most metropolitan areas have large airports, but they also have many small airports that serve VFR aircraft. Such aircraft would have to weave around corridors to get in and out of the metropolitan area and often are limited from climbing out due to protected airspace (Class B) above them. The structure of these corridors would also create chokepoints for VFR traffic, increasing the chance of mid-air collisions. Imagine search & rescue or police choppers trying to do their job in such an environment.

3. Industry trade groups will fight additional restrictions on VFR flights as well as additional aircraft equipage requirements.

Influential groups that represent pilots and commercial operators will fight additional airspace restrictions and delay, if not torpedo, the idea. They will also fight a requirement to add new equipment to an aircraft as it drives up the cost of flying. Look no further than the decades it took to equip aircraft in the US with ADS-B. While the FAA document only indirectly calls for new equipment on VFR aircraft in order to fly through proposed corridors, it is certainly implied in my interpretation of the paper (See section 4.4 of the FAA UAM CONOPS v1.0 paper Any operator that meets the UAM Corridor performance and participation requirements may operate in, or cross, the UAM Corridor.) These pilot groups, rightly I believe, will fight any effort to restrict airspace or require new equipment.

That said, I ask the FAA to consider the following suggestions to address these concerns when drafting UAM CONOPS v2.0:

  1. UAM aircraft will fly pre-planned routes through existing airspace while assuming non-cooperative traffic is the norm and not the exception. Let’s unpack this. First, pre-planned routes are routes that operators, local ATC, and the local community have agreed to and don’t require traditional voice-based ATC comms. There would be no special airspace or markings on charts. With no markings on charts, VFR aircraft would fly as they normally do. Further, these routes could change more rapidly as the industry and market conditions change. Next, and most importantly, aircraft with automated systems should give way to piloted aircraft and the UTM system should be designed around this. This flexibility allows for a safe way to account for all the inevitable unknowns.
  2. Do not create additional airspace restrictions or special use airspace. Do not add complexity to today’s airspace as part of a solution. Instead, think about how we can place the burden on new systems and automation rather than human pilots and controllers. I do agree with Anna when she says that automated traffic management systems may ultimately control all of the airspace, but It’ll be a long while before that happens.
  3. Rather than creating onerous corridor-specific requirements, place separation requirements on UAM systems so that UAM aircraft can operate and intermingle with non-UAM aircraft. When an aircraft is equipped to operate in the UAM system, it can negotiate tighter separation requirements when it knows the aircraft nearby are also in the UAM system. When VFR aircraft (that don’t have UAM equipment onboard) are detected then UAM aircraft can utilize wider separation rules and maneuvers to avoid non-UAM VFR or even IFR aircraft.

I look forward to continuing the conversation with the FAA and am glad that they have taken steps towards integrating new types of aircraft into the busiest and safest airspace in the world.