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Coming to Terms: ConOps
  • 19 Dec 2023 02:51 AM
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Coming to Terms: ConOps

By Al Lawless, Aurora Flight Sciences, and VFS E-VTOL Flight Test Council Chair
Vertiflite, Jan/Feb 2023

This series addresses vague or conflicting vertical flight terminology and proffers descriptions, definitions, or language to clarify and bridge divides. This installment covers “Concept(s) of Operations,” generally abbreviated as “ConOps” in civil communities and as “CONOPS” in military circles.

Vertiflite’s two previous “Coming to Terms” articles summarized the kinds of certification used by the US Federal Aviation Administration (FAA) for showing airworthiness of an aircraft design and for obtaining approval to produce, fly, operate, maintain and repair aircraft. The most recent installment ended noting that the intended concept of operations (ConOps) determines the needed certifications. This leads to clarifying what a ConOps is in the aviation world.

An aviation ConOps is, as a minimum, a high-level description of the operational objectives and needed interfaces between participating people, aircraft, equipment, facilities and services. To be especially useful, it should clearly communicate these interactions at a granular level. The following broad and narrow examples help illustrate how a ConOps ties to the appropriate certifications and approvals.

A broad and complex ConOps familiar to most people is commercial airline transportation. Regardless of who the carrier is, passengers glimpse some ConOps requirements via security measures, evacuation instructions, safety procedures (e.g., fastening seatbelts and disabling cellular transmissions and occasionally unplanned maintenance procedures). Also in the mix are other certifications ensuring airlines have the appropriately certificated aircraft, flight manuals, air transport pilots, maintenance and repair procedures, and more. Baked into this are requirements tied to infrastructure interfaces, such as minimum gradients, obstacle clearance surfaces, communications/navigation equipment and jetways. This also incorporates common-use services such as air traffic control, GPS, airline monitoring and so on.

While the word “concept” implies a grand view and a ConOps name captures the overall idea, a properly exhaustive description details important behaviors and interfaces. A narrow example of such detail is the string of expectations for radio communications. For everything to work out properly, all participants must have compatible frequencies, readback procedures, terminology (e.g., A = Alpha, B = Bravo) and human-machine interfaces. While these interfaces may be generally common throughout traditional aviation, we may expect more stringent requirements for commercial transportation antenna range, redundancy and such. Because an exhaustive description has potentially overwhelming detail, we often compartmentalize the grand view into distinct viewpoints.

Consider a pilot’s viewpoint of the radio example. Typical pilots have little concern for a radio’s internal interfaces or power integration. Their interactions involve communication procedures, radios display, and control interfaces and failure workarounds. Applying this thinking to every other pilot interface item yields the ConOps from their perspective. The same compartmentalization could be done for air traffic controllers, mechanics, inspectors and every other participating element in a ConOps. As noted previously, the FAA deserves great credit for interlacing each of the threads of these compartmentalized views into today’s grand weave. This immensely complicated and elegant weave is required so that all airlines, aircraft and aircrew qualified for commercial airline ConOps can apply it anywhere.

At the low end of the complexity spectrum, consider an “unplugged” ConOps for a general aviation aircraft, such as a 1930s Piper Cub with neither communication/navigation devices nor transponder and a minimal electrical system. Such an aircraft has significant operational limitations and a complete operational portrayal can be a pilot-centric view of interfaces and processes. A pilot might capture this as a simple checklist: check weather using website X, walk the runway to ensure aircraft compatibility, confirm airworthiness (e.g., fuel, weight and balance, paperwork, preflight inspection, etc.), fly per flight manual instructions and limitations, remain “well clear” using daytime visual flight rules, and avoid airspace that requires equipment that’s not installed.

There are many other civil and military examples, but the above make two points. First, a ConOps description captures the systems and process interfaces with the applicable airspace, infrastructure and people. Second, the certification and approval requirements change dramatically with complexity. Putting these together reveals that a clear, detailed ConOps allows defining the appropriate certifications. Sometimes, special certifications for narrow uses are sensible, such as steep approach and departure approval at London City Airport.

With this understanding of what an aviation ConOps entails, consider some anticipated use cases for the coming generation of novel vertical takeoff and landing (VTOL) aircraft. They could fly for recreation, personal travel, commercial commuting, emergency first responders, firefighting, police and surveillance work, and “bucket list” tourism. Each of these would have at least one ConOps but more likely multiple differently detailed versions as they interface with the world around them. To better explain this, examine an emerging use case, urban air mobility (UAM).

As a baseline, consider today’s helicopter UAM ConOps and the incumbent facilities, pilot training, radio and navigation procedures, and air traffic controller instructions. Compare this baseline to the first generation of VTOL UAM operations. If they operate in a nearly identical manner, using the same facilities, fuels, equipment, helicopter routes and so forth, then their ConOps match. Taken to an ideal extreme, these new aircraft could slot right in to replace helicopters with no interface differences beyond pilots needing a different type rating.

In reality, the next UAM aircraft generation will bring at least a few different interactions. Many will require an electric power grid. Many aircraft will be unable to hover for an extend period, and some might have relatively limited field performance. Whatever the differences are, the resulting ConOps changes must be clarified and coordinated with authorities so only executable instructions are given. Each change related to safety requires procedural changes or entirely new approvals such as certifying electric power facilities, aircraft interfaces and personnel. Starting with today’s baseline ConOps as the anchor, early UAM certifications can distinctly address each interface change. This approach — coined as “anchor and evolve” by the FAA’s Dave Webber — is sensible and naturally minimizes disruptions. If all first-generation UAM VTOL aircraft share the same ConOps, then certifications needed for one will apply to all — just as with commercial airlines.

ConOps can evolve with aircraft efficiencies and capabilities, but the ultimate UAM vision may be more revolutionary. Fully automated UAM aircraft with humans only supervising operations takes us so far away from the traditional pilot-centric construct that simple evolution may not apply. With these first three installments clarifying the relevant concepts, silos, approvals and certifications, the next and final article in this series will bring these together to show hurdles to clear for the ultimate UAM vision.

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