A New Weather Standard for Uncrewed and eVTOL Operations: The Foundation for the Future of Aviation Weather

A New Weather Standard for Uncrewed and eVTOL Operations: The Foundation for the Future of Aviation Weather

Key Take Aways:

  • The American Society of Testing and Materials (ASTM) F38 Committee on Unmanned Aircraft Systems (UAS) addresses issues related to design, performance, quality acceptance tests, and safety monitoring for unmanned air vehicle systems.
  • The ASTM F38 Weather Group charter was formed to define minimum performance-based standards for Weather Information Provider (WIP) data and services to UAS Service Suppliers/Providers (USS/USP) and Operators in a UAS Traffic Management (UTM) ecosystem (which has expanded to Provider of Services (PSU)).
  • The proposed F38 Weather Standard will provide a weather data tiering system based on the FAA’s Performance-Based Weather Data Standards and is expected to increase the density of verified and accurate low-altitude weather data.
  • The standard of performance depends on the reporting of data performance accuracy by any provider of weather information reports, analyses, and services to support risk-based decisions by users.
  • The focus of the standard is to prioritize and increase the collection of real-time weather data within the low-altitude airspace from the surface to 5,000 feet, reducing the risk and uncertainty for UAS operations.


As an indicator of humanity’s technological advancement, few examples are as striking as aerospace. In a mere 50 years, we transitioned from the Wright brothers taking flight in the North Carolina coastal skies to transatlantic commercial flights and the introduction of jet engines. Despite the rapid innovation of equipment through the 1950s, there were overwhelming safety concerns tied to the aviation industry, which stunted growth and commercial indoctrination. Industry leaders believed that federal action would be needed for the airplane to reach its full potential. It was not until 1958 that the Federal Aviation Administration (FAA) was established, and the process of creating federally regulated safe flight conditions began. And in 2023, believe it or not, the commercial aviation sector under the FAA is by far the safest mode of transportation.


Fast forward to today, with the emergence of uncrewed and electrified vehicles that have the potential to add 500 million small drone deliveries and 2.5 to 4M air taxi departures by 2030, the aviation industry is at a similar crossroads. Looking to avoid the dangerous innovation stage of early aviation, an extensive process of producing standards and regulations for the industry has begun. Unlike the aviation industry of the past, however, these vehicles will be mostly uncrewed, flown with the operator and vehicle in different locations, or even fully autonomous. The aviation industry is undergoing a rapid regulation phase to produce flight standards for uncrewed vehicles and ground equipment, especially when operating Beyond Visual Line of Sight (BVLOS). The ASTM F38 Committee represents significant cooperation with the FAA and NASA, industry leaders, professionals, and academic researchers. Together, they formulated the vision of what future drone operations and standards will someday look like.


On the weather side, the traditional weather systems and regulations were built in a different era when weather research and science and technology development were primarily government funded and regulated. The requirement for certifying weather instruments and using only government approved weather data and products guaranteed that only validated data was ingested into aviation systems for operator use. Traditional weather systems involved the creation and maintenance of Automated Surface Weather Systems (ASOS) at airports and forecasters focusing on hazards either at the take-off/landing location (airports) or at altitudes where Part 121 commercial aircraft operated. For helicopter or commercial general aviation operations, however, the aviation weather system has given different attention or sensor regulatory oversight. Within Part 91 (General Aviation) and Part 135 (Helicopter) operations, there is a lack of real-time weather measurements in the low altitude airspace or at takeoff and landing locations.


The government has worked to improve low-altitude weather analyses and models. Their data collection methods, however, have stayed relatively consistent over the past several decades: consisting of namely two radiosonde balloon launches a day, remote-sensed satellite data, and limited low-altitude weather data collected around airports. The lack of low-altitude data directly leads to increased uncertainty of weather conditions. Helicopter flight has a much higher accident rate than fixed-wing aircraft, largely due to the need for weather data, especially in areas of terrain and built-up urban areas. Despite this, helicopters are still considered a relatively safe mode of transportation. The fact that the helicopter community has been safe enough to operate is a testament to the best weather sensor on any aircraft: the pilot. The pilot is expected to know the weather it is about to or is flying in and to take appropriate measures to react appropriately to unexpected weather hazards.


Enter uncrewed aircraft and lighter electric vertical lift and landing aircraft. Uncrewed aircraft do not have the pilot as a weather sensor onboard and will fly in regions spatially and vertically where weather data is potentially sparse to non-existent. If data is sparse and/or non-existent at a location, how will operators know if it is safe to fly? That question is the reasoning behind the ASTM F38 Weather Standard Working Group, established in September 2020.


The ASTM F38 Weather Working Group was chartered to define minimum performance-based standards for Weather Information Providers (WIPs) data and services to UAS Service Suppliers/Providers (USS/USP) and Operators in a UAS Traffic Management (UTM) ecosystem. As mentioned before, the legacy aviation weather system was built through government means, with Part 121 operations the priority. ASTM F38, in close collaboration with the FAA and NASA, has produced an ASTM Weather Standard that is expected to increase the density of high-resolution weather data and a framework to communicate weather data with verifiable data quality, accuracy, and reliability without the requirement to certify weather instruments. The future is about a performance-based weather data standard.


The new paradigm for weather data safety standards and practices is the biggest transformation in the aviation weather system for weather observations, reports, and analyses since the WSR-88D Doppler Weather Radar System became operational in the 1990s. Advanced weather technology and innovation to drive improvements in collecting high-density, low-altitude weather data will rely on 3rd Party Weather Providers (3PWPs) to supply the new data sets to the industry. The ASTM F38 Weather Standard provides a new framework for the 3PWPs to leverage cost-effective weather stations, weather data derived from remote sensors such as wind lidars, or Internet of Thing data sets that have met the requirements in the Weather Standard. The standard provides a framework for Civil Aviation Authorities (CAAs), such as the FAA, to ensure any weather data going into flight planning, navigation, and flight management systems remains secure and provides metadata about where, when, and how the data was curated and delivered from approved and certified 3PWPs.  


Accurate, reliable, and verified weather data is essential for safe flight operations, especially as humans are removed from the workflow and autonomous operations scale in the future. Machine-to-machine weather data transfers that are used in automated flight planning and control systems must have controls to ensure the data is not spoofed or delivered from a weather sensor system that is faulty or well out of tolerance. These assurances are necessary for the regulator to allow the data into the aviation system, just as it would not allow bad GPS, detect-and-avoid, or telemetry data. Without the standard, it is not possible to allow 3PWPs to contribute to solving the weather measurement gap and to share data that others would use. Not bringing 3PWPs to the table will limit innovation and agility in accelerating the deployment of advanced weather sensor technology that exists today but is not part of the current aviation weather ecosystem.


Why is having higher-density weather measurements so important? Traditional aviation weather systems rely heavily on modeled forecasts rather than direct weather measurements, especially below 5,000 in the atmosphere and just above ground level. While models allow for an estimate of weather conditions, they can mask potential threats and hazards in the lower atmosphere where drone and air taxi flights occur. Additionally, weather models, no matter the scale and resolution, use a model of what we believe the atmosphere looks like to kick off the forecast simulation, with very little real data in the lower atmosphere. The way to improve weather certainty about what is happening requires real data, and that is TruWeather’s focus. TruWeather recommends sensors to customers and partners that will most likely meet the ASTM F38 Weather Standard and, in some cases, will improve not only operator awareness about what is happening along a BVLOS route of flight but also improve short-range forecasts of winds, cloud ceilings, etc.


             Weather data being verified and validated, with FAA oversight, is of the highest importance for the drone and air taxi industry. At the recent NASA-led AAM Weather Technical Interchange meeting in Washington, DC, the FAA discussed the process for determining how to certify 3PWPs. Referencing the new ASTM F38 weather standard, which was approved on November 8th, 2023, by the ASTM F38 Committee, the FAA seeks to test and demonstrate the standard’s framework that breaks weather data performance into three tiers of accuracy and requires metadata to be provided with each weather measurement or analysis. The FAA envisions it will be up to the 3PWP to verify that the data meets a particular tier and that their internal weather information processes are repeatable and quality controlled. While the FAA will not directly conduct data qualification, the FAA will use a verification process to “trust and verify” that the information being provided by a 3PWP is acceptable. The FAA will qualify a 3PWPs based on their ability to meet a tier. Ultimately, the FAA will soon publish an Advisory Circular on how 3PWPs will become certified.


But how will the FAA decide how 3PWPs certifications are credible? Over the next few years, the FAA has shared that they will conduct research, testing, and use case demonstrations to develop the Advisory Circular guidance. Currently, to operate a drone BVLOS, one must acquire a waiver through the FAA. As a 3rd party weather provider, TruWeather Solutions is preparing to contribute to the FAA data collection and will seek to work with operators who wish to leverage TruWeather’s services under the new Weather Standard framework, submitting an application for Near-Term Approval Process (NTAP) FAA waiver. Future operators could utilize TruWeather Solutions as a means of obtaining a waiver to perform BVLOS operations, and their use cases can be leveraged as repeatable operations to help ensure industry safety.  


Up until now, the FAA has largely allowed the AAM industry to evolve, innovate, and learn under loosely defined weather rules for Part 107, which was appropriate for Visual-Line-of-Sight operations and carefully managed weather risk conditions under BVLOS waivers. The expansion into BVLOS operations, such as commercial drone delivery and air taxi services will demand advanced weather innovation and data certainty; especially when there will be a desire for increased flight time. The lack of weather data could lead to reduced flight times and a burdensome liability risk for operators. 3PWP’s data and weather services can provide a sense of clarity, vision, and trust that the AAM industry can utilize to their advantage.

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