Flying Below the Radar

written by – Lisa Hahn, UAS/Aviation Meteorologist

Key Take-Aways:

• Current weather sensing and radar infrastructure not extensive enough to support drones.
• On marginal weather “edge-case” days, it is generally accepted that businesses will underperform against revenue generation per airframe or client satisfaction metrics. 
• TruWeather is fielding a variety of novel sensors to improve low-altitude weather surveillance.

As drones begin to fly more frequently Beyond-Visual-Line-of-Sight (BVLOS), low altitude weather is becoming more impactful to operations and business return on investment. Current Federal Aviation Administration (FAA) uncrewed flight rules limit commercial drones to flight below 400 feet, require 3 miles visibility and remain 500 feet below the clouds.  The pilot has always been the best weather sensor to compensate for unexpected weather. Without a pilot physically located on the aircraft, micro-weather hazards not captured with current weather measurement systems or weather models, increases flight risk significantly.

The current state of the weather sensing and radar infrastructure is simply not extensive nor granular enough to capture Uncrewed Autonomous Systems (UAS) impacting environmental conditions on a regular basis. Today, up to 30 percent of manned aviation flights cancelled or delayed due to weather COULD HAVE FLOWN.  What causes these unnecessary groundings?  Lack of certainty about what is happening or ambiguity in the weather forecast.

Uncrewed airframes and sensor payloads are much more weather sensitive. They become less effective, and experience reduced range against airframe specifications when encountering certain environmental conditions. Those conditions are not always obvious. Small UAS (sUAS) are particularly vulnerable to otherwise seemingly benign winds Above Ground Level (AGL), low-level altitude wind shear, wind shear in urban built airways, updrafts, downdrafts, cold and hot (density altitude) temperatures, icing, and precipitation. Small or large, no platform is immune. Light winds at the surface during early morning hours can give a false sense of security.  In certain atmospheric inversion situations, strong, turbulent winds lurk below 2,000 feet AGL, and descend through to the lowest 400 feet of the atmosphere when surface temperatures increase a few hours after sunrise.  There have been several documented visual-line-of-sight operations that ended with incidences due to this phenomenon.

Weather radar observations can also evoke a different layer of uncertainty. For precipitation events, what a remote pilot sees on a weather radar display may not be hitting the ground or the precipitation that is occurring is not detectable. On marginal weather “edge-case” days, it is generally accepted that businesses will underperform against revenue generation per airframe or client satisfaction metrics. The US government’s 160-weather radar network has a multitude of coverage gaps. The Forbes article by Jim Foerster, Weather Radar Gaps: Why They Exist And The Related Risk Factors, explains that “The deployment of ‘Next Generation’ (NEXRAD) radars in the early 1990s was a major step forward in being able to sample precipitation and detect severe storms across the continental United States. However, there are still some limitations within the radar network, primarily driven by terrain, geography and curvature of the Earth. Specifically, due to the curvature of the earth, radar beams cannot see the entire atmosphere as the horizontal beam coming out from the radar increases with height as it moves further from its origin. The current radars have a range of 143 miles for highest resolution and can be extended to 248 miles in a long-range/lower resolution version.” The article continues, “Major population centers are fortunate to have the highest of quality radar data available for forecasters, but in some spots in the Plains or Mississippi River Valley the radar beam is only sampling data from 6,000-10,000+ feet above the ground.” In some remote mountainous areas and in areas of the country where the radar beam is 5,000 feet or higher, undetectable phenomena such as drizzle, freezing drizzle, freezing fog, and even lake enhanced rain and snow showers can go undetected and requires a meteorologist to infer what is really happening. 

TruWeather Solutions (TWS) has been focusing on these weather gap challenges in UAS operations over the last 5+ years.  We use crowd-sourced micro-weather data and are working with partners to field a network of networks using novel sensor solutions to close the low-altitude weather measurement gaps that weather satellites cannot adequately provide today, nor will in the foreseeable future. With our partners, we strive to commoditize these novel sensing approaches affordably to better understand weather conditions.  The highest density data, AGL, provides uncrewed operators data that mitigates the absence of a pilot on the aircraft and heuristics. FAA Part 107 allows remote pilots to use non-certified weather sources to fly drones.  Part 135 says the pilot is responsible for knowing the weather conditions in which they are flying.  TWS is educating pilots about the science and technology that is available today and, not part of the aviation weather services and weather apps. The current weather strategy generally used in the industry today is not scalable for BVLOS operations. TruWeather anticipated this and has been preparing to address the weather gap for years, based on 40 years of military weather, logistics and technological experience. TWS is ready to support and protect remote pilots, dispatchers, schedulers in meeting client expectations and business goals when micro-weather uncertainty impacts a BVLOS Go-No-Go decisions. 

With our partners, we are focused on solving real weather shortfalls with real weather data from a suite of novel sensors that can detect micro-climate winds, winds aloft, ceiling, visibility and even icing in cloud.  We use weather model data tuned for UAS pain points at very high fidelity and will roll out this framework out in North Dakota in October 2022. In addition, this fall we will be using capabilities to build an MRI of the near-Earth environment in Hampton, VA using scanning wind lidars.  Improved data will provide knowledge and certainty about precarious weather events for drones and eVTOL operations, determine “all-clear” after a hazardous weather event, and provide longer flights when data makes it safe to do so.  We can plug and play new sensors and deliver the data cost-effectively to you through our APIs or web application.