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The "Windy Radar" Mitigation Project

March 26, 2022

The "Windy Radar" Mitigation Project
By Lt. Col. Kevin McDowell

On Jan 5, 2022, Civil Air Patrol completed a new round of Windy Radar flights for the FAA and USAF.These flights are crucial in developing a plan to mitigate the interference and clutter created by wind turbines located in close proximity to Travis AFB.

Wind turbines cover the landscape of California and across the United States. They are an important part of the energy infrastructure accounting for a significant portion of the electricity supplied in the United States.

However, wind turbines located within the line of site of radar systems create a unique challenge especially for radar systems involved in air traffic control, weather forecasting, homeland security, and national defense missions. One such case is located at Travis Air Force Base, in Northern California.

The wind resource area (WRA) at Travis Air Force Base contains nearly over 600 wind turbines within a 5 nautical mile radius located approximately 9-nautical miles southeast of the base. It penetrates Travis Class D airspace (tower airspace).

Wind turbines may appear as targets identical to aircraft on air traffic control displays, they compromise air traffic control safety with false targets, and they increase workload for air traffic controllers.

The wind industry wants to increase the number of wind turbines in California. Newer turbines will be larger than current ones, cover greater swaths of land, and, consequently, exasperate air traffic control. Therefore, Travis AFB is seeking solutions to be able to cooperate with the wind industry while providing safe air operations.

One approach of providing technical mitigation for wind farm interference and clutter is ‘infill’ radar for coverage in and around the wind resource area. Basically, this involves excluding the currently degraded air traffic control radar that shows interference and clutter from the operator. This excluded area is then filled in with data from the infill radar that can process targets with little impact by the wind farm.

While the process begins with modeling proposed wind turbines and simulating the impact they may have on radar systems, real time data is required throughout all stages of the effort - and that is where Civil Air Patrol comes in. The FAA and USAF tasked CAP to fly a number of flights to assist in modeling, testing and validating the performance of an infill radar.

This effort, in conjunction with Travis AFB, FAA, USAF and other agencies, began in 2018. Major Steve Renwick was initially approached with a request to utilize CAP aircraft to fly a number of patterns in and around the turbine farms south of Travis AFB designed to stress the radars and trackers.

Patterns generally included various forms of parallel lines and expanding/contracting squares – something we know well! The goal of this set of flights was to gather data to allow for the analysis of the interference, determine the performance of the infill radar, and provide information critical to identifying potential changes for air traffic control.

During this initial phase, we flew approximately 140 hours (120 hours of sorties and 20 hours of relocation) utilizing dozens of pilots, observers, ICs, MRO, and staff. The data provided was extremely well received and was crucial in developing a plan to mitigate the interference and clutter. This initial effort, dubbed the Pilot Mitigation Program (PMP), eventually identified benefits for an additional primary radar and provided options for further consideration.

In 2021, CAP was again approached to continue our partnership to help certify and validate changes made to the software and radar infrastructure with a future goal of certifying infill radars for use in the National Airspace System (NAS). The current mission includes two ‘sets’ of flights.The initial set is led by the FAA to test and certify changes to the system. The second set of flights is USAF-led to explore system changes to improve infill radar performance for air traffic control operators.

In total, the current request is for approximately 12 days of flying, utilizing two aircraft each flying two sorties per day. Typical sorties are 2-3 hours.

On Jan 5, 2022, after previously scrubbing the mission due to weather, the first of these flights was completed successfully. This not only included the ‘typical’ parallel and expanding square pattern, but a new pattern – a type of DME Arc, allowing the crew to dust off some, undoubtedly, older skills. A sampling of the GPS data is shown below. The first set of flights were completed on January 26th with almost 50 hours of flight time.

The “Windy Radar” program has successfully highlighted the strengths and capabilities of Civil Air Patrol and California Wing. San Francisco Bay Group 2 has taken the lead with additional resources and support from members throughout the Wing. The flights conducted thus far have been extremely successful and have reinforced the customer’s view of CAP and CAWG as a highly skilled and professional resource. The data provided has been critical in improving the radar infrastructure and, as a result, safety within the aviation industry and allowing for the continued expansion of wind energy as an alternative energy source.

The CAP aircraft flew north of Travis AFB so the FAA could baseline the infill
radar performance in the clear without any wind turbine clutter.

The CAP aircraft flew over the wind turbines (white dots) to demonstrate infill radar
performance with the clutter. The flight profile is challenging for the radar and the
sharp turns are challenging for the trackers.

An infill radar unit that CAP is helping the
FAA with data collections.

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