Phoenix Air Unmanned completes 13,000 miles of BVLOS utility inspections


Phoenix Air Unmanned, LLC (PAU) passed the 13,000 mile mark in utility transmission line inspection flights for Xcel Energy last week. Total mileage is another milestone for a program designed to build on traditional inspection methods in the utility industry and advance unmanned aircraft system (UAS) operations beyond the visual line of sight (BVLOS) in the national airspace system. The flights began in 2019 and have been conducted each spring and summer, with 2021 alone accounting for 5,300 miles.

UAS inspection flights are conducted under the Xcel Energy Waiver Certificate authorizing BVLOS flights without the requirement of visual observers along the flight route. The waiver allows the technology to be used as a means of airspace surveillance and authorizes an operational area covering 18,000 miles of Xcel Energy transmission infrastructure. Xcel first achieved two-year approval in 2019. After two years of successful operations and a safety assurance assessment by the Federal Aviation Administration (FAA), a duplicate two-year waiver has been requested and granted in the fall of 2021.

Getting to the point of repeatable and scalable UAS inspection flights was a step-by-step approach to proof of technology and operational concepts. In 2018, Xcel Energy was granted a site-specific waiver – limited to a set of 30-mile transmission lines requiring the use of visual observers. The company worked with industry partners at L3Harris, Northern Plains UAS Test Site, Phoenix Air Unmanned, LLC and Capital Sciences to establish a scalable BVLOS inspection program. Several 2018 test events took place along the 30-mile stretch, ultimately validating the concept of operations and leading to data sets presented to the FAA for 18,000-mile approval.

“In 2015, we flew the first UAS introductory flights for Xcel, which led to the program being extended over thousands of circuit miles,” said Will Lovett, general manager of Phoenix Air Unmanned. “What was once a few miles of inspections per day has become an average of 40 miles per day, with the highest being 124 miles by a single aircraft and crew. Much of the utility industry continues to wait that the FAA is opening up regulations that would provide that level of efficiency, but it’s a program that has at the forefront of regulatory approvals since 2018.”

Inspection flights capture high resolution images of the transmission line infrastructure. On board the aircraft are two Phase One IXM-100 cameras, providing coverage of the transmission structure and utility right-of-way. PAU has captured over 3,000,000 100-megapixel photographs since the program began. Imagery is organized and delivered to eSmart Systems for analysis. The Norwegian data analytics company uses AI technology to evaluate each image for system cataloging and fault detection.

Brian Long of Xcel Energy has been part of the Xcel UAS BVLOS program since its inception and has remained focused on generating actionable intelligence from inspection flights. “The images from the drone are impressive. The flights themselves are a balance between creating efficiency without sacrificing image quality,” Long said. “The high resolution datasets we are able to put into the eSmart inspection tool provide meaningful results to stakeholders within Xcel and we are able to inspect large parts of the system on an annual basis. . Ultimately, we will have a repeatable inspection method that can help increase transmission system reliability.

The Xcel Energy exemption authorizes the use of aircraft from two different manufacturers to carry out the inspection flights. The Freefly Systems Alta X has completed over 10,000 miles of inspection alone. The four-rotor platform with inspection cameras weighs less than 55 pounds and can fly for just over 30 minutes. Flights are planned using structure locations provided by Xcel Energy as individual flight waypoints. Mission plans are uploaded to the Alta X and average about nine minutes per flight. The plane is never picked up at its original take-off location, but rather downriver by a second flight crew located next to the transmission line.

“Freefly makes a reliable aircraft. When we started the approval process with the FAA, we were able to come forward with comprehensive engineering and test data provided by Freefly to complete the beyond visual line of sight exemption request,” said said William Wheeler, director of operations for Phoenix Air Unmanned, LLC. “After accumulating 530 flight hours at nine minutes per real-world flight, the aircraft’s reliability has been proven beyond bench testing.”

Under the extended geographical approval of the Xcel Energy waiver, flights beyond visual line of sight covered Michigan, Wisconsin, Minnesota, North Dakota, South Dakota, Colorado, Kansas, Oklahoma, Texas and New Mexico. Each year, flight crews start in Wisconsin in the spring and descend to southeastern New Mexico in the fall.

“We are very proud of our accomplishments covering so much ground with unmanned aircraft,” said Tom Stegge, UAS program manager for Xcel Energy. “Without regulatory approval, many inspection programs place as many personnel and aircraft as possible on the ground. Unmanned aircraft inspection flights minimize the manpower required for these programs and have been successful in cover more than 70% of our 18,000 mile transmission network – using just one aircraft and one flight crew.

PAU and Xcel Energy recognize that the success of the program is only one step towards standardized regulatory clearance. Both organizations participated in the Federal Aviation Administration’s Aviation Beyond Visual Line of Sight (ARC) Rulemaking Committee, which formed in June 2021. Will Lovett says many of the concepts and lessons learned from thousands of miles of BVLOS inspection flights were offered during committee discussions and are reflected in the ARC’s published final report.

“Each regulatory approval advances the UAS industry in the United States. Whether the approval is site-specific or as broad as 18,000 miles, each approval guides the regulatory process towards a standardized format. The work of the Xcel BVLOS program proves that safe and efficient UAS operations can be scaled to meet the needs of the utility industry as long as there is support from our federal regulators. This team continues to be at the forefront of complex operations with the intention of going beyond the limits of Part 107,” Lovett said.


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