Maj. Gen. Patrick Doherty, 19th Air Force commander, has ordered an end to the operational pause of the T-6 Texan II fleet, with flying operations resuming Feb. 27 following the collection and analysis of operational flight test data.
The pause was the result of multiple unexplained physiological events experienced by AETC pilots at several bases during the last two weeks of January. The incidents were different from classic hypoxia, which is caused by oxygen deprivation.
“The operational pause was required to provide a robust and intrusive look at every component on every aircraft connected to or critical to the On-Board Oxygen Generating System,” said Doherty. “Our intent was to ensure aircrew awareness of UPEs, as well as newly-required aerospace physiology training, checklist procedures, and flight equipment modifications that ensure aircrew safety.”
Following the incidents, Doherty assembled a team including experts from the Air Force, Navy, NASA, and medical specialties, to aggressively capture and analyze data from the pilots who had experienced physiological events and the aircraft. Collaboration with Navy officials allowed 19th Air Force officials to gain insights and lessons learned from similar events in the T-45 Goshawk.
“The team was tasked with identifying the root causes and driving solutions toward protecting the aircrew,” said Doherty. “After listening to pilots, maintainers, engineers and flight surgeons, it became apparent the T-6 fleet was exhibiting symptoms indicative of a compromise of the integrity of the OBOGS, leading to degradations in performance, which then likely led to the pilots’ physiological events.
“As tests, inspections, and data were gathered, component failures or degradations were identified as affecting the topline performance of OBOGS oxygen pressure, flow, and content,
resulting in various disruptions that negatively impacted the human-machine interface,” said Doherty. “Further investigation by engineers and flight surgeons is needed, but the speed at which professionals descended on this challenge to share their expertise and solutions was phenomenal.”
The engineers will continue studying the data and running further tests for final root cause diagnosis for greater insights and applications for future aircraft designs.
“With 30 years of flying experience, looking at all of the facts and listening to our experts, these particular types of T-6 UPEs aren’t unexplained anymore in my mind,” Doherty said. “We have zeroed in on a handful of components that are degrading or failing to perform and needed to be replaced or repaired more often than the Air Force anticipated when they bought the aircraft.”
With the new, reoccurring inspections focusing on OBOGS components, 19th Air Force officials hope to drive down the number of physiological events in the future.
“I’m very confident the team has reset T-6 OBOGS system back to peak performance for our pilots,” said Doherty.
“Proactive maintenance mitigation practices and inspections based on flight hours, have been created and are being accomplished on a much more aggressive timeline to ensure high performance of the OBOGS,” said Doherty. “The scientists, engineers, and flight surgeons will continue to investigate the UPEs, and will also review the original acquisition and sustainment strategies developed when the aircraft was bought about 20 years ago.”
Doherty also reported that the cadre of more than 40 pilots who participated in the flight tests have a reinvigorated confidence in the reset of the OBOGS system after personally seeing all the data and experiencing the flights.
Instructor pilots will be the first to return to flying to regain currencies, followed by students, who will go back to flying by the end of the week. This will start with warmup sorties to regain currencies before going forward with sorties required by the syllabus.
“The T-6 has been an incredible workhorse for the Air Force and has safely flown more than two million flight hours, but the aircraft is about a third of the way through its lifecycle and we need to institutionally arm our phenomenal aircraft maintenance professionals—the best in the world—with wise maintenance and sustainment strategies and policies that ensure continued safe flying operations for our aircrew in the future,” said Doherty. “I have been able to visit each pilot training base in the last two weeks and after looking each one of them in the eye, I know without a doubt that the T-6 nation is fired up and ready to get back in the air!”