Air Force T-6 Texan II training aircraft returned to the sky this week after a monthling grounding instituted after pilots began experiencing “unexplained physiological events.”
An “operational pause” in place since Feb. 1 was ended Tuesday by Maj. Gen. Patrick Doherty, the 19th Air Force commander, according to a statement from Air Education and Training Command. Instructors were the first back in T-6 cockpits, with students slated to return by the end of this week.
T-6 pilots at Columbus Air Force Base, Miss.; Vance Air Force Base, Okla.; and Sheppard Air Force Base, Texas, had reported 13 incidents involving symptoms different from hypoxia, which can occur when pilots are deprived of oxygen.
During the stand down, medical specialists and experts from the Air Force, Navy and NASA looked at data taken from planes and pilots, and identified component failures or degradations affecting the pressure, flow and content of oxygen fed to pilots, Doherty said.
“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 [On-Board Oxygen Generating System] leading to degradations in performance, which then likely led to the pilots’ physiological events,” Doherty said.
The Air Force has also instituted new T-6 maintenance procedures and inspections based on flight hours and made sure aircrew are aware of the physiological events, new aerospace physiology training, checklist procedures and flight equipment modifications, Doherty said.
Engineers will study data collected during the stand down and run tests before they deliver a final diagnosis that will be applied to future aircraft designs, the statement said.
The grounding has slowed training for the Air Force, which is facing a deficit of about 2,000 pilots amid competition from commercial aviation. Some trainees were transferred to T-38 Talon and T-1 Jayhawk trainers, which prepare pilots to fly fighters, bombers, airlifters and refueling aircraft.
The T-6s typically fly 700 sorties a day out of five bases. They have more than 2 million flight hours and are nearly a third of the way through their expected lifecycle, Doherty said.
“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,” he said.
Vance grounded more than 100 T-6s in November when five pilots reported hypoxialike symptoms in four separate incidents. Flight operations resumed the next month after a two-week investigation into the aircraft’s oxygen system could identify “no specific root cause” for the events.
Unexplained physiological events have been reported in recent years by pilots flying Navy F/A-18 Hornets, Super Hornets and EA-18G Growlers and Air Force F-35A Lighting II stealth jets.
The Navy’s T-45 Goshawk trainer, which is nearly identical to the T-6, was grounded last year following hypoxia incidents.
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