https://aviationweek.com/defense/t-6-pilots-report-eight-new-physiological-events
"U.S. Air Force student and instructor pilots have reported eight additional physiological events in the T-6 Texan II trainer since March 1, but the service is not currently considering grounding the fleet for what would be the second time since the beginning of the year.
The T-6s returned to the skies Feb. 27 after a series of hypoxia-like cockpit events caused an almost month-long stand-down for the fleet. The aircraft, which the Air Force uses to train all new pilot candidates, resumed flying operations even though a team of investigators still had not found the root cause of the incidents.
And even though the Air Force has identified several issues with the aircrew breathing system, particularly with the Onboard Oxygen Generation System (Obogs), pilots are flying without any restrictions to flight parameters or training profiles, Col. Lee Gentile, deputy commander at the 71st Flying Training Wing, told Aviation Week in March.
In response to Aviation Week’s story, Rep. Mike Turner (R-Ohio), chairman of the House Armed Services tactical air and land subcommittee, urged his fellow lawmakers to hold the Air Force accountable for the T-6 incidents.
“These physiological episodes are not individual incidents. At this point we have an aggregate of these mishaps that points to a systemic issue,” Turner tweeted April 17. “As we look to #FY19NDAA, attention must be paid to these unprecedented issues.”
The Air Force apparently decided returning the T-6s to flying status without identifying a root cause was worth the risk, as the service struggles to overcome a critical pilot shortfall. The almost month-long pause came at a significant cost, with undergraduate pilots unable to fit in crucial flight time.
This year the Air Force will fall about 200 aviators short of its goal to ramp up annual pilot production to 1,400—primarily due to the T-6 pause, Air Force Chief of Staff Gen. David Goldfein recently told the House Appropriations defense subcommittee.
The urgency of the pilot shortfall helps explain why the Air Force is hesitant to ground the fleet once more. But service officials stress that the T-6 is safe to fly. The 19th Air Force has taken several steps to mitigate the problem, including implementing new inspection procedures, purchasing new testing and monitoring equipment, improving maintenance, and educating pilots on how to respond to inflight physiological incidents, Gentile said.
The “19th Air Force is not considering an additional operational pause of the T-6 fleet at this time,” Air Force spokeswoman Lt. Geneva Croxton said April 14. “The initial pause was a requirement due to the unexplained nature of the physiological events experienced.”
While the fleet was grounded, the 19th Air Force conducted a thorough inspection of the breathing system—from the engine bleed air port to the pilot’s mask—on all 444 T-6s, officials said. Investigators found several problematic issues with the system, such as excess moisture in the condensers and sticky valves, Air Force Material Command Chief Gen. Ellen Pawlikowski told reporters March 14. The team is fixing those issues, and also is re-evaluating how often certain components of the breathing system should be replaced in maintenance, she noted.
Interestingly, Lt. Gen. Lee Levy, commander of the Air Force Sustainment Center, noted that the service is not responsible for most of the maintenance on the T-6. The majority is all done through the contractor, Textron, he said in an April 16 interview.
“I can’t tell you what the root cause is for these [unexplained physiological events],” Pawlikowski said. “I can tell you they are real, but we have work to do.”
Pawlikowski added that she believes the aging of the aircraft has caused something to change, either in the air flowing into the Obogs or in the guts of the system. But she cautioned against jumping to conclusions.
The Air Force also is considering adding an automatic backup oxygen system to the T-6s, much like the service did with the F-22 fleet after the 2010 death of Capt. Jeff Haney, Pawlikowski said."