JB SAN ANTONIO-RANDOLPH, Texas — Since late last year, a rash of unexplained physiological events such as hypoxia has caused dangerous breathing problems for pilots of T-6 Texan II training aircraft, and led to multiple groundings.

But now, the Air Force is finding more clues, and coming closer to solving the problem once and for all, said Lt. Gen. Steven Kwast, head of Air Education and Training Command.

“Within the next couple of months, you’re going to see some communication from [the safety investigation board at Edwards Air Force Base in California], that they are starting to really discover the root cause here,” Kwast said in a July 23 interview at his office here. “We’re finding insights that we did not know before, that will help us understand what’s going on and give us a pathway to solving the problem permanently. We’re getting close, and you should see something soon.”

For example, Kwast said the board has discovered that the proportion of oxygen in the air sometimes fluctuates more than intended while T-6s are in flight.

“So the question is, what does that do to the human body, when you have a fluctuation of oxygen?” Kwast said. “That’s the kind of work they’re doing as they discover something that is a little … different than what we thought. Because we’re measuring it with more precision; we do the work, the scientific method [to find out] ‘What does that mean?’ ” and what’s causing it.

He stressed, however, that oxygen fluctuation is only one of several possible issues the board is looking at, and that it’s too soon to say whether it is actually causing or contributing to the problem. It could also be a combination of factors working together to cause the so-called unexplained physiological events, or UPEs.

“It’s not just one thing, and that’s the problem with things like this," Kwast said. “To be myopically focused on one thing like oxygen fluctuation does not account for the psychological piece, it does not account for the breathing habits piece, and the fact that this is a human-machine interaction that is a very complicated and complex system. ... It may be contributory, but it may not be causal.”

Lt. Gen. Steven Kwast addresses Air Education and Training Command for the first time after assuming command on Nov. 16. (Sean Worrell/Air Force)
Lt. Gen. Steven Kwast addresses Air Education and Training Command for the first time after assuming command on Nov. 16. (Sean Worrell/Air Force)

The UPE problem has been frustrating the Air Force for months, and drawn criticism from lawmakers who have demanded Air Force officials do more to fix it.

Most recently, the 559th Flying Training Squadron at Randolph grounded its T-6s for a day in late June after pilots reported problems with the On-Board Oxygen Generating System, or OBOGS. The Air Force’s entire Texan fleet was grounded for nearly all of February after 13 pilots at three bases had unexplained physiological events during the last week of January.

Pilots suffering these problems report experiencing shortness of breath and disorientation, which can be extremely dangerous and lead to confusion, faintness or even loss of consciousness. These conditions include hypoxia, or too little oxygen in the body, or hypocapnia and hypercapnia, conditions when the bloodstream has either too little or too much carbon dioxide.

Kwast said the Air Force has found UPEs tend to happen more often at bases where contractors maintain the planes, and less often when there are government maintainers.

“We aren’t sure why,” he said. “Maybe the government maintenance tends to replace parts a little more liberally than contract maintenance, where the cost is such a focus that they’ll let a part go longer. A government maintainer would replace it [even though they’re not required to at that point], a contract maintainer might say, ‘Oh, we’ll let it go another month.’ ”

It’s possible the government and contract maintainers may have slightly different processes, which could lead to UPEs in the contractor-maintained planes, he said. For example, a government maintainer might cover a port before washing the plane, he said, but a contractor might leave the port uncovered, which could lead to moisture getting in the system and possibly contributing to hypoxia or other such problems.

“That is a very nuanced thing that requires some real deep research to know what’s going on,” Kwast said.

Kwast said the UPE incidents are still happening episodically in T-6s, and that investigators are looking for patterns to try to identify the source of the problems.

He also said that the increased awareness and visibility of the UPE problem could be contributing to the increased reporting of issues like hypoxia, because people now know what to look for.

It’s also led Kwast — a former T-6 instructor pilot — to reconsider some of his own experiences in the air. When Kwast looks back on his 650 hours in the Texan, he now realizes that he may have had some physiological incidents in years past that went unrecognized.

“I just thought that I hadn’t drunk enough water that day and so I was feeling lightheaded, or that I was tired because I hadn’t slept well that night, but I felt good enough to fly,” Kwast said. “But thinking back on it, maybe it was that the system wasn’t quite delivering the way it should have been delivering.”

But it also sometimes leads to confusion over whether a rookie pilot is actually experiencing a problem like hypoxia, or simple nervousness.

“A young kid that’s brand new to this, gets in the aircraft, and it’s their first flight, they’re hyperventilating,” Kwast said. “And they go up, and they’re like, ‘I had an unexplained physiological event.’ And it’s really hard to know whether they did, or whether it’s just the fact that they are so new to this, they don’t know what right looks like, and they were hyperventilating."

Without systems to precisely measure whether a pilot is actually having a problem like hypoxia, or simply nervous and hyperventilating, such incidents can get buried in the data alongside actual physiological incidents, Kwast said. This makes it even tougher for investigators to find the true root causes, he said.

“That’s why this effort is so important at Edwards Air Force Base," Kwast said. "Because they can do the scientific method and hold these things constant.”