The U.S. Air Force says it has devised a set of fixes for its T-6 Texan II trainer that will hopefully reduce the number of aviators reporting potentially dangerous “hypoxia-like” symptoms during flights. Unfortunately, the process, which includes a total rework of the aircraft’s on-board oxygen generation system, or OBOGS, a revised software package, and changes in maintenance routines, could take up to four years to fully implement – and there still might be more work to do afterward. The Air Force’s Air Education and Training Command (AETC) announced plans to institute the “corrective measures,” which it had crafted together with Air Force Material Command (AFMC) and with input from the Navy and the National Aeronautics and Space Agency (NASA), late on Sept. 13, 2018. U.S. Air Force General David Goldfein, the service’s Chief of Staff, in an interview with the San Antonio Express-News earlier in the month, had said the news was coming, but had declined to offer any specifics.

“So far, technical efforts to date and analysis of data collected have determined that pilots have been exposed to significantly changing levels of oxygen concentration,” U.S. Air Force Lieutenant General Steve Kwast, head of AETC, said in a statement on Sept. 13, 2018. “The varying levels of oxygen concentration, even though in excess of what the body typically needs, has caused physiological stress that most pilots on most days actually adapt to without noticing.” Kwast said that AETC and AFMC’s six-month review had determined that these fluctuations caused physiological stress in T-6 pilots whose bodies were not able to adapt quickly enough. This, in turn, produced symptoms akin to hypoxia, which is a lack of sufficient oxygen in the body, hypocapnea, or insufficient carbon dioxide, as well as other “related conditions.” Symptoms of these conditions can include headaches, disorientation, and even blacking out, all of which can be especially dangerous for a pilot in the air.

USAF A US Air Force T-6 Texan II.

To ensure consistency in oxygen supply in the future, the Air Force has begun a process to redesign the T-6’s OBOGS. The service has not said what this might entail, but it likely has to do, in part, with the system’s filters and drain valves. After the U.S. Air Force’s 19th Air Force, part of AETC, grounded all of its 444 T-6s in January 2018 over concerns about hypoxia, a subsequent inspection found that those parts of the OBOGS had been failing a higher than expected rate. At the time, one pilot, posting anonymously on the Flying Squadron Forums website, claimed that officials had found the systems to be in an “absolutely horrendous” state. The individual wrote that approximately four out of every five of oxygen generation systems failed in the inspection due to a build-up of dirt and other particulate matter in the filters, stuck valves, and kinks in various hoses, which led to water buildup in some cases. There is still no explanation for why this was the case and why it appears to have only become an issue in recent years, despite AETC having first started flying the T-6 in 2001. In addition, the Air Force is working with the T-6’s manufacturer, Beechcraft, which is now part of Textron, to revise the software that controls the OBOGS to help better regulate oxygen flow and reduce variations. The service says the entire process could take anywhere from two to four years to complete and that it plans to pursue a “broader redesign” of the Texan II’s oxygen system related components and systems to fully address the issue. There is no timeframe from when this second effort might finish up.

USAF An instructor pilot and their student get ready for a training flight in a T-6.

In the meantime, the Air Force will implement new maintenance and inspection procedures to make sure the T-6’s existing OBOGS is working as well as it can. The service said that its review uncovered evidence that having ground crews purge moisture from the system on a more regular basis improves its efficiency. We don’t know what that process entails, how often maintainers will now need to perform it, or how this particular issue managed to escape notice in the nearly two decades that AETC has already been flying the Texan II. It is definitely a good thing that the Air Force has identified likely issues with the OBOGS on the T-6. Beyond problems with the system simply being potentially life-threatening, groundings and flight restrictions have hampered the service’s ability to train new pilots it sorely needs. However, the announcement of these fixes might provide little immediate comfort to Air Force aviators in Texan IIs. The service's senior leaders have now vindicated their complaints, acknowledged that there are issues with their aircraft, and will keep them flying for years before they can fully implement the fixes. In August 2018, Aviation Week reported that there had been an average of eight reports of hypoxia-like symptoms from T-6 pilots every month since February, when the 19th Air Force rescinded its grounding order from the month before and began flying the planes again. There is a hope that the issues the Air Force has uncovered with its T-6’s might help in resolving persistent reports of hypoxia-like symptoms among U.S. military aviators flying other aircraft, especially within the U.S. Marine Corps F/A-18 Hornet and U.S. Navy F/A-18E/F Super Hornet communities. There have also been reports of problems with some of the Air Force’s F-35A Joint Strike Fighters and A-10 Warthog ground attack aircraft. The Air Force was able to quickly link problems with older A-10s that use a liquid oxygen-based oxygen system to poor maintenance rather than a design flaw and fixed those issues. What caused the hypoxia-link symptoms among pilots in newer Warthogs, which have a modern OBOGS that generates its own oxygen continuously, remain unanswered.

USN Pilots flying the US Navy's F/A-18E/F Super Hornets, like the one seen here, have persistently reported hypoxia-like symptoms for years. Just in May 2018, one of the jets had to divert to Incirlik Air Base in Turkey while on a combat mission after the pilot experienced a worrying physiological episode.

On Sept. 11, 2108, the Air Force and the Navy also announced they were pooling their resources to form a Joint Physiological Episodes Action Team, or J-PEAT. “Physiological episode,” or P.E., is the official U.S. military term for unexplained reports of hypoxia-like symptoms. In August 2018, NASA began conducting research flights to have collect baseline data on how pilots’ bodies respond to various stresses of flying to support the U.S. military’s efforts to determine the cause or causes of why aviators do not appear to be getting enough oxygen in various aircraft. The baseline data will help organizations such as J-PEAT understand what they should be seeing compared to the information they are getting from pilots. “Since our T-6 operational pause [the January 2018 grounding], we have made every effort to communicate with every instructor and every student exactly what we’ve found,” U.S. Air Force Major General Patrick Doherty, commander of the 19th Air Force, said in a statement on Sept. 13, 2018. “Transparency remains of utmost importance to use as we all work together to ensure that our pilots are safe and know the way ahead.” For now, T-6 pilots do now know the way ahead, but they also know that it is still years away from becoming a reality. Contact the author: jtrevithickpr@gmail.com