- US Air Force/Master Sgt. Jeffrey Allen
- Numerous Air Force planes were grounded in 2017 after pilots experienced symptoms of oxygen deprivation while in flight.
- Both Air Force and Navy planes have seen such incidents over the past several years, but military officials have struggled to find root causes for them.
- The Air Force has formed a headquarters-level team to take a force-wide look at the problem and recommend steps to reduce and eliminate them.
After a spate of physiological incidents involving cockpit oxygen supplies last year, the Air Force has selected a general to lead a team investigating the episodes.
Pilots flying several types of aircraft experienced symptoms of what appeared to be hypoxia, or oxygen deprivation, which led to the grounding of some Air Force A-10 Thunderbolts, F-35A Lightnings, and T-6A training aircraft.
“As part of the integrated effort to address physiological events, the Air Force is providing more resources to understand [unexplained physiological events], standardize response actions to such events and assess options for more robust aircrew training to recognize and respond to these events,” Brig. Gen. Bobbi Jo Doorenbos, who was picked to lead the team, said in an Air Force release on Monday. “Our ultimate goal is to prevent UPEs.”
A physiological event happens when pilots experience symptoms that can be caused by a number of factors, like hypoxia, that can cause dizziness, confusion, and impair a pilot’s ability to fly.
The team is still waiting for the Air Force’s deputy chief of staff for operations to approve its charter, according to Aviation Week. Once that charter is signed, the team will start to gather information in order to determine if previous recommendations were implemented correctly.
The Air Force grounded all F-35A Lightning II’s at Luke Air Force Base on June 9, 2017, after five incidents in which pilots experienced hypoxia-like symptoms. In each case, the pilot’s backup oxygen system worked and the pilot landed safely.
A few days after that grounding, the Air Force disclosed 15 cases of pilots experiencing similar symptoms between 2011 and 2017. Five took place between May 2 and June 8; the other 10 were considered isolated incidents.
F-35A operations at Luke Air Force Base were cleared to resume on June 21. At that time, investigators hadn’t found root causes for the incidents, but took steps to avoid repeating them, like instructing pilots to avoid altitudes where such incidents took place and increasing the minimum levels for backup oxygen systems on each flight.
Aviation Week reported in early January that dozens of A-10 Thunderbolts had been grounded at Davis-Monthan Air Force Base in Arizona in late November after two pilots experienced in-flight physiological episodes that caused hypoxia-like symptoms. In both cases, the backup oxygen system worked and the pilots were able to land.
- US Air Force
One pilot was using an older liquid oxygen system, which most A-10s have, when the incident occurred. Air Force officials quickly determined the issue with that system and fixed the problem.
The other pilot, however, was using the Onboard Oxygen Generation System, or Obogs, which is found in the rest of the fleet. A third pilot had a problem with the Obogs while on the ground.
Investigators could not immediately determine the cause of the Obogs problem, leading Air Force officials to ground 28 A-10s using the system at Davis-Monthan. Flight operations for Obogs-equipped A-10s resumed about a week after the grounding, though investigators had not determined an underlying reason for the malfunction.
In mid-November, the T-6A Texan II aircraft in use at Vance Air Force Base in Oklahoma were grounded after four physiological incidents with hypoxia-like symptoms that month. T-6A flights resumed in early December, but investigators had not found specific root causes for the incidents, Air Force officials said at the time.
‘We are aggressively addressing these events’
These incidents have not been limited to those aircraft. Pilots of F-22 Raptors, F-16 Fighting Falcons, and F-15 Eagles have reported hypoxia-like incidents in recent years. An F-22 pilot was killed in a 2010 incident in which his oxygen system cut off; the cause for the malfunction has not been found.
Nor is the problem limited to the Air Force – Navy pilots in the T-45 Goshawk training aircraft, F/A-18 Hornets, Super Hornets, and EA-18G Growlers have also experienced hypoxia-like incidents at an increased rate over the past several years. Hypoxia-like symptoms have been linked to the deaths of four Navy F/A-18 pilots.
- (US Air Force photo/Staff Sgt. Jensen Stidham)
The military has struggled to resolve the problem. It’s not clear whether all cases are hypoxia-related – i.e. stemming from an insufficient supply of oxygen – or related to other problems that cause similar symptoms. There are often few common factors, as oxygen deprivation affects pilots in different ways and because different planes in different branches of service use different systems to deliver air to pilots.
Doorenbos told Aviation Week that her team would take insights from previous investigations into physiological episodes – such as changes in maintenance and training procedures – and apply them at a higher level.
Doorenbos, who stressed the rarity of such problems, also said she would work closely with her Navy counterpart. Military officials have said the results of their investigations would be shared with industry partners and academia – as well as with pilots, in order to reduce the stigma related to reporting such incidents.
“Despite the serious nature of these events, the overall historic rate of UPEs is incredibly low. The probability that a pilot will experience a physiological event is less than 1 percent per year,” Doorenbos said in the Air Force release. “Still, we are aggressively addressing these events and communicating with aircrew so they remain confident in their aircraft and weapon systems.”