"The armed services are still unsure why Navy and Air Force pilots are struggling with their Onboard Oxygen Generation System (OBOGS) while the Marine Corps – which uses the exact same systems – has had no problems, the Marines’ top aviator told reporters.
Not a single naval flight student has flown since late March, after a spike in troubles with the T-45C Goshawk trainer aircraft that led to hypoxia, when the pilot receives either a lack of oxygen or contaminated oxygen....
...Lt. Gen. Jon Davis, deputy commandant of the Marine Corps for aviation, told reporters after a Senate Armed Services seapower subcommittee hearing on Tuesday that the
Marine Corps has had zero instances of hypoxia with its F-35Bs or with its AV-8B Harriers, which use the same OBOGS as the T-45C.
“Nothing on the B right now, so we’re not suspending flight ops. We’re watching very closely what’s going on in the Air Force, understanding – almost like
the same OBOGS onboard oxygen generating system that’s in the T-45 is in the Harrier, we have no problems in the Harrier. So it’s one of those things [Naval Air Systems Command] is looking at; is it because we’re pulling air from a different part of the motor? So looking at that, understanding what the differences are. But we haven’t had any problems with OBOGS.”
Asked by USNI News if the Marines maintain or operate their OBOGS differently than their sister services, Davis replied, “we are looking at all that.” He noted that
not all Air Force F-35A squadrons have experienced problems, just those at Luke AFB, so it would take time to understand what is creating that situation....
...Naval Air Systems Command (NAVAIR) is conducting a PE Review on behalf of the Navy and Marine Corps, but NAVAIR Commander Vice Adm. Paul Grosklags said in the hearing that “we’re not doing well on the diagnosis” of the problem. He noted that NAVAIR is simultaneously looking for the root cause and pursuing 10 to 12 “alerting and protective measures” that would make it safe for students to return to the T-45 even without understanding why the OBOGS is failing.
“It is our plan that once we are comfortable that we’ve got those individual items all in place for every single aircraft and air crew down at CNATRA (Chief of Naval Air Training), that is the point where we will consider resuming the training syllabus,” Grosklags told the subcommittee, adding that he hoped that would happen in a matter of weeks rather than months but that a bit more testing of some of the items was still needed.
Finding the root cause of the problem has been a much less successful endeavor so far, though.
“To date we have been unable to find any smoking guns. For T-45s specifically … to date we have not been able to discover a toxin or a contaminant in the breathing gas despite our testing,” the vice admiral said.
“We have taken several of the aircraft from CNATRA, from the training squadron, brought them up to [Naval Air Station Patuxent River] and we have torn some of them apart, to the extent that we took every component in that gas path, that breathing gas path if you will, on the aircraft, starting with the engine and going to the entire system, inspecting all the piping in between, all the way up to the mask and the vest that the aircrew wear. We’ve subjected each one of those individual components to extremes of testing, extremes of environmental conditions in excess of what we would ever expect to see in the aircraft, and we still have not been able to find what we would consider a proximate cause of contamination or something being released into that gas path. We are also doing testing at the system level, we are flying entire aircraft – again, these are aircraft that had issues down at CNATRA – we’re flying entire aircraft with additional instrumentation on the aircraft trying to detect some in-flight real-time. To date we have not been able to find that root cause.”..."
https://news.usni.org/2017/06/14/avi...navy-air-force