F-35 News. Some are speculating that oxygen deprivation led to the Japanese F-35 crash...

Thanks to Fonck for the link!

via Asia Review.

 In the weeks since a Japanese F-35A stealth fighter jet crashed into the Pacific Ocean, the U.S. and Japan have not yet found either the plane or the cause of the incident. But it could be linked to a system that has bedeviled the American military for years.
All F-35s have onboard oxygen generation systems, or OBOGS, which draw oxygen from the surrounding air and supply it to the pilot at the high concentration necessary to operate at high altitudes. The U.S. Air Force, Navy and Marine Corps have used OBOGS for more than three decades, in models including the F-16 and F/A-18 as well as certain training planes.

But since the U.S. began using OBOGS in the F-22 in 2008, there have been more than 20 cases of F-22 pilots experiencing symptoms indicating a lack of oxygen, apparently due to problems with the system. An F-22A crashed in November 2010 in an incident that may have resulted from an oxygen shortage.

Low levels of oxygen in the bloodstream -- known as hypoxia -- can cause sweating, headaches and dizziness, followed by vision problems and trouble making decisions, and eventually loss of consciousness. After the 2010 crash, the U.S. military temporarily stopped using OBOGS in the F-22 while it worked to address the issue, in part by replacing components in the system.

But the problem persisted in multiple jet models, including the F-35A. The military has not worked out the cause but reportedly has increased the emergency oxygen supply provided to pilots in case the OBOGS fails, among other precautions. Put bluntly, it is employing every trick it can think of to keep using the system.

With the Japan incident, the Air Self-Defense Force pilot called a halt to his training exercise just before the crash. This suggests that he realized something was wrong, after which the situation quickly deteriorated. That would fit with hypoxia caused by an OBOGS malfunction.

Story here. 

This fits but is a bit curious at the same time.  The US military has been faced with this situation for awhile now.

I remember the F-22 crash and what was the response?  To blame the pilot.  Later they admitted that the OBOGS system is trash.

Have they solved it?

Nope.

It appears that troubles remain for a system that has been in service for decades.  What I'd like to know is why it's so hard to troubleshoot.  Take a look at when it worked without issue and then trace the changes in its design.

This doesn't seem like it should be a tough engineering problem to solve yet here we are.