"A comprehensive review of the rising number of physiological episodes and the Navy’s response to those PEs determined the Navy’s oxygen-generation and cabin pressure systems are too complex for reliable performance, and that the process for reporting and investigating the root cause of physiological episodes is “fundamentally flawed,” according to the review released this afternoon.
U.S. Pacific Fleet Commander Adm. Scott Swift, who led the review effort, summed up the challenge of addressing the ongoing physiological episodes by writing in his cover letter, “this is a complex issue, one without a single cause, and therefore, without a single solution. The only common thread running through all of these cases is that aircrew were physically affected.”...
...The report also criticizes the OBOGS and the Environmental Control System (ECS) themselves.
“The integration of the on-board oxygen generation system (OBOGS) in the T-45 and FA-18 is inadequate to consistently provide high quality breathing air. To varying degrees, neither aircraft is equipped to continuously provide clean, dry air to OBOGS – a design specification for the device. The net result is contaminants can enter aircrew breathing air provided by OBOGS and potentially induce hypoxia,” reads the report.
“The environmental control system (ECS) aboard T-45 and FA-18 providing cockpit pressurization is a complex aggregate of sub-components, all of which must function for the system to work as a whole. Aging parts, inadequate testing methodologies and numerous other factors are impacting Fleet ECS reliability, inducing several instances of Decompression Sickness (DCS).”...
...The comprehensive review takes aim at the processes currently used to identify and study PEs in the fleet: from a flawed reporting system that relies on self-diagnosis, to an “engineering-centric
PR mitigation effort in which potential causes can be dismissed without full adjudication,” to NAVAIR’s “organizational alignment that does not reflect the complex, integrated human-machine nature of the PE problem” and looks at each component individually rather than studying the entire set of forces acting upon aircrews....
...“We do not have a water separator mechanism in the OBOGS system for the T-45, where we do on similar OBOGS systems in high-performance jets. If you talk to anybody who studies oxygen systems on an airplane, it’s very clear that you need clean, dry air that is being delivered to the air crew in the right pressure and the right volume. Without a water separator in that system, we believe that there’s a potential for water moisture to get in there and not provide the effective dry air that could cause issues with the right pressure and volume. So installing the water separator is critical, so we’re on path to do that. We’ve got 25 or so that are installed and we’re on a path to complete that by the end of the summer, early fall. So that’s one,” the admiral told reporters today.
“Another one that continues to the water moisture in the line in the bleed air shutoff valve that is right at the exit point for the air that comes off the engine and starts into the OBOGS system. For a lot of reasons, years ago that bleed air valve was causing problems because it was shutting off without warning, those sorts of things, and so we either hard-wired them open or took them out altogether. So our analysis is we need to go back and re-engineer, redesign that bleed air valve so that it operates correctly and actually purges the system from water moisture coming off the engine. That is in the works and those valves will be delivered in a tapered way.”..." [PLENTY MORE AT JUMP]
https://news.usni.org/2017/06/15/nav...methods-flawed