VIRGINIA BEACH — The systems used to generate oxygen aboard the Navy’s fighter jets need to be redesigned because they aren’t consistently providing pilots with high-quality breathing air, which can lead to an oxygen-deprivation condition known as hypoxia, according to a report released Thursday.
The Navy considers the breathing problems experienced by its F-18 and T-45 pilots to be its top safety concern and ordered the head of U.S. Pacific Fleet to conduct a comprehensive review of the problem in April.
Hypoxia symptoms include nausea, tingling, fatigue, and disorientation. Pilots also have been experiencing decompression sickness, which causes double vision, headaches, dizziness and other issues. Broadly, the episodes typically are related to unscheduled pressure changes or pilots breathing gas.
The report said the integration of the onboard oxygen generation system — or OBOGS — in the F-18 and T-45 is “inadequate to consistently provide high quality breathing air.”
“To varying degrees, neither aircraft is able 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,” the report says.
The review didn’t determine a root cause for why a growing number of fighter pilots are experiencing oxygen deprivation, but it did identify several ways it believes it could substantially reduce how often it occurs.
Among other things, the report calls for improving the reliability of the F-18’s environmental control system. Aging parts, inadequate testing methods, and numerous other factors have affected the system’s reliability, inducing several cases of decompression sickness, the report says.
The Navy has begun to replace several of the system’s components and will analyze which others should be replaced. The Navy plans to replace components in 48 jets a year.
In a conference call with reporters Thursday, Vice Chief of Naval Operations Adm. Bill Moran said the Navy would study any source of air that enters the aircraft at any point to identify the root cause of the problems each jet faces.
“We have to start with the sources of where we get the air, so either the oxygen system or the cabin air system,” Moran said. “We’re looking at any source of air that goes into the cockpit at any stage of flight or on the ground.”
Many of the breathing problems occurred among F-18 Hornet and Superhornet pilots based at Naval Air Station Oceana, the Navy’s master jet base on the East Coast. However, at least two cases of hypoxia were reported by pilots assigned to the Norfolk-based aircraft carrier USS Harry S. Truman on its last deployment.
Despite the frequency of the hypoxia episodes, the report says pilots remain confident in the safety of their aircraft.
“This confidence stems, in part, from the measures in place and treatment available to mitigate and reduce the risk of loss of life or aircraft from” physiological episodes, or PEs, the report says, noting that breathing problems are manageable using Navy procedures.
The Navy said it primarily has been working to address aircraft system malfunctions.
But the Navy’s examination has been complicated by human factors that contribute to what it refers to broadly as physiological episodes such as fatigue, dehydration, diet, nutrition, anxiety, panic and hyperventilation, the report says.
“To date, finding a solution to the U.S. Navy and U.S. ‘ high-performance jet aircraft PE challenge has proved elusive. The complexity of aircraft human-machine interfaces and the unforgiving environment in which aircrew operate will continue to generate PEs whenever systems do not operate as intended or human physiology is a factor,” the report says.
While the Navy has been working to address breathing problems for years, the issue took on prominence in March after instructor pilots canceled 40 percent of T-45 flights after raising concerns about breathing problems caused by contamination of the T-45’s oxygen system.
The T-45 is a training aircraft used by future F-18 pilots; its commands are based in Meridian, Miss., Kingsville, Texas, and Pensacola, Fla.
The review by Adm. Scott Swift identified fundamental problems he says need to be addressed, including the integration of the onboard oxygen generation system in the F-18 and T-45.
But the report notes there are a variety of other factors that can contribute to the problems aircrews are facing.
“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,” Swift wrote in a memo.
The report also says the current reporting process is fundamentally flawed because most of the data comes from the aircrews who report having potential cognitive impairment.
“Aircrew physiological and performance monitoring before, during and after flight could mitigate this shortfall, but rarely occurs,” the report says.
Since 2010, when new tracking measures were put in place, the number of oxygen-related problems experienced by F-18 pilots has grown from 31 in 2011 to 114 in 2016. There have been 52 episodes among F-18 pilots so far this year, the report says.
The Navy already has taken more than a dozen actions to mitigate physiological episodes among F-18 pilots. That included buying hypobaric recording watches for all aircrew at Oceana because the cabin altimeter gauge is difficult to read due to its size and location, and its audible warnings are ineffective, the report said.
The Navy also installed a recompression chamber aboard the Norfolk-based aircraft carrier USS George H.W. Bush before it deployed in January so it could promptly treat pilots’ decompression sickness symptoms.
So far, two aircrew have been treated in the chamber while on its deployment.
The report makes a series of other recommendations that include replacing the cockpit altimeter in the F-18 with a digital one that is more precise and easier to monitor. The report also calls for the Bureau of Medicine and Surgery to accelerate research into the breathing problems and to alleviate the command’s shortage of aeromedical specialists.
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