The jet had just taken off from Naval Air Station Whidbey Island, Wash., and headed to Naval Air Weapons Station in China Lake, Calif., when it was forced to return to Whidbey Island, according to Cmdr. Ron Flanders, a Navy spokesman.
An environmental control system apparently failed, causing the cockpit temperature to plunge to 30 below zero, and caused “severely limited visibility,” the congressional letter said. The crew flew 60 miles under those conditions and safely landed with the aid of a GPS wristwatch, the letter added.
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Flanders said in an email the cause of the incident remains under investigation.
The Navy did not release the health conditions of either crewmen, but Flanders said one of the aviators aboard the two-seat jet has returned to flight status; and the other “is expected to make a full recovery and return to flight.”
The incident was the latest physiological episode involving military aircraft.
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Investigators have investigated hypoxia-like incidents in the Navy’s F/A-18s, T-45s training aircraft, and the Air Force’s F-22, F-35 and T-6, reports show.
Since 2010, the Navy has reported 716 physiological episodes in aircraft, the service branch said. Within the last five years, the Navy reported nearly 400 incidents variants of the F/A-18; another 88 in the EA-18; 117 in the T-45; 42 in the T-6; and 14 in the F-35B/C, data shows.
Air Force data was not immediately available.
“Physiological Episodes are not a new phenomenon — they have been an inherent risk in manned aviation for more than a century,” Navy spokesman Cmdr. Scot Cregan said in an email. “But the increase we are seeing in these events among our aviators is a serious concern, and addressing it is our top priority.”
A $1.5 million On-Board Oxygen Generation System Laboratory inside the 711th Human Performance Wing at Wright-Patterson hunted for clues to the cause of incidents in F-35A last year.