The U.S. Air Force said it will ground its fleet of T-6A Texan II trainer planes Feb. 1 so it can investigate what caused a “cluster” of recent physiological events at three bases.

The incidents occurred over the past week at Columbus Air Force Base in Mississippi, Vance Air Force Base in Oklahoma and Sheppard Air Force Base in Texas, the Air Force said. 

A T-6A Texan II trainer jet. (U.S. Air Force photo)
A T-6A Texan II trainer jet. (U.S. Air Force photo)

The “operational pause” will allow the Air Force to educate and listen to airmen about the problem, adjust procedures and training, and possibly modify flight equipment, said Maj. Gen. Patrick Doherty, commander of the 19th Air Force. The 19th Air Force is part of Air Education and Training Command at Joint Base San Antonio-Randolph in Texas.

The announcement came less than two months after Vance Air Force Base resumed flying its T-6As Dec. 5 after grounding the turboprops for nearly three weeks due to physiological events (Defense Daily, Dec. 11, 2017). The base said that investigators had not pinpointed the cause of those incidents but that it would “temporarily apply local procedures to mitigate risk to flight operations and aircrew.”

The Air Force has more than 440 T-6As. Raytheon [RTN] Aircraft, now Textron [TXT] Aviation, finished building those planes in 2010.

Several other types of military aircraft, including the Navy’s T-45C trainer jets, have experienced a surge in physiological episodes in recent years, triggering alarm on Capitol Hill. The House Armed Services Committee’s tactical air and land forces panel plans to hold a hearing Feb. 6 on physiological episodes in fighter, attack and training aircraft.

On Jan. 22, the Air Force announced that Brig. Gen. Bobbi Jo Doorenbos will lead a team to coordinate efforts to address unexplained physiological events (UPEs), such as disorientation, oxygen deprivation or unsafe carbon dioxide levels in the blood.

“As part of the integrated effort to address physiological events, the Air Force is providing more resources to understand UPEs, standardize response actions to such events and assess options for more robust aircrew training to recognize and respond to these events,” Doorenbos said. “Our ultimate goal is to prevent UPEs.”