Navy Reveals Only Seven T-45 PEs Since September, Found One Main Cause

The head of Naval Air Systems Command (NAVAIR) said Tuesday the Navy has made progress in reducing physiological episodes (PEs) in the T-45 trainer aircraft, having only seven since last September.

Vice Adm. Paul Grosklags told the Senate Armed Services Subcommittee on Seapower that of those seven cases, two were mechanical failures, one dealt with a flight regime leading to low flow through the aircraft, one was pilot error, and three were human issues, like being sick. Since last fall the T-45 has been flying back conducting full flight operations

A T-45C Goshawk training jet approaches an aircraft carrier. (Photo courtesy of U.S. Navy)

A T-45C Goshawk training jet approaches an aircraft carrier. (Photo courtesy of U.S. Navy)

He explained PEs are a continuing challenge for the service.

 “This remains naval aviation’s top safety issue and has our full attention. While we’ve made clear progress in some areas, solutions to the broader problem still remain frustratingly elusive. In parallel with pursuit of root causes, we are continuing implementation of hardware, software, and procedural mitigations.”

The service originally grounded its fleet of T-45Cs for months in 2017 due to an increase in PEs caused by an issue in the aircraft’s onboard oxygen generation system (OBOGS) (Defense Daily, April 10).

The Navy released a comprehensive review investigating the issue last June, recommending the Navy establish a single temporary organization to lead PE resolution efforts led by a flag or general officer (Defense Daily, June 16).

The service then appointed then-Capt. Sara Joyner, since promoted to rear admiral (lower half) (Defense Daily, Aug. 11).

In October the Navy was letting T-45s fly again after each aircraft was outfitted with new monitors that measure altitude and oxygen flow, as directed by the comprehensive review. This includes the CRU-23 oxygen monitor system, an upgrade to the CRU-99, which monitors oxygen content in air, air flow, and provides a post-flight download of what the system saw during a flight (Defense Daily, Oct. 2).

When pressed by Chairman Roger Wicker (R-Miss.), Grosklags said the primary issue they found in the investigation and reviews “was that there are certain environment conditions during flight where if the power is reduced to too low of a setting in flight, that it reduces the flow of breathing gas from the oxygen generating system to the aircrew.”

He said the Navy did not know this until it added additional sensors to the aircraft last summer, during the operational pause.

“Now that we know that we can see when this is occurring in the aircraft, so that was one of the root causes was that the pilots were not getting sufficient flow – not specifically of oxygen but of entire breathing gas was not getting sufficient pressure to flow to the masks.”

Wicker said it seems like the service has put its finger on the root cause of the T-45 PE issue.

Grosklags agreed but highlighted the Navy has not stopped trying to further mitigate the risk. They are now doing things like “turning up the wick on the engines” so it operates at a slightly higher percentage so there is less chance pilots will get into a flight condition where the low flow scenario is possible.

In his prepared statements, the NAVAIR head said the service has conducted over 30,000 flight hours since the fall, including those seven “minor” PE incidents.

“Beyond mitigating the identified flow problem from the engine, we are integrating an Automatic Backup Oxygen System (ABOS) to improve oxygen generating system performance overall,” he said in the statement.





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