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F-35As at Eielson Air Force Base, Alaska.
Hydraulic fluid contaminated with water froze inside an F-35A’s landing gear, ultimately causing the jet to crash after the pilot ejected in a Jan. 28, 2025, mishap, according to a U.S. Air Force investigation.
Investigators also found the same issue caused another F-35 in-flight emergency nine days later, though the aircraft was able to land safely.
The service on Aug. 25 released its investigation into the incident, which occurred at Eielson Air Force Base, Alaska. The crash destroyed the Lockheed Martin F-35, at a cost of $196.5 million.
The aircraft was the third in a four-ship flight for a training mission. After the initial takeoff, the aircraft’s nose landing gear did not retract properly, preventing a full strut extension and causing the gear to be canted to the left. The pilot ran through checklists, but the gear remained turned 17 deg. to the left, the report states.
As the aircraft was in flight, the pilot started a conference call with Lockheed Martin engineers through the on-duty supervisor. The aircraft stayed aloft for 50 min. as the team determined what to do.
The pilot performed two touch-and-go landings in an unsuccessful attempt to re-center the gear. Additionally, the right main landing gear strut and then the left strut did not fully extend after takeoff as they also formed ice inside.
Following the second touch-and-go, the aircraft’s Weight on Wheels (WoW) sensors showed the aircraft was on the ground, and it transitioned to an “on ground” flight control law even though it remained airborne.
“Because it was actually airborne, the (aircraft) was uncontrollable,” the report states. “The pilot successfully ejected and emergency responders were at the scene within a minute.”
The Air Force Accident Investigation Board determined the unit’s hydraulic fluid was contaminated by water that froze in the struts in flight. “The ice prevented the struts from full extension that led the WoW sensors to declare the (aircraft) was on the ground when it was airborne,” the report states.
Additionally, the report says the crew’s decision-making—including those on the conference call—the lack of oversight for hazardous materials at the base and the lack of adherence to maintenance procedures for hydraulic servicing contributed to the incident.
Nine days after the crash, on Feb. 6, 2025, a similar incident occurred in which an F-35A at the base suffered a landing gear malfunction after takeoff. The jet experienced a nose wheel gear unsafe indication after takeoff, and after following the checklist, the pilot lowered the gear and flew for about 40 min. before landing uneventfully.
A post-flight analysis included towing the aircraft to a climate-controlled shelter to measure nitrogen pressure on the landing gear struts, and then towing it outside to where it was below 15F for 12 hr. The aircraft was jacked up but unable to fully extend the landing gear. Drained fluid showed a significant amount of water in the nose landing gear and left main landing gear struts.
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