General Electric/Rolls-Royce is investigating manufacturing and assembly data on a single F136 engine after it was damaged during a checkout test on 23 September.
The alternate engine for the Lockheed Martin F-35 was shut down "in a controlled manner" after an unknown anomaly at near maximum fan speed on the test stand damaged the front fan and compressor area, the company says.
The GE/Rolls team is continuing to run two test engines after inspections revealed no signs of "similar distress". Five development engines have run for more than 1,000h since early 2009.
As the cause for the anomaly on the eighth development engine continues to be investigated, US lawmakers are debating whether to insert funding to keep the programme alive against the wishes of the Department of Defense.
Since 2006, the DoD has tried to cancel the F136 alternate engine, arguing that the Pratt & Whitney F135 is sufficient to power the F-35.
But a majority of lawmakers have consistently opposed cancellation. The F136's supporters cite the benefits of competition and the risk of relying on a single engine type.