F-35 engine fix coming

The head of the F-35 program office said that by the end of December he expects to have decided on a permanent solution for a design issue that caused an F-35A engine to fail in June at Eglin Air Force Base, Fla. Engine-maker Pratt and Whitney has offered several potential fixes, some of which already are being tested, said Air Force Lt. Gen. Christopher C. Bogdan. The engine failure and subsequent fire were the result of micro fractures in one of the three-stage fan sections that compress air before it enters the engine. These sections are lined with a polyimide material that is designed to rub against the fan blades to reduce pressure loss. In the case of AF-27, the third fan rubbed in excess of tolerance during maneuvers several weeks before the failure, causing the blades to heat to about 1,900 degrees -- 900 more than ever expected, Bogdan said. This led to micro fractures in the titanium part of the rotor, which grew over the next few weeks of flying before finally failing. (Source: AFNS, 10/31/14)