F-35s Flying Again, but Face Continued Test Challenges

 - August 29, 2011, 5:00 AM
The first two F-35As fly in formation. Flight tests have resumed after a recent grounding. (Photo: Lockheed Martin)

Flight tests of the Lockheed Martin F-35 resumed after a two-week grounding. The Joint Program Office (JPO) said that the failure of a control valve had led to the malfunction of the aircraft’s Integrated Power Package (IPP), supplied by Honeywell. But an investigation continues, while a permanent resolution of the problem is being worked, the JPO added.

The impact on the F-35 development schedule is not yet clear. In a report to Congress last May, Dr. Michael Gilmore, the Pentagon’s director of operational test and evaluation, said, “Flight envelope constraints have begun to challenge the program.” Gilmore noted that modifications to the F-35 control laws might not be sufficient to correct some undesirable handling characteristics and higher-than-predicted structural loads that had been discovered during flight tests. The already-troubled F-35B version might need a spoiler system, he added.

Gilmore also questioned whether the October date for completion of Block 1 software testing would be met. Block 1 is required for initial pilot training at Eglin AFB.

However, Gilmore noted that Block 2 flight tests in the F-35 are likely to start in November, per last year’s revised schedule. The definitive Block 3 software should be available in mid-2015, but he warned that “producing and integrating the software that provides the complex capabilities in these later blocks of mission systems will be a substantial challenge.”

Meanwhile, Lockheed Martin was awarded a $535 million contract for long-lead items for the sixth low-rate, initial production (LRIP) batch. This comprises 38 F-35s, including the first two aircraft for Australia and the first four for Italy.