Lockheed Martin says it is “confident that we are on track to meet the software development schedule” and says that prime software design for Block 3F is 41% complete.
Results of tests on the long-troubled HMDS are “mixed, according to comments from the test pilots,” says Gilmore's report. For instance, software to reduce the effects of jitter have done so—but at the cost of introducing another instability, described as “swimming” of the symbology. The fix to light leakage or “green glow” requires the pilot to perform “fine-tuning adjustments” of display brightness as ambient light changes.
Another threat to schedule is weapons integration, which Gilmore characterizes as “very slow.” Synthetic-aperture radar modes have provided inaccurate coordinates, and the electro-optical targeting system (EOTS) has had difficulty maintaining tracks. These problems had to be remedied before weapons tests could proceed.
Some radar and EOTS issues have been fixed, but all the margin built into the IMS, for both Block 2B and 3F weapons testing, has been used up before a single guided-weapon test has been performed. Gilmore writes: “The final Block 3F weapon integration tests are likely to be completed in late 2017, instead of fall 2016. This will make beginning operational testing of Block 3F in January 2018 a challenge.”
Current weapons-test goals include a guided AIM-120 test in November 2013—dependent on fixing software deficiencies—a GBU-12 laser-guided bomb test in October and a Joint Direct Attack Munition guided test in December.
Buffet and transonic roll-off—wing drop in high-speed turns, associated with asymmetrical movements of shock waves—still affect all variants of the JSF, despite control law changes. The program will conduct flight tests this year to assess the problem, but has now reached a limit on what can be done with control laws, Gilmore reports. Further changes would degrade maneuverability or overload the structure.
Earlier DOT&E reports have been critical of the F-35's ability to tolerate accidental or combat damage, and the new report follows that pattern. Gilmore observes that lightning-tolerance testing is yet to be completed and that even then, the fighter's airframe will have to be inspected after known lightning strikes—including skin penetration—because it does not use lightning-tolerant fasteners, Conventional fasteners were selected to save weight. Lockheed Martin says that inflight lightning protection has been approved and the critical design review is closed, with more tests due later this year. On the ground, the current plan is that ground crews will purge the fuel systems of parked aircraft with nitrogen, repeating this process as often as once every 24 hr.
Gilmore also notes that the prognostic and health monitoring system, currently, is unable to provide timely detection of combat damage to the F-35B lift-fan system, which “might fail catastrophically before the pilot can react” during transition to vertical landing. Lockheed Martin comments that “in the remote chance of a failure, the pilot would auto-eject.”