F-35 performance specs lowered

A new report by the Pentagon’s Director of Operational Test and Evaluation has detailed the United States Department of Defense’s intent to lower the performance requirements for the F-35 Joint Strike Fighter, across all three variants. The lowered specifications concern the transconic acceleration and sustained turn rates.

While the F-35C CV carrier variant will see the biggest performance adjustment, the F-35A CTOL will also see changes. “The program announced an intention to change performance specifications for the F-35A, reducing turn performance from 5.3 to 4.6 sustained g’s and extending the time for acceleration from 0.8 Mach to 1.2 Mach by eight seconds. These changes were due to the results of air vehicle performance and flying qualities evaluations,” the report reads.

The report also noted problems with horizontal tail surfaces “experiencing higher than expected temperatures during sustained high-speed/high-altitude flight, resulting in delamination and scorching of the surface coatings and structure.”

Concerns affecting all three variants also included the Helmet-Mounted Sight and Display’s (HMSD) ongoing problems with night vision acuity (although image latency is now within acceptable limits) and software delivery to flight test was “behind schedule or not complete when delivered.”

According to the DOT&E report, 20 per cent of Block 1 software has yet to be integrated and delivered to flight test, Block 2A was delivered four months late and in eight subsequent versions less than 50 per cent of planned capability has been delivered to production, and Block 2B was only 10 per cent complete despite being planned for delivery to flight test by the end of 2012.

The report also notes a problem with the F-35A’s air refueling system: “Delayed disconnects during air refueling required the program to implement restrictions on the F-35A fleet and conduct additional testing of the air refueling capability. The program added instrumentation to isolate root causes.”

Lockheed Martin was quick to respond to the report, releasing a statement saying the program was demonstrating exceptional stability, particularly in comparison to legacy aircraft development programs.

“Flight test is an excellent example of our continuing program performance. As is done in every engineering development program, we have test objectives planned against a program schedule. Each year, as issues are discovered in test, our flight test team identifies additional test objectives that can be accomplished while we resolve the issues discovered. However, it’s more important to look at the overall plan rather than year by year totals.  Through Nov. 30, we completed 20,006 test points against a plan of 19,134, approximately one-third of the overall test plan. While we remain diligent to ensure deferred test objectives are ultimately completed, the aggregate plan remains on track and is consistent with the TBR plan. We’ll use this similar practice in 2013,” the statement read.

“Further, similar and effective progress is being made across software development, structural test, and equipment qualification per the TBR plan.

“From an Operational Test and Evaluation perspective, we fully expect to deliver a qualified product to OT&E as scheduled. We appreciate the feedback from the OT&E community on what remains to be demonstrated over the next three years leading up to the OT&E phase of the program.”

However, the report from DOT&E also noted that progress against planned baseline test points for 2012 lagged by more than 30 per cent due to aircraft operating limitations, higher than expected loads on the weapon bay doors, and deficiencies in the air-refueling system, which reduced testing opportunities.