As the F-35B conducts a second round of developmental tests on the USS Wasp amphibious assault ship, program officials say progress is being made with technical problems that have beleaguered the single-engine fighter program. But, Pentagon procurement czar Frank Kendall says he remains “cautiously optimistic”—though not yet confident—that enough progress will be made in the testing program for him to approve a ramp-up in production this fall for the $400 billion Lockheed Martin program, as planned.

“We will increase production based on progress,” he told Aviation Week at the 16th Annual Space and Missile Defense Symposium last week in Huntsville, Ala. “I am looking at progress on software and on some of the design issues that we have been following, like the tailhook and the helmet.”

Two F-35Bs are on the USS Wasp amphibious assault ship for the second round of developmental testing (DT) trials associated with the aircraft's unique ability to conduct vertical landings and short takeoffs in support of the U.S. Marine Corps. The Wasp trials, slated for three weeks, began Aug. 12.

The objective of these trials is to focus on night flying around, on and off the ship. Night flying from the ship is one of the capabilities needed for the U.S. Marine Corps to declare initial operational capability (IOC) as planned by the end of December 2015.

Also on the agenda is flying, landing and taking off in heavier and more taxing wind conditions and more severe sea states than was experienced during the October 2011 DT trials onboard the Wasp. During tests this month, the Pentagon will check refinements to the F-35B's integrated propulsion and flight control systems. The initial trials in 2011 were “a testament to how well it works on a real deck,” says Steven Wurth, technical lead for F-35 propulsion at Lockheed Martin. “The next deployment, with its higher sea states, will stress the system,” he said during the American Institute of Aeronautics and Astronautics' Aviation 2013 conference in Los Angeles last week. Lockheed refined the integrated propulsion and flight control system based on the results of the 2011 sea trials.

Pilots will also test for the first time the aircraft's behavior on ship approaches, landings and takeoffs while it is loaded with various weapons.

Four pilots have been selected for the DT trials: two are from the U.S. Marine Corps; one is from the United Kingdom, which—along with Italy—is buying the F-35B; and one works for BAE, which produces the aft fuselage and empennage for the aircraft. The U.K. pilot will be the first from that nation to land an F-35B at sea.

During the 2011 DT trials for the F-35B on the Wasp in 2011, officials conducted the first-ever vertical landing of the aircraft on a ship at sea.

Back on land, Lockheed Martin is working on various software releases needed first for the U.S. Marine Corps IOC in December 2015, and a year later for the U.S. Air Force's IOC.

As of Aug. 6, 64% of the Block 2B “onboard” software integration testing is complete, says Laura Siebert, a Lockheed Martin spokeswoman. The latest delivery related to 2B was finished in the last week of July and this software package is being tested on flight-test aircraft in the fleet. The final 2B release is slated for March 2014 with integration of the software into the fleet in mid-2015, she says. The Marine Corps plans to declare initial operational capability with the 2B software, while the Air Force is holding out for the Block 3i.

Roughly 65% of the overall development work is complete on Block 3, Siebert says. Initially, engineers are porting the code from earlier software blocks into the Block 3 hardware baseline; this is slated to go out to flight-test aircraft starting in the third quarter of this year. Actual flight-testing is expected to start by year-end.

A second phase of the Block 3 work will include an additional 840,000 source lines of code that will add “new weapons and expand the robustness of the overall weapon system,” Siebert says. This new code has been operated on the new Block 3 hardware.

However, more progress has been made on the 3i release—which includes new hardware suitable for release to the F-35's international customers—than on the 3F. Sixty-one percent of the “prime” software development for Block 3i is complete while only 34% is finished for the 3F, which will include a larger flight envelope and internal weapons. (Block 2B only includes external weapons storage.) The 3i software is set to be released to the flight-test fleet by the end of the third quarter of this year and will begin being added to Low-Rate Initial Production (LRIP) 6 aircraft by year-end. The 3F is slated for release to the flight-test fleet in September 2014, and will begin to be added to production aircraft in LRIP 9. It is slated for release to the rest of the fleet in the third quarter of 2017.

The F-35 Joint Program Office is planning at the end of this month to brief Kendall on the status of work to overcome technical issues with the F-35 helmet-mounted display system. A downselect between the original advanced helmet design, built by Vision Systems International (VSI, a joint venture between Rockwell Collins and Elbit), and a more rudimentary backup made by BAE Systems was slated for 2014. “If we can get the baseline to where we need to be, then we can downselect,” he said. “If not, then we are going to delay downselect for a while.”

The VSI helmet now in use—the Gen 2 helmet—incorporates an ICIE-10 night-vision camera, which was creating problems with the acuity of imagery projected onto the helmet at night. Flight-testing of the solution, the so-called ICIE-11 camera, and improved image-processing software in the helmet, took place in a Cessna last month. “The testing proved successful, with pilots reporting a substantial improvement in camera capability over the existing ISIE-10 night camera in the Gen 2 helmet,” said Kyra Hawn, a spokeswoman for the F-35 Joint Program Office.

The ISIE-11 camera is not being used for the DT trials on the Wasp; the “Gen 3” helmet (which will include the ISIE-11 and other improvements) is not slated to be ready until the second quarter of next year, Hawn says. All three F-35 variants will be used for the Gen 3 helmet-testing for two months. For the Wasp trials, pilots will use the ISIE-10 camera in the Gen 2 helmet and the digital night-vision capability provided by the Distributed Aperture System, a series of six sensors outside the aircraft designed to give the pilot a 360-deg. view of the surrounding airspace.

Finally, a fix for jitter that occurred for symbiology displayed on the helmet visor during stressing scenarios, such as high-buffet flight, is being flown on an F-35A at Edwards AFB, Calif. The fix is the use of a software “filter” for the inertial measurement unit embedded in the helmet. Flight-testing is underway this month to validate this fix and determine whether additional work is needed.

This fix will have to be tracked as the flight envelope continues to open for the F-35 and as more taxing tasks, such as gun tracking, are undertaken in flight-testing.

Finally, Kendall will review the status of work to correct a poorly designed tailhook for the F-35C. The point of the hook, coupled with its distance from the landing gear, made it susceptible to bouncing and prevented it from scooping under the arresting wire.

Qualification testing for the new design began Aug. 8, and roll-in tests are slated for the first F-35C to receive the hook in December at Naval Air Engineering Station Lakehurst, N.J. Flight tests with the new hook are slated for early next year as preparations for the initial sea trials for the F-35C are completed late next summer, Siebert says. Aircraft built in LRIP 7 will be the first to include the new arresting hook.