* Helmet, logistics systems still need work
* F-35 would "kick in the door" in future operations
* B-model exceeds wind limits of current fleet
By Andrea Shalal-Esa
ABOARD USS WASP, Aug 29 Two F-35 fighter jets have completed dozens of test flights from the deck of this amphibious assault ship over the past three weeks, but several flights were scrapped on Wednesday for maintenance issues, just as more than a dozen journalists arrived for a demonstration.
U.S. Marine Corps officials said the jets had made more than 90 successful vertical landings on the USS Wasp this month, including many at night - showing the growing maturity of Lockheed Martin Corp's F-35B fighter. The officials said groundings were rare during the recent 19-day test period.
But Wednesday's failed demonstration was a reminder of the problems faced by the F-35 program, which has seen repeated cost increases and schedule delays since it began in 2001. Lockheed is developing three variants of the F-35 to replace over a dozen warplane types now in use around the world.
The Marines plan to start using the newest U.S. fighter in combat just two years from now - in mid-2015 - but the $392 billion program, the costliest weapons program in U.S. history, still faces technical and budget challenges.
Brigadier General Matthew Glavy said the radar-evading nature of the F-35 B-model, which can make short takeoffs and land like a helicopter, would make it a key asset in future missions against countries with surface-to-air missiles, like Syria.
"It would kick in the door," Glavy said, highlighting the benefits of the stealthy F-35B during a visit to the Wasp - one of the large Navy warships that will carry the new warplanes when they become operational.
He said the plane's stealth would allow it to penetrate enemy territory undetected, delivering the first punch in future wars.
Glavy said Wednesday's temporary halt in flights was disappointing, but the overall tests had demonstrated progress for other guests, including Pentagon chief arms buyer Frank Kendall and Navy acquisition chief Sean Stackley.
"They've come and seen that this is not a PowerPoint brief. We're flying airplanes ... on and off these ships. That's where they belong," said Glavy, the No. 2 officer for Marine aviation.
The Marines have vowed to safeguard the F-35B, their top acquisition priority, despite tough budget reviews under way at the Pentagon. But the other services may see big changes.
One option under discussion, if U.S. lawmakers do not reverse a 10 percent cut in Pentagon spending for fiscal 2015, would result a two-year pause in orders for the U.S. Navy's F-35C carrier variant, said four sources familiar with the issue.
The sources stressed that no decisions had been made but said mandatory budget cuts were pressuring the program, which is still working through residual technical challenges.
The sea trials also come at a critical time for Britain, which has spent $2 billion to help develop the new warplane. UK authorities are facing its own budget pressures but must decide in coming weeks whether to proceed with the purchase of 14 additional B-model aircraft, a deal worth around $1.5 billion.
TESTING WIND LIMITS
Two test jets were completing about 90 percent of their planned flights until some maintenance issues cropped up this week. At least one of the jets did resume flying later Wednesday after the journalists left, said Pentagon F-35 spokesman Joe DellaVedova.
To date in the sea trials, which will end Friday, the planes had completed 90 short takeoffs, 92 vertical landing, including 19 pairs of takeoffs and landings at night, DellaVedova said.
That compares to 72 shipboard landings and takeoffs during the first sea trials in October 2011. A third round of sea testing is slated for summer of 2016.
U.S. Navy Captain Erik Etz, director of testing and evaluation for both the B- and C-models of the F-35, said the plane had proven during the latest tests that it can be operated at over 35 knots of headwinds and over 15 knots of crosswinds.
"That envelope is in excess of what the fleet has currently had with legacy platforms. It is what we had hoped to get ... so the aircraft is matching expectations," Etz told reporters.
HELMET, LOGISTICS SYSTEM STILL POSE PROBLEMS
U.S. officials say the F-35 has made strides in recent years, but test pilots on the Wasp cited continued problems with a new pilot helmet that fuses data from radars and other sensors and projects it onto the pilot's visor. A computerized operations and maintenance system called ALIS is making progress, but also remains far from pilot-friendly, they say.
Glavy said the helmet being developed by a joint venture of Rockwell Collins Inc and Israel's Elbit Systems was "not exactly" where officials wanted it, but was optimistic that a useable helmet would be ready by mid-2015.
He cited progress on the helmet, but said the Pentagon continued to fund work on an alternate helmet by Britain's BAE Systems through the third quarter of fiscal 2014.
Marine Corps Captain Michael Kingen, one of the F-35 test pilots, said there were still some issues with the helmet's night vision, especially on dark nights; a lag in the data streaming into the helmet; and with some "jitter" in the view.
But he said the helmet did provide pilots with more data than previous aircraft systems, and the overall approach was useful to help pilots accomplish their mission.
Wing Commander Nic Hindley, the UK liaison to Marine Corps headquarters, said Britain was keeping a close eye on the tests since it must decide by October on buying 14 more F-35 B-models.
He said testing results were encouraging, as was recent news that the Pentagon had lowered its estimate for the long-term cost of operating and maintaining the planes.
"It's been impressive to see how this jet has developed. It's a huge leap forward from 2010, when the B-model was on probation," Hindley said, referring to a one-year period when former Defense Secretary Robert Gates had threatened to cancel the B-model variant unless it showed significant progress.