-1x Boeing Share News (BAES)

* 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 (Reuters) - Two F-35 fighter jetshave completed dozens of test flights from the deck of thisamphibious assault ship over the past three weeks, but severalflights were scrapped on Wednesday for maintenance issues, justas more than a dozen journalists arrived for a demonstration.

U.S. Marine Corps officials said the jets had made more than90 successful vertical landings on the USS Wasp this month, including many at night - showing the growing maturity ofLockheed Martin Corp's F-35B fighter. The officials saidgroundings were rare during the recent 19-day test period.

But Wednesday's failed demonstration was a reminder of theproblems faced by the F-35 program, which has seen repeated costincreases and schedule delays since it began in 2001. Lockheedis developing three variants of the F-35 to replace over a dozenwarplane types now in use around the world.

The Marines plan to start using the newest U.S. fighter incombat just two years from now - in mid-2015 - but the $392billion program, the costliest weapons program in U.S. history,still faces technical and budget challenges.

Brigadier General Matthew Glavy said the radar-evadingnature of the F-35 B-model, which can make short takeoffs andland like a helicopter, would make it a key asset in futuremissions against countries with surface-to-air missiles, likeSyria.

"It would kick in the door," Glavy said, highlighting thebenefits of the stealthy F-35B during a visit to the Wasp - oneof the large Navy warships that will carry the new warplaneswhen they become operational.

He said the plane's stealth would allow it to penetrateenemy territory undetected, delivering the first punch in futurewars.

Glavy said Wednesday's temporary halt in flights wasdisappointing, but the overall tests had demonstrated progressfor other guests, including Pentagon chief arms buyer FrankKendall 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 wherethey belong," said Glavy, the No. 2 officer for Marine aviation.

The Marines have vowed to safeguard the F-35B, their topacquisition priority, despite tough budget reviews under way atthe Pentagon. But the other services may see big changes.

One option under discussion, if U.S. lawmakers do notreverse a 10 percent cut in Pentagon spending for fiscal 2015,would result a two-year pause in orders for the U.S. Navy'sF-35C carrier variant, said four sources familiar with theissue.

The sources stressed that no decisions had been made butsaid mandatory budget cuts were pressuring the program, which isstill 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. UKauthorities are facing its own budget pressures but must decidein coming weeks whether to proceed with the purchase of 14additional B-model aircraft, a deal worth around $1.5 billion.

TESTING WIND LIMITS

Two test jets were completing about 90 percent of theirplanned flights until some maintenance issues cropped up thisweek. At least one of the jets did resume flying later Wednesdayafter the journalists left, said Pentagon F-35 spokesman JoeDellaVedova.

To date in the sea trials, which will end Friday, the planeshad completed 90 short takeoffs, 92 vertical landing, including19 pairs of takeoffs and landings at night, DellaVedova said.

That compares to 72 shipboard landings and takeoffs duringthe first sea trials in October 2011. A third round of seatesting is slated for summer of 2016.

U.S. Navy Captain Erik Etz, director of testing andevaluation for both the B- and C-models of the F-35, said theplane had proven during the latest tests that it can be operatedat over 35 knots of headwinds and over 15 knots of crosswinds.

"That envelope is in excess of what the fleet has currentlyhad with legacy platforms. It is what we had hoped to get ... sothe aircraft is matching expectations," Etz told reporters.

HELMET, LOGISTICS SYSTEM STILL POSE PROBLEMS

U.S. officials say the F-35 has made strides in recentyears, but test pilots on the Wasp cited continued problems witha new pilot helmet that fuses data from radars and other sensorsand projects it onto the pilot's visor. A computerizedoperations and maintenance system called ALIS is makingprogress, but also remains far from pilot-friendly, they say.

Glavy said the helmet being developed by a joint venture ofRockwell Collins Inc and Israel's Elbit Systems was "not exactly" where officials wanted it, but wasoptimistic that a useable helmet would be ready by mid-2015.

He cited progress on the helmet, but said the Pentagoncontinued to fund work on an alternate helmet by Britain's BAESystems through the third quarter of fiscal 2014.

Marine Corps Captain Michael Kingen, one of the F-35 testpilots, said there were still some issues with the helmet'snight vision, especially on dark nights; a lag in the datastreaming 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 wasuseful to help pilots accomplish their mission.

Wing Commander Nic Hindley, the UK liaison to Marine Corpsheadquarters, said Britain was keeping a close eye on the testssince it must decide by October on buying 14 more F-35 B-models.

He said testing results were encouraging, as was recent newsthat the Pentagon had lowered its estimate for the long-termcost 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 onprobation," Hindley said, referring to a one-year period whenformer Defense Secretary Robert Gates had threatened to cancelthe B-model variant unless it showed significant progress.