UPDATE 1-US Navy official sees Lockheed F-35 test milestone

* Several more flights needed before vertical landing
* Landing will be "huge step" in testing process
Defense News ~ WASHINGTON, Feb 19 (Reuters) - The Marine Corps version of Lockheed Martin Corp's (LMT.N) F-35 is expected to make its long-delayed first full vertical landing within the next week, a top U.S. Navy official said on Thursday.
Captain Lawrence Burt, strike aircraft plans and requirements officer, said officials testing the short takeoff, vertical landing (STOVL) version of the new radar-evading fighter need to conduct a few more flights before doing the landing maneuver.
"They're three or four flights from a full STOVL vertical landing, which would be a huge step in the testing process," Burt told Reuters after addressing a defense conference hosted by Aviation Week.
Burt said achieving the long-delayed milestone in the testing program would help ensure that the small carriers used for Marine Corps aircraft could be modified to accommodate the new fighter during upcoming scheduled maintenance stops.
That, in turn, would allow sea trials of the new fighters to test their performance in the environment at sea, as well as the plane's coatings, Burt said, noting that the Marines hoped to begin sea trials of the new planes this fall.
"There's a lot of stuff that we've got to learn," Burt said, noting that the carriers would need to be outfitted with new bolts to attach the planes to the deck.
"We are making sure that when we actually take the ship into the yards and do those modifications, that the aircraft will be ready, so that when it comes back out to sea, the plane's coming. We don't want to do it early," he said.
Lockheed spokesman John Kent said the F-35B is completing tests required before it could attempt the vertical landing. "We're progressing through the final series of tests leading up to vertical landing and we expect it to happen soon," he said.
Kent said the timing for testing the F-35B from ships depended on ship preparations, availability and completion of the current flight tests.
The STOVL testing began at a U.S. air base in southern Maryland last November after being delayed for months due to issues with delivery of some parts, a design change in the STOVL engine built by Pratt & Whitney, a unit of United Technologies Corp (UTX.N), and adverse weather conditions.
Program and industry official had hoped to complete the first STOVL mode vertical landing by year's end.

(Reporting by Andrea Shalal-Esa, editing by Gerald E. McCormick and Tim Dobbyn)