WASHINGTON: When then-Defense Secretary Robert Gates told Gen. James Amos that he was going to put the F-35B vertical landing version of the Joint Strike Fighter on “probation” because of testing, structure and propulsion problems, the Marine Corps commandant didn’t argue; he just explained.

“I looked at him and said, ‘Sir, we need this airplane,'” Amos told me in his Pentagon office, recalling a conversation that took place two months before Gates publicly announced his decision last Jan. 6. Gates said that if the B variant couldn’t be put “back on track” within two years, “then I believe it should be canceled.”

After ten months of weekly meetings on the subject with senior Defense Department and Navy officials, as well as executives of the plane’s maker, Lockheed Martin
, Amos says the company and the program office under Vice Adm. David Venlet, have resolved two of Gates’ larger concerns entirely and found fixes for five engineering problems cited that are ready for testing in December and January. Amos — a fighter pilot and the first aviator ever to serve as Marine Corps commandant — is confident those fixes will work.

For that reason, the commandant hopes Defense Secretary Leon Panetta will soon declare the F-35B off “probation” — whatever that undefined, non-regulation term actually means — so the Marine variant of the JSF can shed the taint it acquired when Gates applied his unorthodox label.

“I just think it’s getting a bum rap,” Amos said, sounding a bit like a worried parent. “The airplane’s performing really well now — I mean really well.”

Two of Gates’ criticisms were that flight tests of the short takeoff/vertical landing (STOVL) F-35B were behind schedule and that it had yet to land on and take off from an amphibious assault ship, the type of vessel that will serve as the STOVL’s home away from home in the Marine Corps. Today the facts are much different.

As of Nov. 1, the F-35B had completed 291 of 293 test flights planned for calendar 2011, putting it 13% ahead of its new schedule. By the same date, two B variants had completed more than two weeks of sea trials on the amphibious assault ship USS Wasp, during which they completed 72 short takeoffs and vertical landings, all but flawlessly. One pilot said his biggest problem was putting the nose wheel down in a one-foot square target on the ship’s pitching deck.

The decision on probation is all Panetta’s to make, Amos said, noting that no criteria for making it are to be found in the Federal Acquisition Regulations because “probation” isn’t an official status. In any event, the commandant hopes the F-35B gets a clean bill of health “sooner rather than later.” Image isn’t everything, but Amos figures it’s increasingly important given current crisis negotiations over how much to cut the defense budget.

The F-35, officially the “Lightning II,” is being built in three variants — conventional, vertical and aircraft carrier landing models — for the Air Force, Marines, Navy and eight allied nations that are partners in the program. Like the Marines, Italy plans to buy the STOVL variant, and Spain is a likely customer once its finances improve.

At $379 billion or more to produce 2,443 F-35s for the U.S. services, according to the most recent Defense Department estimate, the project makes a juicy target for those looking for ways to ease the nation’s economic and budget crises by cutting defense spending.
The B variant is particularly vulnerable, for when the option of reducing the size of the massive F-35 program comes up, Amos observed, the fact that Gates put the STOVL model on “probation” is almost always mentioned. To Amos, this seems to imply that the conventional takeoff Air Force version and carrier-capable Navy variant are doing better. “It’s an inaccurate picture,” he said.

The F-35B uses an innovative “lift fan” installed a couple of feet behind the cockpit to provide about half the roughly 40,000 lbs. of thrust it needs to hover or land vertically. Three of the five engineering problems that led Gates to put the plane on probation had to do with the lift fan, a new technology. A fourth concerned overheating in related “roll posts” that bleed hot engine air through ducts and downward from nozzles in each wing to control the aircraft’s roll axis in vertical flight.

Amos offered this rundown of the engineering fixes Lockheed and engine manufacturer Pratt & Whitney are making, with the costs covered by funds already appropriated for development:

— An interior bulkhead that fits around the jet’s Pratt & Whitney F135 engine and extends into the wings has been redesigned because of cracks in it discovered after 1,500 hours of durability testing. The bulkhead in question is titanium in the conventional and carrier versions of the aircraft but aluminum in the B variant to save weight. The redesigned bulkhead has been installed in the 24th F-35B built and corrections will be retrofitted into the first 23 B variants, five of which are being used in tests and the rest of which are in various stages of production.

— Devices that operate the roll post nozzles were overheating when the F-35B hovered or flew forward at less than 60 knots, or about 75 mph, in vertical flight mode. These “actuators” are being insulated and the fix has been successful in flight test. Pratt & Whitney may change an adhesive used in the actuators to solve the excessive heating problem and obviate the need for the insulation in the future.

— The drive mechanism that opens two Auxiliary Air Intake doors behind the clamshell lift fan door on top of the fuselage and holds them steady as the F-35B hovers or flies in vertical mode has been redesigned to be more robust and is being replaced. The change was made because turbulence created by the lift fan door causes the AAI doors to oscillate excessively with the current drive mechanism, making them likely to wear out too soon.

— The driveshaft that runs from the engine to the lift fan to turn its blades has proven to fit imperfectly into its designed space by an “infinitesimally small” amount, as Amos described it. This means mechanics may have to pre-stress the part to install it. That creates problems when the shaft expands and contracts due to changes in its temperature as the aircraft warms up in flight. A thin steel “spacer,” shaped something like a washer and about the diameter of a volleyball, has been incorporated to make the driveshaft fit better in the fifth F-35B variant as an interim fix. A redesigned driveshaft will become a standard production part beginning in early 2014.

— Improved cooling and temperature monitors have been added to ensure safe operation when lift fan clutch plates that sometimes drag against one another during normal flight produce excessive heat. Adjusting the distance between the clutch plates is expected to solve take care of the problem.

Amos wants Panetta’s decision on taking the F-35B variant off probation to be “event-driven,” not made out of a sense or urgency, he said, adding that he wants to “make sure that everybody is comfortable with this.”

The commandant already is.