While live-fire testing in the first F-35, aircraft AA-1, at China Lake, Calif., has confirmed the redundancies and reconfiguration capabilities of the flight-critical systems, it has also shown that ballistic damage to polyalphaolephine (PAO) coolant and fueldraulic lines can cause fires. The report says the program office may reconsider installing the PAO shutoff valve, but not the fueldraulic fuses removed in 2008. The onboard inert-gas-generating system already is being redesigned to address deficiencies in fuel-tank inerting.
Weapons testing is underway for the limited F-35A Block 2B clearance envelope, which comprises internal carriage of the GBU-31/32 joint direct attack munitions, GBU-12 laser-guided bomb and AIM-120 air-to-air missile. “This year, we are focusing on ramping up to 15 weapons tests at both sites [Edwards and Patuxent River],” says McFarlan.
Stovl F-35Bs will return to the assault carrier USS Wasp in August for a second round of sea trials in stronger winds. “We will also bring along weapons,” he says. The DOT&E, meanwhile, says weapons integration has been limited by deficiencies in the radar, electro-optical targeting system, sensor fusion and helmet-mounted display.
Ground and flights tests have demonstrated that the stealthy F-35's radar signature is meeting design requirements, says McFarlan. “We have shown that if the aircraft passes the test in the [anechoic] chamber, it will pass in flight,” he says. “We are now in the mode of showing we can maintain the [low-observable] characteristics after a year in flight.”
In ground durability testing, only the F-35A airframe has so far completed a full 8,000-hr. lifetime. In December, fatigue tests on the F-35B were halted for a second time after the discovery of multiple cracks in a bulkhead flange during the 7,000-hr. inspection. Previously, a crack in a carry-through bulkhead was found after 1,055 hr. of testing, and McFarlan says Stovl test aircraft at Pax River will have to go through structural upgrades beginning this year.
Recent test highlights include hovering the F-35B for 10 min. “It was record, hovering at max performance with more than 5,000 pounds of fuel before doing a vertical landing,” he says. “We have done a lot of night flying to understand the helmet and DAS [distributed aperture system], and done night hovering as well.” McFarlan says testing of the troubled helmet is making progress and now focusing on latency of the DAS imagery projected on the visor during night flying.
—With Amy Butler and Bill Sweetman in Washington.