Though late to the deck, testers are optimistic about F-35B performance in initial ship trials
Within sight of the Virginia coast, the USS Wasp amphibious assault ship has been circling since the beginning of the month in a 20 X 20-mi. box quietly—until now—making history as the host of the very first sea trials of the , which is designed for short-takeoff-and-vertical-landing (Stovl) operations for the U.S. .
Only miles inland, in Washington,officials and lawmakers continue debating the fate of the F-35 Joint Strike Fighter program, which—as the single most expensive planned Pentagon procurement—is perhaps the most vulnerable to funding cuts, in light of deficit talks.
But, last week before wrapping up the first developmental test period for the aircraft, the U.S. Marine Corps and F-35 Joint Program office broke their silence on the testing and invited a handful of reporters onto the amphibious assault ship for a firsthand look. The limited results that have been released have largely indicated no major anomalies. But, it is unclear whether testing progress can save not only the F-35B but the entire nine-nation program as customers scramble to secure funds for their development and purchasing commitments amid mounting national debts.
Only a year ago, test aircraft BF-1 was stuck on the ground related to repairs and the failure to produce the vertical landings needed to clear the envelope for the remainder of the test fleet; this bottlenecked progress with other Stovl test aircraft and earned the variant an “on probation” status by former Defense Secretary Robert Gates.
With a dearth of test data, the Marine Corps at the time was arguing in favor of the program based largely on faith that Lockheed Martin's projections and the company's models would prove valid. Now, however, the service has a windfall of data from work this year as well as from these inaugural ship-based operations. In defending once again against killing the “B”—the most expensive of the F-35 variants—the service now plans to lean on knowledge rather than faith.
The trials were designed to test basic integration of the F-35B with the LHD-class ships; Marines plan to house up to six F-35Bs on the ships to provide air support for activities at sea and during assault landings. Thus far, officials have conducted more than 60 vertical landings and short takeoffs (STO) here.
They have also determined that the B has better deck and hangar-handling qualities than the AV-8B, the aircraft the JSF will replace on these decks, says Capt. Brenda Holdener, the Wasp's commanding officer.
Testing experts at NAS Patuxent River, Md., are combing through data to explore the thermal dynamics on the ship. Test officials are keenly interested in understanding how the Pratt & Whitneyengine, and its hot exhaust, as well as the Integrated Power Pack affects the deck itself and impacts operations.
The vertical landing approaches mirror those used by the AV-8B, says Marine Corps Col. Roger Cordell, director of test and evaluation for the F-35B as well as the “C” designed for aircraft carrier use. He says that pilots initially approached from stern to bow and crossed over above the deck at a 90-deg. angle. Only after ship operators were comfortable with pilots' skills were they able to begin cutting that angle to 45 deg. Harrier pilots use both angles.
Although in land testing the F-35B pilots often conduct hovers around 100 ft., Cordell says that on deck they have narrowed that down to 40 ft. “It is counterintuitive, but the airplane has a less harsh environment hovering at 40 ft. than it does at 100 ft.,” he says. “Land-based, we did most of our hovers at 100 ft. to avoid kicking up rocks . . . and then we worked our way to a reasonable height for the ship.” During descent, the aircraft is set to reduce its altitude by 7 fps.; officials say they will eventually experiment with that number to widen the envelope.
Lt. Col. Matt Kelly, the lead F-35 test pilot at Patuxent River, originally a Hornet pilot, says that his first time conducting a vertical landing on an L-class ship was with the F-35B. “The challenge is not 'am I going to get my aircraft onboard,'” he says. “The challenge really becomes 'can I put my nose tire in a 1 ft. X 1-ft. square box where I want to on the deck.' That is really a testament to the flight controls and the tools that pilots have.”
Kelly acknowledges that the deck motion does impact landing operations, but “the control law you have is so good, you can compensate.”
Thermal impacts to the ship's deck have been a concern leading up to these trials. Though formal data haven't yet been analyzed, Tom Briggs, the integrated test team engineering lead at Patuxent River who is helping to oversee the ship trials, says the aircraft is performing as predicted by the models in terms of heat ingestion on the ship. Officials had been concerned that the F-35B would reingest its own hot exhaust, impacting performance of the propulsion system and potentially damaging hardware. There are no such performance impacts thus far, Cordell says. “We feel like we are running where we intended to crawl.”
Additionally, there is “nothing mysterious” about the thermal qualities of the F-35B on the deck, says Ansis Kalnajs, a test director for Naval Sea Systems Command who is leading the effort to study the aircraft impacts on the ship.
Pilots and crews were qualified in Harriers in advance of the F-35Bs' arrival Oct. 3.
Prior to that work, the ship received a number of standard modifications, such as a new aft non-skid deck coating in parking spots 7-9, Holdener says. The remaining spots on deck appear lighter in color owing to the aging of the deck.
Also, in a square on spot 9, Navy officials laid a new material called Thermion, which is expected to require less upkeep while withstanding the same temperatures as the existing formula. The impacts of F-35B vertical landing operations can be studied on the Thermion as part of these trials.
The yellow tramline used by pilots as a target for the nose gear upon landing was moved roughly 38 in. outboard on the Wasp to accommodate the wider wingspan of the F-35B. Officials also removed a WSC satellite antenna, some life rafts and a missile launcher, and shielded other equipment to reduce the potential of harming sensitive electronics on the aircraft; this was done for testing only.
Though vertical landings are quite similar to those of the Harrier, the STO operations do vary for the F-35 owing to the different lift qualities of the F-35s' stealthy, supersonic-capable design. For testing on the Wasp, the nozzles and control surfaces actuate with 225 ft. of runway remaining on deck, creating an angle of attack and allowing for the wings to produce enough lift for takeoff from the deck, Cordell says. The Harrier's rotation line is at the bow, owing to its wing design creating the required lift without the corresponding angle-of-attack change. Cordell says that the testing equipment at the ship's bow has also not detected any problems with the F-35's nozzle clearance as it takes off.
Pilots were qualified using the heart of the Harrier wind envelope. During testing they have expanded that up to a 30-kt. headwind, 10-kt. crosswind and 5-kt. tailwind. Pilots report good handling qualities, Cordell says.
The goal for STO testing was to establish the wind envelope for at-sea performance of manual settings on the aircraft. There are three methods for takeoff: manual (pilot pulling back on the stick); using a button that actuates the nozzle at the rotation line; or auto STO, which places the aircraft at a known distance from the rotation line. In this auto setting the aircraft will actuate automatically when the pilot reaches that rotation line. Cordell says pilots were able expand the scope to experiment with the auto-STO mode.
Tests have been conducted on the ship by BF-2, designed for flight sciences and BF-4, optimized with a data-collecting pod in the weapons bay, for mission systems. During the Oct. 18 visit, BF-4 conducted two VLs and two STOs. BF-2 had “returned to the beach” at Patuxent River for undisclosed repairs and checkout, Holdener said. Earlier in testing, BF-2 also underwent repairs related to a fuel leak. Several repairs have been conducted on the ship, according to Briggs.
Among them was the replacement of a flat tire, which required an aircraft to be hoisted on jacks in the hangar—a first for the F-35 program. Incidentally, Briggs says the aircraft are using tires at a slower rate while on deck than during testing at Patuxent River. There, maintainers were replacing tires faster than expected in crosswind conditions.
Maintainers also replaced a testy upper lift fan door actuator on BF-4 while on the ship, Briggs says. The aircraft was down for this repair midday Oct. 16 and back flying Oct. 18. BF-4 suffered another problem with this actuator shortly after reporters left the deck. And, BF-2 returned to the Wasp late on Oct. 18. Overall, repairs “haven't gotten worse out there [than at Pax],” Briggs says.
Rear Adm. Kevin Scott, commander of Expeditionary Strike Group 2, says lessons from the Wasp trials could eventually inform F-35C carrier-based testing.
Ground-based trap landing continues by the team at Patuxent River. Briggs says the team is exploring a new tailhook design, as the existing model is not catching the arrested landing wire.
Conducting the Wasp trials was one of five goals for which F-35 prime contractor Lockheed Martin can earn fees in 2011; in 2010 the company earned only $7 million of $35 million in available fees (AW&ST Oct. 3, p. 30). The Marine Corps intends to declare initial operational capability for the F-35B in 2015; the original plan was 2012 and was later slipped to 2014. After the U.K. opted to forgo the F-35B, the Marine Corps and Italy remain its only likely customers.