As thousands on the flight line at Joint Base Andrews outside of Washington, D.C., craned their necks skyward during the Memorial Day weekend open house, Lt. Cmdr. Eric “Magic” Buus made a low pass in an F-35C prototype, adding to the career distinctions he’d racked up in the first half of 2011 by becoming the first pilot to debut the F-35C at an air show.

Three months previously, Buus had become the first U.S. Navy pilot to fly the F-35C after the first C model prototype – CF-1 – was delivered to Naval Air Station (NAS) Patuxent River, Md., in late 2010 to begin flight testing. CF-1 has since been joined by the second and third F-35C prototypes (CF-2 and CF-3).

The trio comprises the test fleet for the carrier variant of the F-35, distinguished by its larger, folding wing and control surfaces, carrier-spec landing gear, tailhook, and other details. Lockheed Martin’s press materials proclaim the F-35C to be “The World’s Only 5th Generation Carrier Aircraft,” lauding its “ruggedized stealth” and its internal/external weapons carriage. Stealth efficacy and weapons flexibility will be tested over the coming few years, but first the F-35C must prove its compatibility with an aircraft carrier.

The C had begun to do so before delivery of the second and third prototypes, when in March CF-1 performed the first test hookup with the TC-7 catapult at NAS Pax River. The test gave rise to a minor alteration to the aircraft’s launch bar, giving it a greater range of motion. Enlightening though that preliminary test was, it will be a footnote to the carrier-suitability testing begun at Joint Base McGuire-Dix-Lakehurst (MDL) in New Jersey in late June.

The very first MDL tests focused on Jet Blast Deflector (JBD) analysis, assessing deck heating, JBD panel cooling, and vibro-acoustic, thermal, and hot-gas ingestion environments. The tests were expected to take about two weeks, and on June 25, CF-2 arrived at MDL with Buus at the controls. Testing commenced the following week.

From there, Buus said, “We’re going to return in mid- to late July to do the initial catapult launches and the initial arresting gear roll-in arrestments.”

The launches began on July 27, 2011, and are taking place during the Navy’s yearlong Centennial of Naval Aviation celebrations. Despite the concurrent development of EMALS (the new Electromagnetic Aircraft Launch System) at Lakehurst, the bulk of F-35C carrier-suitability testing will be done with the current steam catapults owing to their ubiquity in the fleet.

“There was no requirement for EMALS [testing] in the STD test phase of the program,” Buus said. “But obviously EMALS is going to be out there in the fleet, so logically there will be some EMALS testing with the airplane at some point.”

F-35C carrier-suitability testing will hinge on sticking to the test schedule, a feat not easily accomplished with such a complex, new aircraft. In early June, F-35C testing was suspended for six days to remedy a software problem. On June 17, flight test engineers at Pax River discovered a “logic fault” that affected the wing folding mechanism. Flight testing resumed with some minor restrictions and a software fix was in progress in late June.

On board carrier testing is slated for 2013, and in May the F-35C made good strides toward reaching that goal. According to Lockheed Martin, the three variants of the F-35 flew a combined 94 System Development and Demonstration (SDD) flights, the most achieved in a single month thus far. As of May, the F-35C lagged behind its sister variants, having flown 62 times in 2011 versus 183 and 166 flights for the (more numerous) F-35A and B test aircraft.

The F-35C prototypes at Patuxent River represent two different software configurations. The “flight science” aircraft, CF-1 and CF-2, operate with basic Block 0.5 software while CF-3 is a mission-systems aircraft, flying with the Block 1 software version. As of spring 2011, the standard software version for Initial Operational Capability (IOC) will be Block 3 for the USAF and USN while the Marines plan to declare IOC with Block 2B.

The various software blocks are essentially the same across all variants, with little tailoring to each specific model. However, the F-35C’s different aerodynamics and structure do require different flight control laws and other variations within each software block. Buus added that modifications within each block are possible and each of the software packages is configurable to meet future requirements. Nevertheless, he stressed that the differences across type models are minimal at this point.

The same can be said for the F-35’s Pratt & Whitney F135 engine. Save for some attached accessories for the B model, there are no significant changes to the 43,000-pound thrust engine whether situated in an A, B, or C model. Buus added that the engine has the same thrust rating across all three variants and that no special anti-corrosion or FOD (foreign object damage) tolerance modifications have been made for the F-35C.

“I’d go so far as to say nothing at all. It’s the same engine.”

The F-35C test team stresses that they are very early in the aircraft’s development phase, a view echoed by a May report from the Government Accountability Office that stated just 4 percent of the F-35’s overall capabilities had been proven in lab or flight tests. The Pax River-based team has used some of the development done for the A and B models to expand the F-35C flight envelope a bit faster, but Buus acknowledged that not all the development work transfers.

“Because it is a different airframe, most of the flight envelope expansion with the C model has had to be done on its own. The aerodynamic and structural properties of the C are probably the most different compared to the other airplanes.”

Through late spring and early summer 2011, F-35A development continued, with the first low-rate initial production (LRIP) airplanes (AF-6 and AF-7) in use as test aircraft at Edwards Air Force Base (AFB) and later at Eglin AFB for maintenance training. At that time these LRIP aircraft were expected to be limited to a 350 knot/4 g flight envelope for training.

When asked if the C prototypes were similarly limited, Buus replied, “All
I can tell you is that our test aircraft here are flying a faster and higher g envelope than that currently.”

The limits of that envelope are not yet concretely known, but in late spring published reports compared overall F-35 flight characteristics to the F/A-18, citing Energy-Management (E-M) diagrams (which convey aircraft energy and maneuvering performance within its airspeed range and load factors) that resembled those of the Hornet. With respect to the F-35C, Buus, whose flying background is predominantly in legacy and Super Hornets, thinks the comparison is a fair one.

“We’re early on in flight test so we haven’t fully expanded the envelope, but it’s certainly comparable. The projected E-M diagrams are similar and what we’ve found thus far in testing hasn’t differed from that too much.”

Aside from its maximum performance parameters, the user-friendliness of the F-35C is, as with all fleet aircraft, of major importance. Its qualities will soon enough be put in front of fleet pilots. The first Navy F-35 Fleet Replacement Squadron, VFA-101, is slated to stand up at Eglin in March 2012 and is scheduled to receive its first aircraft in September 2012.

What the initial cadre of VFA-101 instructors and operational test pilots are likely to find is a Joint Strike Fighter that, early testing indicates, handles much like a Hornet or Super Hornet, according to Buus.

“We haven’t flown the airplane a whole lot yet but it flies very well. In general the aircraft is similar to a Hornet/Super Hornet. The folks who’ve designed the flight control laws have really done a nice job. You can put the airplane where you want to and let go of the controls and it stays right there.”

Throughout the initial phases of F-35B testing, BAE Systems Lead STOVL (short takeoff/vertical landing) Pilot Graham Tomlinson sang) the praises of the B and its ease of operation in STOVL flight modes as compared to the Harrier. Ease of operation around the carrier will be an important characteristic for the F-35C as well.

Favorable carrier approach/landing characteristics not only enhance pilot safety, the test team points out; the increased boarding rates they generate improve the tactical efficiency of the carrier strike group. Along with the physical development of the F-35C’s launch and recovery equipment and techniques, its around-the-boat flying qualities will be further fleshed out.

“We’re working on the development to do that,” Buus explained. “I don’t know how soon we’ll actually start those handling evaluations, but I will tell you that right out of the chocks the airplane flies really nice on approach. There are certain things we’ll need to tweak a bit but it’s currently comparable to a Hornet in how it flies on approach.”

While the pace of C-model testing has thus far been light compared to the F-35A/B, the flights the aircraft have made since March 2011 have turned up little in the way of surprises, Buus said.

“There are certainly things here and there in flight test that we discover that don’t quite react the way the engineers were expecting, but no major issues have been discovered.”

Among the carrier-centric qualities yet to be fully test/operationally verified is the F-35C’s range. Lockheed Martin nominally lists the C’s max range at 1,200 nautical miles and its combat radius at 640 nautical miles. Boeing’s Super Hornet has a combat radius of 390 nautical miles. Working in the F-35C’s favor is a considerably larger internal fuel capacity, at 19,750 pounds versus the single-seat F/A-18E’s 14,400-pound capacity. Likewise, the aircraft will have internal weapons carriage, aiding its aerodynamic drag profile in addition to its stealth.

“Just from a pilot perspective,” Buus said, “for a comparable loadout, the F-35C is going to be clean, stealthy with no external weapons or pylons out there. It will be a slick airplane with more fuel.”

Though the C will have seven external weapons stations in addition to its four internal stations, it will likely be flown in clean configuration more often than the Hornet, Buus said.

“It will be able to carry off the ship what a Super Hornet will and it will have a meaningful internal strike load. Internally, it will be able to carry 4,000 pounds of air-to-ground ordnance plus two AMRAAMs [advanced medium-range air-to-air missiles], which is certainly an effective loadout.”

Theoretically, such a loadout would enable the airplane to fly the kind of loiter missions Hornets have been flying in Iraq – and more recently, Afghanistan – without external stores. And with a maximum trap weight of 46,000 pounds, the F-35C will have “slightly better bring-back than a Super Hornet,” Buus added.

The fact that the C will not have the tanker capability that the Super Hornet and Growler do is not seen as a negative by Buus.

“For many years to come the air wing is going to be a mix of F-35s, F/A-18Es, Fs, and Gs, so there will be tankers available. There will always be recovery tankers flying around the aircraft carrier.”

USN F-35Cs will have company aboard ship, with the Marine Corps planning to buy 80 copies of the C to fill out five squadrons. The carrier variant of the JSF is now the type model of choice for the United Kingdom as well, and at last report, the British expect to receive their first F-35C in the 2014-2015 time frame. The U.K. test contingent remains at NAS Patuxent River and Buus confirmed that “their focus has certainly shifted.”

Along with remaining an integral part of the F-35 test program, the U.K. has decided to place a number of its pilots in exchange positions with the USN flying F/A-18s and eventually F-35Cs to maintain aircraft carrier operational acumen while it awaits construction of its own new conventional deck carriers.

Predictably, the JSF program still faces headwinds as the test program goes forward. In late June, the top Republican on the Senate Armed Services Committee, Sen. John McCain, specifically said the pending defense authorization bill did not go far enough to stop cost overruns on the F-35 and indicated he may vote against the bill when it goes before the full Senate.

In amusing contrast, Lockheed launched a new website (www.f35.com) complete with a Fort Worth, Texas, rock band playing the company-commissioned song “I’ll go anywhere/I’ll do anything” to shots of the F-35C and other variants in a club setting.

Back in the hangar at Pax, Buus and the test team just get on with test sorties, refining the F-35’s “C” legs.

“We feel very good about the work with respect to the C model,” Buus said. “In fact, since we’ve gotten test airplanes here at Pax, I believe we’ve been beating our flight test expectations for this year. I’m feeling very positive about the airplane so far.”