Wings Magazine

F-35 acing tests according to pilots

March 14, 2011, Patuxent, Md. - The F-35 is getting a thumbs-up from the test pilots flying it.

March 14, 2011  By Dave Majumdar Air Force Times

Both military and civilian aviators give the Joint Strike Fighter high marks on speed, altitude and vertical takeoffs and landings, as well as for its avionics.

The single-engine jet has performed reliably up to Mach 1.2, slightly faster than the speed of sound, and in maneuvers up to 1 G, a unit of force equal to the force exerted by gravity. Now, the test pilots are assessing its ability to handle maneuvers of up to 5 Gs — five times the force of gravity — and angles of attack up to 20 degrees.

Once those flights are complete, the Air Force and Navy can train their instructor pilots and the Marine Corps can train its fleet pilots, said Squadron Leader Steve Long, a British Royal Air Force test pilot assigned to the JSF program. Long holds the record for the F-35’s fastest flight: Mach 1.3.

Ultimately, the test program will push the three variants of the aircraft to 50,000 feet, Mach 1.6 and 700 knots. The B model, the one to be flown by the Marine Corps, will reach a top speed of 630 knots. The Air Force variant, known as the A model, will be cleared to 9 Gs, the B model to 7 Gs and the Navy’s C model to 7.5 Gs.


Bound for Eglin Air Force Base

The F-35 test pilots have been focusing on common speeds and maneuvers so they can release the F-35 to instructor pilots at Eglin Air Force Base, Fla.

“They don’t need to go at Mach 1.6 right now just to become familiar with the airplane and learn how to be instructors and all that sort of thing,” Long said. “There’s no real time pressure on us right now to get the speed headlines cleared out for us.”

The aviators have completed 23 vertical landings with the B-model aircraft, more than half of the 42 needed for the Marine Corps to begin trials at sea aboard an amphibious assault ship.

“We’ve done more vertical landings in the month of January” — 13 — “than we did last year. So this is coming fast now,” one of the test pilots, Marine Lt. Col. Matt Taylor, said in a telephone interview from Naval Air Station Patuxent River, Md.

Landing vertically in the F-35B is easy, Taylor said.

“I’ve flown a lot of airplanes. This is the easiest one there is to land,” said David “Doc” Nelson, who flies for Lockheed Martin, the F-35’s prime contractor.

Nelson said that even pilots who have never flown a vertical-landing aircraft, such as colleague Jon Beesley, have no trouble handling the F-35B.

The test pilots also raved about the JSF’s maneuverability, calling it a nimble machine. For example, the F-35 can handle better than a 40-degree angle of attack, which is related to the amount of lift.

“It flew great on its first flight and it’s flying great now, and we’re tweaking it to make it even better,” Taylor said.

Nelson said: “It’s not quite what an F-22 is, but it’s better than any legacy I’ve seen.”

At subsonic speeds, the F-35 can accelerate right alongside the more powerful twin-engine Raptor. Although the F-35 flies faster than sound, the F-22 is in a league of its own — a maximum speed of Mach 2.

The F-35 variants fly in remarkably similar fashion, the test pilots said.

“They did some trick with the flight controls to make all three variants feel the same,” Nelson said. “When you sit in the cockpit, all the hardware switches are the same. So if you blindfolded a guy, there is a possibility he wouldn’t know which jet he was in.”

Taylor, though, thinks the Navy’s C model, with its larger wings and stabilators, has a “slightly different” feel in parts of the flight envelope, a term that refers to design capabilities usually in terms of airspeed and altitude, and is “slightly draggier” than its sister versions.

‘A’ for avionics

The F-35’s mission systems are even more advanced than its flight characteristics, according to the test pilots.

“To me, the headlines aren’t how fast it goes and how many G’s it pulls, it’s how great that radar is and how great the [Electro-Optical Targeting System] and the [Distributed Aperture System] and the situational awareness that you get over [the Multifunction Advanced Data Link] and all those sort of features in the airplane,” Long said.

The radar, according to the aviators, is almost ready for combat, even with the basic software currently in place.

“I would just comment that the performance of the sensors at this early phase in a program is unlike any I’ve ever been part of,” Taylor said. “The fact that they work as well as they do and are as close to being ready to go to combat today is really impressive. I expect it to hold a lot of promise for how the airplane is going to be when it’s fielded.”

The pilots especially praised the plane’s synthetic aperture radar, which takes photo-quality images of the Earth’s surface, as well as the electronic warfare suite and the communications systems.

“I’ve seen a lot of mission systems programs start,” Nelson said, “and I’ve never seen one start like this.”

A few hiccups

Not all has been perfect, though.

The JSF has an engine “screech,” a disturbance in airflow; a phenomenon called “transonic wing roll-off,” in which it can roll unexpectedly; and a helmet-mounted display prone to latency and smearing. The problems have either been corrected or are being addressed, according to the test pilots.

“We have screech kits that we’re going to attach to the airplane that will trivialize its impact on the envelope,” Nelson said.

“Transonic roll-off, we’re investigating that and we have recently updated the software to minimize its effect on the handling characteristics of the airplane,” he said. “The transonic roll-off is something that has been overcome in many ways by the software update that we just got.”

As for the helmet-mounted display, Taylor said he and his colleagues are “on a path to get that stuff sorted out.”

“Obviously, the problems aren’t too bad, because we’re still flying the airplane and we’re using the helmet on every single flight,” Taylor said.

The helmet display gives the pilot a much larger field of view, and it uses infrared cameras to make nighttime flying similar to flying during the day, Nelson said.

“When the fleet has flown this airplane for several years and the guys are raving about their airplane, the F-35, the reason they’re going to love it is because nobody sees them and they see everything,” Taylor said.

Asked whether the F-35 is their warplane of choice to take into combat, the test pilots had the same answer: an unequivocal “yes.”


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