The X-35C flight test program laid the foundation for the delivery of the F-35C Lightning II, the carrier-capable variant of the fighter jet. The F-35 unites air forces in the air, on land, and at sea because of the innovation and hard work illustrated by many different experts from government, military, and industry during its development.
The flight test program was overseen by engineers, crew teams, and test pilots with a focus on carrier-suitable flying qualities and aircraft performance shown by a series of in-depth evaluations for carrier approaches, landings, wave-offs, and bolters.
The X-35C concept demonstrator aircraft made its first flight Dec. 16, 2000. Glen Harbison was the lead flight test engineer (FTE) on the X-35C for Lockheed Martin. His upbringing was at Skunk Works (Lockheed Martin’s Advanced Development Programs), where he worked on the F-117 Nighthawk, the first fighter jet that could operate completely undetected by an adversary. Steve Reller was involved in the X-35 program during the very early stages of building the prototypes as a manufacturing supervisor on the floor. For this flight test program, he had the privilege of being the crew chief for the X-35C.
“This test program always had a buzz about it. There was always energy in the air. Everybody knew this was a must win program or we were going to be out of the fighter business!” Reller reflected on the intense yet electrifying atmosphere working with the X planes.
Harbison explained that the FTEs were closely involved in the details of the X-35C’s test plan and development.
“There wasn't anything that went on the jet that wasn't covered by paperwork either issued or signed by me pretty much during the whole build phase, including the instrumentation,” said Harbison. “I sat down with the crew chief and the quality assurance inspector to approve things for the flight to make sure I felt good about what we were putting our name on.”
Reller agreed with the meticulous nature of designing, developing, and reviewing the concept demonstrator aircraft.
“Nothing ever went on that airplane without a piece of paper. I’d hear, ‘Steve, I need something reconfigured and here's the flight test service order,’ and we'd have to go work through that document and sell it to quality assurance,” Reller said of his role.
Professionalism was truly engrained in the X-35C's historic first flight. Harbison shared how he received an interesting request about five weeks out from the scheduled first flight – and the pressure was on.
"I got called into my boss [then flight-test director for the Lockheed Martin X-35 program] Dick Burton’s office and was asked by the Navy to knock 10 days off my first flight schedule. Ten days is a lot, especially only five weeks out. I'm looking at the schedule, unsure if this is possible,” Harbison said. "I ended up agreeing to it with the caveat that there be no software drops, which can add two weeks.”
He pressed on and the team adjusted their approach to meet the 10 days by performing tasks out of sequence, taking only parts of the jet to paint or reconfigure; essentially not waiting until it was fully built to knock things off their list.
That December morning was a cold, clear day, and the X-35C was set to get in the air. Although there was a level of competence, according to Harbison, they were on guard because anything could happen during the test period.
The mission for Flight 1 was straightforward: Get the X-35C safely up in the air from Palmdale, California, and safely on the ground at Edwards Air Force Base.
At 9:23 a.m., test pilot Joe Sweeney launched and flew the X-35C for 27 minutes before touching down. The aircraft climbed to 10,000 feet and accelerated to 250 knots (288 mph). Sweeney, a former Navy attack pilot, cycled the landing gear and performed aircraft flying-qualities evaluations. The team at Edwards was responsible for the landing performance and handling qualities testing.
“We had to prepare the X-35C to land, so we did a lot of work on the power approach mode, which means landing gear down, and did a normal nominal conventional landing,” said Harbison “We used an integrated test block approach (ITB), which were a series of pitch, roll and yaw maneuvers, during flight.”
Aircraft flight movement happens around three axes: the longitudinal, lateral and vertical. These straight lines, perpendicular to each other, pass through the center of gravity of an aircraft. Roll occurs around the nose-to-tail line; imagine wings dipping left or right. Pitch happens on the wing-to-wing line; think about the nose or tail going up or down. Yaw occurs on a co*ckpit-to-bottom of the fuselage line; envision the nose going left and the tail right, or vice versa.
The pilot communicated to Harbison that the acceleration felt smooth and predictable during take-off.
“Joe [Sweeney] said he was happy with the performance of the X-35C. Everything was rock solid and steady,” Harbison remembers of Sweeney’s communications in-flight. “We did bring the gear up and we got a gear door light, which meant that the door wasn’t fully closed, but it didn’t hinder the test’s completion.”
“The X-35C did not let any of us down - the initial responses, handling qualities and performance were just as predicted,” commented Sweeney. Because of the high fidelity of the flight simulation technology at the time, it was very clear in his mind what to expect from the jet’s performance. Harbison said that Sweeney's dedication to simulation training contributed to the successful first flight.
Reller recalls that day as one of his proudest moments as the crew chief.
“The crew team got the airplane out there to fuel up and make sure everything's checked out. Quality assurance came in and to check, double-check everything. Once we got the green light from our flight test guys, it was a smooth morning,” he said. “These are true professionals.”
The engineers and crews agreed that it was a good feeling once all was completed, and real-time assessment began. Once it was confirmed that there were no issues with routine landings, the X-35C flew to Patuxent River, Maryland, and saved the aggressive test points for at-sea level. Now, the mission was to demonstrate through a series of evaluations that the test team knew how to provide a design for the carrier variant environment.
“One of my fondest moments was when the X-35C came out of the paint shop. When you build the airplane, frankly, it looks terrible. It has wires hanging out everywhere, it is raw and unpainted,” Reller said about the X plane when it was in the construction phase. “The X-35C came out of the paint hanger and it was gorgeous and on the nose landing door was my name. I was very proud of that,” said Reller.
“It was a good test program. The airplane held together, and we won.”
Harbison spoke about the overall mission of the joint strike fighter competition.
“Looking at the (F-35C) now, I'm glad to see that the Marines picked it up along with the Navy for their at-sea operations,” he said. “You knew you did something good for the warfighter.”
The X-35C test team delivered the fifth-generation fighter into the capable hands of the warfighter. Today, the F-35C serves as one of the most important fighter jets for the U.S. Navy and U.S. Marine Corps. It has participated in numerous crucial operations across the globe, particularly in the Indo-Pacific area, and it will continue to be an integral part of the at-sea strategy of the United States and its allies, as well as a ready response to protect security and peace.
