EDWARDS AIR FORCE BASE, CALIFORNIA, July 20, 2001. Mission X was to be the graduation exercise for the Lockheed Martin X-35B, the Short Take-Off and Vertical Landing (STOVL) concept demonstration aircraft.
The STOVL aircraft fulfills only one of three service roles the X-35 Joint Strike Fighter was designed for. The STOVL design will replace the Marines’ AV-8B Harrier. There’s also a conventional-takeoff-and-landing (CTOL) version for the U.S. Air Force, and a beefier version for the Navy’s punishing catapult launches and arrested landings. The call sign of all X-35 test pilots is “Hat Trick,” which is the term for three goals scored by one hockey player in a single game.
The sortie was to consist of a short takeoff, climbing to 25,000 feet, making a supersonic dash, and returning to the field for a vertical landing. Each event, in and of itself, was not a breakthrough achievement and had been accomplished on a previous X-35B sortie, but putting them all together on one flight would be an aviation first. Previous STOVL aircraft achieved supersonic speeds when they had been put in a steep dive, but today we would up the ante by making a level supersonic dash.
The day started with a pre-sunrise flight brief. The early start allowed our team to complete testing before other units at Edwards started flight operations. Additionally, today the field was to close from 10 to 11:30 a.m. for a memorial service. We planned to be done with our test by 9, so there was little time to spare.
Until now, I had flown the aircraft for only three brief vertical takeoffs and landings, which gave me a total flight time of about three minutes. The first flight of the day would basically familiarize me with STOVL flight, allowing me to get a feel for the airplane while completing just a few test points. After landing, the ground crew would hot-refuel the jet (load fuel with the engine running), and I would take off again. The second flight would be Mission X.
With all the buildup we had given Mission X over the past three years, I suppose I should have been more excited. Actually, I was more focused on completing all the test events and, more importantly, not making a mistake. Although Mission X consisted of only the three basic events, there were several other test events planned to fill the rest of the sortie. As I was gathering my flight cards (which include tests to perform, the order in which to execute them, pertinent cautions or limitations, and space to make notes), the lead military flight test engineer shook my hand and said, “Good luck, and don’t forget to have fun out there.” I guess I must have looked more worried than excited. I thanked him and walked to the hangar to get my flight gear. After suiting up and completing my preflight, I gave the airplane my traditional pat on the nose. I wouldn’t say I’m superstitious, but that day I wasn’t taking any chances.
The first flight went very well, and I was able to get a good feel for the airplane while it was in the STOVL mode. Perhaps the most surprising thing about the flight was that there were no surprises. All that time in the simulator had paid off. In fact, the previous night, the simulator team stuck around late so I could practice the mission profile a few times. Another reason the flight had gone well was that the airplane was very easy to fly. Although the Harrier is a remarkable airplane and an amazing achievement in its own right, it is difficult to fly. It takes a long time to train a Harrier pilot, and he must practice a lot to stay proficient. If the first flight in the X-35B was any indication, we were on the right track to making STOVL flight much easier.
During the few minutes it took to refuel, I went over the sequence of events for the Mission X flight. When the test conductor called on the radio to talk about prioritizing the events in the test cards, I realized that we were going to cut it close to the field closing time. There wasn’t any room for mistakes or repeats. The little bit of extra pressure would help keep me on my toes.
I was finally ready to go. Once in position for takeoff I moved the Thrust Vector Lever (TVL) back about an inch, initiating the process of converting the aircraft from CTOL mode to STOVL. Behind the cockpit, four sets of doors were opening. This would allow air to flow through the lift fan and enable the vectoring rear nozzle to move through its full range of travel. While the doors were opening, the clutch was engaging, transferring power from the engine to the lift fan. The only noticeable change in the cockpit was an increase in noise as the lift fan spooled up.
A “good conversion” call came from the control room, which confirmed the indications in the cockpit. I radioed the chase aircraft that I was ready and slowly advanced the throttle and released the brakes. The aircraft quickly accelerated down the runway, and at 80 knots, after only 200 feet, I vectored the thrust to 60 degrees and the aircraft leapt off the ground. I completed the post-takeoff checks, climbed through 5,000 feet, and converted the aircraft from STOVL mode back to CTOL by moving the TVL fully forward.
Climbing to test altitude, I turned toward the supersonic corridor, the airspace designated for supersonic flight tests. Upon reaching 25,000 feet, I stabilized briefly, then advanced the throttle to full afterburner. As the afterburner engaged and the aircraft rapidly accelerated, I was pressed back in the seat. I watched the head-up display on the windscreen to make sure that I was maintaining level flight, but mostly I focused on the airspeed indicator. As the airspeed passed Mach 1.0, I adjusted the throttle for Mach 1.05, the target speed for the test. In the cockpit, the transition through the sound barrier was barely noticeable.
Now two of three Mission X events were complete—just one more to go. As I started slowing down for the next test point, I checked fuel and time. It was getting close, but there was still enough time to get everything done before the field closed. I set up for the next event, a set of slow-speed flying-qualities tests. These test points consisted of performing pitch, yaw, and roll evaluations at speeds of about 140 knots (160 mph) and below. It took about 10 minutes to complete the set. Checking fuel and time again, I realized that we probably didn’t have enough of either to complete the last set of tests. After a quick discussion with the test conductor, we decided to head back to the field to set up for the vertical landing.
I began the descent and turned the airplane back toward the runway. Passing through 5,000 feet I slowed below 200 knots, converted the aircraft back to STOVL mode, and began my final approach. Once over the runway, I started the deceleration to the hover. I gradually moved the TVL aft, increasing the angle of thrust from 0 degrees (thrust straight aft) toward the hover setting (thrust about perpendicular to the ground). I adjusted the rate at which I moved the TVL by visually judging my deceleration rate as I approached the desired hover spot. The process is somewhat analogous to adjusting pressure on a car’s brake pedal to stop smoothly at a traffic light. The aircraft responds to control inputs in a hover the same as it does in forward flight. Left stick banks and moves the airplane left. Forward stick pitches the nose low. Increasing and decreasing the throttle controls altitude. I set up to come to a stop just short of the landing pad, which was just off the runway at about midfield. I brought the aircraft to a hover over the runway, stabilized for a few seconds, and began to cross over to a position above the landing pad. Once the aircraft was centered over the landing site, I reduced the throttle slightly to begin the descent. Out of the corner of my eye, I caught a glimpse of the many spectators in the observation area. No one was running away from the airplane—a good sign.
The aircraft firmly touched down and I quickly chopped the throttle to idle. “Touchdown,” I called over the radio. Mission X was complete.
During the taxi back to the ramp, I completed the after-landing checklist and had a few minutes to let the events of the past hour sink in. As I began the process of shutting down the airplane, I glanced outside at the crowd that was approaching the airplane and finally started to relax. Things had gone well: We had accomplished most of our test points and made it back before the field closed. By completing Mission X, the X-35B had just made aviation history, with me in the driver’s seat. I glanced at my watch before getting out of the cockpit: just before 10 a.m. All things considered, not bad for a morning’s work.
—Major Arthur Tomassetti, U.S. Marine Corps