Flying the world’s largest airplane—with a wingspan longer than an American football field—is tricky, even for professional test pilots. Evan Thomas should know. He was the first pilot to fly it.
Named Roc, after the mythical bird, Stratolaunch’s twin-fuselage aircraft was designed to carry and launch large payloads in flight. So far, the one-of-a-kind jet with six engines has only flown twice since its debut in 2019.
As Thomas prepares for new missions over California’s Mojave Desert starting in January, he took some time to share fascinating details about what it’s like to operate the massive flying machine.
“I honestly think the thing that surprises most people when they fly it in the simulator is the plane’s flat, Dutch roll,” says Thomas.
For non-pilots, a Dutch roll happens when yaw—rotation around the vertical axis of an airplane—causes the advancing wing to produce more lift than the retreating side. This causes the airplane to roll toward the retreating wing.
“You tend to see the flat modes in military-type aircraft a little bit more,” Thomas says. “In a normal airplane, you put in a rudder input or two and the airplane’s going to move. But because of Roc’s unusual Dutch roll characteristic, that takes so long. You can’t just keep the rudder the same, you have to change it as you’re in the turn because 10 to 15 seconds later, instead of trying to yaw this direction, it’s trying to yaw that direction. It’s a very slow yaw rate that just keeps going.”
“From a pilot’s perspective, that’s the most unusual thing about the airplane.”
Roc’s yawing characteristics, Thomas says, are also the result of adverse aileron drag, and come from “the deflection of the ailerons and the differential of the lift. You also get some raw yaw due to the roll rate of the airplane—a function of the wings rotating” about the longitudinal axis of the airplane.
The upcoming missions will focus on expanding the airplane’s performance envelope and eventually launching hypersonic test vehicles.
For those who may be late to the party, Roc is history’s largest airplane in terms of its 385-foot wingspan. It’s wings are wider than Boeing’s 747-8 or Howard Hughes’s mid-century H-4 Hercules—better known as the Spruce Goose.
But unlike Hughes’s wooden behemoth, Roc is expected to fly for years to come.
Path to Flight
When Thomas was growing up in southern California not far from Lockheed’s legendary Skunk Works aircraft factory, he dreamed of flying. But he never imagined he would end up piloting the world’s largest airplane.
After graduating from the U.S. Air Force Academy, where he learned to fly, Thomas eventually was promoted to command posts with NATO forces and at Florida’s Eglin Air Force Base. His piloting experience runs the gamut from Cessna 172s to F-16s, F-22s, a BAC-111, and even a bit of time in the C-141.
His sights set on becoming a private test pilot, Thomas retired from the military and returned to his home state to serve as senior test pilot at Calspan Corporation; then a test pilot role at iconic Scaled Composites, which built Roc; finally transitioning to Roc’s owner, Stratolaunch.
“Being involved in a first flight project is the goal that most test pilots work towards because there are so many unknowns,” Thomas says. “Everything about the airplane is unknown. Is it even going to fly? Is the air data system going to work? Are all your airspeeds and altitudes going to be off? How well are the flight controls going to work? What are the handling qualities going to be like? You name it.”
As he grew more invested in the project, Thomas says he just ended up as the lead pilot.
“From the time that I got hired, we were all working to do the development work,” he says. “You’re putting yourself in that mindset that you have to prepare the airplane for that flight and the crew that’s going to be on there. Then, as the situation evolved and it ended up being me in the left seat getting to do that landing, which of course was a fantastic opportunity.”
He says it was a privilege to represent such a great team of people—hundreds of men and women who designed and built the airplane and did all the hard work. “And then they turned it over to me to do the hard work of first flight.”
“Every day was different as we came up with a way to overcome whatever challenge.”
Flight simulators and specially configured test articles were used to prep the flight crew for Roc’s first flight.
Then, when the airplane was finally built, it was time to test it on the ground.
“For an airplane of this size, we weren’t going to just take two or three runs down the runway and call it good,” Thomas says. The flight test team rolled out the airplane on the runway for weeklong test events, which included taxi test runs, analyzing data, testing the airplane’s braking performance as well as its anti-skid and handling qualities.
The team decided that, for the first flight, a dry lake-bed runway at nearby Edwards Air Force Base should be available as a divert option in case something went wrong or the handling qualities of the aircraft were worse than expected. The lake bed would provide a longer, wider runway, if needed.
Then, immediately before the first scheduled flight date, it rained—changing the lake-bed runway from a dry, open field to an unusable, muddy airstrip.
For the next four months, the team was forced to wait. During that time, they watched the weather forecasts, rehearsed, and continued to prepare.
“You can sit all day and dream up things that might go wrong,” Thomas says. “But part of the art of going into a first flight is picking out the things that scare you the most—essentially—not only from the engineering side but also just from the piloting side. As a test pilot, you’re the bridge between the engineering design side and the operational, go-fly-the-airplane side.”
By the time conditions were right, Thomas says, “we were very ready to go. The overwhelming thought was: We’re ready. Let’s get this over with. Let’s do it.”
Test Pilot Recalls the First Flight
On the day of Roc’s first flight—April 13, 2019—everyone in the program was aware that a successful mission would change history—eclipsing aviation giants like Boeing and Hughes.
As the gigantic aircraft sat on the runway at Stratolaunch’s test facility in Mojave, California, Thomas occupied the left seat, Chris “Duff” Guarente, the right seat, and flight engineer Jake Riley sat behind.
Before this flight, the largest airplane Thomas ever flew was the C-141—a large cargo jet to be sure—but with a wingspan less than half of Roc’s, and well proven by the time it was his turn to fly it.
“I didn’t have a lot of big aircraft time, which certainly raised some eyebrows when I was coming on the project. But I did have seven years instructing on the Calspan planes that were set up to demonstrate big-plane flight characteristics,” Thomas says.
Inside the right fuselage, the vibe on the flight deck was all business.
“We were all trying to keep it pretty low key,” Thomas says. “No one wanted to say something big and flowery and have something go wrong. So we were all pretty by-the-book.”
In the control room, test conductor Brandon Wood radioed Thomas that Roc was clear for release. As the airplane started its roll, Thomas knew he wanted to avoid a slow rotation that might result in the plane wallowing on the 12,000-foot runway.
“I did a fairly crisp rotation—a 747-type rotation—up to 10 degrees nose high. The nose came right up and stayed there.”
Instead of slowly moving away from the ground, as you might expect with a large airplane during takeoff, Roc immediately started gaining altitude quickly. The world’s largest aircraft with its 385-foot straight wing performed not unlike a glider or a U2, Thomas says.
By the time Roc passed the tower, the airplane was well above it.
“It felt like we were on an elevator.”
After determining a couple of fuel warning lights were false alarms, as well as mitigating the Dutch roll, Thomas piloted Roc to an altitude of about 15,000 feet msl to complete a series of handling quality tests.
The twin-fuselage jet feels like you’re flying a conventional large airplane, Thomas says, “until you look out the window and see the other side of it.” As you might guess, handling Roc is a function of its massive size, Thomas says. “It is a supertanker, it is not a speedboat.”
Lessons Learned from Landing
Roc eventually reached a maximum speed of 165 kias before the flight crew lined it up for a 10-mile straight landing approach to Stratolaunch’s Mojave runway.
With Thomas flying the aircraft and Guarente operating the throttles to reduce the workload, they brought Roc down to about 100 feet off the runway.
“Afterward, a lot of people on YouTube were saying, ‘Oh, they’re doing a flyby,’” Thomas laughs. “No, we were not doing a flyby. Before we land the world’s largest airplane for the first time, we want to get down in that landing environment and see what things are like.”
Following Roc’s first slow approach, Thomas asked Duff and Jake: “Hey—you guys feeling up for the landing?”
They responded, “Yep, let’s go for it,” Thomas recalls.
“The landing,” he says, “was the one spot where there was a giant question mark.” The flight crew had already completed taxi tests up to about 115 knots rolling on the runway. But this was their first chance to make that transition from the air to the surface “and see what it’s like to get the airplane under control and back into the environment we’ve seen before.”
Piloting from Roc’s right fuselage makes landing unique, to say the least. “You cannot land on the [runway’s] center line. The last thing you want to do is swerve back to the center line or try to line up on the center line. We actually will train to offset on to the right side with the airplane.”
“One of our key parameters for landing is to line up the fuselages with the runway, because our main landing gear are in line, kind of like two big in-line skates.” Another challenge: The pilot cannot see the entire left wing from the left seat.
Thomas says the rudders proved very effective for lining up with the runway, but seconds before touchdown, he felt “this perception that we’re getting pushed to the left by the wind. What was actually happening was, we were yawing to the left.” To correct that, Thomas banked a little more into it, which created a little more yaw, which again felt like the airplane was being pushed, which made Thomas bank even more.
“So, if you watch the video of the first flight, we actually landed in more crab than we wanted to, with the nose off to the left.”
Wheels down. Total time in the air: 149 minutes.
“We walked away from the first flight very happy that it had gone 95 percent as predicted,” Thomas says. “The airplane flew great.”
“We all shook hands and did a little whooping for a little bit,” Thomas recalls. After that, he says, it was back to the landing checklist to finish the mission “the right way.”
That first flight offered Stratolaunch two lessons learned. One: During landing approach, pilots on the flight deck need to give each other more flight cues to keep the airplane lined up for a wing-low landing. Two: Engineers needed to make a few flight control changes to adjust for the airplane’s adverse yaw characteristics, including the addition of yaw augmentation.
A few facts about the world’s largest airplane that you may not know:
Many Roc Elements Come From Boeing 747-400s
Roc’s six Pratt & Whitney PW4056 engines come from salvaged 747-400s, as do the airplane’s 6 main landing gear and two nose gear.
Much of the equipment on Roc’s flight deck has been salvaged from 747-400s including:
- Cabin layout including pilot, co-pilot and console in between
- Six engine throttles (modified from the four-throttle 747-400)
- Overhead panel: engine start knobs, controls for generators, mode selection for engines, anti-ice system
- Rudder pedals and yokes
- In 2019, flight deck seats were from a 747-400, but they’ve since been replaced.
The Flight Engineer Continues an Aviation Tradition
Roc flight engineers perform a role very similar to traditional flight engineers who served on mid-century commercial airliners. They sit at a station behind the pilots and monitor the airplane’s hydraulic system, engines, pneumatic system, and electrical system.
The Left Fuselage Is Not Empty
Many people ask: If the flight crew only uses the right fuselage cabin, why does the left cabin have windows? The answer is simple, Thomas says. Because both fuselages need to be pressurized, it was just easier to use the same design—including windows—to build both cabins.
“We’ve made jokes in the past about getting a beanbag chair and strapping someone in over there, but as of yet we have not done that,” says Thomas.
The left fuselage cabin is where the airplane’s generators live. Each powerplant has a generator producing AC electric power in a pressurized environment.
Walking through the fuselages is “a bit like going into a submarine,” Thomas says. “You have a lot of bulkheads with flight-control cables and hydraulic equipment.”
Roc Has Limited Fly-By-Wire
Since its first flight, Roc has been improved to add limited fly-by-wire controls that operate some of the airplane’s flight-control surfaces. Only the outboard ailerons are connected to fly-by-wire controls, which are signaled by the pilot’s control wheel. The inboard ailerons are connected by mechanical cables and moved by hydraulic systems.
So Far, Roc Has Never Retracted Its Landing Gear
During its first flight and its second flight this past April, engineers chose not to retract Roc’s massive 747 landing gear. “The first flight was done without any gear doors, and the second flight we had nose gear doors, but we left them closed.” During the next flight, Thomas expects to successfully raise the gear and complete envelope expansion for the airplane. So far, Roc has achieved a maximum flight level around 17,000 feet msl and a top speed of about 170 knots. Goals for the next flight also include expanding the envelope for altitude and airspeed.
Roc’s To-Do List
Eventually, the airplane is expected to reach altitudes similar to commercial airliners where it will execute mid-air launches of hypersonic test vehicles. Its payload capacity is rated to more than 500,000 pounds.
Before that, Roc’s to-do list includes:
-Mounting the airplane’s center-wing pylon, which will carry Roc’s launch vehicles
-Conducting captive test flights with a vehicle attached
-Perform a safe separation test with a launch vehicle
-Perform a powered in-flight launch with a hypersonic vehicle
Stratolaunch Wants to Expand Roc’s Image
Roc has been on the ground since April, but that hasn’t stopped pilots from training for future flights.
“We do a lot of simulation,” Thomas says. “That’s the primary training method for the airplane.”
Stratolaunch says it has already negotiated a string of private and government contracts going forward. The company wants Roc’s image to transcend its fame as the world’s largest aircraft.
“We hope that in the next year or two people are going to start recognizing that we’re using the plane for something that’s beneficial for our country,” he says. “That means supporting national defense and aerospace research.”