Here’s What It’s Like to Fly an Experimental Supersonic Jet

When Tristan Brandenburg leaves the house at 4 a.m., there’s no one see him off. His wife, Stacia, and 7-year-old daughter have moved to the family’s new home in Colorado, while Brandenburg has stayed behind for work, settling into a friend’s spare bedroom.

The Southern California desert is dark and cold as he begins the 25-minute drive from Rosamond to Mojave. He usually listens to books on tape during the ride, but this morning he goes without. Alone in the silence, Brandenburg runs through the emergency procedures one more time.

When he arrives at Mojave Air and Space Port, he passes the hangar that holds the Boom XB-1, the one-third-scale demonstrator model for the Overture, the first commercial supersonic jet since the Concorde—at least in theory. After 10 years and at least $700 million in development, endless computer modeling and thousands of hours of simulations, neither Boom nor the XB-1 have even approached the speed of sound.

Someone has to be first.

“Welcome to the life of a test pilot,” says Jim Brown, a former U.S. Air Force tester who’s now president of the National Test Pilot School in Mojave. “You can do all the simulations and predictions you want, but until you start putting speed and altitude on it, you never know how an aircraft is going to behave. But once a test pilot is done with his job, everyone else who flies that plane doesn’t have to worry. There’d be no business jet market if there were questions about safety.”

Brown would know. He was around for the early days of the F-22 and witnessed a flight meant to measure vibration in the wings that called for the plane to invert, steady, then go into a roll. The procedure started fine, but the plane rolled slower than it had in the simulator, and when it came out of the maneuver, it was pointed straight at the desert floor at supersonic speed.

The pilot wrenched the stick back and the F-22 pulled out of the dive 500 feet—or two-tenths of a second—short of impact. “Those cactuses were getting awful big, awful fast,” Brown says with a laugh, which he can, because he was the one behind the controls that day.

Most test pilots have close-call stories. Brandenburg has had “plenty of airborne emergencies.” He’s had to shut down one engine numerous times—after ingesting a bird during takeoff, because of an oil leak, because of a cabin pressure leak.

Like most test pilots, Brandenburg’s a product of the military, including the Naval Academy, Naval Flight School, aircraft carrier deployments, a stint as an “adversary” at Top Gun, and the Naval Test Pilot School. “The Navy prepares you to keep a cool head and focus on what you have to do in those situations,” he says.

For the most part, talk of those experiences only comes out “if you meet us in the bar,” Brown says, but they’re never far from mind, especially on an early morning drive through the desert.

It’s 0430 when Brandenburg parks and makes his way into the Boom offices. In the simulator room, he changes into his olive-green flight suit, complete with Boom’s arrowhead shaped patch and another showing his call name: Geppetto.

In the weeks leading up to the flight, he has made a series of cards with notes about each of the tests that he will perform. It’s August 28 and the XB-1’s second flight, but it’s Geppetto’s first behind the controls. It’s been five months since that initial foray and the company’s previous test pilot left for another gig. The plane has undergone significant changes in the interim, rendering this as close to a first flight as possible, especially since it will employ systems and maneuvers that have not yet been used.

At 0500 he reports to the command center for a briefing. The entire crew—some 50-plus people—listen as Geppetto runs through the cards, which lay out objectives, procedures, timing, fuel usage, airspace requirements, and potential emergencies, as well as how the team will respond to them.

Thousands of sensors placed throughout the XB-1 track everything from vibration and torsion to temperature and pressure. The team will monitor all of them from the control room during the flight. If something is going to fail, they’ll often know before it happens.

Test pilots exist somewhere between aviator and engineer. Geppetto loved being in the field, flying the F-18 Super Hornet, but a flight-test engineering class at Annapolis had turned him onto the idea of not just piloting a plane but figuring out how it was performing and how to make it better. That drove him to Pax River, the Navy’s test pilot school at Patuxent River, Maryland.

The year-long program maintains a rigorous daily schedule: four hours in the classroom, four hours in the cockpit and a written evaluation each day—or as the attendees say: “A half day of class, a half day of flying and a half day of writing.”

Brown’s private test-pilot school follows the same model and trains aviators from U.S. allies, such as Canada and Germany. A civilian could sign up, but the student loans would be backbreaking—the course costs about $1 million.

“Test pilots have to be skilled aviators, but they’re also curious,” Brown says. “They’re the kids who took apart the family washing machine to figure out how it worked. In movies the test pilot kicks the tires and goes, that whole romantic Chuck Yeager thing. In real life, it’s science and planning and preparation before the flight, then, after the flight, it’s bringing information back to the engineers.”

When Yeager broke the sound barrier in the Bell X-1, adds Brown, it was his 36th flight on that plane. “He didn’t just show up.”

The brief runs an hour, and at 0600 Geppetto steps out of the control room and, one last time, checks the weather. Jet engines produce more thrust at cooler temperatures and the Mojave air is smoothest early in the day, which is why the flights are scheduled for just after sun up. Any deviation from ideal conditions could bring the plan to a halt, and Flight 2 has already been scratched twice.

Everything looks good, and he heads for the tarmac. Over the years, Geppetto has compiled more than 2,500 hours of flight time in 30 different types of aircraft—everything from a Russian MiG to an HU-16 Albatross—and successfully stuck over 200 landings on boats moving across a tilting ocean, and yet the walk out to the XB-1 brings on the nerves.

He’s concerned in particular about a maneuver meant to test side slip—the plane’s reaction to an off-nose wind. Swept-wing designs like the XB-1’s typically don’t do well in those situations, and the aircraft also “has some difficult handling characteristics, particularly in roll.” It’s the reason a roll-dampening system has been added for this flight and why Geppetto prepped by flying “the F-104 with the stability augmentation system off, which is not something normally done.”  

Then there’s the landing gear. This is the first time it will be retracted—and, hopefully, extended—during flight. The crew has tested it hundreds of times on the ground, but the ground is not the same as a few thousand feet in the air at a few hundred miles per hour.

Geppetto completes his final visual inspection by flashlight and at 0615 and mounts the boarding stairs with parachute and helmet in hand. At the top, the crew chief helps him get into his gear.

Alone again, Geppetto pauses, says a short prayer and climbs into the seat.

Once he’s strapped in, Geppetto falls into the routine of preflight checks. He runs through the pre-engine-start list, and at 0624, he closes the canopy. The ground crew starts the engines externally, filling the air with an urgent whine. Across the tarmac the chase plane, a T-38, fires its engines, too.

The pre-flight safety protocols continue. “We work really hard to make it boring,” Geppetto says.

A phrase permeates the community: “Everyone has the ‘no’ vote.” If anyone on the team has any doubt about any aspect of the construction or performance, they can sound the alarm, at which point the whole team will gather to assess the issue and iterate alternatives until they reach a greater comfort level.

When Geppetto finishes his final checks, it’s nearly 0700 and the sun is rising. Both jets taxi to the end of the runway in the soft light. The crew chief runs through a final inspection. It’s go time.

The chase plane takes off, quickly banking into a long turn that will bring it around to the runway so it can fall in behind the XB-1 as it lifts off. Despite all the sensors and monitors, the chase pilot provides an invaluable set of eyes and ears.

Ten seconds out, the chase pilot issues a call for Geppetto to prepare for takeoff.

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Geppetto eases the throttles half way, revving the XB-1’s engines. “Working with the people who design and build the plane, so you know the story of how every piece was developed provides comfort,” Geppetto says. He’s completed this exact flight on the simulator “thousands of times,” but there’s a GoPro camera mounted over his shoulder and it shows him taking a deep breath as the countdown ensues.

At 0711 the chase pilot calls for a “brake release.” Geppetto lets the XB-1 loose while pushing the throttles to maximum afterburner. His smart watch shows his breathing rate increase as he hurtles down the runway.

In seconds, he’s airborne.

Geppetto reaches roughly 7,000 feet as his breathing slows and begins the testing sequence, starting with a handling assessment. Next, he retracts the landing gear and it folds into the fuselage without incident. He hits the switch to extend it again, and after “a really long 13 seconds” it locks into place. He engages the new stabilizers, alters the angle of attack, and notes the side-slip performance. By 0723, Geppetto has finished his mental notes and turned toward home.

The XB-1 has small wings, which are good for going fast but make landing difficult. They require a high-speed approach at a steep angle of attack that’s more like touching down on an aircraft carrier than a traditional steady-glide path descent. To help, two former Navy landing signal officers, trained experts who stand on the flight deck and observe jets on approach, offering pilots critical feedback—“too high” or “more power” etc.—wait on the runway.  

Geppetto has landed on carriers, but the XB-1 offers another twist. Its long nose restricts visibility. To compensate, it has two cameras that feed into two separate displays in the cockpit. It’s a tricky proposition and to prepare he has been flying the T-38s from the rear seat, which also restricts visibility.

As he approaches, the landing signal officers pipe up. As it turns out, the view on the screen in the actual XB-1 is slightly different than the simulator, causing Geppetto to come in steeper than he should. But with guidance from the crew, he sets it down gently. Time: 0726.

He taxis to the hangar and shuts down the engine. As soon as he’s out of the cockpit, he calls Stacia. As he does the team pours out of the control room for hugs and high fives.

A debrief follows. They talk about what worked, what could be better, what the data shows, and future plans. When they’re done, Geppetto spends a few hours writing up a report.

All the systems have been proven now and future flights will focus on pushing the boundaries by taking “small bites of airspeed and altitude on the way to supersonic,” Geppetto says. “This is a very deliberate process, and it may seem slow and tedious, but it’s the safest way to expand the aircraft envelope.”

At the end of the day, the team gathers at Guido’s, a restaurant and bar on the grounds. Geppetto throws down some money and everyone has a good time.

It’s still light out when Tristan Brandenburg starts his solo drive back to Rosamond. He has been listening to the audio version of Never Panic Early, the NASA veteran Gene Kranz’s book about the near disaster of Apollo 13. As the desert closes in around him, he hits play and lets the sound fill the air.

*Flight 2, covered here, took place on Aug. 26. Brandenburg completed the eighth and most recent flight of the XB-1 on Nov. 16, reaching an altitude of 25,000 feet and a speed of Mach 0.82. The test flights will continue until the XB-1 goes supersonic at Mach 1.0.