In one of his books, Austerlitz, the title character goes flying at night with pilot friend Gerald Fitzpatrick in a “Cessna.” He describes the mesmerizing sight of the familiar constellations overhead. Now, looking up at the stars from an airplane is an entrancing experience, but no one ever had it in a Cessna.

The corresponding photograph, though somewhat distant and blurred, is clearly not of a Cessna but of a small twin-engine, twin-finned airplane that does, however, have a transparent canopy. I got the explanation for this apparent authorial fumble from a Swiss friend: Among nonpilots in Germany, “Cessna” would simply mean a private airplane, no particular brand.

The twin was actually a Miles Gemini, an airplane brought into being, like the original Beech Bonanza, by the anticipated postwar explosion in demand for personal air travel. It had four seats and was equipped with two 100 hp engines of the inverted in-line variety, housed in those nice narrow cowlings that many British and French aircraft of the 1930s and ’40s had. One of its unusual features was a big external airfoil flap.

Despite the flap, however, the published stalling speed of 35 knots cannot have been a calibrated airspeed—45 is more plausible.

Whatever its real landing speed, the fictional Gerald Fitzpatrick crashed fatally in his Gemini. His friend Austerlitz gloomily comments that this was bound to happen, since he was so fond of making sightseeing flights in the south of France.

• READ MORE: Looking at the Physics of STOL Drag

Novelists just won’t give private planes a break.

I wondered how the 3,000-pound Gemini would do on one engine. Late designer John Thorp, contemplating a trip to Europe with his wife, Kay, once propped up a couple of small Lycomings in front of his two-seat Sky Skooter. His friend George Wing, creator of the ubiquitous Hi-Shear rivet, happened to walk in, and thus was conceived the Wing Derringer.

Wing was not taking any chances on O-235s, however. The two-seat Derringer, with 160 hp O-320s, could definitely climb on one engine. The question of how a twin with 100 hp engines climbs on only one was answered, however, by the Champion Lancer, whose woeful single-engine performance was, like Sir John Falstaff, a cause of wit in many men.

Like many other early aviation enthusiasts, Frederick George Miles began in the 1920s as an amateur builder. Miles then started manufacturing small airplanes and eventually turned out a series of products that recalls, in its variety and inventiveness, the career of another homebuilder-turned-professional, Burt Rutan. Like Rutan, who started the Rutan Aircraft Factory with his then-wife Carolyn, Miles found a business partner in his remarkable wife Maxine, nicknamed Blossom, who, in addition to being his beloved, was a pilot, aeronautical engineer, stress analyst, and businesswoman.

In some respects, the paths of Miles and Rutan were different. Miles made airplanes for military and commercial use. Rutan, after leaving the homebuilt plans business that had launched his career, mainly produced one-off prototypes and never certificated any of his designs. (Beech ruined the Starship, he complained, in the process of certificating it. Beech engineers naturally took a different view of the matter.) But the two shared a wide-ranging versatility. Some designers, like Thorp and Dick VanGrunsven, turn out incremental variations and improvements on a basic theme.

With Miles and Rutan, you never knew what might come next. In Miles’ case the variety may have been due in part to his employing other designers, whereas Rutan designed all of his airplanes himself. Both men mastered the art of fast prototyping: Scaled Composites, the company Rutan founded, exploited foam-cored composites for that purpose; Miles’ medium was resin-bonded wood.

Miles’ greatest commercial success came during the pre-World War II years. He developed a number of training and transport airplanes and manufactured them in large numbers for the Royal Air Force. His efforts to produce a fighter were less successful. A 1940 prototype of a small wooden “emergency” fighter, proposed to stop the gap in the event that Hurricane and Spitfire production were hampered by German bombing, had a bubble canopy and a stock Merlin “power egg,” and looked just like a miniature Hawker Typhoon. Despite fixed landing gear, it rivaled the Hurricane in armament and performance, but it was never produced, mainly because the anticipated emergency did not materialize.

During the war, Miles produced a design remarkably similar in conception to Rutan’s first homebuilt. Like the VariViggen, Miles’ original Libellula—Latin for dragonfly—had a single pusher propeller, low wing, and high canard. The configuration was supposed to solve several problems associated with shipboard fighters, but the British Admiralty didn’t bite. A second version, this one with a high wing and low canard, was conceived as a bomber, with the idea that the tandem wing arrangement would provide an unusually large CG range. That airplane also ended up on the scrap heap.

The little Gemini twin, the one illustrated in Austerlitz, was a commercial success, as was a side venture the resourceful Miles got into: ballpoint pens. But the most striking Miles design from the wartime period was something completely different.

• READ MORE: Recalling a Good Pilot Friend and One Curious Character

The M.52, born in 1943, is said to have been the offspring of a ridiculous error. An intercepted German communication referred to the 1,000 kph speed of one of the jets then being developed. Someone failed to perform the conversion, and the belief took root that the Germans were perfecting a 1,000 mph airplane. Inevitably, the British felt they needed to follow suit, and Miles Aircraft earned the contract. (If it isn’t true, at least it’s a good story.)

The result was a 5-foot-diameter cylinder with thin, straight wings and a then-unprecedented, and prescient, powered all-flying stabilizer. Air for its centrifugal-compressor jet engine came in through an annular intake surrounding a shock cone, à la the MiG-17 or SR-71. The pilot sat inside the shock cone. In retrospect, the design looks sound except for its lack of area ruling, and it could probably have gone supersonic, given sufficient thrust. But in 1946, with the first prototype nearly complete, the U.K.’s Air Ministry suddenly canceled the project.

The abrupt cancellation, which was never persuasively explained, fueled a persistent notion among British airplane buffs that their government had abjectly bowed to U.S. insistence on being the first to “break the sound barrier.” Indeed, the Bell X-1 rocket aircraft, which did so in 1947, was being developed at the same time as the M.52.

However, the M.52 may have been shelved simply because of the distinct possibility that its still-unproven afterburning turbojet might not be powerful enough to propel it past Mach 1 in level flight—let alone to 1,000 mph.

This column first appeared in the May 2024/Issue 948 of FLYING’s print edition.

The post The Craft of Providing Variety in Airplanes appeared first on FLYING Magazine.

During a mission that Stratolaunch expected would last 3.5 hours, the flight crew chose to land the aircraft safely after an hour and 26 minutes.

“We opted to just land, fix the sensor, and we’ll try and get airborne again very soon,” chief technology officer Daniel Millman told FLYING. “It was not a big deal at all. We were all disappointed, but without instrumentation, it’s not really a test flight.” Millman said they were able to achieve a limited amount of testing before the flight was shortened. Roc flew to a maximum altitude of 15,000 feet during the mission, Stratolaunch told FLYING.

The next test flight is expected “fairly quickly,” he said, and could be a longer duration to make up for this shortened mission. “We’ll figure out what test cards we can remove from the deck and what other cards we could add. That will be up to flight ops to see what they can do to keep us moving forward. Obviously, we’ve got a schedule we’re trying to stick to.”

Immediately after Roc landed, Stratolaunch announced it had “encountered a test result that made it clear we would not achieve all objectives for this flight. We made the decision to land, review the data, and prepare for our next flight.”

While completing Roc testing operations, we encountered a test result that made it clear we would not achieve all objectives for this flight. We made the decision to land, review the data, and prepare for our next flight. pic.twitter.com/48d61vlxLn

— Stratolaunch (@Stratolaunch) June 9, 2022

The world’s largest airplane by wingspan went wheels up from Runway 30 around 8:15 a.m. PT, on an intended mission to expand Roc’s flight test envelope.

Roc is airborne over the Mojave desert for an approximate 3.5 hour flight #LetsRoc pic.twitter.com/hL1uKT6F6U

— Stratolaunch (@Stratolaunch) June 9, 2022

Albeit shorter than originally expected, this flight took place during a critical time in Roc’s development, as pilots, engineers, and technicians work to complete a complex flight test campaign aimed at making the airplane fully operational by next year. 

The aircrew is boarding Roc and preparing for takeoff at approximately 7:30 a.m. PT #LetsRoc pic.twitter.com/KdgFilctcp

— Stratolaunch (@Stratolaunch) June 9, 2022

Remember, this is an airplane with a very particular set of attributes, including:

• a 384-foot wingspan, longer than an NFL football field
• six Pratt & Whitney model PW4056 engines, acquired from Boeing 747-400s
• a 50-foot height, from the deck to its vertical stabilizers
• eight landing gear, acquired from Boeing 747-400s
• a 1.3-million-pound maximum takeoff weight (MTOW)

• READ MORE: Stratolaunch by the Numbers

New Data Test Boom

Roc was flying with a data boom attached to its 15-foot-by-15-foot, 8,000 pound pylon hanging from the jet’s center wing, where a Talon-A hypersonic testbed vehicle will eventually be mounted. 

“The pylon air data boom will measure the aero environment near Talon-A to ensure we meet our release criteria for future Talon-A launches,” Brandon Wood, senior director of programs at Stratolaunch told FLYING Wednesday. “While Roc also has air data instrumentation on the right cabin, the size of the aircraft warrants a dedicated boom close to Talon-A.”

The mission took place just five weeks after Roc’s previous flight, demonstrating a quickening flight operations tempo toward achieving operational status next year. The previous gap between flights was twice as long. The flight was intended to help engineers perfect the pylon for eventual use as a flying launching pad for hypersonic test vehicles. 

The pylon is the linchpin of Stratolaunch’s business model. The company has already lined up military and commercial contracts to launch small, autonomous, rocket-powered, hypersonic testbeds from altitudes around 35,000 feet. Without a pylon—the critical point where a testbed attaches to the airplane—Roc’s business model falls apart.

• READ MORE: Comparing the World’s Largest Airplanes

Although the airplane was created to serve as a universal air-launch carrier for multiple payloads up to 550,000 pounds, the current pylon is not designed to lift that much weight. But future iterations could be. 

• READ MORE: Google Co-Founder Plans Longest U.S. Airship Since 1930s

Before flight, the hypersonic test vehicle mates with Roc via a winch that’s built into the pylon. Stratolaunch demonstrated that process in a video shared on Twitter.

Welcome to a new chapter in hypersonic flight test. We recently mated TA-0 to Roc for the first time. The team will conduct functional and integration testing in the coming months, culminating in a captive carry and safe separation testing later this year. #LetsRoc pic.twitter.com/1VPAFoJahG

— Stratolaunch (@Stratolaunch) May 27, 2022

Aside from gathering inflight data on the pylon, the test flight team for the sixth mission expected to continue expanding Roc’s flight test envelope, exploring higher altitude levels and increased air speeds. 

• READ MORE: Catch Up on FLYING’s Continuing Roc Coverage

In the coming months, crews will conduct functional and integration testing on the testbed vehicles to ensure the jet successfully completes its first captive carry flight and a safe separation test. Roc isn’t expected to be fully tested and operational until mid to late 2023. 

Why It Matters

As the federal budget reflects intensifying efforts to develop hypersonic weapons, Stratolaunch has already committed Roc to air-launch vehicles for “threat replication” in hypersonic research by the Missile Defense Agency.

Developing hypersonic weapons systems is a “national security imperative,” Stratolaunch CEO Zachary Krevor said last month during a news conference in Washington, D.C. 

The U.S. has been actively pursuing the development of hypersonic arms—weapons that can fly at speeds greater than Mach 5—since the early 2000s. Interest by the Pentagon has increased in response to advances by Russia and China. 

Defending against hypersonic weapons presents a more difficult set of challenges than traditional intercontinental ballistic missiles (ICBM). This is because ICBMs are launched into a highly predictable and more easily trackable parabolic trajectory, while hypersonic missiles can fly thousands of miles at much lower altitudes, performing extensive maneuvers to evade ground-based radar systems. 

For this reason, officials have said tracking hypersonic weapons has become a key part of U.S. defense strategy. Developing these kinds of tracking systems will require “threat hypersonic missile surrogates” that can help scientists evaluate their effectiveness, according to a Department of Defense report. Theoretically, testbed vehicles launched from Roc could serve in these kinds of surrogate roles.  

The post Sensor Malfunction Shortens Stratolaunch’s Sixth Mission appeared first on FLYING Magazine.

This first Talon-A vehicle—dubbed TA-0— is critical to the mission of the airplane known as Roc. TA-0 will be used to test and validate Roc’s sophisticated payload release system. The airplane—the world’s largest by wingspan—completed its fifth test flight earlier this month. 

• READ MORE: World’s Largest Airplane Flies a Fifth Time

“We’re proud to reveal our first test vehicle to the public and our key stakeholders. TA-0 represents the immense progress our company has made toward hypersonic flight in a short period of time,” said Dr. Zachary Krevor, president and CEO at Stratolaunch.

“Our pace of development parallels the nation’s critical need for hypersonic test capabilities, and we are putting forth every effort toward becoming a national test asset for our government and commercial customers in 2023,” Krevor said.

• READ MORE: FLYING’s Continuing Stratolaunch Coverage

The Talon-A testbeds are designed to attach to Roc’s 8,000 pound pylon, which hangs from the airplane’s 95-foot center wing, between its enormous twin fuselages.

Stratolaunch’s business model calls for it to launch small, autonomous, rocket-powered, hypersonic testbeds from altitudes around 35,000 feet. 

This initial Talon-A iteration will not be powered during flight, but upcoming versions will be rocket-powered, autonomous, and reusable—designed to reach hypersonic speeds above Mach 5. First flight tests of the first Talon-A are expected to be conducted later this year.

Eventually, once Roc is fully operational sometime next year, Stratolaunch is expected to provide “threat replication” for the Pentagon’s Missile Defense Agency to help scientists understand how to engage and intercept hypersonic weapons.

The post First Talon-A Test Vehicle Unveiled for World’s Largest Airplane appeared first on FLYING Magazine.

Pilots Evan Thomas, Steve Rainey, and flight engineer Jake Riley put Roc through its paces during a nearly five-hour flight that included tests of the airplane’s eight landing gear assemblies, as well as its autopilot and yaw augmentation systems.

Aboard the chase airplane, pilots Ana Benet, Scott Schultz and flight engineer Vanessa Gonsenheim carefully shadowed Roc as cinematographer Domenic Moen shot the aircraft. Moen used a Sony A9 and a Canon R6 to capture video from inside the Citation’s cabin using a very small shoulder rig. “No need for a gimbal on such calm days with great pilots,” Moen told FLYING.

• READ MORE: FLYING’S Ongoing Coverage of Stratolaunch

It also was Roc’s first test flight with a 15-foot-by-15-foot, 8,000-pound center-wing pylon, under development to eventually carry and launch hypersonic vehicle testbeds. 

Roc’s wing measures 385 feet. That’s longer than an NFL football field as well as the orbiting International Space Station. 

• READ MORE: Longest Test Flight Yet for the World’s Largest Airplane

In the coming weeks and months, Roc’s flight campaign is expected to intensify, as pilots, engineers, and technicians work toward the first release test of Stratolaunch’s Talon-A vehicle demonstrator. Roc isn’t expected to be operational until mid- to late 2023.

The post Stratolaunch Drops Stunning Air-to-Air Video of World’s Largest Airplane appeared first on FLYING Magazine.

Under clear skies and calm winds, Roc’s six Pratt & Whitney PW4056 turbofans and 385-foot wings lifted the 500,000-pound, twin-fuselage jet above Runway 30 at about 7:40 a.m. PT. In its longest test flight so far–nearly five hours–the airplane touched down back at KMHV, at 12:37 p.m. PT.

Pilots Evan Thomas, Steve Rainey, and flight engineer Jake Riley flew Roc with a 15-foot-by-15-foot pylon hanging from the jet’s 95-foot center wing, testing the device for the first time, as well as several other onboard systems. Testing took place at multiple altitudes, including FL150 and FL225, while achieving speeds around 180 kias.

The force is strong in this plane. Roc has successfully landed back at Mojave Air and Space Port and our team is already busy analyzing the data gathered today. #Maythe4thBeWithYou #LetsRoc pic.twitter.com/XK7jz6SEET

— Stratolaunch (@Stratolaunch) May 4, 2022

With a Cessna 550 Citation Bravo chase airplane flying nearby, the crew retracted and extended Roc’s eight landing gear as they did during its previous mission in February. But it was the 8,000-pound pylon that was getting much of the attention.

“It’s exciting to have the pylon on now,” Stratolaunch chief engineer Scott Schultz told FLYING. It represents Roc’s transformation from an airplane to a mission systems airplane. “I’m excited, not only about the pylon, but the fact that we’re turning it into a flying launch pad.”

The pylon’s importance is difficult to overstate. It’s the linchpin of Stratolaunch’s eventual business model to launch small, autonomous, rocket-powered, hypersonic testbeds from altitudes around 35,000 feet. Without a pylon—the critical point where a testbed attaches to the airplane—Roc’s business model falls apart.

Talon-A is a reusable Mach 6 testbed. Plans call for a Talon-A separation test article—measuring about 28 feet long—to be mounted on Roc’s pylon for a separation test later this year. The pylon also includes new data acquisition systems for Talon-A, as well as sensors.

Test Flight Five

Engineers will use data from Wednesday’s flight to look holistically at how Roc performed with the pylon, including any adverse flying qualities.

Our team recently installed a pylon on the center wing of Roc that is used to carry and launch the Talon-A test vehicle. Meet our engineers involved with the hardware integration and learn more about how we are preparing for separation testing and hypersonic flight test. #LetsRoc pic.twitter.com/uxZYskQ7MZ

— Stratolaunch (@Stratolaunch) April 15, 2022

“So one of the things we’re looking at is how this pylon affects the airplane as a whole,” Schultz explained. “How much rudder per beta? How much elevator per alpha? Are we on predictions from an alpha versus CL [lift coefficient] curve, which is how much lift the airplane makes with the angle of attack.”

Engineers documented the visual flow field surrounding the aircraft, using tufts to measure aerodynamics on the pylon surfaces. 

Practice makes perfect! Building on the landing gear testing that occurred during the fourth flight test, the team is continuing tests gear operations through mid-air cycling of the system. pic.twitter.com/Kb5jZigx8w

— Stratolaunch (@Stratolaunch) May 4, 2022

“We’ve also got a significant amount of accelerometers on this pylon and throughout the airplane to measure buffeting coming off of the pylon that would shake the rest of the airplane,” Schultz said.

• READ MORE: FLYING’s Ongoing Stratolaunch Coverage

In addition to cycling landing gear and monitoring the pylon, the crew also tested the airplane’s autopilot and yaw augmentation system. 

Essentially, the yaw augmentation system is similar to what many GA or bizjets have. It’s basically an aileron-rudder interconnect and a yaw damper combination.

Pilot Evan Thomas told FLYING last December that Roc’s yawing characteristics are 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.”

• READ MORE: What It’s Like to Fly the World’s Largest Airplane

When Scaled Composites designed Roc—or Model 351 as it was officially designated—the airplane was intended as a universal air-launch carrier for multiple payloads up to 550,000 pounds. “It’s a really universal system that’s hooked up on four major points on the airplane,” Schultz said. The points are really close to spars, but they’re not right on a spar. … With the spar shape and construction size, sometimes that’s impractical.” Instead, the points join with ribs that are adjacent to spars, but as close to spars as possible.

About the Pylon

The pylon is made of metal and some carbon skin, Schultz said, and will not be the final iteration. “It’s designed for a fairly light launch vehicle like Talon, however, we’ve baked in significantly more weight capability and margin than Talon—but yet still it’s not a half-million pound rocket structure quite yet.”

Central to its design is a canoe-shaped element called an adaptor—the mechanism that connects Talon-A testbeds to Roc’s massive wing. On the ground, when crews mate Talon-A with the pylon, the adaptor detaches from the pylon’s “wing” and is lowered down with winches. The Talon-A is then attached to the adaptor and then winches back up to join with the pylon. 

“We’ll likely end up using a different pylon for most of our big launch vehicle campaigns, which goes back to the airplane’s universal design to basically take whatever pylon you want to put on it. You swap pylons much like an adaptor for an F-15. On this, you’d end up swapping pylons for the different missions.”

• READ MORE: Comparing the World’s Largest Airplanes

Increased Operations Tempo

Stratolaunch is expected to increase its operations tempo for Roc test flights. Beginning this year, Roc has flown in January, February, and now in May. Expect this pattern to increase further moving forward.  

• READ MORE: Roc By the Numbers

As the Pentagon seeks to develop hypersonic weapons, Stratolaunch CTO Daniel Millman is calling on the U.S. military to consider flight testing technologies on low-cost testbeds that are “regular, routine and reusable.” 

Although Roc isn’t expected to be operational until mid- to late 2023, Stratolaunch already has a hypersonic research contract with the U.S. Air Force Research Laboratory. 

• GALLERY: Stunning Images of the World’s Largest Airplane

The company also has agreed to provide “threat replication” for the Pentagon’s Missile Defense Agency to help scientists understand how to engage and intercept hypersonic threats. Last month, Stratolaunch opened a permanent Washington, D.C.-area office to support the acquisition of future contracts. 

The post World’s Largest Airplane Flies a Fifth Time, Moving Closer to Hypersonic Tests appeared first on FLYING Magazine.

Roc, the twin-fuselage behemoth with a wingspan longer than an NFL football field, will have a new piece of equipment on board: a custom pylon attached to the airplane’s center wing. 

• READ MORE: Catch Up on FLYING’s Ongoing Coverage of Stratolaunch

Don’t be fooled by the pylon’s small profile. It’s key to the success of Roc’s business model—to securely carry and release small, rocket-powered, hypersonic testbeds. 

During the upcoming flight, as Roc’s flight engineer and two pilots put the airplane through its paces, experts will be paying close attention to the aerodynamic flow around the pylon and other metrics. 

• READ MORE: Comparing the World’s Largest Airplanes

Let’s run down a few numbers that help tell Roc’s story and why it stands alone as a unique wonder of modern science and technology.

1

Roc has one center-wing pylon measuring 15 feet by 15 feet. Eventually, Roc’s pylon will carry and release an uncrewed, automated, Talon-A hypersonic, rocket-powered testbed vehicle at about FL350 (35,000 feet). 

Our team recently installed a pylon on the center wing of Roc that is used to carry and launch the Talon-A test vehicle. Meet our engineers involved with the hardware integration and learn more about how we are preparing for separation testing and hypersonic flight test. #LetsRoc pic.twitter.com/uxZYskQ7MZ

— Stratolaunch (@Stratolaunch) April 15, 2022

2

Roc has two virtually identical fuselages made mostly of carbon composite and separated by a 95-foot center wing.

3

The airplane’s flight crew is made up of three people: two pilots and a flight engineer.

6

Roc’s six powerplants are Pratt & Whitney model PW4056 turbofan engines. They were acquired from retired Boeing 747-400 passenger jetliners. Other parts of Roc that were sourced from retired 747-400s include:

• engine throttles
• windows
• flight deck console
• overhead panel
• controls for generators
• rudder pedals
• yokes

8

The world’s largest airplane needs a total of eight landing gear for takeoff and landing. Two sets of nose gear—one for each nose of Roc’s twin fuselages—and six sets of body gear—three per fuselage—to support the center of the gigantic aircraft. Like Roc’s engines, these landing gear were acquired from retired Boeing 747-400 airliners.

24

With 24 carbon brakes, Roc has “quite a bit of stopping power,” Stratolaunch lead systems engineer Stuart Yun told FLYING. “Each one is capable of absorbing an incredible amount of energy.” When a pilot hits the brake pedals, it activates a cable system connected to a brake metering valve, which supplies a specific amount of hydraulic pressure to the brake stack. Pilots can modulate how much clamping force is applied to each side of the aircraft.

28

The airplane’s 28 wheels help evenly distribute Roc’s titanic load.

50

The Stratolaunch Roc stands 50 feet high.

238

The aircraft measures 238 feet in length. That’s actually short compared to other large airplanes, including the 747-8 and the Lockheed C-5 Galaxy.

351

The airplane was initially named by the company that made it, Scaled Composites, the iconic aviation design and development company founded by aerospace legend Burt Rutan. It was simply called Model 351.

385

This is the number that sets this airplane apart from any other. Those 385 feet—from wingtip to wingtip—are what makes Roc the largest airplane in the world by wingspan. Its wings are wider than Boeing’s 747-8 or Howard Hughes’s mid-century H-4 Hercules—better known as the Spruce Goose. Roc’s wingspan was more than 90 feet wider than the iconic Antonov An-225 Mriya, which was destroyed during Russia’s invasion of Ukraine last February.

500,000

Roc weighs half a million pounds empty. That converts to 250 U.S. tons. Around 15,000 pounds more than the empty weight of a Boeing 747-8.

1.3 Million

It’s rated for a maximum takeoff weight (MTOW) of 1.3 million pounds—very close to the MTOW of the destroyed Antonov An-225 Mriya.

The post The World’s Largest Airplane: By the Numbers appeared first on FLYING Magazine.

Taking off at about 12:23 p.m PT from its base at California’s Mojave Air and Space Port (KMHV), Roc reached a maximum altitude of 15,000 feet and spent an hour and 43 minutes in the air, lifted by its gargantuan 385-foot wings. 

Time to stretch those legs! We just successfully retracted and extended our full landing gear for the first time. #LetsRoc pic.twitter.com/UUVhC1xmy0

— Stratolaunch (@Stratolaunch) February 24, 2022

With a Cessna 550 Citation Bravo chase plane flying nearby, it wasn’t long before the six-engined, twin-fuselage Roc successfully retracted all eight gear, showing a much sleeker profile against a clear blue sky. A few minutes later, the gear reappeared, fully extended. 

Demonstrating successful retraction and extension of all landing gear was mission critical for Roc and the most important part of this fourth flight test. Verifying full gear operations is a requirement before Roc can move forward in its flight test campaign and eventually serve as a carrier platform to launch hypersonic testbed vehicles. 

“Today’s successful flight demonstrates and validates improvements to the carrier aircraft’s systems and overall flight performance,” said a statement by Dr. Zachary Krevor, Stratolaunch president and COO. “The full landing gear retraction and extension brings the carrier aircraft closer to operational status, a milestone that is necessary to ready the aircraft for Talon-A separation and hypersonic flight test later this year.”

The Gear

Quickly, let’s break down the landing gear:

• 6 main gear, each with four-wheel bogies
• 2 nose gear, each with two-wheel bogies 
• Total gear: 8
• Total wheels: 28
• Total number of brakes: 24
• Total number of moving panels that comprise the landing gear door system: 34
• Roc’s gear and various other components were acquired from existing Boeing 747-400 airliners.

Roc also includes original systems and components as well as components from Cessna, Gulfstream, and other OEMs.

Demonstrating that Roc can retract and extend each of its six main gear and two nose gear in the air, per design standards, required precise coordination and communication between flight crew and Roc’s control room on the ground. Verifying full gear operations was required before Roc could move forward in its flight test campaign and eventually air-launch hypersonic testbed vehicles. 

The Control Room

In the control room during the flight was Stratolaunch lead systems engineer Stuart Yun, who told FLYING earlier this week that, perhaps surprisingly, the Boeing gear hasn’t been modified to accommodate stresses and pressures created by Roc’s unique twin fuselage. 

“We haven’t modified the gear in any way, but we have modified the systems and how they interact with our airframe,” Yun said. “The original design is incredibly robust.”

During Roc’s flight last month, in what you might call a test before the test, the aircraft successfully retracted and extended the left fuselage’s middle main gear alone. This was a precautionary measure to ensure the airplane would be able to land if something had gone awry. Aside from a bit of minor vibration on the gear doors, all went as planned.

We’re preparing for our next Roc test flight. Test 4 focuses on extending and retracting all the landing gear and doors. Today the team conducted tests to find any problems the systems might have while the aircraft is safely on the ground. #LetsRoc pic.twitter.com/bApQq4O8mf

— Stratolaunch (@Stratolaunch) February 13, 2022

“30 Seconds of Fear”

Inside the control room, Yun and his fellow team members were tasked with monitoring the gear during all phases of the flight, using screens placed across multiple workstations. Each team member indicates the time is right and verifies all systems are working properly. Then the flight test conductor—or TC—relays that information, and if necessary, any abnormalities that may be occurring, to the flight crew aboard Roc.

Then, the flight crew goes ahead and puts Roc’s gear handle in the up position. 

It is at this point, Yun jokes, when “there’s about 30 seconds of fear.” Everyone in the control room has their eyes on their screens, Yun says, checking the sequencing and indicators to confirm the gear were retracted and extended successfully.

To verify the gear has retracted properly, the team uses an array of sensors, including on-board cameras, extra hydraulic pressure transducers, and extra limit switches. 

With all gear retracted, engineers were able to gather real-world data about Roc’s performance and flight handling characteristics. These numbers will help the aircraft’s developers form more accurate expectations for operational missions. Those missions, which are expected to begin next year, will launch hypersonic testbed vehicles for U.S. government and commercial research.

Finding Workarounds

Integrating the Boeing landing gear with Roc hasn’t exactly been easy. Some of the most challenging parts of the job have involved using systems within the gear that weren’t necessarily designed to operate the way Roc’s engineers wanted. However, during the build, engineers had the benefit of accessing the Boeing fleet database that was used to maintain the 747-400 gear. This opened the door to repair type manuals, often referred to as a CMM (component maintenance manuals). Engineers were able to refer to these manuals for details such as how to rebuild an actuator or how to rig nose gear. 

Some situations required finding workarounds.

In fact, some of the systems on the gear had to be reverse engineered to fully learn how they functioned before the gear could be integrated into the airplane.

For example, to model landing gear loads, engineers had to take apart a Boeing gear to determine all the internal dimensions and flow characteristics of the hydraulic dampers. They also performed significant testing on components to determine how they work. 

These Are the Brakes

With the landing gear, of course comes Roc’s braking system—also designed and built by Boeing and originally intended to stop a 747-400, which has an empty weight of about 403,000 pounds. 

“We have 24 carbon brakes, so we have quite a bit of stopping power,” Yun said. “Each one is capable of absorbing an incredible amount of energy. These brakes can be tricky to work with at times but they provide the performance we need for an aircraft this size.”

Braking starts when the feet of the pilot in control hit the brake pedals, activating a cable system connected to a brake metering valve, which supplies a specific amount of hydraulic pressure to the brake stack. That way the pilots have the ability to modulate how much clamping force is applied to each side of the aircraft.

What kind of force? Enough to bring Roc—with an empty weight of half a million pounds—to a complete stop. 

• LANDING PAGE: Catch Up On Our Stratolaunch Coverage

Surprising Flight Characteristics

As you might expect, flying Roc is challenging. In fact, pilots have told FLYING that the aircraft has demonstrated a few surprising flight characteristics during its previous test missions. In addition, piloting Roc while sitting in the right fuselage makes lining up for final approach a little tricky. You’re not looking straight down the runway’s center line, which makes the maneuver a bit like landing an airplane mounted on a gigantic pair of in-line skates.

• READ MORE: What It’s Like to Fly the World’s Largest Airplane

Extra Wide Load

Roc is the world’s largest airplane by wingspan, measuring longer than any airplane in aviation history, including the Airbus A380, Boeing’s 777-9, Howard Hughes’ H-4 Hercules (The Spruce Goose), and Antonov’s An-225 Mriya.

In fact, Yun said the maximum gross weight of the Antonov An-225 is very close to Roc’s designed maximum gross weight of 1.3 million pounds. “Just to put that in perspective, we designed this thing from the get-go to handle 1.3 million pounds,” Yun said. “Hopefully, we’ll get there someday.”

• READ MORE: Comparing the World’s Largest Airplanes

Last month’s mission was the most productive so far for the one-of-a-kind jet. During the four-hour and 23-minute flight, Roc successfully expanded its test envelope by:

• reaching a maximum altitude of 23,500 feet
• achieving a top speed of 180 kias 
• successfully retracting and extending the left middle main landing gear
• flying two low-approach maneuvers over the runway before landing

• READ MORE: Roc Completes First Test Flight in Eight Months

In addition to its third flight last January, Roc’s previous test flights took place in April 2021 and April 2019. 

• GALLERY: Images from Roc’s Third Test Flight

What’s Next for Roc

Now that Roc has completed its fourth flight, engineers plan to install a pylon under its center wing, which will enable it to carry smaller aircraft and other heavy payloads. The center wing measures 95 feet between fuselages and is designed to support up to 500,000 pounds. Gathering data on how the pylon affects Roc’s flight dynamics will be part of the airplane’s fifth test flight.

Roc was first conceived as an inflight launch platform for low-orbiting satellites. Eventually, its main mission shifted toward air launching hypersonic testbed vehicles. For that reason, Stratolaunch is developing Talon—a series of uncrewed, autonomous, rocket-powered aircraft designed to fly at Mach 5 or faster. 

The Pentagon’s Missile Defense Agency has contracted with Stratolaunch to provide “threat replication” data to help scientists understand how to engage and intercept hypersonic threats. If Talon development and Roc’s test flights remain on track, the company expects to conduct Talon’s first hypersonic test flight by the end of this year. 

• READ MORE: Stratolaunch Plans Hypersonic Tests

A little background info for those who haven’t been following Roc: Created in 2011, Stratolaunch was the brainchild of the late Microsoft (NASDAQ:MSFT) co-founder Paul Allen. Roc—also known as Model 351 Stratolaunch—was built by Scaled Composites, the iconic company founded by legendary aerospace engineer Burt Rutan. In the wake of Allen’s tragic death in 2018, Stratolaunch’s parent company, Vulcan, sold it to the U.S. private equity firm Cerberus Capital Management.

The post World’s Largest Airplane Flies a Fourth Time for Mission-Critical Test appeared first on FLYING Magazine.

Giddings, along with co-pilot Evan Thomas and flight engineer Jake Riley, successfully completed Sunday’s third test flight of the world’s largest airplane—nicknamed Roc—which is scheduled to begin air-launching hypersonic test vehicles later this year. 

The massive airplane took off from Runway 30 at Mojave Air & Space Port (KMHV) a little before 9 a.m. Visibility was clear, the air was smooth, winds calm. 

“It was a great day to fly,” Thomas says. “The cloud deck was down to 7,000 feet, and we just decided to hope for the best and it kind of opened up and allowed us to fly.”

This was Giddings’ first time in Roc’s left seat. Eight months earlier, during test flight two, Giddings sat in the right seat, running the throttles and watching Thomas handle the landing. This time, it was Giddings’ turn to wrangle the beast. 

The nearly four-and-a-half-hour mission turned out to be the program’s most productive so far, expanding the proven flight test envelope to an altitude of 23,500 feet and a maximum speed of 180 kias. The crew successfully moved Roc’s landing gear doors and retracted and re-extended one of its landing gear, proving for the first time that the system would operate during flight. 

• READ MORE about Sunday’s test flight

So, as a veteran U.S. Air Force test pilot, how did landing an airplane with a 385-foot wingspan rank against landing other notable jets in his career? 

“For me, this was up there with landing the U2,” Giddings told FLYING in an exclusive interview shortly after the flight. “It was definitely exciting.”

To ensure the safest landing possible, the flight crew flew two low approaches over the runway. During the second pass, as Stratolaunch chief technical officer Daniel Millman describes it: Giddings “carefully controlled the airplane about 100 feet off the ground, flying along the black line, to ensure he had the controllability he was looking for— what we used to call in the B-52—a landing attitude demo.”

The team is rounding out a successful Roc carrier aircraft test flight with two low approach maneuvers before landing. We’re excited to get the aircraft on the ground and start analyzing all of the great data we collected today! #LetsRoc pic.twitter.com/FcwHbv8qmo

— Stratolaunch (@Stratolaunch) January 16, 2022

Giddings says it was interesting “because the first approach wasn’t as stable as I wanted it to be. But that was my first time in the pattern. So for the second pass, he worked on increasing Roc’s stability “and all of the training that we did came into play with that.”

His training has taught him that “a nice landing doesn’t come from the end game. It comes from being stable from 10 miles out.” In fact, Giddings had come into the sim facility the day before the flight to practice the entire profile with the parachute and the helmet on. 

“After practicing all those approaches, I had so many cues starting from 10 miles to get the airplane stable.” 

And specifically with Roc, that’s no simple task.

“The plane has definite lateral characteristics and oscillations and they’re pronounced in the landing phase,” Giddings says. “It’s definitely a very high-gain maneuver and you’ve got to make sure the airplane’s track is straight. It’s not very forgiving for any crabbing that you have with the fuselage.” 

• PHOTO GALLERY: Images from Sunday’s test flight

While Giddings flew the low approach, he was simultaneously planning how he was going to handle a lateral deviation or a wind gust during the actual landing. “I had in my mind: ‘If I see this, I’m going to do this. If I see this, I’m going to do that.’ I had practiced that—just focusing on keeping the wings level and the fuselages driving straight down the runway.”

And—even with all of that—the flight crew had to deal with Roc’s quirky yaw characteristics. 

To offset the airplane’s yaw, engineers are testing a yaw augmentation system. The low approaches were also intended to evaluate it. During part of the first approach, the yaw augmentation system would have to be activated. During the second approach it would have to be turned off. 

Essentially, says Thomas, the yaw augmentation system is similar to what many GA or bizjets have. It’s basically an aileron-rudder interconnect and a yaw damper combination.

• READ MORE: What’s it like to fly the world’s largest airplane?

“When you’re flying a one-of-a-kind airplane that has very unique handling and flying qualities and you’re presented with the challenge of landing, that’s kind of why you’re a test pilot,” Giddings says. “You look forward to those kinds of challenges.” 

• MORE ON STRATOLAUNCH: FLYING’s complete coverage

Chase Plane Support

Another key mission goal on Sunday: retract and extend the mid-main gear on the left fuselage in flight for the first time. 

For this, the pilots would need assistance from Stratolaunch’s Cessna Citation chase airplane. Roc pilots have always coordinated with a chase airplane during flight. Chase airplanes are part of the standard formation. Crew aboard the chase airplane become an extra set of eyes for what’s happening with the rest of the airplane. 

And on an airplane the size of Roc, the more eyes the better. 

During the gear test, the crew monitored gear indicators and instruments as well as a slew of cameras to make sure the gear retracted and extended in flight as expected. 

But for the angle they needed to see the mid-main left gear, none of the cameras provided that ideal view. 

Two Stratolaunch design engineers who helped build the gear retraction system and the gear doors boarded the chase airplane, armed with binoculars to view and report to Roc’s pilots how the gear was performing in flight. 

The chase airplane crew was able to position the aircraft in the perfect spot. “It enabled us to make the right call,” Thomas says. 

What’s Ahead

In the coming months, we can expect to see Roc flying more often, Millman says. Plans are already underway for a fourth test flight. Following that, a pylon will be installed on the airplane’s wing on Roc’s fifth flight to allow it to carry and launch its hypersonic test vehicles. 

Later this year, Roc is expected to drop a separation test vehicle over the Pacific to verify the airplane’s ability to launch in flight.

“Before the end of the year, we plan and hope to launch our first hypersonic test vehicle,” Millman says.

Celebration

On Sunday, after Roc landed back at Mojave, Giddings, Thomas, and Riley exited the aircraft to find their colleagues had gathered to celebrate. 

“Everybody—all the maintenance folks and everybody—were all at the bottom of the ladder cheering and clapping,” Thomas says. “Obviously, that makes you feel good. I think everybody was proud of what happened today.”

All mission objectives were met. And for Giddings, there’s a big reason behind that.

“A lot of people think test pilots take a lot of risks,” Giddings says. “Well, I think we prepare, and I felt well-prepared.”

The post Exclusive: Pilots of World’s Largest Airplane Reveal Flight Details appeared first on FLYING Magazine.

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. 

• Read more about Roc’s upcoming missions to launch hypersonic flight 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:

• Windows
• 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.”

The post What It’s Like to Fly the World’s Largest Airplane appeared first on FLYING Magazine.

Mojave, California-based Scaled Composites has taken a major leap in the development of the massive Stratolaunch program. The world’s largest aircraft (by wingspan) took to the tarmac this weekend, blasted its six Pratt & Whitney PW4056 engines to life and completed the initial taxi tests.

As the Stratolaunch rolled down the runway, the wings, which span 385 feet, protruded far past the edges of the 200-foot wide Runway 12-30 at the Mojave Air and Spaceport. The airplane is designed for loads a payload of up to 500,000 pounds.

“It was a lot less intimidating once we had it out there, in terms of how much runway we take up,” said Scaled Composites’ project pilot Joe Sweat. “From a visual standpoint, we had a lot more room than I was anticipating. Getting the airplane moving under its own power was really interesting – just seeing and feeling how the nose wheel steering reacts and how the brakes respond to the inputs.”

The initial slow-speed taxi phase is now complete, though there will be quite a bit more testing before the giant will take to the skies.

“Later taxi testing will include faster speeds and more challenging steering and braking tasks, all in preparation for first flight,” said Scaled’s test conductor Brandon Wood. “It was exciting to see this magnificent machine on the runway for the first time!”

The post Scaled Composites Taxis Stratolaunch appeared first on FLYING Magazine.