In the years following World War II, the economy was booming, Americans were beginning to travel, and aircraft manufacturers were brimming with experienced teams of engineers. With the demand for military aircraft subsiding, virtually all of these companies began exploring new avenues for product development and innovation. It didn’t take Beechcraft long to identify civil aviation as a burgeoning opportunity.

Fresh off the success of the V-tail Bonanza and the larger, 8-to-10 passenger Model 18, Beechcraft management explored the market and noticed a gap in the industry’s product offerings. Prior to the war, types such as the Ford Trimotor, Boeing 247, and Curtiss taildraggers served as the era’s smaller “regional airliners,” but the war effort paused any further development of that segment. Referring to it as a “Feederliner,” Beechcraft reasoned that a small, modernized civil airliner was just what the industry needed.

Dedicating significant engineering and marketing resources to the project, the team got to work. It aimed to position the aircraft as a solution for passenger as well as cargo transport. It opted for a high-wing configuration, an easily convertible cabin layout, and a cargo door in the forward left fuselage, naming the final product the “Twin Quad.”

With a wingspan of 70 feet, a length of 51 feet, and a height of 19 feet, 4 inches, the Beechcraft 34 Twin Quad was a sizable machine. Ironically, each dimension is nearly identical—within 1 to 4 feet—to the Cessna SkyCourier, the latest offering from Beechcraft’s successor. Even the maximum takeoff weight of 19,500 pounds is within 500 pounds of the modern twin turboprop.

The team decided to incorporate a V-tail into the design, first installing it on an existing AT-10 Wichita twin for testing purposes. This enabled them to evaluate the tail’s effectiveness at providing directional control on a multi-engine aircraft of similar size and weight to the Twin Quad before finalizing and freezing the design.

It’s possible the V-tail was pursued primarily because of the technical advantages it was thought to provide. It’s also possible it offered more value to the marketing department as an instantly identifiable branding feature that visually differentiated it from the competition. Whatever the driving reason, Beechcraft ultimately incorporated the V-tail into the final design.

Though the V-tail was the most notable design feature of the aircraft from a visual standpoint, it paled in comparison to the originality and uniqueness of the engine layout. 

In an effort to harness the maximum power in the smallest, most aerodynamic packaging possible, the team opted to utilize four 375 hp Lycoming GSO-580 flat-8 piston engines and buried them entirely within the wing. The engines were configured in pairs, with each coupled together and driving a single propeller via clutches and a gearbox. The clutches were designed so that engine torque compressed and engaged the clutch discs. 

In the event of an engine failure, the failed engine would automatically disengage from the gearbox, and the remaining engine would continue to drive the propeller. This feature was presented as a safety improvement—although the loss of one engine would result in a power reduction, it would present no corresponding asymmetric control issues.  

The Twin Quad used two massive full-feathering, two-blade propellers for propulsion, and naturally, they were driven through reduction gearing. At 11 feet long, if the engines were to turn them directly at a normal cruise rpm, the propeller tip speeds would have exceeded Mach 1.5. The reduction gearing provided a ratio of 40:21, or roughly 2:1, bringing the propeller rpm range down to a quiet and comfortable 1,500 rpm in cruise flight.

During engine shutdown, the engine clutches would disengage entirely. A note in the operating manual advises that if high-velocity wind rotates the propellers after shutdown, the clutches may be reengaged to lock them into position. Presumably, standard operations would call for the clutches to be engaged regardless, as the sight of rotating propellers on a vacant, parked aircraft would naturally create concern for any observers on the ramp.

Because the Twin Quad was designed for airline operations, it was equipped with full anti-icing capability. Two combustion heaters—one for the wing, and one for the tail—provided heat for the leading edges that was distributed along the insides of the leading-edge skins. The propellers were electrically deiced, and the cabin heater ducted hot air into the space between the two panes of glass that made up each cockpit windscreen.

The Twin Quad made its first flight in autumn 1947. Shortly thereafter, the marketing team stopped using the term “Feederliner” to describe the aircraft, instead switching to “Beechcraft Transport.” This indicated a change in marketing strategy to emphasize non-airline operations, which likely included executive transport. 

Detailed cruise performance wasn’t provided in the preliminary flight manual, but VNE is listed as 270 mph and VNO as 220 mph. Minimum takeoff climb speed is listed as 96 mph, and the bottom of the white arc is 75 mph. 

Given the total horsepower available, the Twin Quad’s engine-out takeoff performance seems fairly decent. In the event of an engine failure after V1 at the maximum weight of 19,500 pounds, the charts indicate it will clear a 50-foot obstacle in just below 3,500 feet at sea level. By comparison, the modern Cessna SkyCourier requires 2,740 feet at roughly the same weight with both engines operating and twice as much power available. Landing distance over a 50-foot obstacle is listed as 2,000 feet at sea level and maximum weight.

The charts optimistically include separate listings showing performance with 40-mph headwinds. It is unclear whether this is a function of an overly optimistic marketing team or simply reflected the reality of everyday weather conditions in Wichita, Kansas. 

Range figures aren’t provided, but endurance can be calculated with the available data. Given the Twin Quad’s total fuel capacity of 536 gallons and the fuel consumption figures of 130 total gallons per hour at maximum continuous power and 80 total gallons per hour at 75 percent power, the resulting endurance would have been 4.1 to 6.7 hours.

Tragedy struck during a certification test flight in Wichita on January 7, 1949. Just after liftoff, an electrical fire occurred. While attempting to extinguish it, a crew member reportedly turned off an “emergency master switch” that resulted in both engines shutting down. The aircraft then stalled and went down, killing one of the pilots.

Following the incident, Beechcraft terminated the program entirely. No specific reason was provided, but it’s possible the decision was driven in part because of a lukewarm response from the market. Ultimately and unfortunately, what remained of the Twin Quad was scrapped.

Today, all that remains is a small handful of photos and scraps of documentation. And while the large Bristol Brabazon airliner flew with a nearly identical engine/propeller arrangement later that year, it would ultimately succumb to the same fate—canceled, scrapped, and relegated to the dusty shelves of aviation history.

The post Beechcraft Twin Quad: A ‘Feederliner’ That Almost Was appeared first on FLYING Magazine.

If an aerospace engineer was given their choice of time periods in which to work, it’s likely the 1960s would be a top pick. With swept-wing jets like the Boeing 707 and Douglas DC-8 having made their first flights just a few years prior, the decade ahead would see the introduction of such groundbreaking aircraft as Concorde, the Boeing 747, and the XB-70 Valkyrie. Research and development budgets were robust, competition was fierce, and a young engineer looking for employment must have felt like the proverbial kid in a candy store. 

While the majority of action in the U.S. centered around the production of civil airliners, military jets, and the space race, there were some less flashy but thoroughly intriguing programs taking place in some of the industry’s quieter, less-traveled corridors. One of which was a research program led by Northrop, the U.S. Air Force, and the U.S. Army. The objective? Explore how a wing’s lift could be artificially boosted to reduce drag and increase performance, particularly in large, long-range aircraft designs—some of which would be supersonic.

Drag reduction efforts were nothing new in those days. From simple efforts like flush riveting to more complex concepts like area ruling, massive progress was made in a relatively short amount of time. In the 1950s, boundary layer control (BLC) was integrated into a number of aircraft designs, a system in which compressed air was directed over sections of the wing and control surfaces to delay the separation of air over the airfoil’s surface, thus artificially increasing lift at lower airspeeds.

The team at Northrop opted to study and test something called laminar flow control, or LFC. The basic premise behind LFC is that a large number of tiny slots would be drilled into the upper surface of a wing, and a vacuum system would draw air inward through them. This would cause the thin film of air clinging to the surface of the airfoil to cling more effectively, thus reducing friction drag attributed to air turbulence over the wings by as much as 80 percent.

Because the program would be aimed at the development of civil airliners, the team chose an aircraft that would best replicate the category—the Douglas B-66 Destroyer. Specifically, it was the WB-66 weather reconnaissance version, of which 36 were built in the late 1950s. Using two examples as testbeds, the team modified them with all the necessary systems to test the LFC system.

The team began by cutting a vast series of ultra-thin slots in the upper surface of a newly-designed wing that was larger and less swept than the B-66’s original wing. These slots varied in thickness from approximately 50 percent to 200 percent of the width of the cutting edge of a razor blade. Perhaps drawing inspiration from the Bede XBD-2 that flew just a few years prior,  they utilized computers to drill an intricate pattern of 800,000 pin-sized holes beneath the slots and installed hundreds of small plastic ducts inside of the wing, each one carefully tuned to a specific length to ensure proper distribution of vacuum pressure across the entirety of the wing’s upper surface.

The X-21’s GE J79 non-afterburning turbojet engines—relocated to the lower aft section of the fuselage—provided bleed air to power special compressor pumps housed in a pair of sleek nacelles mounted beneath the wing. These pumps would draw air through the slots in the wing and through the ducting to activate the LFC system. Rather than simply ejecting this compressed air overboard, it was ignited and discharged through thrust-augmenting exhaust nozzles at the aft end of each nacelle.

By the time the X-21 was completed in 1963, only the landing gear and tail surfaces remained the same as the WB-66 once was. Even the engine intakes were altered, incorporating “egg-shaped forms” within each intake that could be moved forward and aft to alter the incoming airflow. This was in anticipation of developing movable inlet cones for supersonic flight—as would be utilized on the SR-71 the following year.

The X-21 proved docile to fly, and the LFC system worked as designed. Despite having no flaps, the modified aircraft demonstrated a ground roll of 2,600 feet—significantly shorter than the required takeoff distance of the standard B-66. But while a second X-21 was built, and both contributed valuable data to the program, the team discovered a number of concerns that would preclude the adaptation of LFC into operational aircraft fleets.

As detailed in an October 1964 NASA report, the LFC system could not be relied upon during flight in clouds, haze, and high humidity. Because the tiny holes in the upper surface of the airfoils had to be kept perfectly clean and free of contamination, issues such as icing, moisture, and even insect buildup were anticipated, all of which would result in erratic performance of the LFC system. Additionally, such factors could create a dangerous asymmetric lift condition that would lead to controllability issues.

When the test program was completed, both X-21s were placed into storage at Edwards Air Force Base. Later, as their condition deteriorated, they were unceremoniously parked out in the desert, in the Edwards Photo Impact Range. There, they continue to be used to test cameras, mapping systems, and remote sensors.

This is typically where the story of such unique aircraft ends. More often than not, the scrapper is the ultimate destination, and any physical examples of the aircraft are permanently erased from history. But in the case of the X-21s, there is hope. That hope comes in the form of the Air Force Flight Test Museum, also located at Edwards Air Force Base.

There, director George Welsh is keenly aware of the X-21s and their historical value. He has already begun laying the groundwork to one day recover both examples and eventually utilize parts from both to create one representative example for display in the museum. His team has even identified a number of missing parts and has proactively scavenged them from an unrelated donor B-66, to make the future restoration process go more smoothly.

As is typically the case with even the world’s most renowned museums, funding is the primary obstacle. Having begun construction of new museum facilities, the Flight Test Museum still has to raise millions of dollars to complete that project before embarking upon the transport, storage, and restoration of the X-21s. But the museum leadership has done its duty to ensure they will be spared from the scrapper.

For now, both X-21s remain out in the desert. With any luck, the museum will soon secure enough funding to complete the new facilities so the unique jets can be restored and put on display for future generations to appreciate.

The post The High Speed, Low Drag Northrop X-21 appeared first on FLYING Magazine.

It would surely require a unique set of circumstances to convert a utilitarian twin-turboprop cargo airplane into a swept-wing four-engine jet. It would be especially peculiar if these modifications resulted in a maximum cruise speed of only 160 knots and a maximum range of only 256 miles. But in the late 1970s, this is precisely what occurred when NASA designed and built the Quiet Short-Haul Research Aircraft, or QSRA.

The genesis for this unique aircraft occurred when researchers around the world were investigating the concept of inner-city airports. These airports, sometimes called STOLports, were envisioned to become the next evolution of air transport. Proponents claimed that by building smaller airports in urban centers, population centers could be more easily and quickly connected with the larger air travel network.

Because such airports would be limited in footprint, they would utilize shorter runways. And because the population surrounding these airports would be so dense, any aircraft utilizing them would have to be significantly quieter than existing types. These design constraints were among the key areas of study in the QSRA program, and NASA’s job was to explore how such aircraft might be designed and certified.

NASA was constrained by a tight budget, so when it discovered that it could acquire a deHavilland Canada C-8A Buffalo at no cost from the National Center for Atmospheric Research, they seized the opportunity. Their tactical frugality continued with the discovery of six used AVCO-Lycoming YF-102 turbofan engines left over from the Northrop A-9A prototype ground attack jet. As the A-9A had lost the military contract for which it was competing to the A-10, the engines were available and were provided to the QSRA team at no cost.

Now in possession of an airframe and engines, all that was left to do was design a wing and assemble the aircraft so testing could commence. NASA contracted Boeing to design and fabricate the wing. Rather than utilize a traditional straight wing as was originally fitted to the Buffalo, the QSRA was fitted with a swept wing that incorporated a complex system of flaps and Boundary Layer Control, or BLC.

The BLC system would divert bleed air from the engines to small nozzles positioned on top of the wing ahead of the flaps and ailerons. This bleed air would help to keep the boundary layer attached, delaying the onset of a stall, increasing control surface effectiveness, and enabling flight at slower airspeeds. In addition, the engines would be placed on top of the wing to utilize the Coanda effect, an aerodynamic effect deflecting thrust downward and increasing lift.

NASA recognized high-speed cruise efficiency would provide little value to the program. They also anticipated the steep approaches and high rates of descent necessary for their testing could easily result in significantly greater impacts upon touchdown. Accordingly, they modified the landing gear to be non-retractable and strengthened it to withstand firm landings that would routinely exceed 700 feet per minute.

The first flight of the QSRA took place on July 6, 1978, at Boeing Field in Seattle. A wide variety of testing followed shortly thereafter to fulfill data gathering for a number of projects. These projects ranged from the compilation of data to help regulatory agencies establish certification criteria for future STOL airliners to measuring the effects of steep approaches and departures on noise footprints.

The performance of the QSRA was impressive—65-knot approach speeds were standard, and low-speed flight was demonstrated down to only 50 knots. This is particularly notable as the aircraft’s maximum takeoff weight was 60,000 pounds—a full 7,000 pounds heavier than a fully-loaded, 50-passenger CRJ200 regional airliner.

Maximum-performance takeoffs resulted in ground rolls of 664 feet, and STOL landings produced ground rolls of only 550 feet. But the ability to utilize shorter runways wasn’t the only goal. In order to reduce the noise footprint during approaches and departures to and from urban airports in densely-populated cities, the team wanted to evaluate the feasibility of utilizing a steep, 7.5 degree approach path as opposed to the standard 3 degree glideslope.

As these tests were conducted, the team discovered that such approaches could reduce the aircraft’s noise footprint by 80 to 90 percent. This steep glideslope, they noted, would place the aircraft more than twice as high as a conventional passenger jet at any point along the approach. NASA even suggested touching down at the runway midpoint or performing spiraling descents directly above the airport to confine the noise footprint to that of the airport itself and thus not affect adjacent communities. It is unclear whether the team considered the effect such approaches might have on the passengers aboard.

The QSRA would go on to conduct a wide variety of testing. In addition to studying controllability and noise footprints, it was even utilized for a joint NASA/U.S. Navy test program in which it flew onto and off of the USS Kitty Hawk aircraft carrier. This particular testing evaluated the use of advanced propulsive-lift technology, and the QSRA successfully completed a series of unarrested landings and unassisted takeoffs from the carrier deck.

When the last test programs were completed, the QSRA was retired and put out to pasture. Today, visible on Google Maps, it resides on a quiet ramp at the NASA Ames facilities at Moffett Field in Mountain View, California, weathered from the elements but otherwise intact. With any luck, it will one day be fully restored and put on display indoors where future generations can fully appreciate the work it and its teams conducted.

The post The Quiet Little Life of NASA’s QSRA appeared first on FLYING Magazine.

In the film Back to the Future II, the antagonist Biff Tannen steals a sports almanac containing scores from every major sporting event over a 50-year time span and delivers it to his younger self via a time machine. Armed with this knowledge from the future, his younger self then utilizes the almanac to gamble, amassing a fortune estimated by fan websites to exceed $3.1 billion and forever altering the trajectory of that timeline. 

While there’s no concrete evidence a similar chain of events occurred in the world of aeronautical engineering, the concepts utilized by the Dayton Wright RB-1 certainly suggest at least one time machine was involved in its development.

When the RB-1 was constructed in 1920, the vast majority of aircraft were still rickety-looking contraptions. Most were biplanes utilizing fabric covering, external wire bracing, and spindly-looking fixed landing gear. World War I-era rotary radial engines were still commonplace, their crankcase and cylinders spinning in their entirety as though the engine manufacturers were sponsored by gyroscopic precession itself. 

At the time, developments like a variable-camber wing and retractable landing gear must have resembled science fiction to most, but not to the people at Dayton-Wright in Ohio. There, a small team of engineers was tasked with creating an aircraft specifically to compete in the Gordon Bennett trophy race in France. This prestigious race consisted of three laps of a 300 km (186 mile) course, and a victory would bestow enviable bragging rights to the aircraft manufacturer.

Favorites for the 1920 race included aircraft built by Neuport, Spad, and Verville-Packard. All were among the fastest aircraft in the world at that time. But all were also open-cockpit biplanes, seemingly designed and built with little regard for parasite drag. 

Dayton-Wright identified this as an opportunity. In a flight regime where any horsepower gains are quickly overshadowed by exponentially-increasing drag, they designed and utilized features unheard of in that era. Features that in the following decades would become commonplace on virtually all aircraft built for speed.

Prioritizing drag reduction from the beginning, they designed a fully-enclosed cockpit and opted for a single wing instead of a biplane configuration. They utilized a cantilever wing, avoiding extraneous wing struts or bracing cables that would slow the airplane down. They understood that a smaller wing would be more efficient at higher speeds, but they also understood that additional lift would be necessary for takeoff and landing. 

To balance these opposing demands, they introduced what is thought to be the first wing with adjustable camber via leading-edge and trailing-edge devices. Like a modern wing with slats and flaps, the RB-1’s wing could be configured in flight by the pilot. For takeoff and landing, camber would be increased and slower airspeeds would be possible, but for high-speed cruise, the wing could be flattened and streamlined to reduce drag.

The engineers didn’t stop there. Recognizing that landing gear is a massive source of drag at higher speeds, they developed (and patented) a novel retractable landing gear design. By turning a hand-operated crank linked to chains and gears, the pilot could raise the gear in approximately ten seconds and lower it in approximately six.

The engineers also linked the landing gear to the variable-camber wing. Retracting the gear also retracted the leading and trailing edges of the wing. When it was time to land, everything extended at once, in unison.

The entire front section of the airplane was dedicated to the engine’s massive radiator, which completely enveloped the crankshaft. No forward windscreen was provided to the pilot; like the Spirit of St. Louis, they would have to make do with the side windows and utilize their peripheral vision for takeoff and landing.

Having sculpted the monocoque fuselage and wing to their liking, Dayton-Wright turned to the powerplant. They chose a water-cooled inline six manufactured by Hall Scott and producing 250 horsepower. At the RB-1’s maximum takeoff weight of 1,850 pounds, this gave it a better horsepower-to-weight ratio than a similarly-loaded Republic P-47 Thunderbolt. 

The RB-1 first flew in 1920, not long before the trophy race. Test pilots conducted a short series of test flights at the company’s facilities near Dayton, Ohio, and estimated the airplane’s top speed would approach 200 mph. Afterward, the airplane was disassembled, packed into a crate, and shipped off to France.

When the big day came, the RB-1 took off from Ville Sauvage near Étampes in the company of the other competitors, only to have to abandon the race and return to the airport after only 15 minutes. Sources vary with regard to the reasoning. Most claim the pilot was unable to retract the gear and flaps, but Flight magazine reported that he experienced “difficulty with his steering.” 

Given the complexity of the wing, it’s possible only one wing had experienced mechanical issues, thus introducing asymmetry and affecting the control and steering. In any case, the RB-1 returned safely. It was shipped back to the U.S., and it never flew again. It remains unclear why no further flying attempts were made.

Today, the RB-1 is on display at the Henry Ford Museum near Detroit, Michigan. It has been properly restored and hangs with its gear and flaps retracted. An elevated walkway provides visitors with a view of the unique flap mechanism on top of the wing.

Although unsuccessful in its intended mission, the RB-1 brought a blend of remarkably futuristic technologies to light in an era of relatively primitive aircraft and permanently altered the trajectory of aircraft design. To date, no evidence of time travel has been discovered in the development of this groundbreaking aircraft.

The post Dayton Wright’s Race To Build a Time Machine appeared first on FLYING Magazine.

Mention the term “X-plane,” and most envision shadowy experimental military aircraft with mind-numbing performance. From the X-1, which was the first to break the sound barrier, to the X-15, which could cross the Karman line and enter space, X-planes have historically been defined by immense power, blinding speed, and sleek lines reminiscent of fictional spaceships.

Conversely, when discussing X-planes, most tend not to envision design features like an open cockpit, fixed landing gear, and a maximum speed only four knots faster than the cruise speed of a Cessna 182. Most also would not expect this category of aircraft to utilize second-hand Beechcraft parts. But these characteristics define the bizarre Bell X-14, an experimental vertical takeoff and landing (VTOL) jet with a somewhat agricultural aesthetic. Further differentiating it from other X-planes was a second life as a trainer for NASA astronauts to refine their moon-landing skills and a dramatic last-minute rescue from a scrapyard. 

Conceived by Bell Aircraft as part of a U.S. Air Force order to explore and develop VTOL technologies, the X-14 first achieved vertical flight in February 1957. It was among several of the first jet VTOL aircraft to take flight in the mid to late 1950s, a small group that included the Ryan X-13 and the British Short SC.1. The following year, the X-14 successfully transitioned from vertical to forward flight and began comprehensive flight testing at Bell’s facility in upstate New York.

Originally utilizing two nose-mounted Armstrong Siddeley Viper turbojet engines, the X-14 was later upgraded to General Electric J85 turbojet engines—as used in the Cessna A-37 Dragonfly—that produced a total of 6,000 pounds of thrust. This thrust was controlled by a series of vanes within the belly to maneuver the 4,269-pound aircraft. Rather than employ separate engines for forward thrust, the system could direct the thrust downward for takeoff and landing or rearward for conventional flight.

Accurate pitch, yaw, and roll control has historically been a challenge for jet-powered VTOL aircraft. To achieve this, the X-14 utilized a system of bleed air and mechanical spool valves at the tail and at each wingtip. With careful application of the stick and rudder pedals, the pilot could command short blasts of bleed air to nudge the aircraft into the desired attitude during flight.

Bell and the U.S. Air Force tested and evaluated the X-14 and invited pilots and engineers from abroad to participate, thus supporting the development of what ultimately became the VTOL Harrier attack jet. As the X-14’s first chapters of testing drew to a close, NASA took interest. The Apollo program was about to begin, and officials recognized the need for specialized astronaut training. While Gemini had proven astronauts could get to and from space, NASA now needed to train astronauts to precisely maneuver the lunar lander to a predetermined point on the moon’s surface. 

Lacking easy access to a training environment with limited gravity, they employed the X-14, reasoning that the bleed air maneuvering system bore a reasonably close resemblance in practice to the thrusters used to maneuver the Lunar Module. After shipping the X-14 to the Ames Research Center at Moffett Field, California, astronaut flight training commenced. NASA also utilized the X-14 to help develop a more comprehensive training platform, the Lunar Landing Research Vehicle (LLRV).

Among the numerous pilots to fly the X-14 was Neil Armstrong. He put the aircraft through its paces, learning to “perch on a bubble of hot air,” as he reportedly described the hover. Armstrong also reportedly claimed the X-14 was the only aircraft in which he could execute a zero-radius loop, flopping around its center of mass “by deft manipulation of the throttle, nozzle control, and stick.”

All such maneuvers were conducted directly above the airfield of origin, as the total fuel capacity of 110 gallons resulted in as little as 20 to 30 minutes of endurance. Armstrong reportedly ran the tanks dry on more than one occasion, and he compared its glide characteristics to that of a Cessna 206. With Beechcraft wings, the handling would have indeed seemed docile, particularly compared to the F-104 and the hypersonic X-15 he had been flying.

After the X-14 had served its purpose with NASA, it was entrusted to a government entity that initially had plans for restoration but ultimately placed it into long-term storage. Decades of being disassembled to various degrees and moving from place to place took a toll. Sections of the airframe were damaged, the brightly-polished aluminum skin became weathered and dull, and when it ultimately began to resemble a pile of discarded scrap, the entire thing was eventually sent to a scrapyard. 

When an aircraft arrives at a civilian scrapyard, it typically doesn’t take long for it to be erased from existence completely. Fortunately for aviation enthusiasts and historians, however, a man named Rick Ropkey learned about the X-14 before it succumbed to that fate. In the late 1990s, upon learning of its condition and of the plan for it to be scrapped, he purchased it and arranged for it to be trucked to his family’s military history museum in Indiana, the Ropkey Armor and Aviation Museum. 

Ropkey was not satisfied with rescuing only the aircraft itself. He also managed to locate and salvage a massive amount of materials related to the X-14, including large-scale blueprints, various forms of test data, and boxes of manuals, some of which had been initialed “N.A.” Familiar with the aircraft’s history, Ropkey reached out to an old fraternity brother who knew Neil Armstrong personally and eventually got in contact with the legendary astronaut. Before long, Ropkey and Armstrong were on a first-name basis, and Ropkey was able to gather unique, first-hand accounts of the X-14’s history.

Over the years, Ropkey and his son Noble gradually worked through the restoration process, restoring one part at a time while keeping the X-14 on display in their museum. When Ropkey’s father died in 2017, the museum was forced to relocate. Presently, plans are afoot to display the X-14 again, and the restoration is nearly complete. 

While the family has no intention of ever flying the X-14, they are striving to complete a full restoration and share it with the public. Presently, the most significant challenge is sourcing parts for the GE J85 engines, and Ropkey hopes to find a source willing to donate surplus engine parts. “It’s been a labor of love for the last three decades,” Ropkey said, and added, “It’s going to be in the Ropkey hands for a long time.” 

After surviving 24 years of operation with no major accidents or serious injuries, and after countless landings by astronauts-in-training, aviation and history enthusiasts alike are fortunate that the unique X-14 has landed in the hands of a family with a strong appreciation for it and its legendary history.

The post How NASA’s Unconventional Bell X-14 Almost Landed in the Scrapyard appeared first on FLYING Magazine.

Throughout the late 1980s and early 1990s, McDonnell-Douglas was struggling to secure contracts for the production of tactical military jets. In 1986, after submitting multiple proposals for the USAF’s Advanced Tactical Fighter (ATF) program, the company was excluded from the running. Later, it partnered with Northrop Grumman to develop the YF-23, only to lose to the F-22 in 1991.

Reeling from these losses, company leaders decided they needed to make up lost ground. Recognizing that stealth technology and affordability were key elements in future success, they launched a program in 1992 to develop their capabilities. This program entailed the design, manufacture, and testing of a cutting-edge research aircraft that would become known as the Bird of Prey.

Named after a Klingon spacecraft from Star Trek and given the designation ‘YF-118G,’ the jet incorporated dramatic design inside and out, albeit in very different manners. The fuselage, wing, and exterior were designed to explore multiple facets of stealth technology above and beyond, minimizing the radar cross section (RCS). While the RCS is estimated to be as small as a mosquito, engineers also buried the engine deep within the fuselage to minimize the infrared signature and even carefully designed the paint shading to visually mask the actual fuselage shapes in daylight—a measure not utilized by other stealth aircraft such as the F-117 and B-2.

Less visible but no less significant were the efforts made toward the company’s goals of streamlining the design and assembly processes and ultimately improving affordability. By utilizing rapid prototyping techniques through the use of computer programs and 3D rendering, engineers were able to simulate the performance of individual parts and systems aboard the aircraft, thus minimizing the need to continuously produce and test multiple iterations of physical parts. These efforts even extended to making tooling easier and more affordable to manufacture.

A parallel effort was made to reduce the cost of the aircraft itself through the use of off-the-shelf components wherever possible. By selecting an off-the-shelf business jet engine, landing gear from Beechcraft turboprops, an ejection seat from a Harrier, and cockpit controls from various existing tactical jets, the team scavenged scrap yards and kept the balance sheet under control. Ultimately, the entire program reportedly cost $67 million, less than the cost of two new 737s at that time.

When the Bird of Prey made its maiden flight in September of 1996, it quickly became clear that the aircraft, with its highly-swept, 23-foot-span wing, did not exhibit good flying performance. Fortunately, it didn’t need to. With an airframe that placed far greater value on low observability than on aerodynamic performance, the speeds, altitudes, and handling characteristics were less than impressive.

The Pratt & Whitney JT15D engine, basically the same engine as used by the Cessna Citation V and Beechcraft Beechjet, produced 3,190 pounds of thrust. Maximum takeoff weight was 7,400 pounds, producing a similar thrust-to-weight ratio as those jets. The optimization for stealth performance, however, resulted in an “operational speed,” as reported by an official Boeing press release, of 260 knots and a maximum operating altitude of 20,000 feet. A Pilatus PC-12 can fly both higher and faster.

Nevertheless, the Bird of Prey went on to fly 38 test flights between 1996 and 1999, and the program was successful enough to survive the Boeing acquisition of McDonnell-Douglas in 1998. After the program was publicly unveiled in late 2002, the aircraft was given to the National Museum of the United States Air Force in Dayton, Ohio, where it remains on display today.

Despite being put on display, one curiosity remains—an apparent lack of any publicly-available photos of the cockpit or instrument panel. While it’s unlikely these are still officially classified, the jet currently hangs at a height that keeps them well out of view. Additionally, the cockpit windows of the similarly spooky Tacit Blue stealth testbed were painted black for display in the museum, also preventing any views into the cockpit.

Whether these efforts are coincidental or intentional, they certainly lend an air of mystery to aircraft that themselves were shrouded in secrecy from the beginning.

The post Boeing Bird of Prey Shrouded in Secrecy Still appeared first on FLYING Magazine.

When designing a single-engine jet, there are only so many places one can mount the engine. To avoid asymmetric thrust, it must be mounted on the centerline of the fuselage, and doing so introduces new challenges. Something must be done to provide the engine with clean, undisturbed air for the intake, for example, and the design must somehow prevent the hot exhaust from damaging tail surfaces.

In mid 2007, when many manufacturers were developing new designs for the newly-identified very light jet (VLJ) category, Piper began development of their own VLJ with the goal of finding the simplest solution possible. They decided against housing the engine within the fuselage, as this would present complex challenges with regard to ducting airflow cleanly through inlets. Additionally, an engine housed within the fuselage must be engineered to minimize the risk to the occupants in the event of an uncontained compressor blade or disk failure.

Avoiding such constraints necessitated an engine positioned outside of the fuselage, and to ease cabin access with shorter, lighter landing gear, this meant on top. Piper needed to protect the tail surfaces from the aforementioned hot engine exhaust, but they wanted to avoid the use of relatively heavy and complex designs like some competitors were using. The Eclipse 400 Concept Jet, for example, utilized a V-tail that required a separate engine pylon, and Adam Aircraft opted for a massive twin-boom design for their A700.

Perhaps drawing inspiration from the McDonnell Douglas DC-10 airliner, the team opted to integrate the engine with the vertical stabilizer. This configuration offered several significant advantages. Chief among them, the engine would be provided with clean, undisturbed airflow, and there would be no concerns about hot engine exhaust affecting the airframe.

The simplicity of this configuration provided some ancillary benefits, as well. Because the fuselage was relatively conventional, existing components could be used. For the proof-of-concept aircraft, the team repurposed a Meridian fuselage. The wing was also conventional and didn’t require any significant engineering beyond that of existing aircraft. Compared to an entirely clean-sheet design, these factors would reduce the complexities of certification and production.

This would also enable the team to focus on the unique engineering challenges introduced by the tail-mounted engine…and after the aircraft’s first flight took place in July of 2008, they discovered several to address. The most significant was identified early on in the design program – the high thrust line. Because the engine was placed so far above the aircraft’s center of gravity, the application of thrust would result in a nose-down pitching moment, and a thrust reduction would result in a nose-up pitching moment.

This thrust/pitch coupling could be addressed in several ways. Various systems like vectored thrust and active trim could be utilized, but systems like these introduce weight, complexity, and additional points of failure. Piper instead developed a simple and clever fixed nozzle system that produced a variable thrust angle. 

The nozzle did so through the Coanda effect, in which air clings to a surface and can thus be aimed via this air pressure alone. At low speeds, the Coandă effect was pronounced and created a greater thrust vector that effectively countered the high thrust line. At high speeds, the effect was minimal and resulted in a 2.2 percent geometric loss of thrust, which was considered acceptable. 

This system was a success. Even with the high thrust line, go arounds could be accomplished hands free, a rare handling characteristic even among more conventional designs. Test pilots reported power changes had a less pronounced effect than propeller-driven aircraft. 

The team encountered another challenge when they discovered that the use of full flaps could produce a tail-plane stall. This would result in an uncommanded pitch down, which is obviously an undesirable characteristic. The issue was resolved by altering the horizontal stabilizer, increasing its span, increasing the elevator size, and adding 30 percent of sweep, which moved the aerodynamic center aft and solved the problem.

With significant engineering accomplishments under their belt and 180 pre-orders for the $2.2 million aircraft, Piper moved forward with development of a new version called the Altaire. The Altaire would incorporate a larger, roomier cabin, and projected performance of a 35,000-foot maximum cruise altitude, a 360-knot maximum cruise speed, and a 1,200- to 1,300-nm maximum range.

Despite the numerous engineering accomplishments and an optimistic initial outlook, the PiperJet program ultimately succumbed to market conditions. Economic and market forecasts became bleak, and rather than risk the company on a single new aircraft subject to the projected market downturn, Piper put the program on indefinite hold.

When it became clear the program would progress no further, the Smithsonian expressed an interest in acquiring the sole prototype, with the caveat that Piper include the first Piper/Taylor E-2 Cub ever sold. The Florida Air Museum in Lakeland also expressed an interest in acquiring the prototype but included no such contingencies and ultimately received the aircraft. 

There, the sole PiperJet remains on display for the public and future generations to admire.

The post The Rise and Stall of the Piper PA-47 PiperJet Program appeared first on FLYING Magazine.

Postwar aircraft development, particularly throughout the 1960s and 1970s, was an interesting chapter in general aviation. Light singles saw a wide variety of new and creative designs launched and tested, ranging from small experimental aircraft like the Rutan Quickie to larger-sized design studies like the Cessna XMC. Some of these more unique types like the pressurized Mooney M22 Mustang even reached limited production.

Light piston twins saw considerably less variety and experimentation than singles. While a few less-conventional examples like the Piper Aerostar and Angel 44 made their marks, the scene was dominated by relatively conservative designs like the Piper Seneca, the Beechcraft Baron, and Cessna’s 300 and 400-series cabin-class twins.

Among the more obscure and unique specimens was the Burns BA-42. Launched by businessman Sam Burns in 1963, the program was a product of a collaborative design effort from a group of engineers and students at the Mississippi State University’s Department of Aerodynamics. One member of the group was none other than Al Mooney, and as one might expect from Al, much effort was focused on the aerodynamic cleanliness of the airframe.

The BA-42 is a compact aircraft, with an understated presence that would be overshadowed by even a Beechcraft Duchess. The mid wing provides for a low-slung appearance, and the relatively long fuselage enables the use of a compact vertical stabilizer. Looking at it from across a ramp, one might not guess that it is a 4,300 pound, six-place airplane.

Examine the BA-42 up close, and additional details shed light on the goals of the design team. Flush riveting indicates strong concern for drag reduction, as is the lack of any major flat surfaces on the airframe. Such design elements place emphasis on performance rather than cost-effective manufacturing.

One of the most striking aspects of the airframe is the positioning of the 210 hp Continental IO-360-D engines. In an attempt to minimize Vmc (the speed below which aircraft control cannot be maintained if the critical engine fails), the engines are placed as close to the aircraft’s centerline as possible. Only two fingers can be placed between the prop tips and the fuselage, and one wonders just how loud the cabin would be at high power settings.

The effectiveness of this engine placement is unclear. Early press about the BA-42 touts Vmc being below stall speed, but a look at the airspeed indicator in the aircraft itself suggests otherwise. If the white arc on the airspeed indicator is to be believed, the stall speed is 76 mph. Additionally, the FAA type certificate data sheet (TCDS) and the red line on the airspeed indicator both define the BA-42’s Vmc as 95 mph.

The BA-42 first flew in 1967, four years after initial design work commenced. Very little information is available regarding the airplane’s performance, but one early review mentioned a 218 mph cruise speed at 75 percent power. If accurate, this would have been impressive, besting comparable Cessna and Beechcraft models with 50 fewer horsepower per engine. The company claimed that the BA-42 has less frontal area than a Cessna 182. If this is indeed the case, such a cruise speed might be plausible. 

Burns had high expectations and equally high optimism for the airplane. The circular fuselage cross section was chosen in part for the ability to more easily adapt pressurization in future derivations. More powerful engines were anticipated, as well, including turboprops that would greatly increase cruise speed and service ceiling.

As is all too common among new aircraft manufacturers, however, the project died in 1973. The market for light twins was relatively crowded at that time, and although the BA-42 was granted FAA type certification, weight and balance issues emerged. Specifically, the type certification was predicated upon a limitation to only four seats as opposed to six as originally planned.

Two BA-42s were ultimately built. After the initial corporation ended the program, it was later purchased in whole by the Mael Aircraft Corporation in Portage, Wisconsin. A family-owned company, Mael put further effort into completing certification for the six-place design and has reportedly entertained multiple proposals over the years to put the airplane into full-scale production. To date, however, none have come to fruition.

Presently, both BA-42s are being kept in Portage, Wisconsin. The example being kept outside shows considerable wear from the elements, but a representative from Mael reports that the second aircraft has been preserved indoors and could be returned to an airworthy state with relatively little effort.

With any luck, this little-known Al Mooney design will one day take to the skies again.

The post The Short Run of the Burns BA-42 appeared first on FLYING Magazine.

Most aircraft engineers, tasked with designing a new STOL aircraft, wouldn’t opt to drill 160,000 holes in the wing and utilize two piston engines to drive a single pusher propeller. 

But then again, most engineers aren’t Jim Bede. 

While still enrolled in the aeronautical engineering program at Wichita University, Bede designed an aircraft that would incorporate a number of unique technologies. His vision was to integrate these technologies to provide superior performance to existing designs. Integrating new systems and complexity into an entirely new aircraft design, however, would prove to be challenging even for him. 

Bede started with an entirely clean-sheet design. Envisioning an eventual family of multiple aircraft varying in size and passenger capacity, he began with an experimental prototype of the Bede BD-2, which he called the XBD-2. Intended as a proof-of-concept and testbed and first flown in July of 1961, it was boxier and more utilitarian than the sleek, streamlined concepts he endeavored to build, but it would function well for its intended purpose.

At first glance, even an experienced pilot or engineer might not guess the XBD-2 is a twin-engine aircraft. But it is, and two 145 horsepower six-cylinder Continental O-300s are snugly nestled in the aft fuselage, stacked one above the other. While such an engine configuration is decidedly unconventional, Bede was of the opinion that it offered several advantages.

Most obviously, housing the engines within the fuselage provides for a clean wing, undisturbed by engine nacelles and far more aerodynamically efficient. From a controllability perspective, an engine failure would be a non-event, as there would be no risk of asymmetric thrust. The lack of engine nacelles helped to reduce overall drag, enabling an 18:1 glide ratio. 

A system of 10 belts and multiple clutches enabled operation at any combination of engine power, and the pilot could shut one engine down completely to maximize endurance. Bede even mounted each engine on a slide-out rack, a design he claimed enabled an engine to be removed in only 30 minutes. Presumably, little time was required to decouple an engine from the system of drive belts.

It was a complex system, but Bede wasn’t finished. With the assistance of Mississippi State University’s aerophysics department, he introduced further complexity to the aircraft by integrating a Boundary Layer Control, or BLC system, into the design. Utilizing 160,000 strategically-placed pinholes in the upper wing and aileron surfaces—holes roughly 30-50 percent as large as those in a typical air hockey table—the system would draw air into the wing to create additional lift. By causing the boundary layer to stick to the wing at high angles of attack, the system effectively increased lift and lowered the stall speed.

The BLC system drew air into the wing via a pump driven by the propeller shaft. So long as the propeller was being turned by at least one engine, the BLC system would operate. Ingested air was ducted back to the engines to provide additional cooling. The system proved to be effective, lowering the stall speed from 64 mph to only 42 mph—an impressively slow speed for an airplane with a gross weight of 3,300 pounds. Bede even claimed that the system would be undeterred by rain.

The most visually notable feature of the XBD-2 is the shrouded propeller. Bede was of the opinion that the aerodynamics at the tips of a standard propeller was one of the greatest sources of inefficiency, and he claimed his testing found that “a correctly-designed shroud” would increase the static thrust of a given propeller by over 100 percent. While many would be interested in seeing figures to back up this rather extreme claim, his other claim that a shroud greatly reduces propeller noise is perhaps more palatable and easy to accept.

The basic performance figures of the XBD-2 are impressive. At 9,000 feet, max cruise speed was said to be 179 mph at 16 gallons per hour. Max rate of climb at maximum gross weight was listed as 1,050 feet per minute with both engines operating and 720 feet per minute with one engine shut down, and the service ceiling was 21,000 feet on two engines and 14,500 feet on one. 

Takeoff distances were similarly impressive. While the company didn’t specify at what weight the numbers were achievable, they claimed only 300 feet was required for the takeoff roll, and 500 feet was required to clear a 50-foot obstacle. 

Ultimately, the XBD-2 logged approximately 50 hours of flight time before being permanently retired. No further derivatives were ever produced, and neither the BLC system, the coupled twin engine configuration, nor the shrouded propeller would make an appearance in any of Bede’s subsequent designs. Today, the sole XBD-2 is on display at the Manitowoc County Airport in Manitowoc, Wisconsin.

The post Bede XBD-2: Experimental Prototype for Unique Technologies appeared first on FLYING Magazine.

During the 1960s and 1970s, many aircraft companies developed twin-engine derivatives of their existing single-engine offerings. Piper produced the Seneca, which was essentially a Twin Cherokee Six. Cessna produced the Skymaster, which could be considered a twin 210. And Grumman created a twin-engine version of the single-engine Tiger called the Cougar.

Whether the demand for twins was a function of a real or perceived lack of engine reliability, or whether it was simply a sign of the industry taking advantage of robust demand for aircraft across all categories is unclear. But what is clear is that aircraft owners and operators had twin fever, and in the rush for market share, even smaller, more specialized companies like Helio responded to the demand and began designing twins.

Starting with their successful short takeoff and landing (STOL) Courier, Helio engineers removed the original engine and placed two 250 hp Lycoming O-540 engines on the wing. With nothing remaining in the nose, they cleverly solved one common challenge among taildraggers—poor forward visibility—by incorporating a helicopter-style bubble window in the nose.

To improve forward visibility even further, they also shrunk the instrument panel, relocating many gauges, switches, and the throttle quadrant to an overhead panel. This had the added benefit of placing engine-related controls and gauges closer to the engines themselves. When combined with the glass nose, the tiny panel afforded pilots outstanding forward visibility.

To maintain the single-engine Courier’s utility in challenging, off-airport operations, they retained the tailwheel configuration as well as the traditional Helio wing design. Utilizing large flaps and slats for better performance at high angles of attack, the wing also incorporated roll control spoilers that deployed with the ailerons to improve roll response at low airspeeds. Helio added a thin, slotted airfoil spanning the two engine nacelles to later models, reportedly to improve boundary layer control over the center section of the wing.

First flight took place in April 1960, and it quickly became evident the engineering worked. Helio touted a 320-foot takeoff distance over a 50-foot obstacle, though it is unclear upon what weight this was predicated. A 1964 evaluation flight by Air Progress, however, reported a takeoff ground run of only 250 feet at a light weight with a 7 mph headwind.

Other performance specs were similarly impressive. The FAA type certificate data sheet lists a single-engine minimum control speed (Vmc) of 59 mph, and Helio claimed a minimum speed of 35.7 mph. Rate of climb with both engines operating was said to be 1,600 fpm, and single-engine rate of climb, 310 fpm. Range was listed as 808 miles.

FAA type certification was awarded June 11, 1963, and Helio gave the Twin Courier a designation of H-500. Foreseeing military use, the U.S. Air Force assigned the designations U-5A and U-5B to the naturally-aspirated and turbocharged versions, respectively. But despite the certification and preparation, only seven examples would ever be produced.

The operational history of these seven aircraft is as unique as their appearance. While Helio publicly stated that all Twin Couriers were delivered to the CIA, they would go on to operate in clandestine operations under various entities of the U.S. military and government. Over their operational lives, some would be given USAF markings, while others would wear civilian paint schemes and civilian registration numbers. The N-numbers were registered to entities speculated to be shell companies for the CIA.

Tracing their operating missions, locations, and agencies is no small feat. Dr. Joe F. Leeker of the University of Texas, Dallas, has compiled what might be the most comprehensive history of the Twin Courier. In it, he traces the progression of each airframe through its respective history, noting that they saw service in Nepal, Bolivia, Peru, and the U.S. before being transferred to—and disappearing in—India. From there, the trail goes cold, and no Twin Couriers are known to exist today.

We can speculate, however. Given the rugged, remote areas in which the aircraft were known to operate, demanding airstrips and conditions likely claimed more than one aircraft. It’s plausible that one or more examples went down in inhospitable terrain and were swallowed by nature and the elements. Others were probably cannibalized for their rare parts. And given their shadowy history, it’s also possible that every trace of the type was intentionally scrapped and concealed from public view.

Considering the clever engineering and intriguing history of the Twin Courier, it’s unfortunate none exist today to be admired in person by future generations. Despite being certified by the FAA, it’s unlikely more will ever be built. In the meantime, we’re left with a small handful of photos, tiny scraps of unclassified U.S. government documentation, and a five-second cameo in the 1965 Jean-Paul Belmondo film, Up to His Ears.

Ultimately, the Twin Courier was an example of the long-standing effort to blend rotary-wing utility and fixed-wing speed, able to operate into and out of tiny, unimproved clearings while still providing relatively brisk cruising speeds. Today, tiltrotors fill the role admirably, but had the Twin Courier been given more of an opportunity to prove itself, it’s possible it would have provided similar functionality in a smaller and considerably less expensive package.

The post The Clandestine Legacy of the Helio Twin Courier appeared first on FLYING Magazine.

The late 1950s were an exciting time for Cessna. Demand for general aviation aircraft was robust, and thus, the company invested significant resources into identifying and pursuing emerging markets. One such market during that time was corporate travel.

Corporate aviation had existed for decades, but the post-war environment rekindled the segment. A handful of companies converted larger, former military types into executive aircraft, but most new models under development—such as the Aero Commander 500 series and Beechcraft Queen Air—had relatively small cabins. Others, like the Twin Beech, were relatively slow and lacked pressurization. Cessna saw an opportunity.

Launching a massive market research project, Cessna interviewed several hundred executives and corporate pilots who either operated or were interested in purchasing a new corporate aircraft. As Cessna’s marketing team categorized and studied the responses, they identified six very consistent concerns: safety, all-weather capability, comfort, speed, economy, and general utility. Using these themes as guidance, the engineers got to work.

In 1956, the Cessna 620 emerged. Its name derived from having twice as many engines as the 310, the four-engine pressurized corporate aircraft was something altogether different for Cessna as well as for the market as a whole. With a wingspan of 55 feet, a fuel capacity of 535 gallons, and a maximum takeoff weight of 15,000 pounds, it was by far the largest civilian Cessna model to date.

The 620s design and performance reflected the marketing study perfectly. The four-engine configuration was regarded as a significant safety feature compared to existing twins. It was equipped with a Garret turbine auxiliary power unit (APU) that pressurized the cabin, and supercharged, 350 horsepower Continental GSO-526 engines that enabled a service ceiling of 25,000 feet and provided a means of flying above inclement weather.

The 620’s tall cabin enabled comfortable movement within. [Credit: Textron Aviation, Inc, all rights reserved]

Compared to existing 6- to 8-place cabins, the 620’s cabin was massive. The oval cross section provided six feet of height, various seating configurations could be utilized, and niceties such as a lavatory and baggage area were installed for long-distance comfort. Comfort was important, as achieving the maximum 1,700 miles of range at a cruising speed of 260 mph would mean long stints aloft.

The cruise speed was reportedly considered acceptable by the focus group, however. This was fortunate, as it enabled the use of smaller piston engines as opposed to turboprops, which Cessna reasoned would have resulted in an unacceptably high purchase price. Cessna also touted the piston engines as more easily serviceable at out-of-the-way locations than turbines.

Convinced the 620 had a bright future, Cessna constructed a full-size cabin mockup and sent it to trade shows, where it was showcased alongside existing aircraft. Smaller mockups and technical displays accompanied the cabin mockup, touting the 620’s ability to utilize its APU where ground power wasn’t available. The marketing team also displayed individual technical components of the aircraft such as an engine and a propeller.

Cessna’s marketing effort for the 620 was strong, utilizing both miniature and full-sized cabin mockups. [Credit: Textron Aviation, Inc, all rights reserved]

In August 1956, the 620 made its maiden flight. Test pilots reported great handling characteristics, and Cessna began collecting refundable deposits. The price of the 620 had increased substantially above the original target price, however, and had reached $375,000—the equivalent of $3.9 million today.

For perspective, the Learjet 23, which was only about five years away, would initially sell for $489,000. While still a significant premium above the 620, it would be a sign that smaller corporate jets were poised to take over. Additionally, sales numbers of corporate piston aircraft such as the Howard 250 were relatively small, further suggesting the segment’s future would burn jet fuel. 

Cessna President Dwane L. Wallace (left) poses with the 620. [Credit: Textron Aviation, Inc, all rights reserved]

Just over a year later, Cessna made the decision to cancel the 620 program entirely. The single prototype was scrapped, and the company’s largest corporate aviation offerings would be limited to the 400-series twins until 1968, when the Fanjet 500 would make its debut. This, of course, would evolve into the wildly successful Citation series of business jets. 

Whether the 620 would have captured a significant share of the market during that ten-year gap is arguable. It’s possible Cessna could have sold enough of them to create a notable chapter in corporate aviation history. But it’s also possible the development, launch, and manufacture of the unusual four-engine airplane might have robbed critical resources from the development of what would become the Citation, thus hobbling the company for decades to come.

The 620, therefore, is relegated to a curious and unique footnote in the history of corporate aviation, demonstrating what can be accomplished with outside-the-box thinking…and also what can be accomplished by instead opting to pursue more viable alternatives.

The post The Four-Engined Cessna and Its Corporate Mission appeared first on FLYING Magazine.

In the world of aircraft design, the late 1930s and early 1940s were defined by rapidly-expanding technologies and open minds with which to pursue them. Tricycle landing gear had recently surfaced, and retractable landing gear enjoyed new popularity. All-metal airframe construction quickly gained traction as well, replacing fabric coverings. 

As aircraft designs advanced, engineers pushed the limits ever further. In late 1939, when the Army requested a new fighter that performed better than any existing fighter at a lower price, the Curtiss engineers indeed challenged convention. They responded to the Army proposal with a swept-wing canard, powered by a 1,275 hp Allison V-12 as found in P-38s, P-40s, and P-51s. Unlike these more conventional aircraft, however, the XP-55 design mounted it behind the pilot and drove an aft-mounted pusher propeller.

Curtiss reasoned that the XP-55 would provide many benefits over traditional designs. They claimed the unusual configuration would achieve equal or better speeds, better maneuverability, and superior outward visibility. They also touted design aspects that would make the XP-55 a safer aircraft for the pilot, including the superior ground handling characteristics afforded by the tricycle gear and engine placement that would help protect the pilot from engine fires. 

One unique safety-related feature was a jettison system for the propeller. In the event the pilot was forced to bail out, they could first pull a lever that would detach the propeller entirely. The propeller would depart the aircraft, thus providing a clear exit path for the jumping pilot.

The Army awarded Curtiss the contract, and Curtiss proceeded with building a flying testbed to test flight characteristics. Designated the CW-24B, it utilized a diminutive Menasco C6S-5 Super Buccaneer 6-cylinder inline engine that produced 275 horsepower—1,000 less than the XP-55.  Because of the lower power rating, Curtiss engineers reduced weight wherever possible, utilizing a fabric-covered steel tube fuselage and fixed landing gear that occasionally sported wheel pants. 

Although the CW-24B could reportedly only attain 180 mph, it sufficed for testing purposes and produced valuable data. As a result of 169 flights between December 1941 and May 1942, engineers determined the need for various aerodynamic modifications. They increased the wingspan, added larger vertical stabilizers to the wingtips, and added dorsal and ventral fins to the engine cowl—all to improve stability and controllability.

The first of three XP-55s made its maiden flight in July 1943, only to reveal significant controllability issues that the CW-24B failed to uncover. In addition to insufficient pitch authority on takeoff, the first prototype struggled with inflight stability—so much so that when a test pilot entered a stall, the aircraft flipped over and entered an unrecoverable, inverted descent. The pilot managed to bail out, but the first prototype was destroyed. 

Curtiss proceeded to build and fly the second and third prototypes, and testing continued. Despite significant efforts to address the aircraft’s deficiencies such as poor stall recovery, insufficient engine cooling, and performance that remained inferior to existing, conventional designs, these issues would remain unsolved. In addition, the jet-powered Bell P-59 Airacomet had, by this time, been flying for nearly two years, and it was becoming clear that jets would replace propeller-driven fighter aircraft. The XP-55 program was, therefore, discontinued.

In 1945, the third XP-55 was chosen to fly in an airshow held in Dayton, Ohio. Tragically, while performing a roll in front of the crowd, the aircraft dove into the ground, killing the pilot and leaving the second prototype as the sole remaining example of the type. Today, that XP-55 is on display at the Air Zoo aviation museum in Kalamazoo, Michigan. 

The post The Short, Unconventional Life of the Curtiss XP-55 Ascender appeared first on FLYING Magazine.

The National Museum of the U.S. Air Force is the world’s largest military aviation museum. Its 19-acre campus holds an unprecedented collection chronicling not only the history of the U.S. Air Force but also the history of flight and advancements in aviation and space. Nestled throughout this impressive collection of more than 350 aerospace vehicles is a one-of-a-kind collection representing the invention and evolution of stealth technology.

Whether you are drawn to the speed and maneuverability of stealth fighters, or the size and endurance of the lethal stealth bomber, you can see it all when visiting the National Museum of the U.S. Air Force.

Until the mid-1950s, speed and altitude provided the cover necessary to shield aircraft from the threat of enemy jets or missiles. But in 1960, a U-2, piloted by Central Intelligence Agency (CIA) civilian pilot Francis Gary Powers, was shot down over the USSR while photographing missile sites. Speed and altitude no longer guaranteed successful surveillance operations and the race to develop new technology began.

Since that time, the United States has developed ever-increasing proof-of-concept aerial vehicles that allow its military forces to successfully penetrate enemy defenses without detection.

“Stealth technology is largely a function of visual acoustic, heat, infrared, and radar reduction processes,” said National Museum of the U. S. Air Force curator William McLaughlin. “High frequency waves measure distance and size by the amount of time it takes for the wave to bounce off the object and return to the originating station. In order to effectuate stealth technology, the aircraft must minimize its radar cross-section.”

SR-71 Blackbird

The SR-71 Blackbird is the genesis of stealth technology while still using speed as a major component of its safety and defense mechanisms. Developed by Lockheed’s “Skunk Works” program for the CIA’s overflight and surveillance program, the SR-71 is an early predecessor to the technologies of today, including radar diffracting coating and sawtooth paneling that absorb radio waves that hit the aircraft. 

F-117A Nighthawk

“Speed and the SR-71 still provided great tools to the U.S. Air Force, but not every air platform is capable of that,” said McLaughlin. “You need to have different aircraft that are capable of lowering the threshold to penetrate enemy integrated air defense systems allowing the lethal strike package to follow.”

The world’s first true operational stealth aircraft capable of attacking high value targets without being detected by enemy radar went into development in the 1970s—the Lockheed F-117A Nighthawk. This revolutionary airframe featured hard angular deflections, a radar-absorbing coating, a platypus tail made of ceramic and composite materials to disperse heat signature, and sawtooth paneling on the wings. It first saw combat during Operation Just Cause in December 1989 and was awarded the 1989 Collier Trophy for its significant achievement in aviation. The Nighthawk came to fame during Operation Desert Storm flying 1,300 missions with no losses and 40 percent aggregate target strikes, destroying the Iraqi air defense system and its command-and-control nodes, according to McLaughlin.

B-2 Spirit

Maturation and advancement of the F-117’s development principles were applied in the development of what would become the U.S. Air Force’s stealth bomber fleet.

The Northrop Grumman B-2 Spirit merged the successful stealth technologies present on smaller fighter jets and unmanned surveillance vehicles into a long-range bomber capable of delivering large payloads of conventional or nuclear weapons. With the support of the U.S. Air Force tanker fleet, the B-2 has true global reach, with the ability to fly from Whiteman Air Force Base (KSZL) to almost anywhere in the world and back. Visitors entering the Cold War Gallery are immediately greeted by the B-2’s “flying wing” design that incorporates composite materials, special coating, and classified stealth technologies, which make it practically invisible to even the most sophisticated air defense radar systems.

F-22 Raptor

The U.S. Air Force soon identified the need for a new air superiority fighter—enter the world’s first stealthy air dominance fighter, the Lockheed Martin F-22A Raptor. The Raptor’s design is a collaboration with Boeing (wings and aft fuselage), Pratt & Whitney (engines), and Lockheed Martin (forward fuselage) to create stealth, maneuverability, and the ability to fly long distances at supersonic speeds (known as “supercruise”). The cockpit is painted with a composite material that aids in radar deflection, allowing the pilot to maintain a broad aerial view without risking radar detection; and the thrust vectoring allows it to enhance maneuverability by changing the angle of the thrust emitted by the aircraft. “This speed and stealth combination make it one of the premier fighters in the world today,” said McLaughlin. When paired with the F-35, the U.S. truly has an almost unmatched air superiority package.

Don’t Miss the Rest of the Stealth Collection

The museum’s stealth collection goes beyond these iconic aircraft. During your visit, you can also see:

• The Lockheed D-21B, a highly advanced, remotely piloted aircraft
• YF-12, a high-altitude, Mach 3 interceptor to defend against supersonic bombers
• Boeing Bird of Prey, named for its resemblance to Star Trek’s Klingon spacecraft, this single-seat stealth technology demonstrator was used to test “low-observable” stealth techniques.
• Northrop Tacit Blue, a proof-of-concept aircraft that demonstrated stealthy aircraft could have curved surfaces leading to later aircraft such as the B-2.
• The Northrop McDonnell Douglas YF-23A Black Widow II, which was designed to replace the F-15 Eagle; two prototypes were built, but full-production was halted in favor of the Lockheed F-22A.

Visit the website for the National Museum of the U.S. Air Force today and begin planning your visit.

The post National Museum of the U.S. Air Force – Stealth Aircraft appeared first on FLYING Magazine.

Among the many post-war aircraft that were developed in the late 1940s and 1950s, one of the more interesting and lesser-known examples is the Convair L-13. Tasked with creating a multi-purpose liaison aircraft with STOL capability, the designers strongly prioritized function over form. The result was an aircraft that visually seems to have been cobbled together by Dr. Frankenstein’s aerodynamicist cousin, yet met its challenging design goals nicely.

The L-13 was initially developed by Stinson, and the first two prototypes were constructed in their Michigan facility. When Stinson’s parent company, Consolidated-Vultee, sold the Stinson division to Piper in 1948, the L-13 was retained and ultimately marketed and built as a Convair. Roughly 300 examples were built between 1946 and 1947.

In photos, the L-13’s size seems to be on par with other liaison aircraft of the era. In person, however, its relatively large size becomes apparent. With side-by-side seating for the two occupants up front, the cabin can also accommodate two stretchers, enabling air ambulance duties. 

The aircraft originally came with a six-cylinder, geared Franklin O-425-9 that produced 245 horsepower. Because of the massive wing and airframe it was asked to pull through the air, cruise speed of the L-13 was only 92 mph. Fortunately, the low-speed STOL performance was exceptional.

Sporting an empty weight of 2,023 pounds, a “design gross weight” of 2,900 pounds, and a “max overload” weight of 3,700 pounds, the L-13 was far heavier than other 2-seat liaison aircraft of the era. Nevertheless, at 2,700 pounds, it was able to take off in 230 feet and land in 227 feet. At that weight, the flight manual lists stall speed as 43 mph, and the company’s public relations material noted that to achieve this landing distance, the pilot must fly the approach at 43.5 mph. 

Though the wing was entirely different from existing Stinson wings, it did incorporate the leading-edge slots as found in the smaller 108. These helped to maintain airflow over the ailerons when flying at high angles of attack, thus preserving roll authority during low-speed STOL operations.

More Stinson DNA is evident in the fuselage—the occupants are protected by a steel-tube structure, again like the 108. Given the airplane’s intended mission of operating in challenging, remote areas, the increased crashworthiness must have been appreciated by pilots and passengers alike.

Because many of these areas were so remote, the military demanded that the aircraft be easy to transport. Stinson obliged with some creative innovations. Most obvious is the aircraft’s ability to be folded down to a small size. By folding the wings backward and the horizontal stabilizer upward, it could be made small enough to load into the back of transport aircraft of the era such as the Fairchild C-82 Packet.

The military also wanted to be able to tow the aircraft behind a Jeep using existing roads. To accommodate this, Stinson enabled the main gear to be pivoted inward to reduce the width. While the gear were still too wide to fit into the tire tracks of the Jeep’s narrow track, they folded to within a half inch (61.6 inches) of the Jeep’s overall width.

When the military desired to transport the aircraft across vast distances where no suitable roads existed, they could tow it behind a larger aircraft with more range, such as a Douglas C-47. This could be accomplished without having to remove the propeller at speeds of up to 150 mph. When the aircraft arrived over the destination, the L-13 pilot would release from the tow cable, start the engine, and proceed to the landing site under their own power. 

As no engine heat would be available with the engine shut down, one hopes those long flights were conducted with the winterized L-13B. Designed specifically for operations in cold climates, the B-model came equipped with a 50,000 BTU combustion heater, engine intake vanes, and blankets fastened to the walls of the cabin to retain heat.

As the military transitioned to helicopters to handle much of the L-13’s intended roles, the L-13 fleet was gradually released to civil owners. Faced with the reportedly challenging task of maintaining the relatively rare O-425 engine, many were converted to small radial engines such as 300 hp Jacobs and Lycomings. These radials provided increased horsepower and were easier to maintain than the original flat-six. 

Today, approximately 15 remain on the FAA registry. Several are on static display in museums, and a handful are maintained and flown by dedicated owners, casting large, slow-moving shadows upon observers below.

The post The Large, Slow-Moving Shadow of the Convair L-13 appeared first on FLYING Magazine.

At first glance, it bears a strong resemblance to the Cirrus SF50 Vision Jet. A sleek, low-wing, V-tail jet with a single engine mounted in a dorsal pod, the two aircraft share the same layout and look nearly identical. But in fact, the aircraft pictured is the sole Eclipse 400, and flew a full year before the Vision Jet’s maiden flight.

Initially known as the Eclipse Concept Jet, or ECJ, the 4,700-pound jet was intended to gauge market interest for a compact, four-place “personal jet,” and would have complemented Eclipse’s primary offering—the larger, six-place Eclipse 500. With their hands full with Eclipse 500 production, the company turned to a firm called Swift Engineering to engineer and build the smaller 400.

On one hand, the project was relatively straightforward, at least compared to a clean-sheet design. Swift would begin with a standard Eclipse 500, shrinking the cabin, redesigning everything aft of the wing, and maintaining 60 percent commonality with the existing jet. But on the other hand, the deadline was extremely tight, and the project would have to be completed in record time.

Using NASA’s secure Wallops Island facility on the Virginia coastline, the team got to work. Only 200 days later, the Concept Jet flew for the first time. Three weeks after the first flight, it flew to Oshkosh, Wisconsin, to be unveiled at EAA AirVenture 2007.

During the unveiling, Eclipse founder Vern Raburn announced that the $1.35 million aircraft ($1.8 million today) would initially be made available only to existing Eclipse 500 customers. He touted the jet’s efficiency, claiming a fuel burn of 45.5 gph at 350 knots. For comparison, Daher’s six-place TBM 960 turboprop will burn 57 gph at 308 knots, and the seven-place Cirrus SF50 Vision Jet burns around 65 gph at 300 knots.

The design similarities between the Cirrus and the Eclipse were perhaps more a function of convergent design as opposed to inspiration. Faced with the requirement to develop a single-engine jet, there are only so many places to position the engine, and every option naturally requires placement along the centerline of the fuselage. Because internal volume was a priority, it would have made little sense to stuff the fuselage full of engine and intake ducting. And in the interest of utilizing smaller and lighter landing gear, there would have been no space for a ventral engine slung beneath the belly.

A dorsal engine mounted atop the fuselage, therefore, was the only remaining option. There were multiple ways to keep the tail surfaces clear of the hot engine exhaust, including a H-tail or a Skymaster-esque twin-boom arrangement. Ultimately, both Cirrus and Eclipse/Swift found the V-tail configuration solved the problem in the lightest and most elegant manner. Looking at the two side-by-side, it becomes evident that the smaller, sleeker Eclipse is the sports sedan equivalent, and the larger, bulkier Cirrus is the SUV, complete with a third row of seats.

Despite garnering substantial interest and reportedly attracting nearly 100 deposits in the year following its unveiling, the Eclipse 400 program would progress no further. Eclipse’s business and financial woes would prove to become insurmountable, and bankruptcy, liquidation, and restructuring would relegate the sleek V-tail jet to a quiet corner of an Albuquerque hangar.     

There it remains to this day. Some parts have been taken from it to keep Eclipse 500s flying, but it is otherwise intact and could theoretically fly again one day. Given the realities of economics and liability, however, this seems unlikely. 

Whatever its ultimate fate, one hopes it won’t be dumped at a scrapper and destroyed. With any luck, it will eventually be donated to a museum, where future generations can appreciate it for what it is—a striking example of clever engineering and huge optimism for a market that wasn’t quite there at the time. 

The post The Little Eclipse Concept Jet That Almost Was appeared first on FLYING Magazine.

Ukrainian aircraft manufacturer Antonov is rebuilding the iconic An-225 Mriya, the world’s largest cargo airplane destroyed during Russia’s invasion of Ukraine, the company has announced.

Days after fighting began in late February, the iconic Soviet-era strategic airlift cargo airplane with the 290-foot wingspan was destroyed amid fighting at Gostomel Airport (UKKM).

• READ MORE: Ukrainian Officials Reveal Fate Of World’s Largest Cargo Aircraft, ‘Mriya’

Months later, however, Antonov said it had collected nearly a third of the materials needed to build the aircraft.

2/2 За наявною експертною оцінкою,на теперішній час є близько 30 відсотків комплектуючих,які можна використати для другого зразка. Вартість побудови літака оцінюється щонайменше у 500 млн Євро. Проте про конкретну суму поки говорити зарано. Більше інформації буде після перемоги

— ANTONOV Company (@AntonovCompany) November 7, 2022

“According to the available expert assessment, currently there are about 30 percent of components that can be used for the second sample,” the company said in a statement on social media. “The cost of building the plane is estimated to be at least 500 million euros. However, it is too early to talk about a specific amount. More information will be [available] after the victory.” 

• READ MORE: Mourning the World’s Largest Cargo Airplane: An-225 Mriya

Initial reports suggested that construction of the new aircraft was 30 percent complete—a figure Antonov later corrected as representative of the components required to build, according to the Kyiv Independent.

“Work on the new machine is being carried out at a secret location,” Antonov acting director general Yevhen Havrylov said, Kyiv Independent reported Monday. “The second An-225, which was never completed, will be supplemented with parts from the bombed machine and new parts.”

• READ MORE: New Images of World’s Largest Cargo Jet Show Details of Destruction

“Work on the new machine is being carried out at a secret location,” Antonov Acting Director General Yevhen Havrylov said. “The second An-225, which was never completed, will be supplemented with parts from the bombed machine and new parts.”

— The Kyiv Independent (@KyivIndependent) November 7, 2022

Earlier this summer, a former captain of the Mriya revealed details about plans to build a second version of the destroyed airplane. In a two-part interview released on Aerotime Hub, pilot Dmytro Antonov discussed how engineers would use an existing second fuselage of the An-225 to construct a complete airplane. He also offered reasons why the iconic type should return to the skies. 

“Everybody knows that we are going to do it, no matter what,” Antonov said. “It is confirmed at the highest political level, so, things are in motion.”  

• READ MORE: Ex-Captain on New An-225: ‘We Are Going To Do It’

Mriya‘s Unique Features

Built in the mid-1980s, the An-225 Mriya was a record breaker from the time it rolled off the production line, according to Simple Flying. And for good reason. In addition to being the heaviest aircraft in the world, the An-225 is known for having the largest wingspan and for carrying the longest piece of air cargo: two test turbine blades.

• READ MORE: New Video Shows Last Flight of An-225 ‘Mriya,’ the World’s Largest Airplane

#Ukraine‘s President Zelensky thanks the students and employees at “Antonov”, the Ukrainian airline, who created a model of their “Mriya” (Dream) aircraft, the world’s heaviest and with the largest wingspan, which the #Russians destroyed in the first days of the war. pic.twitter.com/AghJdEyh7o

— Kyle Orton (@KyleWOrton) June 20, 2022

Thom Patterson contributed.

The post Antonov Rebuilding World’s Largest Cargo Aircraft, ‘Mriya’ appeared first on FLYING Magazine.

“Holy snakes!”

Those were the first words out of my mouth when I laid eyes on the Hughes Flying Boat, aka the Hercules, colloquially known as the Spruce Goose. Not terribly poetic, I know, but it was from the heart.

The last time I was inside the Evergreen Aviation & Space Museum in McMinnville, Oregon, was 20 years ago, when the facility was under construction. At the time, the Spruce Goose was across the street in pieces, shrink-wrapped and waiting for installation. The museum was in the excavation stage, and I stood in the 7-foot deep pit that had been dug to hold the hull of the behemoth aircraft. 

On Friday, November 4, 2022, I was back, and face to face with one of the most iconic and impressive feats of aeronautical engineering ever achieved. Up until that moment, the largest airplane I had been physically close to was a Lockheed C-5 Galaxy that Dad had taken me to see when I was a kid. For the record, the Spruce Goose wingspan bests the C-5 by approximately 97 feet, and the tail of the wooden behemoth is over 100 feet tall. I submit the exclamation was warranted.

Let’s Take a Tour

The museum campus sports three buildings: a theater, a wing for more modern aircraft, spacecraft and the SR-71 Blackbird, and the structure that houses the Hughes Flying Boat. There are also several aircraft outside on static display, including multiple military jets, a Douglas C-47 that towed gliders on D-Day, a Boeing 747 painted in the livery of Evergreen Flying Service, and a McDonnell-Douglas VC-9C that served as Air Force Two for decades. There is also a waterpark, Wings and Waves, for those who desire a more kinetic experience.

The star of the museum, of course, is the Flying Boat, the largest seaplane in the world, which was apropos for my visit on a really rainy day even by western Oregon standards—ducks were donning rain gear and frogs were wearing flotation devices. 

Barry Greenberg, the secretary/treasurer of the museum, chairman of the collection and acquisitions committee, and founder of the Spruce Goose Advisory Board, escorted me to the center of the main building where the Flying Boat reigns supreme.

I had been warned that the aircraft is so large that it’s hard to comprehend as you approach it. This is true. It takes you a moment to realize that the big silver-gray thing that is overhead is a wing. The aircraft sports eight Pratt & Whitney R-4360 Wasp Major 28-cylinder, air-cooled radial piston engines with four-bladed propellers—each blade longer than I am tall. I was told the hull measures 265 feet wide and the mid spar of the wings measures 322 feet.

Although the hull is countersunk into the floor by about 7 feet, a staircase is necessary to reach the main boarding door of the aircraft. There is a platform there with an informational plaque and a cadre of well-informed docents waiting to show you the aircraft.

We were greeted by Wayne Swanson, one of the docents who specializes in tours of the Spruce Goose. The docents at the museum wear green vests covered with military patches. The first thing Swanson showed me was a sample of the material from which the airframe is crafted—Duramold. The sample Swanson pulled from his pocket looked more like the layers from a Kit Kat candy bar rather than a slice of modern plywood. Duramold is a composite material made from birch wood impregnated with phenolic resin, then laminated and put under heat and pressure resulting in something as light and strong as steel.

“The skin is made of nine plies, but don’t call it plywood,” he said, as he tapped gently on the fuselage. The sound is unmistakably wooden. According to Swanson, 8,000 nails were used to hold the wood layers together as the three different types of glue and heat were combined to cure the material that would become the wings. A special nail gun was developed to put the nails in and another tool created to take the nails out when the wood and glue layers had cured.

Inside the Engineering Marvel

You enter on the cargo deck and the ceiling is high above you. It is almost like stepping into a cathedral. The aircraft smells different from the other restorations I have been aboard—it took me a moment to realize I was smelling the wood. Most large aircraft smell of plastic and metal. The first thing you want to do when you enter the flying boat is look towards the aft section. The museum has taken care to light the aft deck so you can see allllllll the way down the tail—a distance of approximately 200 feet down a tunnel of ribs that become progressively narrower. You get the impression of looking into infinity.

• READ MORE: When the ‘Spruce Goose’ Took Flight

Using a flashlight—a necessity as for the most part, the lighting inside the Spruce Goose is subdued—Swanson pointed out the details of the great airplane. For example, the

I-beams are made from laminated wood and are “super strong,” and the corner brackets—also made of wood, some of which are as thin as a playing card or a credit card, depending on the angle.

How can something so thin be so strong? Swanson explained, “In the 1940s they rotated the grain of each ply. The first one was vertical, the second was 45 degrees off, then 90, so everytime they put a ply in, they rotated the grain. Today they call that engineered plywood.”

Swanson proceeded to tap on the aircraft as he described the ribs of the aircraft, which measure 3 by 5.5 inches and larger where the wing joins the fuselage.

“That wing is 322 feet long,” he continued. “That’s end to end, and so big that you can’t build it in one piece. You have to build it in at least two pieces. They had a left half and a right half as you couldn’t even transport a 322-foot I-beam.”

The aircraft has a gross weight of 400,000 pounds. “[It’s] the same as a 747 and could hold 120,000 pounds of cargo,” he said.

Fuel Tanks

A lighted hatch leads to a bilge that holds the fuel tanks. The aircraft burned the 130 octane aviation gasoline available in the period. “Each tank has 900 gallons, and there are 14 tanks, which gives you 12,600 gallons,” Swanson said, adding, “Multiply that by 7 because each gallon weighs 7 pounds and that gives you almost 100,000 pounds of fuel.” (I did the math: it comes out to 88,200 pounds of fuel.)

Fuel hoses run from the bilge to each engine. Electric pumps moved the fuel. Hughes liked redundancy, noted Swanson. “Everything is in parallel. There are two fuel hoses and two pumps on each engine so if one fails, the other one takes over. He did an analysis of everything that could fail on the airplane, everything that could keep the engines from running and made sure it had two sources so there are two fuel sources, two oil sources, two hydraulic sources, two electric sources.”

The wings and the engine compartments are large enough for a man to stand in. The engines are placed at 20-foot intervals on the wings. According to Swanson, the original engines were rated at 3,000 hp, but then they were modified to 3,500 hp.

“A person can go to that engine in flight and adjust the throttle or tighten up hoses and things as all the accessories are on the back of the engine,” he continued. “A series of intercom radios enabled Hughes to communicate with the crew, which on the flight consisted of a pilot, [a] copilot, and [an] engineer for engine instruments, and a second engineer for utilities such as hydraulic pressure.”

A hydraulically actuated control system—developed by Hughes—was a necessity, as the size and therefore the weight of the control surfaces were far beyond anything that had come before. The ailerons, for example, measure 140 feet long. Although they were covered with fabric, it was said it would take the strength of 200 men to move them if the aircraft was rigged with cables and pulleys like the multiengine bombers of the day.

Fire Extinguishers and Beach Balls

Inside the cargo hold just behind a stanchion rope there are 16 red fire extinguishers—two for each engine—and a pile of inflated red, yellow, and blue beach balls. The beach balls are there for buoyancy should the aircraft go down on the water.

The application of the beach balls was a take on Hughes’ 1938 around-the-world flight where concerns about ditching at sea inspired him to load his aircraft with 80 pounds of ping-pong balls in the wings and fuselage to keep the aircraft afloat in the event of a water landing.

“He couldn’t get enough ping-pong balls for this airplane so he went with beach balls,” Swanson said, “although there is some controversy as to if they were on board during the one and only flight.”

Another Hughes engineering marvel was an electrical system of 120 volt DC, which allowed for the use of smaller cables and wires, saving considerable weight despite the miles of wiring required for the system.

The Flight Deck

The flight deck is above the cargo hold, accessed through a circular staircase. One of the first things you will notice when you get there are rows of what look like theater seats behind the raised platform where the pilots sit. This flight deck is spacious in every sense of the word. On the port side, there is a series of plexiglas windows that were installed when the aircraft was on display in Long Beach, California—the other side is solid bulkhead, leading a person to wonder how dark the aircraft was back in the day, when the only source of natural light came from cockpit windows.

The aircraft featured built-in coffee urns. [Courtesy: Meg Godlewski]

Hughes was known for eccentricities but he did like his comforts—there are built-in coffee urns on the flight deck.

The flight engineer’s station is located aft of the pilots’ seats on the starboard side of the fuselage. It is a wall of dials stacked 11 high and eight across next to panels of annunciator lights and switches. The dials measure manifold pressure, tachometer, oil temperature and pressure, fuel pressure, cylinder head temperature, and fuel flow—that’s how you keep track of eight engines. The other panels display the output of the three electrical generators, and monitor the aircraft systems for fire—a bad thing in any aircraft but particularly dangerous in one that is made primarily of wood.

Across from the engineer’s station are monitors for a series of strain gauges installed for the taxi tests. “They ran the engines when the aircraft was under construction but they couldn’t run them under load until the test flight,” Swanson explained, adding that the wing load of the aircraft had an arc of 13 feet “so they needed to structurally test where it was overbuilt or underbuilt.”

The information from each strain gauge was recorded on magnetic tape.

I was offered the chance to try out the left seat—and, of course, I had to put on the Hughes-esque hat that you must wear when you do this. Barry graciously took the right seat for the full effect.

The first thing struck me about the left side of the cockpit was the throttle quadrant—eight levers in all. As a multiengine pilot, I’ve had the experience of having to bring both throttles up simultaneously. I very gingerly stretched my hand out to see if I could get all eight levers at once. I didn’t move them—but hovered over them. The answer is yes, I can reach all eight at once. I share this as one of my siblings, when we were watching the movie, The Aviator, asked if I would be able to fly the Spruce Goose. I said yes, as it was all physics—bring the throttles up to get enough thrust to get airflow over the wings and up she goes.

There is another set of throttle levers on the copilot’s side—Hughes’ redundancy again.

The arrangement of the instrument panel is confusing by today’s standards. Most of the aircraft I have flown are post-1967 designs with the standardized placement of the so-called six pack: airspeed on the top row, far left; the attitude indicator then altimeter; then on the second row, left to right, the turn coordinator/slip skid indicator, heading indicator, and vertical speed indicator.

On the Spruce Goose, I had to spend a few minutes looking for these instruments—trying to do an IFR scan in this airplane would definitely be difficult. Some of the instruments are located below the pilot’s field of view, underneath the yoke.

The airplane has a slip skid indicator—two actually—without the upside-down “doghouse” markings, although there is a yaw indicator next to the one on the pilot’s side at eye level. The attitude indicator is the 1940s-style black ball with tick marks at the top to indicate bank angle and a stylized aircraft for pitch. The vertical speed indicator is located directly beneath the attitude indicator.

On the lower part of the panel there is the other slip-skid indicator, a radio direction finder and another AI.

There are dials to show aircraft trim for aileron, elevator, and rudder, which are managed by a joystick on the left side of the cockpit. There is a centralized gauge to indicate pitch. “DOWN” is in red. In addition, there is a mark on the windscreen, sort of a first-generation “heads up display” to help the pilot determine aircraft attitude.

The avionics, which were likely state-of-the-art at the time, consist of an ADF (automatic direction finder), an RMI (radio magnetic indicator), and a radio direction finder. (Hughes didn’t like getting lost.)

To the right of the pilot’s seat is a console filled with toggle switches and annunciator lights for all the aircraft systems—Hughes was known for always wanting to be in control, and this console is a testament to that. By comparison, the copilot’s panel feels rather sparse in instrumentation.

Directly over the cockpit is a roof hatch, which, if you are tall enough, gives you a great view of the top of the aircraft—and/or the harbor when you’re on the water.

During the one and only flight of the Spruce Goose, it only flew for 1 mile at an altitude of approximately 70 feet above the surface of the water; some say it never got out of ground effect. We will never know what its service ceiling was or how it handled during maneuvers—but that doesn’t take away from the feat(s) of engineering required to build it.

What the Visitors Say

I was not the only visitor that rainy Friday—there were several children, a few accompanied by parents and at least one school group. The children were as impressed as I was—I heard the exclamation “WHOAAAAA!” several times as they walked around the museum. One can only hope the next generation is inspired.

The post Inside the ‘Spruce Goose’ appeared first on FLYING Magazine.

November 1988 was an eventful month in the world of aviation. Within a two-week period, both the Lockheed F-117 Nighthawk and the Northrop B-2 Spirit were first unveiled to the public. This popularized the term “stealth” in the context of aviation, and it became known as a shadowy, top-secret technology that was able to render aircraft virtually invisible to radar. 

Fast-forward to April 1996, and another stealth-focused design was unveiled to the public with decidedly less fanfare. One look at the aircraft explained why. Rather than portraying a dark, ominous look, like the preceding two types, the Northrop Tacit Blue battlefield surveillance aircraft furrowed eyebrows and evoked more confusion than awe.

With a widely-spaced V-tail, a bulbous fuselage, and a large chine wrapping around the fuselage and giving it a boxy look from above or below, the Tacit Blue looked more bizarre than intimidating. Despite being engineered for low radar observability, this was not immediately apparent at first glance, and it lacked the matte black color of other stealth aircraft. Those working in the program gave it the nickname “Whale” and “Alien School Bus.”

The unconventional look of the Tacit Blue could be explained by the unique approach and constraints undertaken by the design engineers. They followed two requirements. The first was to create an efficient stealth reconnaissance aircraft that could loiter at low speeds near a battle zone while remaining undetected by the enemy. The second was to design the aircraft around a large side looking array radar (SLAR) with which the crew could provide real-time targeting data to a ground command center.

This was rather opposite from the existing convention. Historically, radar systems had been designed to accommodate an individual aircraft’s space and payload restrictions. But in the case of the Tacit Blue, they designed the aircraft around the radar.

This resulted in a unique airframe shape with odd proportions, and correspondingly unique solutions had to be found to make it flyable. The wing, for example, was just over 48 feet in span and utilized the 1930s-era Clark Y airfoil. An airfoil utilized by the Hawker Hurricane and the Spirit of St Louis, this was chosen in part for its efficient low-speed performance that provided good endurance. The aircraft was naturally unstable, however, so Northrop engineers designed a quadruple-redundant digital fly-by-wire flight control system to remedy this.

Two Garrett ATF3-6 turbofan engines—like those used in the Dassault Falcon 20—were selected to power the Tacit Blue. Unlike the Falcon, however, the engines were buried in the aft fuselage, necessitating the use of a single dorsal intake that fed both engines. This complicated certain operational aspects such as engine starting, but it also provided valuable internal space that could be used to cool the engine exhaust, reduce infrared emission, and help keep the aircraft from being detected by the enemy.

With all four flight control computers operating normally, pilots reported excellent flying and control characteristics. Predictably, these characteristics deteriorated as computers failed or were taken off line. Without any of the flight control computers operating, a Northrop vice president described the Tacit Blue as one of the most unstable aircraft ever flown. An engineer likened the stability with one operating computer to that of the notoriously unstable Wright Flyer.

Over a three-year period, test pilots logged approximately 250 hours in the Tacit Blue, validating both the stealth technology incorporated into the airframe as well as the massive SLAR contained inside. The resulting data aided in the development of several weapon systems, including one that evolved into the E-8 Joint STARS radar system. Additionally, multiple stealth characteristics were incorporated into the B-2 Spirit strategic bomber.

Only one Tacit Blue was built. Today, it remains on display at the National Museum of the U.S. Air Force in Dayton, Ohio.

The post Northrop Tacit Blue: Ugly Duckling of Stealth Aircraft appeared first on FLYING Magazine.

November 2, 2022, marks the 75th anniversary of the one and only flight of the Hughes Flying Boat, the so-called Spruce Goose. The massive machine is the crown jewel of the Evergreen Aviation & Space Museum in McMinnville, Oregon. The one-of-a-kind aircraft is the centerpiece of the museum in a building that was—quite literally—designed around it. And you better believe the museum is celebrating the 75th anniversary.

The Hughes Flying Boat

The aircraft was first conceived during World War II, when there was a growing need to get men and supplies over to England and Allied ships were being sunk at an alarming rate by German submarines.

In 1942, Henry Kaiser—a steel magnate and shipbuilder—came up with the concept of a giant seaplane to transport men and supplies. He enlisted the help of Hollywood producer and aircraft designer Howard Hughes. At the time, aluminum and steel were considered strategic materials needed for the war effort, so this aircraft had to be designed from non-strategic materials, such as wood.

It was constructed of Duramold, a composite material made of birch and resin, which is then laminated together.

The aircraft was originally designated as the HK-1, but when Kaiser dropped out of the project in 1944 due to frustration over construction delays, the behemoth aircraft was re-named the H-4 Hercules.

Delays would continue and the aircraft was not completed until 1946 after the war had ended. The aircraft cost $23 million to build, or about $352 million in 2022 dollars.

The name Spruce Goose was a pejorative nickname given to the project by Hughes’ critics. It was said that Hughes hated the name, as he thought of the aircraft as an engineering marvel, not to mention the aircraft was not constructed from spruce.

(Historians would later note that some of the men who worked on the airplane allegedly referred to it as The Birch Bitch, so perhaps Hughes accepted the lesser of two evils.)

The size of the price tag, not to mention the size of the airplane itself, raised eyebrows in Congress, as lawmakers who had allocated the funds for the airplane demanded proof that it could actually fly. The first step was to conduct taxi tests for the mammoth seaplane.

Thousands of people and scores of journalists turned out to watch the flight on November 2, 1947. Hughes was at the controls as he took the H-4 from its berth in Long Beach into the harbor. On board were dozens of crew members, along with a significant number of journalists from both radio and newspapers. Many more stood on the shore watching the spectacle.

Hughes made two taxi passes, keeping the aircraft below its 95 mph lift-off speed. On the third pass, he accelerated, allowing the aircraft to lift off.

“Two hundred tons are airborne!” crowed the newsreel announcer as the aircraft in the flickering black and white footage cruises over the water. 

The aircraft flew for approximately one mile at an altitude of approximately 70 feet over the water. When Hughes was asked if the 30-second flight was intentional, he replied, “Certainly. I like to make surprises.”

After the Flight

The H-4, however, never entered production and never flew again. 

Hughes had the aircraft moved into a climate-controlled hangar in Long Beach Harbor. It was off limits to the public. Despite this, until the end of his life, Hughes had standing orders that the aircraft was to be kept “one phone call away” from flight. 

The annual cost to mothball the airplane was $1 million, which included the salaries of the people whose job it was to keep the aircraft ready to fly. There were people who spent their whole career caring for an aircraft that never left the ground.

After Hughes’ death in 1976, the lease on the hangar expired and plans were made to dismantle the aircraft. Summa Corporation, Hughes’ holding company, wanted the aircraft to be divided up so components of it could be sent for display in several aviation museums.

The Aero Club of Southern California and the Wrather Corporation, which managed outdoor exhibits in Long Beach, California, such as the Queen Mary, stepped in to thwart the plan. The H-4 was removed from the hangar and transported by barge to Long Beach, where it became a tourist attraction next to the Queen Mary. The aircraft was placed under a large shell and put on display for the public. As the 1980s drew to a close, the Spruce Goose as it was now known had been sold to the Disney Corporation, and was now in need of a permanent home.

In 1992, Michael King Smith and his father Delford M. Smith, founder of Evergreen Aviation, founded the Evergreen Air & Space Museum and submitted the winning proposal to provide a home for the Spruce Goose. Both father and son were accomplished pilots and wanted to preserve the iconic airplane.

Years in the salt air under the shell had taken their toll. Smith’s plan called for the aircraft to be relocated to McMinnville, Oregon, where Evergreen Aviation was located. The Spruce Goose would become the centerpiece of an aviation museum.

The Big Move

The aircraft was disassembled, and the fuselage, control surfaces, wings, horizontal stabilizers and vertical tail were carefully shrink-wrapped to protect them. The disassembly took six weeks and left the airplane in 38 pieces. There were, however, a few surprises along the way. When the massive tail was pulled off the empennage, for example, it let go with a loud “pop!” like a champagne cork. The engines and propellers were also wrapped and shipped by truck. 

A hole had to be cut in the shell so that the rest of the aircraft could be loaded onto barges for its journey up the West Coast. It would travel up the Columbia and Willamette Rivers to Portland, Oregon. From there, it would be trucked to McMinnville some 50 miles away.

The conditions had to be perfect for the barges to negotiate the rivers. If the water level was too high, the barges could not pass beneath the bridges. It took several months for the barges to travel the distance to the location where the Spruce Goose was placed on flatbed trucks for the last 50 miles of the journey.

The last part of the journey was well documented, as people lined the streets. The pace was slow and methodical. In certain places street signs and telephone poles and wires had to be removed so the trucks with their bulky cargo could make it safely down the road. The entire trip took 138 days.

Restoration Begins

The first stage of restoration was accomplished over several months in a temporary facility at Evergreen Aviation at McMinnville Airport (KMMV). While the aircraft was restored, the museum, located about 800 feet away across the road, began to take shape. Sadly, Michael King Smith would not live to see the museum open. He was killed in a car accident before the building was completed. His father insisted on continuing the project.

On September 16, 2000, the aircraft—still under restoration—was painstakingly and slowly moved across the road to the museum. The work on the aircraft continued as paint was stripped, the skin re-sanded and the control surfaces reskinned.

When the museum officially opened on June 6, 2001, the Spruce Goose was in the center of the building, but not completely together. Its flight control surfaces were still undergoing restoration. The final assembly was completed on December 7, 2001.

The Spruce Goose Reigns Supreme

Today the Spruce Goose is one of 108 aircraft on display at the museum. It sits in the center of the building, its keel countersunk about seven feet into the floor.

The airplane is so large, according to the museum Curation & Collections Director Lydia Heins, that some visitors don’t realize they are looking at an airplane when they first lay eyes on it. After a few minutes, the sheer size of it registers, and they take it in, with some even venturing inside the mammoth aircraft.

“The cargo hold is available to enter and view with general admission to the museum, and visitors can take a guided tour of the flight deck with an additional ticket,” Heins said,  adding, “For the 75th anniversary year, we are workshopping new ways to enhance the aircraft experience for guests using more modern exhibitry tools available while preserving the integrity of this historic artifact.”

According to Heins, the museum staff are careful to protect the integrity of the artifact, as it is sensitive to climate conditions and external contaminants. Of particular concern is sun exposure, which degrades the composition of Duramold, as well as humidity, and extreme temperature fluctuation. The museum’s mission is to keep the airframe healthy enough to keep it on display.

“We are raising money during the 75th anniversary year to investigate supports for the wings and tail as the aircraft and Duramold material ages,” Heins said. The museum is focused on preserving the mechanical components and, “exploring what it would take to restore the Flying Boat to its original condition before it was placed on display in Long Beach,” she added.

Dispelling Rumors

There are some wild stories out there about the Spruce Goose, according to Heins, among them that the Spruce Goose has termites (not true), that the engines are fired up annually (not true), or that there is more than one Spruce Goose (so not true).

None of that is true, Heins said, adding that the termite reference was someone’s idea of an April Fool’s joke online that went viral. Termites are not an issue because the combination of preservation practices and the aircraft’s Duramold construction, which is essentially a chemically processed wood product, make the Spruce Goose unappetizing to the insects.

Hughes, who was renowned for his eccentricities, was also known for his engineering skills. As part of its collection, the museum is in possession of the technical data for the Spruce Goose. The material came to the museum “with more than a million pieces of paper about the fabrication and construction of the airplane,” Heins said. “We call that collection of documents the Hughes Archives, and it consists of original concept designs, original engineering drawings of every part of the aircraft, photographs and moving images, and testing reports.”

The Movie Connection

In 2003, when the Hughes’ biopic, The Aviator, was in production, movie production staff visited the museum several times as they worked to design and build sets for the all-important Spruce Goose flying scene.

The museum staff worked with set designers that built the full mockup of the flight deck, which required the recreation of the flight stations down to the levers and dials.

“The movie costume crew also visited the museum for information about the types of clothing worn by the workers who constructed the Flying Boat,” Heins said. “The color historic film footage also came from the museum’s collection.” 

After the release, the miniatures that were used in the production of the movie were donated to the museum and are currently on display.

The post When the ‘Spruce Goose’ Took Flight appeared first on FLYING Magazine.

In the early 1960s, the West German government presented aircraft manufacturer Dornier with a daunting challenge. Concerned that a conflict might destroy existing runways and render its airfields unusable, authorities asked Dornier to develop a vertical takeoff and landing (VTOL) transport aircraft. With significant experience developing unconventional aircraft, Dornier rose to the challenge and began designing what would become the Do-31, a transport jet capable of carrying 36 troops at speed up to 351 knots at 35,000 feet.

At the time, jet-powered VTOL aircraft had successfully flown, but all were smaller tactical and experimental types. Hawker had successfully built and flown the P.1127, which evolved into the Harrier attack aircraft. Other manufacturers had built similarly small VTOL jets, such as the Dassault Balzac V, the Short SC.1, and the EWR VJ 101. But no manufacturer had successfully integrated VTOL capability with a cargo platform.

Recognizing that engines are often the element that makes or breaks a design and budget, engineers first evaluated the existing market to see what, if any, off-the-shelf engines could be utilized. With such a limited selection of usable options, it didn’t take them long to decide on the Rolls-Royce Pegasus turbofan—as used in the Harrier—for the Do-31’s main powerplants. Unlike the Harrier, however, the engines would be mounted in underwing nacelles like modern turbofans. 

Each underwing Pegasus incorporated two inboard and two outboard rotatable nozzles for control. With two wing-mounted engines suspending the aircraft in vertical flight, a significant challenge presented itself—how to maintain altitude and control in the event of an engine failure? Unlike propeller-driven designs like the Boeing MV-22 Osprey and like Dornier’s own Do-29, there was no feasible manner of mechanically transferring engine power from one wing-mounted engine to the other.

Dornier’s solution was to add additional engines. Many of them, in wingtip pylons. Engineers weren’t able to find a suitable off-the-shelf option, and thus, Rolls-Royce was contracted to design and build the RB.162 turbojet specifically for the Do-31.

The diminutive RB.162 weighed only 280 pounds but produced 4,409 pounds of thrust—more thrust than the engines utilized on the Hawker 800 business jet. Dornier placed four of these wingtip lift engines in each wingtip pylon. This satisfied the Do-31’s thrust requirements, but more importantly, it enabled the aircraft to remain flyable and controllable even in the event of a main engine failure.

As outlined by NASA in a flight evaluation, the effect of a wingtip lift engine failure would be small and easily compensated for by the remaining engines. But even one of the main Pegasus engines failed, NASA found that “the aircraft can be balanced and a thrust-weight ratio in excess of 1 can be developed.” A look at the reference charts indicates this would only be true in cooler temperatures, but it nevertheless proves the design concept.

By rotating the main engine nozzles forward and aft, and by adjusting the power of the smaller wingtip lift engines, roll and yaw could be controlled. For pitch, bleed air from the main engines was plumbed to multiple nozzles in the tailcone. These nozzles would emit bleed air upward or downward to match the desired pitch control inputs of the pilot. 

Dornier ultimately succeeded in flying the 49,500 pound Do-31 both in the traditional fixed-wing aircraft regime as well as in VTOL flight. Two flying examples were built and went on to perform a variety of demonstrations and even set several world records. The technical and financial demands of procuring and maintaining the Do-31 proved to be insurmountable, however, and the project was abandoned in 1970. 

Fortunately, both flying examples were preserved, and remain on display at the Dornier Museum in Friedrichshafen, Germany, and at the Deutsches Museum Flugverft Schleissheim near Munich. To this day, the Do-31 remains the first and only VTOL jet transport ever built. 

The post Dornier Do-31: World’s First and Only VTOL Jet Transport Ever Built appeared first on FLYING Magazine.