The story of the prototype 707.
- By R.G. Thompson
- Air & Space magazine, May 1987
Shortly after 3:30 p.m. on July 15, 1954, at Boeing Field in Seattle, a pilot who would have been tall even without his cowboy boots climbed down from the cockpit of Boeing’s Model 367-80 and allowed that “she flew like a bird, only faster.” Alvin M. “Tex” Johnston had just completed the maiden flight of what the Boeing crew had come to call Dash 80, after the final digits in its model number. Now that its first flight had been smooth as silk, the big four-engine jet, the prototype for the country’s first jet airliner, could finally be called an airplane.
Johnston may well have been so nonchalant because he knew that the prototype for the 707 commercial transport and KC-135 aerial tanker was no great engineering gamble. Boeing was the world’s foremost builder of large military multi-engine jets, specifically the B-47 and B-52 bombers, and Dash 80 was a logical descendant. In accounting ledgers, however, it was a huge gamble--$16 million in long-term red ink. After that first flight, and for a good while to come, Boeing would not have a single order to show for its investment.
The gamble eventually paid off, of course, in the sale of thousands of jet transports and tankers, in the domination of today’s market for transport fleets—and in the creation of the remarkable Dash 80, whose performance, usefulness, and longevity as a company aerial laboratory for new designs far surpassed its backers’ visions. In its 16-year flying career, Dash 80 made true believers out of the doubters in the commercial transport industry, who thought jets were uneconomical and ungainly. It flirted with the speed of sound, hung on the air by its claws at speeds as low as 80 mph, and served as the trainer for the first generation of commercial jet pilots. It gave birth to ingenious control surfaces and gave pilots their first look at video display cockpits and scores of other new instruments. It landed in mud as a double for Boeing’s version of the C-5A Galaxy, and it represented its builder in the SST race.
But as spectacular as Dash 80 was at its debut, a swept-wing, four-engine jet was anything but a hot item in the airliner market of the mid-1950s. The airlines had balked at the idea of a jet transport from the late 1940s, when the concept had first surfaced. The air carriers were still paying for the enormous number of piston-engine aircraft they had just bought as replacements for the pre-World War II equipment. Price-conscious airline executives thought jets would cost more to purchase and fly than their current fleet. They doubted that jets would fit into small airports and that an air traffic control system designed for smaller piston-engine aircraft could manage them. They worried that passengers would never accept airplanes without propellers. And these were Boeings. Virtually every airline had been buying Douglas aircraft for years. Boeing built bombers.
Despite the odds, Boeing president William Allen was determined to launch the commercial jet age and put his company in the lead. A reluctant executive, Allen had served as Boeing’s lawyer for 17 years before being virtually dragooned into accepting the president’s job in 1945. Although he had almost no experience in aviation, in a remarkably short time Allen had acquired a grasp of the company’s true position and possibilities. He realized that no competitor had Boeing’s experience in jet design and manufacture, but the company suffered from a near-total dependence on military contracts he knew that another piston-engine airplane would pose no threat to Douglas’ primacy in airliners. What Allen needed was a credible presence in the market.
Boeing’s only commercial transport at the time was the Model 377 Stratocruiser, a wonderfully comfortable but woefully uneconomical failure. A mere 56 had been sold at a loss of more than $13 million. Fortunately, the KC-97 military tanker derived from it had more than covered the bills. If Boeing’s piston-engine aircraft were faring poorly, the jet transport picture was even worse. The Boeing sales force had been soliciting orders for a commercial jet for three years with no luck. On the military side, the Air Force was also pinching pennies. It had refused to participate in the development of a jet tanker that would match the performance of its jet bombers. The Strategic Air Command could jolly well get by with its KC-97 tankers, even though the speed and altitude limitations of these slow, fat flying barges made the task of refueling fast, high-flying jets a dicey proposition for the crews on both ends of the refueling booms.
Believing that an airborne demonstrator would tip the scale in both the commercial and military markets, Allen met with his board of directors in May 1952 and persuaded them to bet every penny in Boeing’s coffers on a one-design, two-market prototype. He pushed for and won a $15 million commitment that later went up another million.
It was probably Allen the lawyer, not Allen the executive, who carried the day at that long board meeting. Although he may have cited the company’s lead in large-jet design and the eventual inevitability of the Air Force switching to jet tankers, it seems far more likely that he concocted a brilliant case designed to woo a jury rather than drawing up a reasoned strategy for investors. The minutes of that meeting remain locked up at Boeing, so very few people know what actually transpired. But whether it was the lawyer or the executive who won, any dissenters on the board would have long since rejoiced that one of them did.
Work got under way virtually the morning after the meeting. The project was code-named 367-80, to encourage competitors to think Boeing was having its 80th go at a variation of the Model 367, the company’s designation for the KC-97 prototype. In fact, Boeing’s preliminary design for a jet transport had been in the works since the late 1940s. Construction of the prototype began in a walled-off corner of Boeing’s Renton, Washington plant in November, and the rollout took place in May 1954—just 18 months later. The next year, Douglas decided to skip the prototype stage and go ahead with production of a four-engine jet called the DC-8.
To those who thought the Douglas DC-7 and the Lockheed Super Constellation were immense, Dash 80’s 128-foot fuselage and 130-foot wingspan were shockingly huge. But it looked like a pretty ordinary piece of work to the folks at Boeing—not that large compared to the B-52, and perhaps even a bit conservative in wingspan.
It was not the size but the design of the wings and engine mounts that gave Boeing its most important lead over its competitor. The 35-degree sweep of the wing and tail had been established through research that included a series of flights in a Bell L-39, which was a Bell P-63 with its wings swept. The same angle had been used on both the B-47 and B-52. With this angle, Dash 80 turned out to be 20 mph faster than the DC-8, with its 30-degree sweep.
The practice of mounting engines in pods on pylons below the wing began in 1947 with the B-47. Suspending the engines from pylons left room in the wings for fuel tanks. And in a crash landing, a pod could break away without damaging a wing or rupturing one of its fuel tanks. Unlike the bombers, which had their engines in pairs, Dash 80’s design called for a single engine in each pod, so if an engine blew up, it wouldn’t damage its neighbor. The arrangement also provided a more even distribution of the engine’s weight and allowed for lighter wings. And the pods opened up so that airline mechanics had easy access to each engine.
It was an impressive design, but not perfect: Dash 80 had some bugs in its tail assembly and landing gear, and test pilots Johnston and Richard “Dix” Loesch, along with engineer James Gannett, were responsible for shaking them out. Boeing could not have brought together three more diverse personalities. Chief pilot Johnston had all the swagger you expect in someone named Tex, though he could be reserved when he talked about airplanes. Gannett was his exact opposite, wiry and quiet. Loesch was the most reflective of the trio and easily the most emotional about the project and his memories of those days. But then, it was his luck to catch some of Dash 80’s wildest rides.
Landing an 80-ton airplane at speeds of 150-mph and less had been done before. But using only the wheel brakes to get one stopped within 6,000 feet on a wet or icy runway hadn’t, and that was as much room as the largest airports of the day had to offer. Large military aircraft landed on 10,000-foot runways with the assistance of a drag chute, an impractical system for airline operations.
Faced with these constraints, Boeing designers gave Dash 80 thrust reversers to accomplish what the reversing propellers on piston-engine aircraft did to reduce ground roll distances after landing. After evaluating three final candidates, the designers chose the folding W-shaped design that is now seen on the aft end of almost all jet engines. They also came up with a new version of the conventional tricycle landing gear, one that gave test pilots and engineers many headaches.
On the eve of the scheduled maiden flight, the left main gear collapsed after some taxiing tests. “Well, now is the time to learn these things,” Johnston said as he stepped out of the airplane. Dash 80 lay on the ground like an exhausted bird. At least the gear had performed as advertised: it broke away without damaging the wing or the fuel tanks. Dash 80’s first flight was postponed while engineers beefed up the gear structure and healed minor wounds.
Less than a month later, the airplane lost its nose gear. It happened after Johnston had been heating up the brakes with a series of high-speed ground runs and stops, then taking off to see what happened in the cold temperatures aloft—“cold soaking,” as engineers called it. What happened was an expansion of the hydraulic fluid on the ground and a contraction in the air. Unbeknown to Johnston, the hydraulic system responded by forming bubbles in the lines, which sensors interpreted as a broke brake line. Performing as designed, the sensors promptly shut off fluid flow to the brakes.
Johnston landed daintily, stepped on the brakes, and realized he had none. On one side of the field sat a row of private aircraft; on the other, a line of B-52s. Johnston had one place to go: a grassy median between the two runways. He hoped the soft earth would slow Dash 80 enough to let him swing the airplane around and roll to a stop. He recalls a sudden crunch. Contractors making runway repairs had left a big block of concrete exactly where Dash 80 would find it. It knocked the nose gear off and damaged the belly, but Boeing had Dash 80 flying again in about three days. A redesign of the braking system sensors solved the hydraulics problem.
Not long after that, Dash 80 chalked up a midair landing gear explosion and fire when the new anti-skid brakes turned out to be spectacularly efficient heat reservoirs. Johnston had heated the brakes doing ground runs, then had flown with the wheels down for 15 minutes to cool them. But as soon as the landing gear was retracted, there were several explosions accompanied by the smell of burning rubber. “There was smoke everywhere,” he recalls, “so I speeded up, put the gear down, and blew the fire out.” He didn’t need brakes to stop after landing—5 of the 10 tires were flat.
The final thrill involving Dash 80’s gear occurred during a test of the thrust reversers. After a series of landings, a hydraulic line let go and the flammable fluid leaked out onto a hot brake. The resulting blaze caused the crew to holler for the fire truck and abandon ship. Boeing replaced the entire hydraulic system with one that used less flammable liquid. “It was just another part of the learning curve,” Gannett said.
There were also problems with the design of Dash 80’s tail. All three test pilots had been aware of them from the start of the test flights, and apparently they were noticeable to others as well. However, they were not great enough to prevent Johnston from doing a seemingly impromptu barrel roll in front of 200,000 spectators. Then, for anyone who had missed it, he rolled Dash 80 again. In fact, Johnston’s famous rolls were a sort of pointed rebuttal. “I’d heard that Douglas was telling people our prototype was an unstable airplane,” Johnston says, “and I believe that when you fly for a company, you sell the product by demonstrating what it can do.”
The International Air Transport Association was meeting in Seattle, and airline executives from all over the world were scheduled to be at Lake Washington for the Gold Cup hydroplane races. “I knew we had to do something to impress ‘em,” Johnston recalls.
Earlier, when Allen had asked him to fly over the race course, Johnston decided he would impress ‘em by rolling Dash 80. Copilot Gannett had gotten an inkling of what was coming several hours earlier, when Johnston flew the airplane through a couple of rolls during a test flight. Allen, however, had no idea. When he looked up and saw his company’s biggest investment on its back, he looked like a clinical example of apoplexy, according to people seated near him. Everyone loved the stunt, but Allen never got over it. He fired Johnston at least a thousand times before they met the next morning and cooler heads prevailed. Nonetheless, the infamous maneuver was a forbidden subject in Allen’s presence for many years. At his retirement dinner in 1980, he was given a huge photograph taken from one of Dash 80’s windows while the airplane was upside down. He left it behind.
The stunt may have impressed airline executives, but it didn’t cure the problems in Dash 80’s tail fin, which had both a bad case of flutter and persistent Dutch roll.
Flutter is a vibration in the airframe that is induced at high speed in response to aerodynamic forces. It usually arises on an extremity, and, if left unchecked, it can intensify until it breaks up the strongest airframe. Dutch roll—so called because of its resemblance to the rolling side-to-side gait of ice-skating Dutchmen—occurs in all airplanes, but is harder to check in those with swept wings. As the airplane yaws from side to side, one wing advances and develops additional lift, causing the airplane to roll to the opposite side, which results in a combined rolling and yawing motion. If this motion continues, it creates a cycle of alternating, increasing yaw angles that can result in uncontrollable roll.
Dash 80’s original tail fin was short, compared with the fin of the B-52, and not much of a yaw inhibitor. Its size, coupled with the lack of a power boost for the rudder, may have contributed to its tendency to flutter. “Flutter…it was a black science then,” Dix Loesch says. “When the flutter guys started talking to their bosses, everybody else just sort of looked at the ceiling.”
Johnston hunted for flutter in Dash 80 early on, and he found it near maximum speed, where it can be expected. Even though the flight engineer’s instrument panel was shaking so hard the mounting bolts broke, Johnston coolly reported, “We’re experiencing an appreciable vibration up here.” Later, however, Loesch encountered flutter during normal climb.
“I did the normal things to fight it—leveled out, throttled back. They didn’t work. I thought the airplane was going to shake itself to pieces. All of a sudden the rudder froze, and the flutter stopped.” A minor structural failure saved the day—a balance weight had broken loose and jammed the rudder.
Whatever it was that caused Dash 80 to shake, rattle, and roll, Boeing discovered that changing the fin’s internal balance weights, increasing its size, and adding an electronic yaw damper and a hydraulically boosted rudder control ended the problems with flutter, yaw, and Dutch roll.
Late in 1955, orders started trickling in, then flowing. Douglas’ DC-8 orders were not far behind. By the end of 1959, 100 707s had rolled off the production line at Renton, and the first of several hundred KC-135s had been delivered to the Strategic Air Command. Dash 80’s career as a prototype and dealer demo was finished, but Boeing was not yet ready to put it out to pasture.
In the early 1960s, Dash 80 was used to test some modification that would later show up in the 727. These tests led in turn to a long stint with NASA and Boeing testing wings that can generate enough lift for the airplane to remain airborne at extremely low speeds. Dash 80 had averaged 612 mph during a transcontinental speed record flight in 1957. Now it was creeping around Seattle skies at 80 mph and landing at 92 mph. Dismayed commuter airline pilots had to S-turn their Douglas DC-3s on final approach to Boeing Field to avoid overrunning what appeared to be a 707. To preserve control at such ridiculously low speeds, Dash 80 sprouted a lush profusion of leading- and trailing-edge devices on its wings. Their appearance alone was enough to make test pilots blanch.
Gannett continued to fly Dash 80 throughout the low-speed tests, but Johnston and Loesch had moved on and were replaced by S. Lewis Wallick, recently retired from Boeing, and Thomas Edmonds, who is still a test pilot there. In test of leading-edge slats for the wing, engineers experimented with the curve of the slats by applying the file and fiberglass to the devices between flights. Leading-edge symmetry is critical—without it, an airplane tends to roll uncontrollably in a stall. This imprecise shaping of the wing made for occasional imbalance and some very sporty flying. Edmonds recalls a day when one flight was enough: “We stalled, rolled over to about 90 degrees to the horizon, did a split-S, and ended up headed in the opposite direction. We looked around, kind of startled, and decided there was no point in doing any more stalls that day.”
Dash 80 wore its high-lift wings to the end of its career, and Boeing and NASA engineers tested a series of design ideas that depended on solid control at slow speeds. The aging airplane was landed on grass, dusty lake beds, soft earth, and even mud, using a landing gear system being considered for what would become the Air Force’s enormous C-5A Galaxy transport. The landing gear spread the weight of the aircraft over 20 tires instead of Dash 80’s 10. The tires’ flotation allowed the airplane to land on dust-covered mud only marginally more supportive than yogurt.
In 1965, with a long needle-like sensing unit, a comical face painted on its nose in honor of its 11th anniversary, and computer-mediated controls, it imitated the landing characteristics of a series of supersonic designs for NASA. A second set of controls enabled the copilot to take over and fly the airplane normally, a precaution that allowed the computer to crash without the airplane following suit. Dash 80 also tested scores of cockpit instruments and controls, some of which later showed up in the video display cockpits of the 757 and 767. But this was the stuff of swan songs.
On January 22, 1970, after completing the last of a series of flights designed to test an automatic landing system for the space shuttle, Dash 80 went into retirement. Its logbook showed 1,691 flights over 16 years for a total of 2,349 hours and 46 minutes, but it was not quite closed. In 1972 Boeing returned Dash 80 to nearly original condition for a reenactment of the record-setting cross-country flight. It ended in Washington, D.C., where Boeing presented the grand old 707 prototype to the National Air and Space Museum.
After the ceremonies, Wallick and Edmonds ferried it west to Davis-Monthan Air Force Base in the preserving climate of the Arizona desert. For the past 15 years it has sat patiently at an aircraft storage depot, awaiting a slot at the Museum. The paint scheme Boeing once described as “an eye-catching blend of canary yellow, chocolate brown, and silver” has faded, but Dash 80’s legend and legacy are likely to endure at least as long as its tired aluminum can hold together.