Profile – Boeing 747 Pt I

In May 1964 the US Air Force initiated a design competition for a heavy logistics transport aircraft that would supplement its Lockheed C-141 Starlifters that were coming into service. The requirement was for an aircraft with the capability to airlift a payload of 56,700kg (125,000lb) over a range of 6900nm (12,800km), the ability to operate from the same length of paved or semi prepared runway as the C-141, and to land on 1220m (4000ft) semi prepared runways in combat areas. Known as the CX-HLS (Cargo, Experimental Heavy Logistics System), three companies, Boeing, Douglas and Lockheed were awarded contracts to develop designs that they had submitted further.

At the same time as design of the CX-HLS was taking shape, Boeing had two other major projects underway, a supersonic transport (SST) to rival the Anglo-French Concorde and Tupolev’s Tu-144 and, in its Aerospace Division, a manned orbital laboratory, MOL for deep space. These were new and challenging ventures but the CX-HLS, the designation for which changed to C-5A, was a well timed practical enterprise. C-5A plans were duly submitted to the Air Force but, after evaluation of the final proposals, Lockheed was declared winner of the competition on September 30 1965 and became prime contractor for the USAF’s new transport. It would enter service as the C-5A Galaxy and ironically nearly end up bankrupting Lockheed.

News of losing the military contract was understandably not greeted with cheers at Boeing considering the effort it had put into its CX-HLS design studies, but it meant that the company could now concentrate on a giant commercial transport. Even before declaration of the winner, a small design team had already begun working on a possible civil aircraft. With the competition over, it could now concentrate on its Model 747, the new addition to its 7X7 family of civil designations that had originated with the 707 not that many years before. If one venture had failed perhaps the other would enjoy success.

Under Chief of Technology Joe Sutter, who had helped develop the 737, Boeing engineers re-examined research used to design the big C-5A. They came up with some startling figures. The results of high lift studies coupled with improved leading edge and trailing edge flaps, would now enable a giant aircraft to land at existing world airports, a vital feature for sales success. Such an aircraft was also possible now because General Electric and Pratt & Whitney were developing completely new large, powerful turbofan engines. Using engines that were to have powered the C-5A, the superjet could promise a 25% reduction in per seat kilometre fuel consumption and so operate at much lower cost. Both Pratt & Whitney and General Electric had competed for the C-5A powerplant contract which General Electric had won. Now, both Pratt & Whitney and Boeing were therefore in the same boat. P&W had spent six years on developing its JT9D high bypass turbofan. The company had built a special factory just to assemble the engine because of the completely new tooling and methods of fitting parts. Boeing asked the obvious in that the JT9D now be perfected for its new Model 747.

The JT9D engine’s 2.44m (eight foot) diameter inlet was twice the size of the 707’s P&W JT3D long range turbofans yet it was only 325cm (128 inches) in length. It weighed 3845kg (8470lb) and was capable of generating up to 53,000lb (237.4kN) thrust. In order to test the engine in actual use, P&W leased a B-52 from the Air Force. After extensive modification to reinforce the wing, the huge engine was mounted in the place of two J57s. Trial results exceeded expectations.

To address the long range high traffic problem, Boeing at first considered a stretched 707, but this idea was already being put into effect elsewhere. Rival Douglas was in the process of extending its DC-8 production by a dramatic programme of stretching in its Super Sixty series. This idea was abandoned. Discussions with Pan American World Airways emphasised the need to build an aircraft that could accommodate as many as 430 passengers capable of speeds of more than 520kt (960kmh). Initial studies covered aircraft up to a gross weight of about 272,155kg (600,000lb). On its side, Pan Am was looking for a big aircraft that would save from 30-35% per seat mile. This would mean lower fares and cargo rates and give it a considerable market edge.

Even now it was thought at Boeing that the SST would capture most passenger traffic, so in planning the 747 fuselage shape designers considered that the basic 747 should be a freighter with container carrying capability. Double-bubble schemes with two pressurised tubes full of passengers, either side-by-side or superimposed, were studied as well as a single giant tube with two decks inside. A two deck ‘double-bubble’ fuselage with each deck some 4.57m (15ft) wide featured in initial proposals that were considered by a number of airlines. This failed to appeal so the project was reappraised. Maritime container shipping had proved successful, and in line with this thinking, a body was developed that would comfortably hold two 2.4m x 2.4m (8ft x 8ft) containers side by side. This was the origin of the ‘wide body,’ which at first had little to do with passengers or their comfort. The aircraft beginning to emerge from the drawing boards had a configuration that would take either passengers or freight, or a combination of both in a single tube but with only one enormous floor, extending right to the nose. In the long run, the SST would be cancelled and so it had no effect on the passenger market.

The high wing layout which had been considered ideal for the military transport was changed initially to a mid wing configuration with the two deck ‘double-bubble’ fuselage idea. Rejection of this led, in early 1966, to what looked basically like a ‘big brother’ of the 707, featuring the same low wing configuration, four wing mounted podded engines, a similar conventional tail unit, and tricycle undercarriage. Before production actually began, Boeing devoted 14,000 hours of wind tunnel testing to a variety of models.

The final version of the 747 fuselage had three decks. The flight deck, on a level above the main deck high on the forward fuselage, within the characteristic ‘hump’ fairing, permitted straight-in loading through a hinged nose door in freighter and convertible models. Behind the flight deck on some passenger models there was a comfortable upper deck lounge, reached by a spiral stairway from the main deck. The main deck could seat up to 500 passengers in high density 10 abreast seating (3+4+3), but 350 was judged a more likely number with a luxurious first class section (seating passengers in pairs along the sides of the nose) extending right up to the radar compartment filling the tip of the nose. First production 747 layouts were for 58 first class passengers, and 304 in economy. It could also be used for freight or a combination of freight and passengers. Below the main deck there was space for 26 containers, capable of holding 15 tonnes (16½ tons) of baggage, mail and cargo. There were three galleys, and the average crew consisted of the captain, the first officer, flight engineer, a steward, and 10 flight attendants.

The fuselage was of almost circular cross section, the flight deck high on the forward fuselage within the now easily recognisable ‘hump’ fairing, allowing the main passenger cabin to extend beneath it into the nose of the aircraft. Underneath there was room in the capacious bays for electronics, electrics, air conditioning and hydraulics, as well as cargo holds of unprecedented size. If necessary, galleys and other passenger service items could also be at the lower level. The most staggering feature of this fuselage was its sheer size. It provided a cabin 6.13m (20ft 1½in) wide 156.39m (185ft) long, looking in mock up like the imagined interior of some 21st century spacecraft, with an internal volume that appeared almost limitless. In fact the cabin was as long as the Wright Brothers’ first flight!

While Pan Am was considered to be the most likely launch customer, until there was positive airline interest Boeing could not make a final commitment to actually build the 747. Boeing was apprehensive about facing the massive development costs of such an airliner – at least $500 million in then year dollars. Each aircraft had an estimated price tag of more than $US17 million. It was too big a gamble for a single company ‘private venture’ construction and development programme. On April 13 1966, Pan Am brightened Boeing’s day by signing a $525 million contract for 25 aircraft, two of them freighters, together with spares. However, it was not until additional orders had been received from Japan Air Lines and Lufthansa that Boeing decided to begin construction. Not only did Boeing have to build the 747, it also had to create a new factory complex to do it. In June 1966, three months after the 747 programme was launched, 315 hectares (780 acres) of land were purchased next to Paine Field, Everett, Washington, for the construction of a special manufacturing complex. The new plant had the largest building (in cubic capacity) in the world, originally measuring 5.7 million cubic metres (200 million cubic feet). The building was later enlarged to accommodate production of Boeing’s 767 airliner and yet again for the 777.

First production operations at the Everett plant began in January 1967. The buildings were occupied in stages throughout the year as each was completed. Activation of the mammoth assembly line began on May 1, 1967, just over a year after the 747 programme was announced. Actual assembly of the first aircraft commenced the following September and later that year, components for the first nose section arrived from Boeing’s Wichita, Kansas Division. Because the job was so big, contracts were made with other industry related firms to make a variety of parts. Without outside help, 747 production would have suffered. Concurrently with the nose section, other components manufactured by major contractors arrived, and the job was at last underway.

While parts for the 747 were taking shape, another aspect of the project reached a conclusion. This was the ‘selling’ of the Class III 747 mock up on January 12 1968. The mock up was a full scale aircraft, minus engines, seats and one wing. Its purpose was to verify engineering drawings, determine assembly crew sizes and the tooling needed, set instruments for flight testing and check out specific airline cabin and cockpit arrangements. The ‘buyers’ were two Boeing men, the chief of Model 747 mock up engineering, and the chief of mock up quality control. Their acceptance meant that crews could start on non structural items such as wiring, panel making, tubing and pumps. The wing and body sections were already under construction.

The first wing assembly was removed from the assembly jig in March 1968. Pan Am’s appraisal of Boeing’s design had resulted in some changes being made, these including increased wing span, modification of the landing gear layout, and increasing the maximum takeoff weight to 308,443kg (680,000lb). The wing weighed 12,700kg (28,000lbs), ten times the gross weight of Boeing’s very first aircraft, the Model 1 “B&W” floatplane. The leading edge of each wing incorporated 10 variable camber flaps outboard and three section Krueger flaps inboard, while the trailing edge had inboard (high speed) and outboard (low speed) ailerons, and triple slotted flaps. Forward of these trailing edge surfaces were four flight spoilers (outboard) and two ground spoilers, or lift dumpers (inboard).

To ensure that the 747 could operate from existing runways, the aircraft required landing gear that would support and distribute the load effectively without causing damage to the runway. The tricycle landing gear as planned originally was to have had all four main units (two beneath the fuselage and one beneath the inboard section of each wing, mounted in line abreast), but this was changed before production so that the underfuselage units (retracting forward) were forward of the underwing units (retracting inward). The resulting main units, four in total, each had a four wheel bogie, and the nose unit featured twin wheels. All of the 16 main wheels had disc brakes and individually controlled anti-skid units.

Everything about the 747 was big from the very beginning. A new division of the Boeing Commercial Airplane Company, the 747 Division, was established and made directly responsible for all design, development, and manufacture. Not surprisingly, the first press reports of the aircraft were full of adjectives which implied that everything was on a giant scale. Very soon it was called a jumbo sized plane and this in turn led to the name “jumbo jet” by which it became popularly known throughout the world.

No prototype of the 747 was built. The original aircraft (RA001), intended to be the Company’s demonstrator, was rolled out at Everett on September 30 1968. By January 1969 the plane’s major systems had been activated, and its landing gear and flight controls operationally tested. Compass calibration, fuelling and engine tests were next. The 747’s first flight was scheduled for February 9, 1969. The three men in the cockpit were pilot Jack Waddell, copilot Brien Wygle and flight engineer Jess Wallick. At 11.34am, after travelling 1300m (4300 feet), less than half the length of Paine Field runway, the main gear left the concrete. Takeoff speed was 142 knots (264kmh). Waddell circled back over the airfield and climbed to the 15,500 feet (4725m) test altitude accompanied by an F-86 Sabre chase plane.

According to one of the witnesses on the ground, the engines “made no more noise than a stiff breeze through a forest.” After a series of sideslips and other tests, including one simulating the loss of hydraulics, he landed at 12.50pm. Quietly, almost serenely, the age of “widebody” transport jets had dawned. After ten hours flying time, the 747 was taken to Seattle for more trials. Testing now began in earnest with the participation of four more aircraft as they became available. The 747 testing programme was to be the most extensive ever undertaken in commercial aviation history. In addition to laboratory tests of parts and components, the programme included the assignment of the five Superjets to a $28 million, year long Boeing and Federal Aviation Administration flight testing and certification programme.

Boeing’s major difficulty was in keeping the gross weight of the 747 as close as possible to the originally projected figure of 308,443kg (680,000lb). Despite the most strenuous efforts there was a steady increase of structural weight, and growing system complexity added to the total. This meant that in order to maintain the payload/range performance which had been specified, it was necessary to increase maximum takeoff weight and this, in the case of the initial 747-100, rose to a figure of 322,051kg (710,000lb).

Another major problem, closely related to weight, concerned the Pratt & Whitney engines. As the gross weight of the airframe increased it became essential that the engines should develop greater thrust. Although a JT9D-3 rated at 43,500lb (194.9kN) thrust was readied for the production aircraft, it suffered from countless teething troubles. One of these was “ovalizing”. They changed shape after running under extreme loads. This distortion of the casings caused the blades to rub in a way that had not been apparent in more than two years of ground testing and flight development using the B-52. Pratt & Whitney had to devise a Y-shaped frame to hang the engine differently. In the meantime, airframes were lining up waiting for redesigned engines. By mid October 1969, 22 airframes were idle at the Everett plant, 17 of these without engines. Only when similarly rated but modified JT9D-3A engines were introduced into service later in 1970 were these problems finally overcome. Boeing customers could in the meantime select the engines of their choice.

By the time the first aircraft had rolled off the production line on September 30, 1968, a total of 158 orders had been received from 26 airlines. Aside from Pratt & Whitney, General Electric offered the lighter and equally powerful CF6-50 series derived from the C-5 Galaxy, chosen by several airlines, while Rolls-Royce’s RB211-524 series late comers in the field, were shorter and heavier but offered lower drag and unequalled low fuel consumption.

Static testing, using one of the non-flying airframes, verified the strength of the entire frame. In one test, the 747 wing tips were deflected upward 8m (26 feet) before structural failure occurred. Fatigue testing on another non-flying airframe duplicated the stresses experienced in day to day airline flying. The airframe was taken through the equivalent of 20,000 airline flights, or 60,000 hours. Following this, fail safe testing with the structure cracked or sawed through in 28 critical places, put the equivalent of 12,000 additional hours in airline flights on the structure. On June 3, 1969 the first 747 flew 4480nm (8300km) across the Atlantic for the Paris Air Show to prove that the giant airliner was capable of worldwide travel. Meanwhile, by the end of the year, the five 747s under the test programme had logged more than 1400 hours of flight time in 1013 trips aloft.

The FAA finally gave certification on December 30 1969. After they completed their tests, four of them were refurbished and delivered to waiting airlines for service. The fifth 747, the first one to fly, remained in test flight status with Boeing to check out various modifications for production improvements and is still performing this task today, a quarter century later. When Boeing delivered two 747s to Pan Am for pilot training, Pan Am’s president, Najeeb Halaby, took one up for a test of his own. His praise was lavish. The 747 “was the safest most comfortable, most magnificently built plane in history.”

The 747-100s, which first entered service with Pan Am had a maximum fuel capacity of 178,709 litres (47,210 US gallons), sufficient to enable a two seat light plane such as a Cessna 150 to fly a distance of almost one million nautical miles (1.8 million km). They could carry 385 passengers over a range of 4927nm (9136km) and land with specified reserves, giving it about the same fuel efficiency, but cruise six times faster than the light plane. All flight controls were powered, and an advanced automatic flight control system eased the pilot’s workload not only during long periods of cruising flight but also in making automatic landings under suitable conditions. So well planned was the flight deck and equipment of the 747 that they could be handled without difficulty by a flight crew of three, usually all pilots or two pilots and a flight engineer. Navigation to great accuracy was catered for by standard avionics systems, plus duplicated (later triplicated) inertial navigation systems.

On January 21 1970, Pan Am prepared to inaugurate its first transatlantic flight with the type, introducing it on the crucial New York/London route. It was made into a grand occasion, with many VIPs attending. The pilot started the JT9Ds but then cut them off. One engine was overheating and the flight was sadly aborted. After a 24 hour delay, on January 22, they tried again. The 747 taxied out but again the engine overheated and the flight was delayed. Ignoring the embarrassment of another false start, Pan Am quickly substituted another 747. This one took off without problems.

The age of the “Jumbo Jet” had arrived. Next issue: The 747 family begins to grow.