Boeing - 707-320
The development of the Boeing 707 had been driven primarily by the requirements of Pan American World Airways, which under the direction of its charismatic President Juan Trippe had ordered 20 of the initial version the 707, the -100. Ominously for Boeing, Trippe had also ordered 25 Douglas DC8-30s, a heavier and more capable aircraft than the 707-100. Boeing enjoyed a one year lead on Douglas’s DC-8, but Trippe’s Director of Operations John Borger had intimated to Boeing directors that it was because of this year’s lead that Pan American had ordered the 707, so as to be the first American airline to operate jets. If Boeing could not produce a 707 which would meet Pan American’s requirements future orders would be for the DC-8. The 707s wing was the problem, it was too small. Pan American’s consultant Charles Lindbergh had counselled Boeing during the development of the 707, that they should incorporate ‘stretch’ into the design, but it was clear that the existing wing would need to be improved. This situation catalyzed Boeing into producing the 707-300, a heavier, larger and more powerful intercontinental aircraft to compete with the DC-8-30. The 707-100 was marginal on transatlantic operations and required a west bound fuel stop under most conditions. The competing DC-8-30 promised non-stop transatlantic operations all year round. Boeings solution was increase the wing area of the 707 by inserting a new wing section in the existing wing which increased the wingspan by 3.53m.
The 707-300 was powered by Pratt & Whitney JT4A-3 turbojets producing 75.2kn, or alternatively JT4-9s producing 75.2 kN or JT4A-11s producing 78.4kN. In addition the fuselage was stretched by 2.56m to accommodate a maximum of 189 passengers and fuel capacity increased by 28%. Range with maximum fuel was 9910 km and with a maximum payload of 24,948 kgs range was 7076km. The combination of the extended wing and more powerful engines resulted in an aircraft which was competitive with DC-8-30 As a result orders were placed by Pan American for 26, Air France 21, TWA 12, Sabena 7 and South African Airways 3. Deliveries commenced on 19 July 1959, with the first Pan American aircraft, Air France receiving their first aircraft 3 months later on 21 October. The last of 69 Boeing 707-300s was delivered to Sabena on 19 January 1963.
In 1954 Rolls-Royce the UK aero engine manufacturer had begun producing the world’s first turbofan engine, the Royce Conway. Boeing offered this engine as an alternative to the JT4 on the 707-300. Producing 78.4kN the Conway offered more power than the initial JT4-A3, was quieter, and offered an increase in performance. The 707 which resulted was designated the 707-400, which apart from the engines and associated systems was identical to the -300. The 707-400 was some 907 kg lighter than the 707-300 and had reduced fuel consumption compared to the JT4 powered aircraft. In comparison with the 707-300, the 707-400 could fly 925 km further with a maximum fuel load and carry an additional 907 kg payload. During UK certification testing, concern was expressed regarding directional handling during asymmetric engine flight. To meet UK certification requirements the 707-400 fin was increased in height, the powered rudder controls were enhanced, and a ventral fin was fitted. These modifications were subsequently incorporated into all production 707s and retro-fitted to existing aircraft, although not all aircraft were fitted with the ventral fin as it was later found to have been unnecessary. The advantages of the 707-400 were overtaken by the arrival of the 707-300B, a JT3D powered version of the -300, which with better operating economics became the preferred variant for intercontinental operations. A total of 37 Boeing 707-400s were produced, the first being delivered to Air India on 18 February 1960 and the final delivery taking place on 11 November 1963. The largest operator of the 707-400 was BOAC which took delivery of 19 aircraft. Other orders were received from Air India (6 aircraft) Lufthansa (5) EL AL and Varig (3) and Cunard Eagle 1.
Lloyd Dunning-Mitchell
