Boeing - 707-320B
The 707-300 with the larger wing and JT4 engines provided airlines with an intercontinental range aircraft to compete with the DC-8-30, but in December 1960 Douglas flew the JT3D powered DC-8-50 an aircraft which would out-perform the 707-300.
Boeing’s lead in jet transport design had initially given them a technical advantage, but Douglas had committed considerable resources in an effort to retain its dominant market position, and also enjoyed a closer relationship with airlines.
Extracting more performance from the 707 design would require a new wing, the development costs of which would extend the pay back period and raise the break-even point in the production cycle.
Boeing initially considered increasing the wing area by inserting a new wing section between the fuselage and the existing wing, but Boeings aerodynamicist W. T. Hamilton pointed out that this would not produce the required performance. Instead he proposed designing an entirely new wing which would provide the 707 with a competitive edge .The decision taken by Boeing management to approve the new wing was pivotal, not only in the competition between the 707 and DC-8 for market share but eventually between Boeing and Douglas as producers of commercial jet aircraft.
Boeing (uniquely) had owned the strategic asset of a wind tunnel capable of operating at Mach 0.97 since 1941 and it was utilised round the clock in the development of a new wing for the 707. After six weeks the wing that emerged was more efficient than the DC-8’s simpler wing.
Compared to the 707-300 it had full span leading edge slotted flaps, larger trailing edge flaps, and drag reducing wingtips. Combined with the JTD-3D turbofan the new wing would give the 707-300B (320B) a performance advantage over the DC-8 that was to prove unassailable. It also marked the point where Boeing competency in jet transport wing design and its new willingness to aggressively compete and win market share was to position Boeing as the premier western manufacturer of commercial jet aircraft. Compared with the 300, the 300B was some 3.6 % heavier empty and had a 10% reduced maximum payload but could carry that payload 27% further.
Pan American received its first -300B on 12 April 1962 and eventually went on to order 60, other orders included TWA (38) and Northwest who ordered 10 including 4 with a 2.31 x 3.4m port side cargo door which were designated 707-351B (SCD) but did not feature a strengthened cargo floor like the later 300C. The 707-300B Advanced featured a number of modifications which included modifications to the engine cowlings and added extra sections of Kruger flap. A total of 173 707-300Bs were built, the last aircraft being delivered to the Fuerza Aerea Argentina on 11 June 1975.
No 707-300Bs remain in airline service but small numbers operate in a variety of other roles including VIP, cargo, and aerial refuelling..
Lloyd Dunning-Mitchell
