Boeing 707 - Update
The 707 and 720 were developed commercially from the 367-80, which Boeing had produced as a private venture technology demonstrator at a cost of $16m. Boeing’s heavy reliance on military business resulted in the 367-80 first being offered to the United States Air Force, leading to development of a dedicated air refueling tanker, later to become the KC-135. Early efforts to market a commercial version were unsuccessful, and development by Douglas of the much roomier DC-8 forced Boeing to increase the width of the 707 fuselage to allow a 3+3 seating arrangement. Pan American placed the first commercial order for the 707 in October 1955, and brought the aircraft into service with a flight from New York via Gander to Paris, on 26 October, 1958. Once in service, the 707 quickly proved itself, and it became the mainstay on transatlantic routes in particular throughout the 1960s. However, by the end of the decade it was becoming increasingly clear that the transatlantic market required a larger aircraft, leading to development of the 747. Despite this, the 707 remained popular throughout the 1970s and into the 1980s before the poor economics (and high noise levels) of the aircraft’s JT3D turbofans forced airlines to re-equip.
Survivor numbers continue to decline as redundant airframes are reduced to scrap, with the only remaining commercial operator being Omega Air, whose small fleet of active 707s provided air refueling support for US Navy training missions and airframe manufacturers' flight test programmes. The US Air Force has retired its fleet of E-8s, leaving Iran and Israel as the sole remaining military operators of the 707.
The 707 was also developed as the basis for the United States Air Force’s Airborne Early Warning & Control System (AWACS) and United States Navy’s Take Charge and Move Out (TACAMO) submarine communications command post. These versions, known as the E-3 Sentry and E-6 Mercury respectively, are considered 'beyond scope'.
First flight: Model 367-80 - 15 Jul 54 (c/n 17158, N70700); 707 - 20 Dec 57 (c/n 17586, N708PA).
Production: 881, at Seattle, WA, comprising 1 367-80, 726 707s and 154 720s.
First delivery: 30 Nov 58, to Pan American (c/n 17586, N708PA)
Last delivery: 3 Oct 91, to the United States Air Force (c/n 24503, 88-0322). This was the proof-of-concept YE-8B; the last delivery of a 707 ‘proper’ was to the Government of Iran on 03 May 78 (c/n 21396, EP-HIM), although this was post-dated by the last of the Imperial Iranian Air Force 707 tankers (on 20 Dec 78) and a 707 tanker for the Royal Moroccan Air Force (on 10 Mar 82), the latter converted from the 707-720 test aircraft.
Variants: 707-120 - initial production version, powered by 4 Pratt & Whitney JT3C-6 turbojets, with a maximum range of 4,040 nm and seating for up to 179 passengers (57 built, including 3 for the US Air Force as VC-137As);
707-138/138B - short body version of 707-120 developed for Qantas, with extended range and accommodation for 154 passengers (7 built as -138, all of which were returned for Boeing for installation of turbofans, and 6 as JT3D powered-138Bs; first flight 20 Mar 59);
707-220 - 707-120 powered by Pratt & Whitney JT4A-3 turbojets for increased performance at high altutude, ordered by Braniff for its Latin American services (5 built, first flight 11 May 59);
707-320 - intercontinental development of 707-120 aimed at the transatlantic market, with redesigned wing and 4 JT4A-3 turbojets, seating for up to 189 passengers and a range of over 4,600 nm (65 built, first flight 11 Jan 58);
707-420 - turbofan version of the 707-320 powered by Rolls-Royce Conway 508s, and the first 707 variant to feature an increased height tail fin, susbequently available for retrofit onto earlier models (36 built, first flight 19 May 59);
720 (initially designated 707-020) - lighter weight 707-120 aimed at the US domestic market, powered by JT3C-7 turbojets and with redesigned wing, shortened fuselage and reduced fuel capacity, and seating for up to 165 passengers (65 built, first flight 23 Nov 59);
707-120B/720B - turbofan versions of the 707-120 and 720 respectively, powered by JT3Ds (60 707-120B and 89 720B built, and many 707-120/720 converted, including the 3 US Air Force VC-137As, which became VC-137Bs (and later, C-137Bs));
707-320B - 707-320 with improved and larger wing, powered by JT3D-3 turbofans (170 built, including 2 for the US Air Force as Presidential transports, designated VC-137C; first flight 31 Jan 62);
707-320C - 707-320B with forward cargo door and strengthened cabin floor (329 built, including 6 of a batch of 13 as air refueling tankers for the Imperial Iranian Air Force); 8 ex-American Airlines 707-320Cs were acquired by the United States Air Force for operation as communications relay aircraft (EC-18B) and cruise missile mission control platforms (EC-18D);
707-720 - 707-320C powered by 4 SNECMA CFM-56 turbofans (1 built, subsequently converted to JT3D powered 707-320C; first flight 27 Nov 79);
E-8 - 707-320C modified by Grumman for Joint Surveillance, Targeting, Attack and Reconnaissance System (J-STARS) role by installation of side-looking antenna under the fuselage and other mission equipment (20 converted at Melbourne, FL, consisting of 3 E-8A development aircraft and 17 E-8C production aircraft, the latter powered by JT8D-219 turbofans; first flight 22 Dec 88);
YE-8B - proof-of-concept new-build E-8 powered by 4 CFM-56s (1 built, subsequently stripped of mission equipment, supplied to Royal Saudi AF as a conversion trainer and later redsignated RE-3B; first flight 7 Dec 90).
Other conversions: 707RE - 707-320C re-engined with Pratt & Whitney JT8D-219 turbofans by Seven Q Seven, a sister-company of Omega Air (first flight 21 Aug 01). In addition, Israel has re-engined a number of 707-320s with turbofans.