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Aviation History
1973
1973 - 0155.PDF
The 720 test aircraft, right, has used freighters in Puget Sound for surveillance targets; below left, tactical crew stations looking aft; below right, sonobuoy launch tubes and stowage racks Boeing's sub-hunter CANADA ISSUED REQUESTS FOR PRO POSALS on November 1 for a maritime - reconaissance aircraft to replace the CL-28 Argus. While Hawker Siddeley has proposed the' Nimrod and Lockheed the Orion, types which are already in service, Boeing is actively developing a new derivative of the 707 for anti-submarine warfare, known as the 707-ASW. The potential market for maritime reconnaissance aircraft was outlined in Flight September 7, together with details of Lockheed's proposals and its estimates of fleet-operating costs. While no formal demonstrations in Canada of the Nimrod and Orion have been arranged, the two aircraft are in world-wide deployment and the Canadian Armed Forces is familiar with their abilities. Deliveries of P-3C Orions to the US Navy will continue during 1973 and no finance has been made available for a follow-on aircraft. Boeing has not been a traditional supplier of MR aircraft and in order to demonstrate the potential of the 707 the company has modified a second-hand 720 and has carried out a considerable amount of company- financed flight-testing. The definitive ASW aircraft will be based on the 707-320C, which has a maximum take off weight of 334,5001b, 152,000kg, and will be considerably heavier and larger than either of the other designs com peting for the Canadian order. Despite having a 15ft, 4-6m shorter fuselage and a maximum take-off weight about 100,0001b, 45,000kg below that of the -320C, the 720 was considered suffi ciently representative for demonstra tion and test purposes and is described by Boeing as a "full-scale flying mock- up." Reflecting the Canadian desire that its new aircraft should be capable of Arctic surveillance, land-resources ex ploration, troop transport and fighter refuelling duties in addition to the classic MR roles, Boeing is stressing that its proposal is suitable for a variety of missions. The Canadian Armed Forces already operate five 707-320CS, two of which have been converted to tankers to support their Northrop/Canadair CF-5s, and is in a position to assess the controlability of this large aircraft on Arctic airfields. The 707-320Cs' factored take-off dis tance to 35ft, 10-7m of 10,620ft, 3,240m is significantly longer than those required by the Nimrod or Orion. Like the Orion the 707-ASW has no bomb-bay but mounts four pylons in board of the engines. These can carry a variety of stores including bombs, missiles, spare engines or surveillance pods. The 19,0001b, 84-5kN-thrust JT3D-7 powerplants have a bypass ratio of 1-43:1, compared with 0-7:1 for the Spey and it is not yet certain whether the aircraft will be capable, like the Nimrod, of conducting patrols with two engines shut down for economy. The 707 was designed for long- range, high-speed cruise and Boeing has developed a new automatic flight- control system for it to improve hand ling during low-altitude tactical manoeuvres. The Sperry SPZ-1 autopilot, of the type developed for the Boeing 747, has been used as the basis for the new system and brings to this long-range patrol aircraft the benefits of all- weather autolandings, an inertial navi gation system, cruise altitude hold and an airways navigation performance. The system has two independent chan nels, each including independent sen sors, an inertial platform and an air- data computer. These independent channels drive dual hydraulic control servos which allow a failpassive condi tion to exist should a system failure
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