Canadair CP-107 Argus

The Canadair CP-107 Argus (company designation CL-28) is a maritime patrol aircraft designed and manufactured by Canadair for the Royal Canadian Air Force (RCAF). In its early years, the Argus was reputedly the finest anti-submarine patrol bomber in the world. The Argus served throughout the Cold War in the RCAF's Maritime Air Command and later the Canadian Force's Maritime Air Group and Air Command.
Design and development.
In 1949, Canadair recognized that the RCAF would soon be looking for a replacement for the Avro Lancasters being used in the maritime patrol role and proposed the CL-29, a variant of the North Star, itself a variant of the Douglas C-54 Skymaster or DC-4 transport. When the RCAF issued the specification in 1952, it was for a larger and more capable aircraft, and two proposals were received. These included a Lockheed Constellation variant from Lockheed, however its low speed handling was deemed inadequate by the RCAF, while Bristol proposed a variant of their Britannia airliner but concerns were raised over its floating controls, where they were controlled via servo tabs rather than direct linkages. The RCAF preferred the Bristol proposal, but it would be developed in Canada. Canadair presented two proposals, the CL-28 also based on the Britannia, which was accepted, and a lowest cost design called the CL-33 which was described as a fat Lancaster. It would have been comparable to the Avro Shackleton already being operated by the RAF, but significantly lighter, and was to be powered by the same engines as were used in the CL-28, or similar radial engines.
Canadair began work on the CL-28 in April 1954 and at the time it was the largest aircraft to be built in Canada. The hybrid design, initially referred to as the 'Britannia Maritime Reconnaissance', or 'Britannia MR', was derived from the Bristol Britannia airliner, having the same wings, tail surfaces and landing gear except for being "Americanized" – meaning that it used the same general design, but changed from British materials, dimensions and standard parts to American ones. Due to the greater stresses from flying at low altitude for long periods of time, even the components taken from the Britannia needed substantial reinforcement, and to meet these demands, extensive use of a locally developed metal to metal bonding was used. The Argus represented the first large scale use of titanium in the structure, as well as structural plastic, which was used to electrically insulate the top of the fin for the sensors mounted there. 
The fuselage was completely redesigned by Canadair, going from the pressure cabin used in the Britannia to an unpressurised one with two long bomb bays fore and aft of the wings. The engines were also changed from the Bristol Proteus turboprop engines to Wright R-3350 turbo-compound piston radial engines, which had lower fuel consumption necessary for extended missions at low level. At the design stage the Napier Nomad, another turbo compound engine was also considered, although the Nomad was later cancelled.
Test program.
Seven aircraft were used for the development program, with each one specializing in specific systems or problem. Argus 20710 tested controls and stability, 20711 equipment and environment, 20712 did cold weather testing, 20713 structural tests and demonstrating RCAF requirements, while 20714 was used for weapons testing, and 20715 completed the operational evaluation. In July 1960, a CP-107 Argus visited Eglin AFB, Florida for hot weather testing.
Operational history.
The Argus replaced the last of the Avro Lancasters as well as the Lockheed Neptunes that had been bought as an interim measure pending the arrival of the Argus in the maritime reconnaissance or patrol role. 
One of the most effective anti-submarine warfare (ASW) aircraft of its day, the Argus was a mainstay for the RCAF. A large amount of equipment was carried, including: search radar, sonobuoys, electronic counter measures (ECM), explosive echo ranging (EER) and magnetic anomaly detector (MAD). Up to of weapons could be carried in the bomb bays, including torpedoes and depth charges.
A flight crew of 15 consisting of three pilots, three navigators (Observer Long range), two flight engineers and six radio officers (observer rad) until the early 1960s when the crew included both commissioned officers (tactical navigator/radio navigator) and non commissioned officers (observers), the number of which was dependent on the mission. Four crew bunks and a galley were provided to extend the efficiency of the crew on long patrols (average 18 hrs). The CL-28 had an endurance of approximately 26½ hours with full armament. 
An Argus flown by 407 Maritime Patrol Squadron on 1-2 October 1959 held the Canadian military record of slightly over 31 hours for the longest flight by an unrefuelled aircraft, while covering a distance of from RNZAF Base Ohakea in New Zealand to Naval Air Station Barbers Point in Hawaii, before continuing across the rest of Pacific and most of Canada. Due to unexpectedly strong headwinds that greatly increased fuel consumption, they chose to land in RCAF Station North Bay where they had less than an hour of fuel remaining, after an additional 20 hours of flying. The 31 hour record flight broke the previous distance record, set by another Argus from the same squadron, of . 
The principal difference between the Mk.1 and Mk.2 was in the different navigation, communication and tactical electronic equipment fitted internally. Externally, the Mk II had a smaller redesigned nose radome and additional ECM antenna above the fuselage.
The Argus flew its last service mission on 24 July 1981, and was replaced by the Lockheed CP-140 Aurora.