Саундерс-Ро SR.177: Британский перехватчик 1950-х годов, не взлетевший в небо.

1950s British cancelled interceptor aircraft project

The Saunders Roe SR.177 was a 1950s project to develop a combined jet and rocket powered interceptor aircraft for the Royal Air Force (RAF) and Royal Navy. It was an enlarged derivative of the Saunders Roe SR.53, which was itself an experimental combined jet and rocket interceptor aircraft. The SR.177 principally differed from the smaller SR.53 in its adoption of a nose mounted airborne interception radar unit, which allowed it to scan for and lock onto its own targets; a more powerful turbojet engine was also incorporated. In addition to British interests in the aircraft, the German Navy had also expressed their interest in the project and closely evaluated its progress with an eye towards its potential procurement. However, the SR.177 was ultimately cancelled as a result of changes in Britain's military policies in 1957. A much larger derivative of the SR.177 had been studied, which was designated as the SR.187, and was being developed with the intention of meeting the requirements of Operational Requirement F.155. However, this work was also cancelled in 1957. By the time of termination, approximately 90 per cent of the first prototype had been completed, while several other prototypes were in various states of completion. The prototypes were stored for several years while attempts were made to revive the project; while interest was present, including from Japan, nothing more came of the project and the remaining assets were broken up.

In 1952, Saunders Roe had been awarded a contract to develop a combined rocket and jet propelled interceptor aircraft, which was designated as the Saunders Roe SR.53. However, as development work on the project progressed, the shortcomings of the design became increasingly evident. Most particularly, as with the German rocket powered interceptors of the Second World War, the range and endurance of such an aircraft were limited by the high rate of fuel consumption by the rocket engine. However, as turbojet engines developed and became increasingly powerful and efficient, new powerplants were quickly becoming available that would make such aircraft more practical. Maurice Brennan, the chief designer of the SR.53, had also become convinced of the necessity for an airborne radar unit to be carried by the aircraft, as the SR.53 was reliant upon on ground based radar guidance and the pilot's own vision to intercept aircraft. While it had begun as an advanced design concept for the SR.53, upon the issuing of a development contract by the Ministry of Defence in May 1955 (to meet specification F.155), the project was given its own designation as the SR.177. As work continued on the SR.53, a separate High Speed Development Section was formed by Saunders Roe to work on the SR.177. Initially, the SR.177 was a straightforward development of the SR.53, sharing much of the same configuration and equipment, and it was envisioned that the first test flight would take place during the first half of 1957. However, in February 1955, an extensive redesign of the SR.177, with the aim of making the type suitable for use by both the RAF and the Royal Navy, was commenced.

In September 1955, Saunders Roe received instructions to proceed on the SR.177 from the British Ministry of Supply. From the onset, the SR.177 faced competition in the form of an enlarged derivative of the Avro 720, which had itself been devised as a competitor against the smaller SR.53. Avro promoted the 720 to the Royal Navy, hoping to win favour away from the SR.177, which had by this point reached the detail design phase. The Ministry ultimately opted to cancel all work on the Avro 720, primarily as a cost saving measure, as well as to concentrate development work on HTP based rocket motors, such as those powering the SR.53 and SR.177. The most significant difference between the SR.53 and SR.177 was the latter's use of a jet engine with nearly five times the thrust of the one adopted for the former. While the SR.53 had relied mostly on its rocket engine for climbing, the SR.177 would be able to add considerable endurance by conserving use of its rocket for the dash towards a target only. Following the maiden flight of the SR.53 in May 1957, the development of the SR.177 became the main focus of activity at Saunders Roe. At this point, the project was viewed as having considerable large scale potential, as both the RAF and Royal Navy appeared to be set to be customers for the SR.177. The RAF sought to operate it alongside the incoming English Electric Lightning interceptors while, according to aviation author Derek Wood, the Royal Navy also had considerable interest in the programme. Negotiations on the exact number of aircraft sought by either service were protracted; but it had been established that there was demand for an initial batch of 27 SR.177 aircraft, and that sufficient tooling should be produced to enable the programme to transition rapidly to full rate production. During 1957, a development contract for the SR.177 was announced for its use with the Royal Navy. By January 1957, the design of the main component jigs was 70 per cent complete while the component assembly jigs were almost 50 per cent complete; the manufacture of a quantity production batch was nearing, which would have likely been subcontracted to another aviation company due to the high level of workload at Saunders Roe's Cowes facility. Armstrong Whitworth, who had already taken over work on the basic wing design of the SR.177, had been selected as the second production outlet for the type. The selection of a production center for the SR.177 was complicated by a favourable event; interest in the programme from the West German government. The prospects of a large German order for as many as 200 aircraft, and for the SR.177 to be manufactured under licence in Germany by the recovering German aircraft industry, were soon being aired, of which the British government declared its openness towards. In January 1957, the Anglo German Standing Committee on Arms Supply reported that General Kammhuber, the Commander in Chief of the German Air Force, was concerned that, due to a lack of available financing until April 1958, the delivery timetable may not be satisfactory. According to Wood, Germany was keen to issue an order as soon as possible by this point.