Saunders-Roe SR.177

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 aircraft 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.

Design and development

Background

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.

Project launch

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.

Decline and cancellation

During 1957, the fate of the SR.177 was to be subject to a massive re-thinking of air defence philosophy in Britain, being principally outlined in the 1957 Defence White Paper, which called for crewed combat aircraft to be replaced by missiles. Very shortly afterwards, OR.337 was cancelled and the prospects of an order from the RAF had evaporated. This was a serious blow, while it the Royal Navy and Germany remained potential customers for the SR.177, the confidence of both parties was shaken by the move.

Work on the SR.177 continued for a little longer, however, in the anticipation of continued interest from Germany. In September 1957, Aubrey Jones, the Minister of Supply, was keen to support the programme and had agreed to continue funding development of five of the six prototypes. The Minister had visited the German government in November 1957 as the Germans wanted the arrangements to be between governments instead of between their government and Saunders-Roe.

Of the remaining aircraft under consideration, the West German Government chose to purchase a development of the American Lockheed F-104 Starfighter interceptor instead to meet the role of "high-altitude reconnaissance machine, a tactical fighter-bomber, and an all-weather fighter",

Following the withdrawal of German interest and there being no requirement for the SR.177 by the RAF, the existing Royal Navy requirement was considered not worthwhile to proceed with. Accordingly, the Ministry of Supply soon chose to cancel the project. On 24 December 1957, a letter from the Ministry was received by Saunders-Roe, announcing the decision to terminate. Saunders-Roe announced that it expected to make 1,000 workers redundant

|prime units?=imp<!-- imp or kts first for US aircraft, and UK aircraft pre-metrification,

met(ric) first for all others. You MUST choose a format, or no specifications will show -->

<!--

General characteristics

-->

|genhide=

|crew=

|capacity=

|length m=

|length ft=

|length in=

|length note=

|span m=

|span ft=30

|span in=3

|span note=with missiles, without missiles

|upper span m=

|upper span ft=

|upper span in=

|upper span note=

|mid span m=

|mid span ft=

|mid span in=

|mid span note=

|lower span m=

|lower span ft=

|lower span in=

|lower span note=

|swept m=

|swept ft=

|swept in=

|swept note=

|dia m=

|dia ft=

|dia in=

|dia note=

|width m=

|width ft=

|width in=

|width note=

|height m=

|height ft=14

|height in=3.5

|height note=

|wing area sqm=

|wing area sqft=327

|wing area note=

|swept area sqm=

|swept area sqft=

|swept area note=

|volume m3=

|volume ft3=

|volume note=

|aspect ratio=

|airfoil=

|empty weight kg=

|empty weight lb=14,533

|empty weight note=

|gross weight kg=

|gross weight lb=25,786

|gross weight note= (normal warning)

|max takeoff weight kg=

|max takeoff weight lb=28,174

|max takeoff weight note= (extended warning)

|fuel capacity=

|lift kg=

|lift lb=

|lift note=

|more general=

<!--

Powerplant

-->

|eng1 number=1

|eng1 name=de Havilland PS.50 Gyron Junior

|eng1 type= turbojet with afterburner

|eng1 kw=

|eng1 hp=

|eng1 shp=

|eng1 kn=

|eng1 lbf=14,000

|eng1 note=

|power original=

|thrust original=

|eng1 kn-ab=

|eng1 lbf-ab=

|eng2 number=1

|eng2 name=de Havilland Spectre 5A

|eng2 type=liquid-fuelled rocket engine

|eng2 kw=

|eng2 hp=

|eng2 shp=

|eng2 kn=

|eng2 lbf=10,000

|eng2 note=

|eng2 kn-ab=

|eng2 lbf-ab=

|eng3 number=

|eng3 name=

|eng3 type=

|eng3 kw=

|eng3 hp=

|eng3 shp=

|eng3 kn=

|eng3 lbf=

|eng3 note=

|eng3 kn-ab=

|eng3 lbf-ab=

|more power=

|prop blade number=

|prop name=

|prop dia m=

|prop dia ft=

|prop dia in=

|prop dia note=

|rot number=

|rot dia m=

|rot dia ft=

|rot dia in=

|rot area sqm=

|rot area sqft=

|rot area note=

<!--

Performance

-->

|perfhide=

|max speed kmh=

|max speed mph=

|max speed kts=

|max speed note=

|max speed mach=2.35

|cruise speed kmh=

|cruise speed mph=

|cruise speed kts=

|cruise speed note=

|stall speed kmh=

|stall speed mph=

|stall speed kts=

|stall speed note=

|never exceed speed kmh=

|never exceed speed mph=

|never exceed speed kts=

|never exceed speed note=

|minimum control speed kmh=

|minimum control speed mph=

|minimum control speed kts=

|minimum control speed note=

|range km=

|range miles=

|range nmi=

|range note=

|combat range km=

|combat range miles=

|combat range nmi=

|combat range note=

|ferry range km=

|ferry range miles=

|ferry range nmi=

|ferry range note=

|endurance=

|ceiling m=

|ceiling ft=67,000

|ceiling note=

|g limits=

|roll rate=

|glide ratio=

|climb rate ms=

|climb rate ftmin=60,000

|climb rate note=

|time to altitude=<br/>

brake release to - 1 min 27 s
brake release to - 2 min 3 s
brake release to - 3 min 6 s
brake release to - 3 min 51 s

|sink rate ms=

|sink rate ftmin=

|sink rate note=

|lift to drag=

|wing loading kg/m2=

|wing loading lb/sqft=

|wing loading note=

|disk loading kg/m2=

|disk loading lb/sqft=

|disk loading note=

|fuel consumption kg/km=

|fuel consumption lb/mi=

|power/mass=

|thrust/weight=

|more performance=<br/>

Level acceleration at from top of climb at Mach 1.4 to Mach 2 - 1 min 6 s
Radius of turn (at Mach 1•6 at ) -
Rocket full power endurance - 7 minutes

<!--

Armament

-->

|guns=

|bombs=

|rockets=

|missiles=<br/>

Initially 2 x de Havilland Firestreak air-to-air missiles
Later 2 x Hawker Siddeley Red Top (Firestreak Mark 4)

|hardpoints=2

|hardpoint capacity=

|hardpoint rockets=

|hardpoint missiles=

|hardpoint bombs=

|hardpoint other=

|avionics=AI.23 aircraft interception radar

References

Notes

Bibliography

London, Peter. Saunders and Saro Aircraft since 1917. London: Putnam & Company Ltd., 1988. .
London, Peter. "Saunders-Roe's Rocket Fighters." Aircraft, Vol. 43, No. 7, July 2010.
Mason, Francis K. The British Fighter since 1912. London: Putnam, 1992. .
Winchester, Jim. "TSR.2." Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft. Kent, UK: Grange Books plc., 2005. .
Wood, Derek. Project Cancelled: The Disaster of Britain's Abandoned Aircraft Projects. London: Jane's, 2nd edition, 1986. .

External links

Unreal aircraft
Saro 177
Rocket interceptors and S177

Design and development

Background

Project launch

Decline and cancellation

See also

References

Notes

Bibliography

External links