The S.R.177 is being built to O.R.337, issued by the Air Staff on 2nd December, 1955. This is a development of an earlier requirement, O.R.301, first issued in 1951. The aircraft being built to this latter requirement is the S.R.153.


May 1951.Particulars of a proposed requirement for a rocket propelled fighter were circulated to the Air Staff by A.C.A.S.(O.R.)'s staff. Because of the limitations of the early warning system and the likely scale of enemy attack, it was thought that a large force of high performance day fighters would be required. The ability of the fighters then being developed to deal with the very high altitude raider was doubted. The aircraft proposed was intended to fill the gap until effective Guided Weapons became available and to provide a strong backing for the day fighter force against mass daylight raids of B.29 type bombers. The operational role of the aircraft was to be based on an exceptional rate of climb, probably obtainable only by rocket propulsion. Target date for the first production aircraft was Spring, 1954. The aim was to combine simplicity and ease of manufacture with operational efficiency. Certain operational refinements were therefore to be sacrificed.

August O.R.301 was issued for a rocket fighter with the following main features :
(a) Climb 60,000. ft. in 2 1/2 mins.
(b) Speed. Aircraft of this type were required ultimately to be supersonic above 30,000ft. In the first instance, a maximum speed of M = 0.95 would be acceptable if this would shorten development time substantially.
(c) Landing speed. A low landing speed - this was more important than supersonic speed since landings would have to be made from the glide.
(d) Armament: Battery of 2" air-to-air rockets, with provision for fitting direct hitting air-to-air guided Weapon as an alternative.

November Ministry of Supply accepted O.R.301.


January. Ministry of Supply issued Specification (F.124T). This enlarged on O.R.301 by specifying that provision should be made for carrying Blue Jay.

February Ministry of Supply circulated the specification widely to aircraft firms and invited tenders from Bristol, De Havilland, Fairey, Blackburn and A.V. Roe. Tenders were submitted by Bristol, Fairey, Blackburn, A.V. Roe, and by Westland and Saunders Roe.
While firms were preparing designs, the Air Staff decided to ask for an ancillary jet engine to assist the return to base phase.

July The Tender Design. Conference decided to recommend to C.A. that three prototypes each of the Avro and Saunders Roe aircraft should be ordered.

October Ministry of Supply raised a Technical Requisition to initiate contract action.


Advisory Design Conference decided on the specification.

May Ministry of Supply awarded a contract for three aircraft to Saunders Roe. The history of the Avro design is not followed in detail hereafter.

June Ministry of Supply issued Specification (F.138D) calling for Spectre, (Rocket) and Viper (jet) engines, supersonic performance above 40,000 ft. and a subsonic cruising ceiling of not less than 70,000 ft. The rate of climb and endurance originally specified were slightly relaxed, mainly because of the limitations imposed by the external carriage of Blue Jay.

August The Air Staff. issued O.R.301 (2nd Issue). This followed closely Specification F.138D, but stated a requirement for a subsonic cruise ceiling of at least 75,000 ft. (as against 70,000. ft.) and supersonic capability with armament at all heights above 30,000 ft. (instead of 4.0,000 ft.). The target date for the aircraft to be in service was 1957.


January. For reasons of economy, the Ministry of Supply order was reduced from three prototypes each from Saunders Roe and Avro to two prototypes each.

June The Ministry of Supply forecast the first flight of the first Saunders Roe prototype for July 1955.


January. The D.R.P.C. decided that for reasons of economy, either the Avro or the Saunders Roe development should be stopped. The Ministry of Supply made a study of the relative merits of each aircraft and its development potential.
March D.M.A.R.D.(R.A.F.) concluded that the Saunders Roe aircraft was likely to be more successful and would have an attractive performance in its developed form.
July A.C.A.S.(O.R.) recommended to D.C.A.S. that the Air Staff should support the Ministry of Supply's proposal to abandon the Avro aircraft.


The first prototype S.R.53 is expected to fly in July, 1956.

March Delays have been due to two main reasons, each of which would have held up the first flight date
(a) The fuel and designing a H.T.P. system were more difficult than was first realised and required a large amount of testing.
(b) Development of the Spectre rocket has slipped and the engine has not yet been airtested. Tests with a Canberra are expected to begin in March, 1956.



January The Air Staff considered the further development of the aircraft to O.R.301. A.C.A.S.(O.R.) suggested that the O.R.301 prototypes might be used to provide early technical information for building a more advanced aircraft on similar principles.

February Saunders Roe submitted a brochure to the Ministry of Supply proposing that a jet engine of similar thrust to that of the rocket be fitted to the aircraft being built to O.R.301.

June Ministry of Supply asked R.A.E to assess the performance of the aircraft proposed by Saunders Roe when fitted with a Gyron Junior engine.


February Ministry of Supply raised a Technical Requisition for design studies of the possibility of using an engine of 7,000 to 8,000 lbs. thrust in the P.138D.

May Ministry of Supply issued a contract for a design study on the basis of the Technical Requisition.

August Air Staff circulated Draft O.R.

September Ministry of Supply issued a further contract instructing the company to proceed with fullscale design, pending a main contract, on the basis of the Draft O.R.

December The Air Staff issued O.R.337. The preamble stated that the main threat to the country was still subsonic, but attacks by aircraft capable of speeds up to M = 1.3 at heights up to 55,000 ft. might be expected in 1960/62. The main features of the O.R. were:-
(a) Climb to 60,000ft at M= 1.6 in not than than four minutes.
(b) 1 1/2 G ceiling - 65,000 ft. at not less than M =1.6.
(c) Speed supersonic speed above 40,000 ft.; not less than M = 1.6 at 60,000 ft; M= 2 for a short period.
(d) Endurance - about 4.5 minutes, depending on flight profile, extensible to 75 minutes with overload tanks.
(e) Armament - 2 Blue Jay with 2 rocket batteries as an alternative.
The flexibility given by A.I., navigation aids and auto-pilot facilities was essential.
The aircraft was required in service as soon as possible and not later than July, 1959.


January The Ministry of Supply accepted the O.R. with the following conditions:
(a) the aircraft should be confined to the high altitude interceptor role with a possible g restriction for operation below 40,000 ft.
(b) the acceleration time from M= 0.95 to M = 1.6 to be extended by approximately 1 minute.
(c) cruising altitude when carrying overloads to be reduced from 40,000 ft. to 36,000 ft.
(d) Target date for C.A. release to be mid-1960.

February D.R.P.C. accepted the S.R.177 as a development project for R.A.F. and Navy. Ministry of Supply sought Treasury approval to place an order for a development batch of 27 aircraft. As this was not readily forthcoming, in April the Firm were authorised the expenditure of a further £100,000 to maintain continuity.

February The two S.R.53 prototypes are now regarded primarily as a lead in to the F.177, rather than as a research project.

April Advisory Design Conference held. Specification agreed.

July Specification [handwritten F177 to meet OR337] issued by Ministry of Supply.

July Treasury agreed to a development batch of 27 aircraft, but authorised the build of only 9 aircraft with long dated materials being allocated to support the remaining 18 aircraft. The delay in Treasury approval being granted was due to reviews of patterns of fighter defences of the future, and the atmosphere of financial stringency and economy generally.

July The S.R.53 has not yet made its first flight. [handwritten The first F177 (SR177) is scheduled to make its first flight in April 1958, but this is likely to slip by 6 months]

September Ministerial approval having been granted, O.R.337 is formally accepted for action by the Ministry of Supply. Design work has however been proceeding since September 1955. The main adverse effect of the delay in placing the final contract has been that it has prevented Saunders Roe placing sub-contract orders.


March The first flight of the S.R.53 remained "imminent" until the end of 1956, but it has not yet flown and is scheduled for mid-April 1957. There have been troubles with the Spectre engine, but the airframe also is not fully ready.

handwritten 29th March. Air Staff cancellation of OR337 was formally sent to the M of S on the 29th March.

from Public Record Office file AIR 2/13418

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