In May 1951
requirement particulars for a rocket propelled fighter were circulated
to Britain's Air 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, their
capabilities to exceed those of the fighters then being developed.
aircraft proposed was intended to fill the gap until effective
surface-to-air missiles became available, and to provide a strong
backing for the day fighter force against mass daylight raids of the
equivalent of the B.29 type bombers. The aim was to combine simplicity
and ease of manufacture with operational efficiency. Certain
operational refinements were therefore to be sacrificed.
O.R.301 was issued for a rocket fighter with the following main
- Climb 60,000. ft. in 2½ mins.
- Required ultimately to be supersonic above 30,000ft. In the first
instance, a maximum speed of Mach 0.95 would be acceptable if this
would shorten development time substantially.
- A low landing speed, this was more important than supersonic speed
since landings would have to be made from the glide.
- Armament was to be a battery of 2-inch air-to-air rockets, with
provision for fitting direct hitting air-to-air guided weapon as an
In February 1952, the Ministry of Supply circulated the specification
to aircraft firms and invited tenders from Bristol, De Havilland,
Fairey, Blackburn and A.V. Roe. Tenders were submitted by these firms
as well as by Westland and Saunders Roe.
original requirement called for a ramp-launched rocket powered fighter
which would climb under power and glide back to land on a skid. Later
the requirement added a conventional undercarriage and a jet engine.
Saunders-Roe and Avro each won contracts to build prototypes for a
evaluation, with Avro producing the Type 720 and SARO the SR.53.
Although the Avro 720 was ready to fly earlier than the SR.53, it was
kept grounded because the RAF wanted both flying at the same time for
evaluation. The government decided that for reasons of economy, one
project or the other would have to be stopped. The Saunders-Roe
aircraft was seen as likely to be more successful and would have an
attractive performance in its developed form. The government withdrew
funding from the Avro 720 after £1 million had been spent, leaving the
SR.53 alone in the field.
There followed a number of setbacks, among which were problems in the
fuel system design and development of the rocket engine. The aircraft
suffered an explosion of its tail section during a rocket test in late
1955. Finally, the first SR.53, XD145, was rolled out in June 1956. The
finished aircraft was 45 feet in length, with a wingspan of 25 ft. 1
in. It was fitted with dummy De Havilland Firestreak guided
missiles on the wing tips to emphasise its fighter role.
The SR.53 was taken by road to RAE Boscombe Downs, and flew for the
first time on 16th May, 1957, also appearing at that year's Farnborough
The SR.177 design had been initiated in late 1953 as the ultimate
derivative of the SR.53, then also in the preliminary design stage. The
company designation was actually SR.53 and the specification number was
F.155, both designations combining to give a project name of "SR.177".
The project was submitted to Britain's Ministry of Supply in 1954 as a
land-based aircraft for the RAF. The Royal Navy became interested in
March 1955 and a design development contract was awarded in September.
This was followed by a contract in 1956 for six evaluation prototypes
for the Royal Navy and RAF. There were no major differences between the
two service types apart from an arrester hook and some local
strengthening for catapult spools in the navy version.
The SR.177 was roughly similar to the SR.53. It had a Gyron Junior
turbojet (8,000 lb st / 3630 kgp) in place of the Viper (1,750 lb st
/794 kgp). The 8,000 lb (3630 kg) Spectre 5A rocket motor was common to
both aircraft; but the relative positions of the jet and rocket motors
were reversed, the turbojet being the lower power plant in the SR.177.
Owing to the far greater power of the Gyron Junior engine, the small
dorsal intakes of the SR.53 were replaced by a large chin intake on the
SR.177, topped by a radome for the A.1 radar.
In the SR.53, the rocket motor was intended for use during
interception, the jet using the remaining fuel to return to base. The
better fuel economy of the Gyron Junior in the SR.177 allowed full
exploitation of the benefits of mixed power. The turbojet would be used
for subsonic cruise up to Mach 0.95, at which stage the rocket would
carry the aircraft to its maximum speed of about Mach 2.35.
The Spectre 5A was a bi-fuel motor burning kerosene and hydrogen
peroxide, controllable from 10% to 100% power. It drew its primary fuel
from the same tanks as the jet engine. Full power endurance was
estimated at seven minutes.
In addition to its interceptor role, the SR.177 was also intended to
perform strike, low-level reconnaissance and attack roles, purely on
high subsonic speed using only its jet engine. Provision was ultimately
to be made for in-flight refuelling and operation from short airstrips.
In July 1956, Treasury agreed to a development batch of 27 aircraft,
but authorised the building of only 9 aircraft initially, delaying
construction of 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
The SR-177 had still not flown; it was scheduled to make its first
flight in April 1958, but this was thought likely to slip by six
months. But in 1957 a Defence White Paper put an end to many British
projects. It decreed that the English Electric Lightning would
be the RAF's last manned fighter. This eliminated any chance of the
SR.177 being ordered for the RAF, but the short-sighted paper did not
affect the Royal Navy for whom, by then, the project was being
primarily developed. Air Staff cancellation of OR337 (the December 1955
updated requirements for the project) was formally sent to the Ministry
of Supply on the 29th March.
Shortly afterwards, it became evident that developing the aircraft to
serve such a relatively small order would be uneconomical. Overseas
interest in the aircraft failed to solidify into actual orders. Work on
the six prototypes ended, and the government-backed SR.177 project was
abandoned at the end of 1957.
Mixed power, consisting of a Gyron Junior turbojet of 8,000 lb s t
(3630 kgp) and a Spectre 5A rocket motor, also of 8,000 lb (3630 kg)
25,500 lb (11567 kg)
MAX. CLIMB RATE (expected):
Over 60,000 ft/min (305 m/sec)
67,000 ft (20420 m)
30 ft 0 in (9.14 m)
50 ft 0 in (15.24 m)
14 ft 0 in (4.27 m)
Two Red Top infra-red air-to-air missiles on wing tips in
interceptor role. Underwing stores of 1000 lb (453.5 kg) with
wingtip fuel tanks in strike role.