The Rolls-Royce Spey (company designations RB.163 and RB.168 and RB.183) is a low-bypass turbofan engine originally designed and manufactured by Rolls-Royce that has been in widespread service for over 40 years. A co-development version of the Spey between Rolls-Royce and Allison in the 1960s is the Allison TF41.
Intended for the civilian jet airliner market when it was being designed in the late 1950s, the Spey concept was also used in various military engines, and later as a turboshaft engine for ships known as the Marine Spey, and even as the basis for a new civilian line, the Rolls-Royce Tay.
Aviation versions of the "base model" Spey have accumulated over 50 million hours of flight time. In keeping with Rolls-Royce naming practices, the engine is named after the River Spey.
|An RB.168 Mk 202 Spey as fitted to the F-4K Phantom|
|Major applications||BAC One-Eleven|
JH-7 Flying Leopard
AMX International AMX
|Developed into||Rolls-Royce Marine Spey|
In 1954 Rolls-Royce introduced the first commercial bypass engine, the Rolls-Royce Conway, with a 21,000 lbf (94 kN) thrust aimed at what was then the "large end" of the market. This was far too large for smaller aircraft such as the Sud Caravelle, BAC One-Eleven or Hawker Siddeley Trident which were then under design. Rolls then started work on a smaller engine otherwise identical in design derived from the larger RB.140/141 Medway - which itself had been cancelled after British European Airways (BEA) had demanded the downsizing of the Trident, the RB.163, using the same two-spool turbine system and a fairly small fan delivering bypass ratios of about 0.64:1. Designed by a team under Frederick Morley, the first versions of what had become the 'Spey' entered service in 1964, powering both the 1-11 and Trident. Several versions with higher power ratings were delivered through the 1960s, but development was ended nearing the 1970s due to the introduction of engines with much higher bypass ratios, and thus better fuel economy. Spey-powered airliners continued in widespread service until the 1980s, when noise limitations in European airports forced them from service.
In the late 1950s the Soviet Union started the development of the Sverdlov-class cruisers that would put the Royal Navy at serious risk. After studying the problem, the RN decided to respond in a non-linear fashion, and instead of producing a series of new cruisers themselves, they would introduce a new strike aircraft with the performance needed to guarantee successful attacks on the Soviet fleet. The winning design was the Blackburn Buccaneer, which had an emphasis on low altitude performance (to evade enemy radar) as opposed to outright speed.
Flying at low altitude, in denser air, requires much more fuel; the air-fuel mixture in a jet engine needs to be kept very close to a constant value to burn properly, and more air requires proportionally more fuel. This presented a serious problem for aircraft such as the Buccaneer, which would have had very short range unless the engines were optimised for low-level flight. The early pre-production versions, powered by the de Havilland Gyron Junior, also proved to be dangerously underpowered.
Rolls-Royce attacked this problem by offering a militarized version of the Spey, which emerged as the RB.168. The resulting Spey-powered Buccaneer S.2 served into the 1990s. The Spey proved so successful in this role that it was produced under licence in the United States as the TF41 and F113, and was used in a number of British and US designs.
The British versions of the McDonnell Douglas F-4 Phantom II (designated Phantom FG.Mk.1 and FGR.Mk.2) replaced the 16,000 lb wet thrust J79 turbojets with a pair of 20,515 lb wet thrust Spey 201 turbofans. These provided extra thrust for operation from smaller British aircraft carriers, and provided additional bleed air for the boundary layer control system for slower landing speeds. The air intake area was increased by twenty percent, while the aft fuselage under the engines had to be redesigned. Compared to the original turbojets, the afterburning turbofans produced a ten and fifteen percent improvement in combat radius and ferry range, respectively, and improved take-off, initial climb, and acceleration, but at the cost of a reduction in top speed because compressor outlet temperatures would be exceeded in an essentially subsonic civil design..
During its lifetime the Spey has garnered an impressive safety record. Its relatively low maintenance costs provide one of the major reasons it continued in service even when newer designs were available. With the need for a 10,000 to 15,000 lbf (44 to 67 kN) thrust class engine starting up again with the removal of the Spey from service, Rolls-Royce then used the Spey turbomachinery with a much larger fan to produce the Rolls-Royce Tay, a more modern design whose ancestors can be traced to the 1950s.
A fully updated version of the military RB.168 was also built to power the AMX International AMX attack aircraft.
Examples of the Rolls-Royce Spey are on public display at the: