RM8A
When the Viggen-project was given the go-ahead, there was only one engine available that fit the specification, the new P&W JT8D-22. As a civil engine, the JT8D could not handle the strains of supersonic flight and manoeuvring at higher altitudes so the engine would have to be modified. In order to make the JT8D satisfactorily handle turbulence, bird-strike and thermal strain, the engine had to be redesigned to the extent of leaving only nuts and bolts interchangeable between the JT8D and the RM8A. For example: a new first-stage fan to cope with bird-strike and turbulence, new materials in combustion and turbine sections to cope with higher thermal load and a new fuel system for reliable single-engine operation. In the end, the changes of the JTD8 needed for military operation where far more profound than first anticipated. The six initial engines were produced for bench testing and the subsequent 11 engines for flight testing. In July 1968, 195 engines were ordered and the first production engine was delivered on 28 September 1970; a total 207 RM8A engines were produced (9001 - 9207).
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