Hoppy
The 'B' series was developed for the Tristar -500 and each step along the evolution bought an improvement in the SFC.
The -524b-02 was the first engine for the -500 with 50000lbs of thrust.
The -524b3-02 same thrust of 50000lbs with an improvement of -2.8% in the SFC. This engine had changes to the fan and improved gasflow.
The -524b4-02 same again but another improvement in the SFC (-4.8%). This engine had a new fan, new 05 module (I.P./L.P.turbines) and the cooling air offtakes were revised.
The other growth path was for the B747 with improvements in thrust and SFC.
They started life as the -524B2-19 (-19=B747)
[This message has been edited by gas path (edited 19 May 2001).]