Wx 31B (RAN) was 125ft/30ft. I was under the impression that the W3 FCS was a duplex system and so reliable that, when fitted to the SK50, was made simplex. Certainly in my time on RAN SK's I cannot recall an FCS failure - went like it was on rails from 200ft to 70ft and back - all this in the South China Sea.
GAGS
E86