Loftyc, IIRC that is a retractable wireless antenna. You would reel it out after take-off when you needed to use the radio and reel it back in before you landed.
Three RFC Brass Hats were strolling down a street in London. Two walked into a bar, the third one ducked.
Former Cold War Warrior, USAF Security Service 1974-1978, E-4, Morse Systems Intercept, England, Europe, and points above."pippy-pahpah-pippy pah-pip-pah"