Thanks for the explanation CJ.I vaguely remember seeing the yellow whlrlwinds from TI when on holiday on Hayling Island in the 70's.Years later,when I was an ATCO at West Drayton,one of my colleagues,an ex 'siggie'who had flown as a winchman on Whirlwinds in Libya,said he used to climb up the outside of the A/C in flight,to light his pilot's cigarette,but on one occasion realised he'd not been wearing his 'monkey-harness',- Gulp !