More or less OT - we did trials at Boscombe on the Seaking using the underslung hook with a 'jungle penetrator' - a heavy anchor-like device, the prongs of which folded out to provide 'seats' for four persons to be extracted from deep jungle. Trials used (naturally) dummies and the deployed line was IIRC 300' long. Trial was to work up in speed stages to check flyability and stability. Extraordinary result at (from memory) 50-60 kts, the rope developed a motion that I can only describe as a 'rotary sinusoidal whip' which increased in amplitude and eventually detached itself and pax for unimpeded let-down onto Salisbury Plain. Don't think it went into service!!
