CH47 HC1 had a VNE of 160 kts, I explored this limitation en-route RAF Gutersloh in I think 1983 trying to catch a Puma .going to the same destination. I was overhauling the Puma when I saw the airfield passing below. Quick power reduction took ages to slow down and late call finalls to land. Not many helicopters are able to maintain VNE straight and level!