TTO,
Yes the Wessex 60 was always a twin, but in the military it operated as the Wessex 1 and 3, both of which were singles and as the Wessex 2 (RAF), Wessex 4 (Royal Flight) and Wessex 5 (RN). The Wessex 60 had excellent single-engine performance for its day and an excellent fuel control system. As SAS says the 58ETs were modified by Bristow from ex German military machines, the old radials being changed to PT6s. In the cabin you could still see some of the ex-military markings in German! I could never understand why Bell never went for the much easier Sikorsky system of a manual flight idle gate, rather than an electric idle stop. The Bristow aircraft had engine air bleed heaters which were never as effective as the BAH paraffin burners, and the passengers often complained in winter when the cabin only attained a few degrees above freezing. They were very smooth because of the bifilars and the worst thing the company did was to remove them from aircraft on the Teesside contract to save weight. We operated them from many bases in UK - Aberdeen, Sumburgh, Haverfordwest, Southampton, Bournemouth and Skye that I remember. This gave us lots of variety. I was also lucky enough to operate one in Portugal for a few months from the old BEAS pad in Figueira da Foz in support of Shell's last offshore well in Portugal in 1977.