Used the "split controls" procedure every now and then on the Wessex 3 (ASW) and I've also used it occasionally in a North Sea sim ride. It's a good means of reducing the workload of the PF when things are going a bit pear-shaped, as long as you brief the other pilot on exactly what to do. On the downwash issue, I was landing on my destroyer in our Wessex while she was replenishing from a tanker on the upwind side. As I moved over the deck we arrived in the downwash from the aft superstructure and landed with pretty much full up collective, much to our surprise and fortunately in the centre of the deck.