When we were on holiday in Corfu this year, my brother who is a member of Cabin crew' lol ', only joking, phoned and said he had gone out of hours because the a/c had gone Tech due to a bleed valve fault, so my Dad said he didn't want anything to do with it as he was on holiday, as we were on the phone to my brother he said it had been Tech for 18hours and he said all he could see was some Tech with his head under the cowling and a load of line engineers standing round troubleshooting, now when my brother informed my father of this fault he said straight away, they need to change the PRSOV, now I knew what this stood for but my dad has been a licenced a/f engine guy for 28yrs, and would you believe it, my Dad got a phone call on holiday informing him of the situation from maintrol, and the action taken was a PRSOV change, I really did find this amasing and extremely impressive, but what does a PRSOV do? I couldn't believe all he was told was minimum info and he knew what to do straight away!!! does anyone know what a PRSOV does? and how do you become that good at troubleshooting??