Chris: drifting I admit, but to follow on your story of the 2 edged sword and differing rules. In early 80's I was in Corfu B732 with a UK airline, departing for EDI from the northly; i.e. towards the mountains. We had RTOW tables from our in house performance guru. No mater how sharp the pencil we could not get the fuel on and had to plan a tech/fuel stop in BHX. Meanwhile, another operator, with the very same ac/ & engines, who was operating charters on behalf of my host airline, loaded up and blasted off for GLA in one foul swoop. How on earth?
I year later I was in a night stop hotel and found a crew from the other airline and asked the question. They did not have RTOW tales and used QRH figures, i.e. balanced field. I asked about the obstacles and mountains. they said this was assessed beforehand and they decided that if anything untoward happened before 1000' they would turn right avoiding the granite visually. Good game.
A few years later I flew for them and they had progressed from B732 - B733. That also was a catalyst for stringent SOP's & RTOW tables. They complained bitterly that 'the fun had gone out of it.' An easy job had become difficult. However, to be fair, they did wise-up and realise that the gung-ho days were over and they needed to join the party.
But this screen height difference I don't get. There needs to be a buffer in missing the terrain, that is a screen height, and a 'net' climb gradient. The net value has an inbuilt buffer in it. It's safe or it isn't. 15' that is. Why, when conditions are better, do you need more margin? If 15' is safe on Monday, why is it not on Tuesday? What does FAA use? I admit I do not know more than I was taught in basic Perf A, and Chris's story might be a key to it. Why then has it not been reviewed and revised? Is the FAA different? If yes, then EU pax on a code share flight with an FAA carrier will be subjected to differing safety standards in their ignorance. That was always the case about FTL's etc before EASA levelled the field. But in global terms is the field level with all the big boys? What rules do the Far East & M.Easy guys use?