Keith . .. .Well done. Great stuff.. .. .A comment though if I may:. .. .15 years ago in the UK the Rolls people I dealt with talked only of Surge. But there were two types of surge, Self Clearing (your Stall) and Locked In (your Surge) and of course only one surge line to go with the running line.. .. .In the USA at that time everyone seemed to use the word Stall instead of the word Surge.. .. .I would be interested to know when the ATPL definitions you describe came into use.. .. .Regards. .. .John