LEM,
Sorry old chap, but you have missed the point of the calculation completely.
The point of the exercise is to get the BIGGEST single engine circle that you can - it is quite a complex calculation if you do it properly, involving take off at max weight, climb to max practical cruise altitude for the weight, cruise for a period of time, have an engine failure, descend to a single engine cruising altitude etc etc (from my distant memory!)
Old Smokey gave his company's number - 432 nm.
In our company it depends on engine, airframe and winglet configuration but varies around 410-430nm (roughly).
By using the calculation methods that you used you limit yourself to using airports within your 280 nm range ring, which in practical terms is quite limiting.
edited to change depressurise to have an engine failure - thinking about something else at the time!!
Last edited by Dehavillanddriver; 29th January 2006 at 02:15.