From experience with the Turbomeca engines (Arrius - the Arriel NEVER fail), be very careful with the OAT when doing engine condition checks. We've found that plotting the graphs using the aircraft OAT gauge will often fail the engine. This gauge is not calibrated normally so could be well off. We take a calibrated digital temp gauge along for comparison, which was suggested to us by Turbomeca. Another thing with the Eurocopter aircraft is that if you fly low for the condition checks, say up to 1500ft the engines will often fail, try flying 3-4000 and see what happens - best to be in the fat part of the graph rather than at the low end. As far as performance height climbs go the CAA have some interesting rules if anyone would care to know...........