SAS, to do a rotors running download and analysis of the HUMS data on the 225 takes about 5 minutes. The output at the top level is a traffic light system, green obviously requires no further thought, amber or red and the engineers "drill down" to the problem. We have a support contract with EC (something not all operators have) and so a well defined process to determine what to do about it. There have certainly been plenty of cases where a departure is cancelled or at least delayed because of a non-green traffic light.
We can RRTR HUMS analyse on all our fleet - the old IHUMS aircraft such as 332L, S76A, S61, B214, and the new ones although I am not sure about the S92. When the L2 was introduced, with OEM HUMS system, in a typical failure to understand how oil support aircraft are operated, it did not cater for RRTR downloads but we did not operate any L2s so not a problem for us. When we were contemplating the 225 it was a stipulation that we must be able to RRTR download the M'ARMS. EC modified the design to cater for this and of course charged us a considerable sum for the pleasure. This is the kind of thing that Bristow does, that some other operators wouldn't have done. Of course the other operators now benefit from our investment since RRTR HUMS download is now standard on the 225.
There could be an argument for downloading after each landing. Crews would have to take a laptop and process the data offshore. That is fine when you get a green traffic light. If there was a slight problem then it would be difficult to despatch the a/c even though it would probably be OK, and it would be back to shore on a boat a a fairly routine occurrence! That sounds like I am saying we would rather not know that there is a problem because we want to get home, and I suppose there is some truth in that sentiment. The saviour is that in nearly every case, HUMS picks up problems many hours before a failure and to fly for say 3 hrs between downloads is quite adequate if not ideologically perfect. ALARP springs to mind.
HC