I am sure 99% of the problems are due to parts . My question is what level of spares should the operator be expected to have on hand ? I know that Eurocopter used to provide a recommended list of spares depending on the size of the fleet. I doubt that many operators believed or provisioned based on these lists How should the financial burden of spares support be split between the manufacturer and the operator? I feel it is the responsibility of the manufacturer to build and have available on the shelf sufficient spares to support the worldwide fleet . After all they have the data on MTBUR and hopefully are tracking total fleet hours. The operator should keep stock of frequently used parts. I am sure the sales man would love you to buy 50% of the value of tha aircraft in spares but I am sure that even government agencies have to justify how much money they have tied up in spares. Why is the large disparity between fixed wing and rotary in terms of fleet availablity. I don't think the mechanics , operators or pilots are smarter so what is the cause .
Edited for grammar.