SDRs, on the other hand, were supposed to be items of a lesser degree of importance, less life-threatening, yet important to note, inspect and perhaps replace or correct over time. This would be the right place for something like my air filter, for example. Over the years, the two programs have grown to resemble each other so closely that there is now very little to distinguish them. Thus, the uses of the two separate reports are nearly interchangeable. The important thing is not to get bogged down in which form is required when, but to get the information into the database.
Trouble is, the system only works if everyone adds information to the databank.
If mechanics are gun-shy about sending in the form, and shops don't report when they see problems requiring immediate attention by a manufacturer, we might discover something a lot more serious than my air filter deterioration. Yet because he had never submitted a Service Difficulty Report, his secret did no one any good. Perhaps if he had sent in a report, pilots and mechanics would have watched for the potential problem, perhaps catching deterioration before it had progressed to the mess staring back at me on preflight. I also asked a couple of local mechanics about SDRs, wondering how often they submit reports on things found during inspections. I can understand a mechanic's reluctance to invite the FAA for shop visits.