Stumbled across this accident report re: the _1 nose gear leg which is quite interesting:
https://www.mitma.gob.es/recursos_mfom/ ... ort_nm.pdf.
It suggests that Diamond is currently working with Transport Canada to update the existing airworthiness directive. This would bring the AD in line with the latest MSB which moves the inspection interval from 200 hours to 100 hours for the original part and the _1 part. Apparently this is held up due to the type of dye penetrant testing that should be performed. I noticed that on this years inspection SouthTec used a kit from Diamond to perform the test. The accident report suggests that it may be fairly common that the previous tests may give false confidence based on the type of penetrant test performed (type I vs type II penetrant).
Installing the _2 part is supposedly the terminating action for the as yet unreleased AD. However, the AMM still requires inspection of the NLG at 100 hours. However, this is purely a visual inspection unless cracks are suspected, when a penetrant test should be performed.
It looks like the _2 part has an additional 1mm of wall thickness on the nose leg fork pivot. Tests suggest that the _2 part may last 6 to 10 times longer than the _1 version.
Finally, the report suggests that the failure in this case was rather sudden. The accident airplane was just 110 hours since the recent 200 hour penetrant test and 11 hours since the last 100 hour visual inspection. This suggests the failure occurred rapidly between 100 and 110 hours. That was my experience as well.