in reply to the issues of the through bolts breaking in my experience (mining engineering major shutdown project manager) concurs with a couple of points:
1/ Rolled threads are the norm in Grade 8.8(standard high tensile bolts)
2/ High tensile bolts should be tension only once and to a wet( lubricated value) or a dry value, over tightening will lead to failure.
3/ Cracks propogate from points such as shap edges ie machined threads under high levels of vibration.
4/ Ultra critical bolts are tightened using a bolt stretcher this ensures no torsional loading on the bolt and ensures the correct force is applied.
Iam not claiming to have the answer and are looking at purchasing a Jabiru and have a problem understanding why so many have engines with differing hrs to airframe hours for relatively new aircraft this suggests that there is problem with engine quality to me a student pilot. however this makes me think twice before purchasing a Jabriu
