Lost oil pressure - forced landing

[jjbardell]

Twice I had a hairline case crack going from the cylinder #1 radiating through a head stud and continuing out toward the main case bolt. My oil was a tiny weep until it went through a heat cycle on a hot day and I lost 2 quarts in less than 1 minute. Thankfully I happened to be on final when the crack let lose. The final crack looked like the attached, hardly noticeable to the eye but enough to cause oil pressure loss.

In talking with some bug tuning experts, in their opinion, that the additional weight and mounting style of the turbo (one hard support bar to engine mount then using the exhaust to support the rest of the turbo could cause stress on the heads/cylinders as the engine vibrates and moves about with that rigid bar. Plus the additional weight of the turbo on the heads, all resulting in possible hairline cracks where cylinders meet the case on magnesium cases since Mg is brittle and cracks easy with stress.

I would clean the case well and then go over it with a close magnifying glass if none of the other more obvious causes surface.

Side note: I ask the factory or other Aerovee supporters not jump on me for the bugger tuner theory. I want to reiterate they have no experience in aircraft applications and it was just one theory as to why I struggled with hairline case cracks twice. After inspecting my case and engine setup, this was their opinion. They have seen similar issues in the drag world which is why the AL reinforced case is commonly used. It flexes more and handles swings in temps, stress and weight to the heads. I am only trying to assist Robbie, if he chooses to continue searching to identify the issue, so others can learn and prevent another power off landing.