Jabiru 3300 Prop strike

[builderflyer]

Joe,

I have no knowledge as to whether or not subsequent owners of N173CP were aware of its earlier prop strike. I only became aware of it when Marty spoke freely about it to me at Oshkosh one year while he still owned the airplane. It may be clearly documented in the log books, or not. I have no idea but until I learn otherwise, I'll assume that all involved parties have done the right thing by not hiding this important information.

Art,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,Jabiru 3300 #261

[mike.smith]

My experience is with the AeroVee, but prop strike results are pretty similar between any direct drive engine. I had a prop strike that broke off one blade of my Sensenich composite prop, and broke the tip of the other. The nose/spinner never hit the ground. Only after I took the engine apart did I find the prop hub had sheared the woodruff key and rotated a half inch around the end of the crank. Prior to taking it apart the crank appeared to turn normally, so that was certainly not a good indicator. I replaced the crank, prop hub and bearings. I have 350 hours on the engine since I rebuilt it and other than the first flight after the rebuild, have never given the health of the engine a second thought. That's called peace of mind, and that's worth a lot.

For me, there is no way I would fly behind an engine that had even a "mild" prop strike. "Mild" is a hopeful term and not one that matches the reality of physics. The amount of sudden stress on a multitude of connected parts is impossible to guess at. There is very little that can be measured or observed on the outside of an engine, to prove or disprove its health, so I think you need to throw out positive external observations as having very little meaning.

Always ask yourself what a crash investigation would say about your decisions. And more importantly, ask yourself if your very life is worth the risk.

[peter anson]

I had a prop strike while taxiing about 5 years ago. My very early model engine had done 190 hours at the time. Going by the damage to the Prince P-tip prop, Jabiru Australia recommended a bulk strip and new crank which was going to cost A$10,000. I decided to do the work myself. My experience is with motorcycle engines although I have done partial rebuilds on a couple of car engines. The Jabiru is quite straightforward to work on although it is very compact and the designers have obviously been at pains to minimize weight. I did find things wrong with the engine, but nothing to do with the prop strike. I checked the crank for run-out and had it magnetic particle inspected; all good.
I repaired the faults and did several upgrades including dowelling the flywheel to the crank and fitting a newer type exhaust system. My cost was about A$2500 for parts. If you are comfortable (and permitted) to work on your engine I think this is a good approach. I gained more confidence in the engine and in fact it is now a better engine. It no longer has oil weeps from the cylinder base gaskets and no exhaust leaks. The engine has done a further 260 hours since.

Peter