Attached are links to video, stills and pilot testimonial to a piston racing engine installed in Relentless NXT hand grenading from loss of engine oil pressure. Prop to flat pitch, engine seized due to oil loss, prop hub and blades snapped off and the sound was impressive. Pilot then made a deadstick safely, and CFR hosed down the engine cavity.

 

Let me speculate further.

 

The oil line/fitting to the prop governor fails. The prop goes to fine pitch. The engine fails from mechanical

over-speed, not loss of oil pressure. Looks like it pulled a rod into two pieces and beat itself to death.

 

Although the pilot chose not to trade excess speed for altitude in this case, and did a fine job of recovering the aircraft, it may be a better choice if you are not in the center of a big airport to capture that energy while it is available. For us slow thinkers, lots of altitude means more range and more time to think.

 

Not pointed out was the aluminum fitting failing through the threads. In almost all cases a "Bending" failure will be "Through the threads" That is where the smallest cross section is and the greatest concentration of stress risers. The question should be: How did this fitting get itself into a bending load?

 

Was that "B" nut tightened without backing the fitting up with the correct aluminum wrench or was it a Chinese fake Crescent wrench? Was there an Adel clamp close by to take up the weight of the hose in those high G turns?

 

The other favorite activity among the unwashed is to turn the fitting with the pipe threads just another 1/4 turn to get the other end to point in the right direction. Keep a selection of such fittings and from different manufacturers, and hand select the one that goes in with the correct torque and ends up where the free end needs to be. Over torque the fitting to get the direction right is a bad idea. A damaged 90 and an undamaged 90 look the same and go back into the fittings drawer to be used years later on your friends airplane.

 

Or use a straight fitting with a 90 degree hose end or better, a sweep 90. And support the hose per the catalogue.

 

There are rules for installing hose and fittings. Found in every hose catalogue.

 

And yes, I have pulled a few rods apart on the dyno.

 

Lynn E. Hanover