Oil Pressure warning in WOT/climb, part deux

[John Courte]

Last weekend, I had a bit of a scare in the form of a momentary low oil pressure warning in climb at WOT.

First thing I did was check the grounds going to the engine monitor module (MGL RDAC). Sure enough, the main ground was not connected to anything at all. The wire was actually pinched between the left mag adapter and the accessory case, crushed flat between the adapter and the gasket and making little if any contact with anything metal. The good news is that the ring terminal wasn't dangling inside the accessory case and shredding itself on the magneto gear or some other thing. What was also happening is that the ring terminal was making contact with the engine block most of the time, until I

1: Exceeded a certain angle of attack (didn't take note of the number) and
2: Pushed the RPM high enough that heat and vibration overcame the tension on the wire holding the ring terminal against the block.

I'm sure this happened the last time I timed the mags. I repaired the wire and reattached it to the engine block.

I'm not sure if the next step was the right thing to do, but I did it anyway: I removed the oil filter, which is a Tempest with the magnet at the end. I found no metal on the magnet after cutting the filter open, and I found no metal in the pleats of the filter. I was going to change the oil and inspect the sump screen, but after finding absolutely nothing on the filter magnet, I decided to skip that.

The next step was to install a mechanical gauge. After I did this, I fired up the engine. The EFIS reading and the mechanical gauge agreed with each other to within 3 psi, as far as I could tell.

Next was a test flight. Runup was fine, warmup was fine, the gauge and the sensor agreed with each other. I did a quick pattern, no issues. I did a climb to 5000' at 100mph, the conditions of the original warning. No issues. The mechanical gauge stayed around 78 during the climb, oil temps were around 165, and cruise was 72psi. At least as far as I remember. I was flying the plane rather than staring at the instruments, which is how you're supposed ot do it, if I recall correctly. Tonight I'll check the flight logs from the EFIS and plot the graph of the whole flight.

I landed, decowled and looked for anything interesting. Nothing found.

So I resumed my phase 1 climb tests, checking for anomalies. In 4 runs from 1500 to 5500' at 100mph and 110mph (8 total), no abnormal oil pressure or temperature readings. CHT's never went above 400.