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So far so good. Now consider that the amount of heat that the sump itself (the metal tub or oil pan) can absorb and shed or radiate, depends on how much oil is in it. Suppose you have a large sump that is only 10% full, most of its surface area is wasted. It will not absorb and shed as much heat...

Consider a hypothetical oil sump that is infinitely large. Every drop of oil the pump draws from the sump and pushes through the engine starts at ambient temperature, much cooler than the hot temperatures in the engine. As that drop of oil passes through the hot engine, it absorbs some of that...

Here's one possible explanation for this notion. I don't know whether it is correct, but it seems intuitive to me. As each drop of oil travels through the engine it gets hot. Once it passes through the engine and falls back into the oil sump, it cools because the the sump is not as hot as the...

Agreed, this is the most likely explanation. With a fixed pitch prop, any time the airplane hits any updraft, downdraft, or pocket of air having slightly different temperature or density (which it does all the time), the engine will speed up or slow down slightly as the airplane descends or...

Interesting. On a related note, COMM radios can jam GPS and other signals into the GHz range because they always have some amount of harmonic distortion. The 12th & 13th harmonics of COMM frequencies hit the GPS bands. That's why one sometimes has to install lowpass filters on the COMM radio...

Sure, but if you somehow mess up (hard to imagine how) sliding it in and out of the rack, the impact is the same. You're allowed to remove & reinstall the radio, but if you mess that up you lose the VOR, which is just as bad or worse as losing the DME. Perhaps the distinction is this: DMEs and...

Sure, but why? Most regs are based on some kind of reason. Often that reason is clear, but in this case I can't imagine why it's fine to remove & reinstall slide/tray/rack/mount radios, but not a DME.

Why not DMEs?

The coolant additive that Subaru recommended for the model years that were prone to head gasket failures was Holt's Radweld. It smells like ginger. That car never had this additive when new, but Subaru recommended it later when the head gasket issues became apparent. I did add the recommended...

UOA should also detect this condition. The typical case is high Potassium, but there may also be other elements like Sodium involved.

If the car is not overheating, any amount of air ingested should be small and naturally bubble out as you run the engine. As it does, it will draw in more coolant from the reservoir. Just check the reservoir before every drive and ensure it's full. Not full to the top, because coolant expands...

A few years ago I had a similar question with a 2004 Subaru at 100k miles. It was gradually consuming coolant and that was a year when they had more than their fair share of head gasket failures. If that happens the repair can cost more than the car is worth. I took an oil sample and sent it for...

My O-360-A4M has a max of 8, but anything more than 7 blows out the breather quickly. I fill to 7 and add a quart when it drops to 6. The prior O-320-D2G was the same. I like to keep the oil at the highest level that doesn't blow out, since it gives peace of mind and with some engines it can...

Phillips 20w50 XC with Camguard. If my airplane sat unused for more than a week or two between flights, I would consider straight weight 40 or 50. But it doesn't.

Agreed. That's much weaker than the common 95% / P=5% standard, but it's not nothing. If you had to flip a coin, at 67%, it's more likely than not to be real, so if you guessed there was a non-random influence at play you'd be right more often than you'd be wrong.

So the curves do suggest some evidence of something more than random (such as fatigue), but that evidence barely rises above the noise. As you and others have mentioned (and I agree), if that relationship exists it is likely something obvious, such as how the aircraft is used: flying at gross...

This seems to imply that the blue bulge from 10k to 15k means something. Put differently, between 10k and 15k hours, we see a greater proportion of failures than would be expected if the failures followed your definition of random. Past 15k hours the blue line merges back with the red line, but...

Another question about the graph showing random vs. observed failure: true (orange) vs false (blue) should sum to the entire population. For example if 80% are true then 20% must be false. Yet the curves don't add up this way. Blue, orange, and their sum, all increase with hours. So that means I...

In the graph showing random vs. observed failure, the blue line (observed failure) is above & left of the red line (expected random failure). And the graph shows a bulge from 10,000 to 15,000 hours where the difference is greatest. It seems to me that this suggests a trend where airframes having...

When I repainted my airplane I considered this essential. Otherwise you have no idea what is going on under that paint. Corrosion is a killer and anyone who thinks it's cheaper not to strip off all the old paint is fooling himself in the long run. Also take the opportunity to replace wingtips...