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Idle (600-800 RPM) when full rich promotes plug fouling, and hold short would be a bad time for that, since you've already done your run-up and you're about to take off. If you lean aggressively after the runup, then the plugs won't foul at idle and if you forget to enrich before takeoff (you do...

That's true. However, "not lean enough" is a common problem. Many engines can't get lean enough to reduce temperatures. The engine gets rough before it gets that lean. So the pilot leans as much as he can, just rich of rough, which puts the engine in the red box. He gets good fuel economy and...

I keep it as terse as possible. For example when flying from Seattle to the San Juans: "Whidbey Approach, Skyhawk XXXXX, Bush Point, VFR to Orcas". This follows the overall communications format from the AIM 4-2-3.a.1: WHO you are talking to WHO you are WHERE you are WHAT you want The fact...

Yes, excessive fuel does cool the engine. And it's better for power because the mixture vs power curve is asymmetric: being X% lean loses more power than being X% rich. Yet it is also less efficient (obviously) and over time it gunks up the valves. At the risk of stating the obvious, for the...

Running in the "red box" kills valves. If you lean it enough, you're out of the box. If you enrich enough, you're out of the box. The worst case is to lean it, but not enough to get out of the red box.

Yep, with the magnetometer the DG becomes an electronic compass instead of an acceleration & integration instrument.

The AI calibrates itself when you first turn it on. If the airplane is parked on a non-level surface, the AI will get a false horizon. It will adapt to that and shift back to normal, but it will take several minutes. Parking on a non-level surface is more of a problem for the DG. It will drift...

It's not about "away" or "toward". It's not about "left" or "right". It's about fly a heading on the side the needle swings toward. Think of it as, the needle is pointing toward a heading you need to fly to intercept whatever is at the top of the dial.

It is correct. It doesn't matter which radial you put on top. For example, 45 or 225. One way, the needle swings left, the other way, it swings right, but in both cases, the headings you need to turn to are on the same side the needle swings. This method eliminates the bugaboo of "reverse...

I get the same symptom during ultra endurance sports events as I approach my limits. First, I start to lose peripheral vision. If I don't slow down or stop, it gradually tunnels in and then colors fade to grey. When pushing the limits I keep aware of this so I can avoid pushing too hard, passing...

Regarding reverse sensing, here's a way to think about it differently. If the needle is not centered, then it's swinging left or right. If you look at the radial numbers around the dial, following any of them on the same side as the needle, will take you to radial that is dialed in at the top...

If "Sats to 84" means your blood O2 saturation level was 84%, that is too low and unsafe for flying, at risk of impaired judgement and cognitive function.

If you have an O2 sensor, just go ahead while monitoring. Start descending if the O2 drops to the low 90s. One thing that is helpful at high altitude is called pressure breathing. Exhale more completely than you do with normal breathing, and same with inhaling. Not quickly, it's not...

Indeed. If adding as little as 0.05% of TEL makes a significant difference in performance, then removing it obviously does too. Yet the original question was whether removing it significantly changes the ratios of the remaining ingredients, specifically octane boosters like Xylene and Toluene...

How much the ratios of remaining ingredients changes, depends on the volume of TEL that was removed. We can quantify this. The data sheet for 100LL says it has 0.53 mL / L of TEL. By my calculations that's 0.053%. If you remove it, the total volume drops by that fraction, to 99.947% of what it...

The ideal experiment is a random controlled trial over a large number of airplanes, better yet blind so the people fueling, flying, and measuring valve clearances don't even know which fuel was used. The UND study got one part right: a large number of airplanes. But they didn't randomize or...

Correct. What is your point?

True, and this is even more so for carburetors having a full throttle enrichment circuit (sometimes called the "economizer") which distorts the mixture distribution even more. Put differently, at WOT it enriches all cylinders, but some more than others.

When running 100LL in an O-360 or O-320, you can and should lean it any time you are less than 70% power. That's actually good for the engine, keeps the plugs and valves clean. Just make sure you have sufficient airflow for cooling. But if you don't and the engine temps start to rise, usually...

These O-360 engines have STCs for 91 octane mogas in some configurations. For example, the O-360-A4M in the Cessna 172. If that caused valve recession one would expect to know this already since it's been out there for years. Is there something different about 94 UL versus 91 auto gas?