I think I'll side with the Boeing guys, NASA, and Lockheed guys on this one. Maybe a few airline guys, too. Also there was a guy named Koch, his name appears frequently in runway length vs. density altitude charts.
Respectfully,
dg
When it applies to piloting full size aircraft, especially when a wrong compensation for barometric pressure can cause the apparent altitude of runways to differ from the measured heights above sea level, the values and calculations are far more critical and are corrected for a number of variables. As far as your altimeter is concerned you plug in the correction and away you go. It's all done by a calculator, chart or software now. Plug and play. Of all the items that require such calculation having your instruments calibrated to account for atmospheric conditions that is the most important so you don't accidentally fly into the ground during limited visibility conditions, or report the wrong altitude and put your self into a collision condition.
In our application, and that is where this whole topic started, is model airplanes. These effects are trivial, Unless and let me stress! Unless you are at the edge of the envelope of the wing design. (wing loading, drag, etc.) There are elements that factor much more, and effect flight performance than differing air density changes on a Hot Day vs Cool.
If your plane flies crappy in Hot lesser density air, Some thing is wrong with your model and not the air. I bet if you compared your flight against someone who had a model with a light wing loading they would not be having such problems. Garf and I both fly mainly in Florida. HOT HOT, and most times very humid. My old Vector 40 weighed in at 39.5 ozs powered by a LA40.
That plane turned like the edge of a razor blade even when the air temp was 95 degrees +. Engine runs in those temps and humidity were a challenge to get right and some of my engines at the time would not hot start after a flight in those conditions without a significant cool down period. Also had a OS 40 FSR start without even having the battery connected, I was turning it over by hand to get it primed and all of a sudden the dang thing fired up.
Engine runs, power, rpm's torque are impacted far more from atmospheric temperature, density and humidity levels. The window of the fuel / air mixture ratio is much much tighter. So small changes in temperature, density, humidity play a much more significant role. Especially since we are still using the most primitive fuel delivery and atomization system ever devised.
This was a fun and enlightening discussion though and it's great when everyone contributes something, certainly made me think and go back and do some research.
I knew I had a pretty good grasp of it as it could be a matter of life or death when going SCUBA. In diving you live and die by atmospheres of pressure, the partial pressures of gasses, Boyles law, the solubility of differing gasses in body tissues and blood stream. Effects of super saturation and and a ton of the very stuff that put you to sleep in college or high school.
Go under water and you realize the importance of all those things that you thought you would never ever use.
Did you know that Pure Oxygen becomes toxic at depths of 30ft?