Vernon Tryon says:

Hi Capt Jeff. Thanks for another great podcast, #56. I was fortunate to have a 2 hr drive today and could get through the whole thing. You deserve another cup of coffee for getting through that one. Here are some random comments: Thanks for addressing my question about the quality of cabin air–can’t believe you researched it to the point to quoting a GAMA article–very interesting and informative. — One comment on the vapor trails. H2O is a by product of combustion. As you said, if atmospheric conditions are just right, that exhaust becomes frozen, and visible (thus the gap between the exhaust of the engine and the visible moisture as it cools and freezes). I was lucky enough to witness the 1966 altitude record set by Walter Cable (Cable Airport, east of L.A.) when he exceeded 43,000 in a stock Cessna Turbo 210 (I believe the record still stands for the category of aircraft). Anyway, to a point, we could observe a very slight vapor trail produced by his piston engine. The temp at that altitude was about -60 deg F. Come to think of it, I think my pickup leaves a “vapor trail” of sorts from its exhaust on these cold Colorado morning when it’s near freezing. — You had a listener with a question about blood sugar and flying. One time when I was teaching ground school at a community college I was showing a graphic on aircraft lighting. A student asked how I could tell between the red light and the green light on the wing tips. I immediately suspected he had a problem with color blindness and suggested he get an FAA Medical. You have many listeners who want to pursue a career in aviation and I relate that story to illustrate the importance of making sure there are no medical issues standing in the way before spending a lot of money pursueing the career. — I’m surprised no one has mentioned how you end your podcasts. I love the bird chirping, followed by a low level jet pass then the beep, beep of Roadrunner. I hope everyone listens all the way through to hear that. —Thanks for your dedication. Keep the sunny side up and the greasy side down. Vernon, retired CFI, Fort Morgan Colorado.