OT: RF propogation in cold weather

Any ultralight time?

Jon

How can you apply PV=nRT to derive temperature versus altitude?

John

Keep everything constant except P and T. Note how P changes with altitude, and voila! ...the dry adiabatic lapse rate.

That sounds great, until you actually plug in the numbers. Try it.

John

The numbers certainly worked fine when I derived the DALR in the undergrad meteorology course I took in '73.

snipped-for-privacy@att.bizzzzzzzzzzzz a écrit :

Yup, but the DALR isn't related to the (average) vertical temperature gradient of still air that JL refers to, which is, on average, 0.65°C per 100m. Rather, DALR describes how air cools down when moving up, in an adiabatic manner, and is 1°C per 100m. It's that difference that set a limit to the height thermals can rise.

Try 0 to 1000 feet. The air pressure is about 0.96 atm at 1000'. So using P and T in the equation, 300K at ground level suggests about 12K lower at 1000 feet. Almost 22F. Factor of 6 from reality.

John

About 30 minutes ... just enough to scare the bejesus out of me.

Jim

Ex-lax is cheaper.

hehe. I got all enthused with the idea way back before the FAA had __ANY__ rules and it was considered "hang gliding with a lawn mower engine." Still have the original plans for a WEEDHOPPER, nicely folded up in storage. Never tried to build it, though. Still haven't put any time in one. Look at them, wondering if I might someday. Maybe not.

Anyway, I was talking with one of the controllers up in the Hillsboro control tower, some years ago. They told me a recent story (then) about an ultralight that PDX had picked up above 18k', somewhere around the Troutdale area. They had no idea how the pilot had managed to get it up there, but knew it wasn't flying IFR and couldn't possibly have been equipped for it, either. I guess that story made the rounds.

If someone had managed to get an ultralight anywhere close to the height they were discussing, I can only imagine how nuts that guy must have been. Wonder if he's still alive, even. (The 'old'/'bold' pilot saying comes to mind...)

The engine that had attracted me (mostly because I get curious about unusual things) was a $2500 unit made up in Seattle called the "Pong Dragon." Custom made to order, it was a 6 cylinder radial with two offset stacks (3 cylinders per) and a separate carburetor for each of the 6, that had to be individually set up. Produced almost 2HP/lb and weighed

Guess I'm lucky I never did much more about it and stayed with the Skyhawk, Skylane, and Arrow. Might have killed myself by now, otherwise. Or might have had some fun. ;)

Jon