"Steven P. McNicoll" wrote in message
hlink.net...

"Greg Goodknight" wrote in message
hlink.net...

6 degrees, at the equator, is 24 minutes, do the math (remember, 360
degrees in 24 hours) but that's at the equator.


No math required, read the regulation.

I did. What is the working definition of "sunrise" and "sunset" here?




When Grass Valley (O17) had a night
closure a few years ago over a trees and obstruction light snafu,


SVFR is not available at O17.

I didn't say it was. I *was* relating how the local FSDO popped up with 30
minutes for a local regulatory issue.




I pressed the issue with the local FSDO; they came back with
30 minutes being the rule of thumb they use in the 48 states.



The US has fifty states.

Ya don't say! Brilliant observation, Sherlock. Trying to be snotty, are we?
The US has 50 plus some occupied territory (including D.C.) but I was
talking about 48 of them. You can guess which ones if you try. I probably
could have said 49 but I wasn't sure if Hawaii was included in the factoid.


It's not a "rule of thumb", it's a regulation. The regulation clearly
states that fixed-wing Special VFR operations may only be conducted
between
sunrise and sunset (or in Alaska, when the sun is 6 degrees or more below
the horizon) unless the pilot and airplane are capable of IFR flight.

Yes, Alaska sometimes doesn't have a sunrise or sunset.

The ICAO has the 6 degree rule to define twilight; not the sun 6 degrees
below the horizon, but the midpoint of the sun being 6 degrees below the
horizon. For some of that time the sun is showing, and around here there is
light good enough for unlit airport operations until about 30 minutes after
the sun's midpoint is on the ideal horizon, or 30 minutes before for
"sunup". Since that reg calls it sunrise and sunset for 49 states but in
essence quotes the ICAO definition for twilight for Alaska, I'm going to
believe they were not defining a lower standard for Alaska but rather
letting Alaska's aviators figure it out for themselves when they don't have
most would call a daily sunrise and sunset, and when you can see sunlight in
the morning (which is six degrees) it's sunrise, and in the evening and you
can't see sunlight that's sunset.

If controllers really do stop day SVFR operations in California when it's
still light enough to see, I stand corrected; and it could be a lower light
standard in Alaska because the light levels change slowly there. You may
have caught me this time, Steven. It's about time you got one right!

-Greg