End of Season Sunset Warning for SSA-OLC Participants

Fred:

Sorry, but I still disagree.

The time of sunset is the point at which the limb of the sun disappears
to an observer. This is an exact legal definition.

I don't think you'd get far in a court of law if a dozen eyewitnesees
said the sun was still visible but you said your mathematical equation
predicted that it had set!

For convenience, we use a mathematical model that uses a constant term
to correct for atmospheric refraction and you can look up those times
in published tables. However, the correction is approximate and
subject to error.

I merely suggested that since the actual time of sunset was not known,
we should allow folks some slack if they land close to sunset to allow
for this error.

The same goes for pressure altitude, by the way.

Mike

Overcast? What's that - I live in Arizona!


The issue is not atmospheric refraction.

The issue is not the definition of sunset.

The issue is the defintion of _time_ of sunset.

If the "time of sunset' is defined by a mathematical model,
then the time of sunset is independent of the actual atmospheric
conditions and therefor does not vary with them.

That was my point, and I am sorry that I was unclear.

The issue at hand was what time should be used to determine
if a pilot has landed befor sunset. OP's complaint was that
'time of sunset' was highly uncertain. My point is that it is
only highly uncertain if you use an entirely impractical
definiton of 'time of sunset'.

As an astronomer who knows a sunset when he sees one,
how do you know the sun has set when the sky is overcast?

--

FF

Mike the Strike wrote:
Fred:

Sorry, but I still disagree.

The time of sunset is the point at which the limb of the sun disappears
to an observer. This is an exact legal definition.

I don't think you'd get far in a court of law if a dozen eyewitnesees
said the sun was still visible but you said your mathematical equation
predicted that it had set!

Probably not, even if the law specified that the legal defintion of
sunset was that estimated by the exact legal model. But mens
rea isn' t really at issue here, is it?


For convenience, we use a mathematical model that uses a constant term
to correct for atmospheric refraction and you can look up those times
in published tables. However, the correction is approximate and
subject to error.

I merely suggested that since the actual time of sunset was not known,
we should allow folks some slack if they land close to sunset to allow
for this error.

My suggestion for dealing with the ambiguity of the actual time of
sunset is to not use the actual time of sunset. Use the putative
time of sunset, as calculated by a standard formula for the
published lattitude and longitude of the airfield in question instead.
That eliminates the ambiguity. All the pilot needs is to plan
ahead by looking up the putative time of sunset for the various
airfields and an decent clock. If he has a GPS receiver, he
has an extremely accurate clock.

Do you suppose the FAA has addressed this issue?

Allowing them some slack is fine, but does not address the problem.
When does the grace period begin and when does it end?
I'm not addressing the issue of what should be done about
those who land after the deadline, whatever it would be. Only
the practical issue of what to base that deadline on. If you
base it on the 'actual' time of sunset, no one knows what
that deadline is, not in advance, nor even after the fact.

As for what is fair and what is not, IMHO the more objective,
precise, and predicable a rule is, the more fair it is regardless
of how arbitrary it is.

--

FF

wrote:
Do you suppose the FAA has addressed this issue?

ARTHUR:
The swallow may fly south with the sun or the house martin or the
plover may seek warmer climes in winter, yet these are not strangers to
our land?
SOLDIER #1:
Are you suggesting coconuts migrate?
ARTHUR:
Not at all. They could be carried.
SOLDIER #1:
What? A swallow carrying a coconut?
ARTHUR:
It could grip it by the husk!
SOLDIER #1:
It's not a question of where he grips it! It's a simple question of
weight ratios! A five ounce bird could not carry a one pound coconut.
ARTHUR:
Well, it doesn't matter. Will you go and tell your master that
Arthur from the Court of Camelot is here?
SOLDIER #1:
Listen. In order to maintain air-speed velocity, a swallow needs to
beat its wings forty-three times every second, right?
ARTHUR:
Please!
SOLDIER #1:
Am I right?
ARTHUR:
I'm not interested!
SOLDIER #2:
It could be carried by an African swallow!
SOLDIER #1:
Oh, yeah, an African swallow maybe, but not a European swallow.
That's my point.
SOLDIER #2:
Oh, yeah, I agree with that.
ARTHUR:
Will you ask your master if he wants to join my court at Camelot?!
SOLDIER #1:
But then of course a-- African swallows are non-migratory.
SOLDIER #2:
Oh, yeah.
SOLDIER #1:
So, they couldn't bring a coconut back anyway.
[clop clop clop]
SOLDIER #2:
Wait a minute! Supposing two swallows carried it together?
SOLDIER #1:
No, they'd have to have it on a line.
SOLDIER #2:
Well, simple! They'd just use a strand of creeper!
SOLDIER #1:
What, held under the dorsal guiding feathers?
SOLDIER #2:
Well, why not?