Why The Hell... (random rant)

"EridanMan" wrote:
Note - this was a semi-inebriated, pedantic rant, I just thought it
might stimulate some good discussion

Isn't there a Usenet regulation of 8 hours between drinking and posting?
Or is it 8 hours of drinking before posting?

And frankly I'm shocked, shocked I tell you, to see pedantry on Usenet!

On Apr 4, 2:52 pm, Mxsmanic wrote:
Early ships navigated using a compass as one important instrument, but a
compass along was never good enough. It wasn't enough four hundred years ago,
and it's not enough now. If all you have is a compass, you're in deep
trouble.

Sorry, I have to mildly disagree as far as flying goes, that you'd
automatically be in "deep trouble". Many pilots use just the
compass / DG for cross-country flying.

For cross-water... an airplane, at a sufficient area altitude, does
not have to worry about running aground. Therefore a simple compass
was "good enough" for winged flight across the Atlantic starting in
1919. which is not "four hundred years" ago.

True, when crossing longer distances towards smaller targets (such as
islands in the Pacific), star sightings were important, or even on
shorter distances with unknown wind, but the compass was still the
main direction finder.

Kev

writes:

For some people, quite often, and for some others, all the time.

And for still others, never.

You do understand there are real, flying, airplanes with no electrical
system, don't you?

Yes, but none that I'd want to fly, any more than I'd want to cross the
Pacific in a log raft.

--
Transpose mxsmanic and gmail to reach me by e-mail.

Peter Dohm wrote:

The magnetic compass has exactly one thing in its favor, and that is just
plain old Brute Reliability.

I like the mag compass too. While they don't rely on any aircraft systems
to work, there are things that can cause them to be innacurate. The earths
magnetic field varies in strength and isn't all that constant in all
locations (and it's getting worse).

I was reading Lindbergh's book about his transatlantic flight and at one
point, both his whiskey compass and Earth Inductor Compass were just wobbling
around uselessly. Eventually, they both started working again on their own,
but he was guessing at his heading for nearly an hour.

I can relate. I have a video that I took on a cross country flight, of my
mag compass doing rapid 360s. It lasted about 5 min. and there were no
magnetic anomolies listed on the chart in that area. There were also no UFO
sightings reported that day :-))

John Galban=====N4BQ (PA28-180)

--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums...ation/200704/1

writes:

A sensor to find true north in an airplane in flight doesn't exist.

GPS finds true north. And, just incidentally, you can find true north by
looking at the sky. ANS will do that, and people can do it, too.

The isogonic lines on a chart take care of all the problems of where
the actual north/south magnetic poles are.

Documenting them doesn't really eliminate them.

Wrong again, bucko, there is nothing better for finding north in an
airplane in flight.

GPS is better, and more accurate, to name just one.

The only ways to find true north are celestial navigation and a true
gyro compass.

You can find true north by looking at the sky, or with GPS, or with ANS
(automated looking at the sky), or with an INS. The latter usually has to be
on the ground, although some systems support align-in-motion with a longer
setup time.

You can't use celestial navigation unless you have a clear sky, an
almanac, a precise clock, and the necessary instruments to measure
celestial angles and the training to be able to use it all.

You need a precise clock to do just about any navigation. The need for the
rest is debatable, depending on how resourceful you are.

GPS could be used to indirectly find either type of north, but it
doesn't work without power, which is an important concideration
when flying a real airplane without a pause button.

Unless the airplane is a glider, you have power.

Inertial navigation requires an initial set up against something
else, constant updating measured in minutes, and again, power.

One third correct: it requires power, but engines provide power. It doesn't
have to be set up against anything else to find true north. It doesn't need
to be constantly updated; the whole idea is to be fairly autonomous.

--
Transpose mxsmanic and gmail to reach me by e-mail.

writes:

Sorry, I have to mildly disagree as far as flying goes, that you'd
automatically be in "deep trouble". Many pilots use just the
compass / DG for cross-country flying.

A compass / DG is not just a compass.

You can't do much with just a compass alone. You need a clock, some charts,
other things ... not _just_ a compass.

Therefore a simple compass
was "good enough" for winged flight across the Atlantic starting in
1919. which is not "four hundred years" ago.

They had more than a simple compass. In particular, they had accurate clocks,
and charts.

--
Transpose mxsmanic and gmail to reach me by e-mail.

It's a nuisance for maintenance, but it frees
the pilot from calculating the variation at
the operative time. Just to off-load the pilot.

A good answer. Same for winds in flight, etc. Everything is based on
the magnetic to make it easier for the pilot. [..]

Oops! I can't believe I wrote that about winds in flight. Of course
they're true, so they can be used over a wider area. Winds at the
_airport_ are magnetic, is what I meant to say... so the pilot doesn't
have to convert while landing.

Hmm. So if we switched to true North navigation, then runways would
all need repainting... but at least they and the VORs wouldn't have to
be changed ever again ;-) Seems like something the government would
come up with to save money!

Kev

I was wondering whether to mention something about the probable long term
causes of drift in variation--and then I finally noticed the smiley.

Thanks :-)))
Peter

"EridanMan" wrote in message
oups.com...
...
Why in gods name are VOR's Mag heading based?

Because that's how God intended it.

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

"Mxsmanic" wrote in message
...
Maxwell writes:

What did you have for dinner last night, Welsh Rarebit????

My point is that you have to strike a balance between assuming all
equipment
will work perfectly and depending on that, and assuming that all equipment
will fail and trying to plan for that. In reality, chances are that all
equipment will work; and the chances of equipment failing diminish rapidly
as
the number of simultaneous failures increases.

It's true that a compass always works--more or less, since compasses are
so
finicky even when they are "working"--but I'm not sure that this is really
much of a practical help if nothing else works. All a compass can do is
tell
you your direction of flight in a very approximate way. That isn't much
use
for getting where you want to go. Charts help a lot, but you need more
than a
compass to find out where you are on the chart, and if you don't know
where
you are on a chart, a compass won't help.

Early ships navigated using a compass as one important instrument, but a
compass along was never good enough. It wasn't enough four hundred years
ago,
and it's not enough now. If all you have is a compass, you're in deep
trouble.

You're actually better off with an accurate watch and a way to shoot the
stars. But even that is more of a theoretical method than a practical
method
these days.

When people talk about how this old method or that old method is reliable,
they tend to forget how many people died in the days when these "reliable"
methods were the only ones available.


So....ya say ya went back for more.

"Mxsmanic" wrote in message
...
writes:

Sorry, I have to mildly disagree as far as flying goes, that you'd
automatically be in "deep trouble". Many pilots use just the
compass / DG for cross-country flying.

A compass / DG is not just a compass.

You can't do much with just a compass alone. You need a clock, some
charts,
other things ... not _just_ a compass.

Therefore a simple compass
was "good enough" for winged flight across the Atlantic starting in
1919. which is not "four hundred years" ago.

They had more than a simple compass. In particular, they had accurate
clocks,
and charts.


You need to go back to the breast feeding forum, at least you have some
recent and actual experience in the subject......or was it just for
mothers?????