Like AM radio, magnetic headings are still with us, even though
navigation in general has advanced by leaps and bounds. When will
true headings be used? The magnetic poles are in continuous motion;
the rotational poles are stable.

Eventually, the magnetic poles will move so far that every station and
aircraft everywhere will have to be recalibrated to account for it,
and all charts will have to be changed. And the poles occasionally
reverse, which would also be somewhat of a disaster for
magnetically-based aviation.

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

Mxsmanic schrieb:

> When will true headings be used?

Never, I hope, as it would render the whisky compass as a reliable
navigation aid near to useless.

> Eventually, the magnetic poles will move so far that every station and
> aircraft everywhere will have to be recalibrated to account for it,
> and all charts will have to be changed.

I'm hoping you fly with the newest maps.

> And the poles occasionally reverse,

Occasionally... :-)))

Stefan

"> Like AM radio, magnetic headings are still with us, even though
> navigation in general has advanced by leaps and bounds. When will
> true headings be used? The magnetic poles are in continuous motion;
> the rotational poles are stable.

There is one, and ONLY one instrument in the aircraft that does not require
a power source or have a common catastrophic failure mode. The sucker will
work and get you home even after it has poured a few tablespoons of kerosene
all over the instrument panel.



>
> Eventually, the magnetic poles will move so far that every station and
> aircraft everywhere will have to be recalibrated to account for it,
> and all charts will have to be changed. And the poles occasionally
> reverse, which would also be somewhat of a disaster for
> magnetically-based aviation.

Charts are in constant revision for magnetic pole movement. Runway numbers
are reassigned and painted on a regular basis. We can take a pole reversal
and in a week's time have a method of compensating for it.

Why are you posing these old chestnuts here? Can't you google on past
discussions on the matter(s)?

Jim

On Sat, 2 Sep 2006 11:31:55 -0700, "RST Engineering"
> wrote:
> There is one, and ONLY one instrument in the aircraft that does not require
> a power source or have a common catastrophic failure mode. The sucker will
> work and get you home even after it has poured a few tablespoons of kerosene
> all over the instrument panel.

Although after losing the kerosene, it tends to jiggle around a bit
more... Been there, done that...

"Grumman-581" > wrote in message
...
> On Sat, 2 Sep 2006 11:31:55 -0700, "RST Engineering"
> > wrote:
>> There is one, and ONLY one instrument in the aircraft that does not
>> require
>> a power source or have a common catastrophic failure mode. The sucker
>> will
>> work and get you home even after it has poured a few tablespoons of
>> kerosene
>> all over the instrument panel.
>
> Although after losing the kerosene, it tends to jiggle around a bit
> more... Been there, done that...

Lose even more kerosene and it'll stop tracking. Done all of the above...

KB

RST Engineering writes:

> Charts are in constant revision for magnetic pole movement. Runway numbers
> are reassigned and painted on a regular basis. We can take a pole reversal
> and in a week's time have a method of compensating for it.

I was wondering about that. Seems like the airports around me have
had the same runway numbers for quite a while, but maybe my memory is
poor, or maybe I'm in a lucky position with respect to the magnetic
pole.

> Why are you posing these old chestnuts here? Can't you google on past
> discussions on the matter(s)?

If you don't want to answer or participate, you don't have to.

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

"Kyle Boatright" > wrote in message
. ..
>
>>
>> Although after losing the kerosene, it tends to jiggle around a bit
>> more... Been there, done that...
>
> Lose even more kerosene and it'll stop tracking. Done all of the above...

Only if the turbulence is so bad that it jumps the needle off the pivot.
Otherwise, as stated, it just jiggles around a bit.

Done it more than once.

Jim

On Sat, 2 Sep 2006 15:05:55 -0400, "Kyle Boatright"
> wrote:
> Lose even more kerosene and it'll stop tracking. Done all of the above...

Not quite so sure about that on my compass... The best I could tell,
it had lost all of the kerosene by the time I got around to fixing it
*right*... I tried a couple of quick fixes prior to getting a repair
kit for it, but they ended up eventually leaking also...

Mxsmanic,

> Seems like the airports around me have
> had the same runway numbers for quite a while,
>

The direction has to change by up to 10 degrees for a change in
numbering.

--
Thomas Borchert (EDDH)

Mxsmanic,

Huh? What's the problem with magnetic? Charts change all the time
because of many reasons. Oh, and the main advantage with magnetic
headings is that compasses tend to indicate them. You need more flying
experience...

> And the poles occasionally
> reverse,

Very occasionally.

--
Thomas Borchert (EDDH)

Mxsmanic wrote:
> Like AM radio, magnetic headings are still with us, even though
> navigation in general has advanced by leaps and bounds. When will
> true headings be used? The magnetic poles are in continuous motion;
> the rotational poles are stable.
>
> Eventually, the magnetic poles will move so far that every station and
> aircraft everywhere will have to be recalibrated to account for it,
> and all charts will have to be changed. And the poles occasionally
> reverse, which would also be somewhat of a disaster for
> magnetically-based aviation.
>
Any Earth-based coordinate system is bound to be out of date soon.
We'll be navigating to the moon and other planets and the concept of
"North" won't be relevant. So, we need to figure how navigation will
work in the Solar system and embed Earth navigation in that system. My
guess is that a system similar to GPS but with stations on the other
planets will work until we venture out of our Solar system.

"RST Engineering" > wrote:
> There is one, and ONLY one instrument in the aircraft that does not
> require a power source or have a common catastrophic failure mode.

You mean the wings or the pilot?

<Ducks and runs>

"Thomas Borchert" > wrote in message
...
> Mxsmanic,
>
> > Seems like the airports around me have
> > had the same runway numbers for quite a while,
> >
>
> The direction has to change by up to 10 degrees for a change in
> numbering.
>
> --
> Thomas Borchert (EDDH)

No, >5 if perfectly aligned to start, <5 in one direction and >5 in the
other if not aligned.

On Sat, 02 Sep 2006 16:14:32 -0400, Stubby
> wrote:
> Any Earth-based coordinate system is bound to be out of date soon.
> We'll be navigating to the moon and other planets and the concept of
> "North" won't be relevant. So, we need to figure how navigation will
> work in the Solar system and embed Earth navigation in that system. My
> guess is that a system similar to GPS but with stations on the other
> planets will work until we venture out of our Solar system.

I seem to remember some talk awhile back about each star having it's
own electomagnetic signature and the attempt to base a navigational
system upon this... Awh, 'ell, this is probably classified, so just
forget that I said anything... <grin>

<this-message-will-self-destruct-in-five-seconds>

Joe,

> No, >5 if perfectly aligned to start, <5 in one direction and >5 in the
> other if not aligned.
>

Let's assume Runway23. It's designated when the real direction is 225.
Now, how much has the real direction to change upwards for it to be
designated 24?

--
Thomas Borchert (EDDH)

On Sat, 02 Sep 2006 21:30:18 -0000, Jim Logajan >
wrote:

>"RST Engineering" > wrote:
>> There is one, and ONLY one instrument in the aircraft that does not
>> require a power source or have a common catastrophic failure mode.
>
>You mean the wings or the pilot?
>
><Ducks and runs>

What about a compromise?
Calibrate the compass as normal but have the lubber line variable so
you can preset the magnetic variation for the area you fly. That way
you can use true headings based on the compass. Maybe a problem if
your partial panel and are using the compass.

The only snag I see is in areas of very large variation. If the
variation was too large I guess you start getting parallax errors too.

Do the modern solid state compasses have provision to change the
variation? That would make it easy or am I missing something?

Thomas Borchert writes:

> Let's assume Runway23. It's designated when the real direction is 225.
> Now, how much has the real direction to change upwards for it to be
> designated 24?

Eleven degrees.

However, if it is designated 22 (it can be 22 or 23 if the real
heading is 225), an increase of only one degree in its true magnetic
heading would require a change to 23.

The rule is to round the true magnetic heading to the nearest multiple
of ten and then drop the last digit. If the true heading ends in 5,
you can round up or down (there is no preference).

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

Jim Logajan writes:

> You mean the wings or the pilot?

Both wings and pilot have some catastrophic failure modes, although
those modes are not typical.

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

Grumman-581 writes:

> I seem to remember some talk awhile back about each star having it's
> own electomagnetic signature and the attempt to base a navigational
> system upon this... Awh, 'ell, this is probably classified, so just
> forget that I said anything... <grin>

The SR-71 navigated by finding stars in the sky and obtaining a fix
from them. I think it needed only three stars in order to do this.
It could do it even in daytime. It wasn't quite as accurate as GPS,
but it was more accurate than anything other than an INS at the time,
and it had better long-term stability.

I think the details of the system may still be classified. I always
wanted to know how it could see stars in daylight (although it could
not see them through cloud cover).

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

DCA (Washington) changed its 00-18 to 01-19 a few years ago.


Mxsmanic wrote:
> Thomas Borchert writes:
>
>> Let's assume Runway23. It's designated when the real direction is 225.
>> Now, how much has the real direction to change upwards for it to be
>> designated 24?
>
> Eleven degrees.
>
> However, if it is designated 22 (it can be 22 or 23 if the real
> heading is 225), an increase of only one degree in its true magnetic
> heading would require a change to 23.
>
> The rule is to round the true magnetic heading to the nearest multiple
> of ten and then drop the last digit. If the true heading ends in 5,
> you can round up or down (there is no preference).
>

Mxsmanic > wrote:
> The SR-71 navigated by finding stars in the sky
> [...]
> (although it could not see them through cloud cover).

I thought the SR-71 flew above all the clouds.

Roy Smith writes:

> I thought the SR-71 flew above all the clouds.

It did, but the aircraft's ANS would take a preliminary fix even as it
taxied out to the runway, if the sky was clear.

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

Mxsmanic,

> However, if it is designated 22 (it can be 22 or 23 if the real
> heading is 225), an increase of only one degree in its true magnetic
> heading would require a change to 23.
>

Hence my use of the words "up to".

--
Thomas Borchert (EDDH)

On Sat, 02 Sep 2006 21:09:00 +0200, Mxsmanic >
wrote:

>I was wondering about that. Seems like the airports around me have
>had the same runway numbers for quite a while, but maybe my memory is
>poor, or maybe I'm in a lucky position with respect to the magnetic
>pole.

Since the markings are to the nearest degree, how often would they
have changed in your neighborhood?

"Roy Smith" > wrote in message
...
> I thought the SR-71 flew above all the clouds.

And high enough that the sky was dark even when the sun was out -- at least
from the photos that I've seen published...

And it was VERY fast. Look up the records they set and then
do some algebra. KC 135 tankers can do about 500 knots and
the SR 71 refueled twice on the record trip California to
London. Just figure out the maximum speed of the SR if it
spent a total of 30 minutes in the refueling process on a 2
hours flight...dash speed of 6,000 maybe.



"Grumman-581" > wrote
in message
...
| "Roy Smith" > wrote in message
| ...
| > I thought the SR-71 flew above all the clouds.
|
| And high enough that the sky was dark even when the sun
was out -- at least
| from the photos that I've seen published...
|
|

And then there is DFW where parallel runways are 17L, 17C, 17R, 18L and
18R. ;)
--
Gene Seibel
Gene & Sue's Aeroplanes - http://pad39a.com/gene/planes.html
Because we fly, we envy no one.




Mxsmanic wrote:
> Thomas Borchert writes:
>
> > Let's assume Runway23. It's designated when the real direction is 225.
> > Now, how much has the real direction to change upwards for it to be
> > designated 24?
>
> Eleven degrees.
>
> However, if it is designated 22 (it can be 22 or 23 if the real
> heading is 225), an increase of only one degree in its true magnetic
> heading would require a change to 23.
>
> The rule is to round the true magnetic heading to the nearest multiple
> of ten and then drop the last digit. If the true heading ends in 5,
> you can round up or down (there is no preference).
>
> --
> Transpose mxsmanic and gmail to reach me by e-mail.

A Blackbird would use less fuel if it didn't leak prior to take-off.


Jim Macklin wrote:
> And it was VERY fast. Look up the records they set and then
> do some algebra. KC 135 tankers can do about 500 knots and
> the SR 71 refueled twice on the record trip California to
> London. Just figure out the maximum speed of the SR if it
> spent a total of 30 minutes in the refueling process on a 2
> hours flight...dash speed of 6,000 maybe.
>
>
>
> "Grumman-581" > wrote
> in message
> ...
> | "Roy Smith" > wrote in message
> | ...
> | > I thought the SR-71 flew above all the clouds.
> |
> | And high enough that the sky was dark even when the sun
> was out -- at least
> | from the photos that I've seen published...
> |
> |
>
>

Mxsmanic wrote:
> Like AM radio, magnetic headings are still with us, even though
> navigation in general has advanced by leaps and bounds. When will
> true headings be used? The magnetic poles are in continuous motion;
> the rotational poles are stable.
>
> Eventually, the magnetic poles will move so far that every station and
> aircraft everywhere will have to be recalibrated to account for it,
> and all charts will have to be changed. And the poles occasionally
> reverse, which would also be somewhat of a disaster for
> magnetically-based aviation.
>

So what instrument would you suggest we use for true headings? GPS does
not give you true heading; it can only give a true course. You can't
reliably use a GPS for verifying your runway heading. GPS headings only
work when you are in motion. Remember the Comair accident? I suspect
such accidents will increase if we switch to GPS based true headings.

Your suggestion will only work if we install gigantic beacons at the
true poles which everyone can navigate by. At present mother nature has
given us such a beacon, albeit a less than perfect one.

Because that's the way it's always been done?

Andrew Sarangan wrote
> So what instrument would you suggest we use for true headings?

Airliners have had 'true heading' available from their INS for
many years.

> GPS does not give you true heading; it can only give a true course.

But isn't it 'true course' that I really want to fly? That line
that I drew on the chart? No more correcting for wind, variation
or deviation, just plot and fly true course. Someday it will happen.

Bob Moore

Bob,

> But isn't it 'true course' that I really want to fly? That line
> that I drew on the chart?
>

Actually, no, I'm flying the magnetic course line my GPS just drew on
its moving map display ;-)

--
Thomas Borchert (EDDH)

Thomas Borchert wrote
> Actually, no, I'm flying the magnetic course line my GPS just drew on
> its moving map display ;-)

Hmmmm....seems as if that really started out computed as 'true course'
to which the GPS added the local variation. :-)

Bob

"Grumman-581" > writes:

> And high enough that the sky was dark even when the sun was out -- at least
> from the photos that I've seen published...

Yes, but the ANS could recognize stars even from the taxiway in broad
daylight. I still don't know how it managed that.

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

Stubby writes:

> A Blackbird would use less fuel if it didn't leak prior to take-off.

The leakage was trivial, and it rapidly warmed up enough to seal the
leaks.

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

Andrew Sarangan writes:

> So what instrument would you suggest we use for true headings?

A combination of INS and GPS would work. It would be at least as
accurate as a compass.

This could be cross-checked against a magnetic heading internally as
long as the exact location of the geomagnetic poles are known.

An ANS could give you true heading even standing still.

> GPS does not give you true heading; it can only give a true course. You can't
> reliably use a GPS for verifying your runway heading.

As soon as you move, GPS can give you a heading, and an INS can
maintain it for you.

> GPS headings only work when you are in motion. Remember the Comair
> accident? I suspect such accidents will increase if we switch to GPS
> based true headings.

How you navigate with true headings is irrelevant here; the important
thing is that true headings never change.

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

Bob Moore wrote:
> Andrew Sarangan wrote
> > So what instrument would you suggest we use for true headings?
>
> Airliners have had 'true heading' available from their INS for
> many years.
>
> > GPS does not give you true heading; it can only give a true course.
>
> But isn't it 'true course' that I really want to fly? That line
> that I drew on the chart? No more correcting for wind, variation
> or deviation, just plot and fly true course. Someday it will happen.
>

Actually, I have never worried about accounting for wind correction,
variation or deviation. I plot the course on a computer, estimate a
heading and then during flight I fiddle with the heading until the
ground track agrees with the plotted course. It makes very little
difference whether the plotted course was in true or magnetic. If there
is an absolute reference for your system, either one should work the
same. With magnetic, we have the compass as the absolute reference.
With true direction, it is not that easy. I don't know enough about INS
systems or how they are used as an absolute reference, but those are
not within the reach of most GA pilots. So, I still don't agree that
navigation systems have advanced to the point where we can abandon the
magnetic based instruments.

Andrew Sarangan wrote
> So, I still don't agree that navigation systems have
> advanced to the point where we can abandon the
> magnetic based instruments.

Hmmmm....I wonder how we used to navigate 'over-the-pole'
back before INS? Hint....Grid Navigation, an unslaved
DG referenced to true north.

Bob Moore

Bob Moore wrote:
> Andrew Sarangan wrote
> > So, I still don't agree that navigation systems have
> > advanced to the point where we can abandon the
> > magnetic based instruments.
>
> Hmmmm....I wonder how we used to navigate 'over-the-pole'
> back before INS? Hint....Grid Navigation, an unslaved
> DG referenced to true north.
>
> Bob Moore

Way back when I was a navigator on a KC-135 using Grid Navigation we
referenced the DG to Grid North, not True North. Big difference between
the two, although I think I know what you're hinting at.

And, I remember taking a celestial shot every 15-30 minutes or so to
check for gyro precession. That would be hard to do in the Warrior I'm
flying nowadays. :>)

--Walt Weaver
Bozeman, Montana

Walt wrote
> Way back when I was a navigator on a KC-135 using Grid Navigation we
> referenced the DG to Grid North, not True North. Big difference between
> the two, although I think I know what you're hinting at.

Right! And at PanAm, we paid real big bucks for those 'low precession'
gyros. Actually they had an anti-precession controller into which one
would set the latitude as one progressed.

Bob Moore

Bob Moore wrote:
> Andrew Sarangan wrote
> > So, I still don't agree that navigation systems have
> > advanced to the point where we can abandon the
> > magnetic based instruments.
>
> Hmmmm....I wonder how we used to navigate 'over-the-pole'
> back before INS? Hint....Grid Navigation, an unslaved
> DG referenced to true north.

I don't claim to know anything about navigation over the poles, but if
it is as simple as you say it is, why do we continue using the
magnetic compass for every-day navigation? My guess is that it must be
complex, difficult, expensive or unreliable.

Mxsmanic wrote:
> "Grumman-581" > writes:
>
> > And high enough that the sky was dark even when the sun was out -- at least
> > from the photos that I've seen published...
>
> Yes, but the ANS could recognize stars even from the taxiway in broad
> daylight. I still don't know how it managed that.

Jupiter, Saturn, and Venus are visible to the naked eye in broad
daylight at sea level, if you know exactly where to look. I've
seen them all, at times when I knew their approximate position
relative to the moon. You must look in exactly the right place --
an error of a half degree or so puts them out of the central field
of view of your eyes and renders them invisible against the
glare of daylight.

The brighter stars are just outside the ability of most people's
naked eyes to see in broad daylight, but a small pair of
binoculars will pick a few out nicely. Again, proper aim is
crucial. Only a handful of the brightest stars will typically be
visible at any given time, but you don't need very many for
navigation.

It sounds like the optics of the SR-71's nav system are at
least as good as a standard issue Mk 1 pair of eyeballs
coupled with a 7x35 pair of binoculars. It may be that, for
rapid startup, the system needs some hint of the location
and time of day to figure out where to begin its search for
stars, but I'm just guessing on that point.

wrote:
> Mxsmanic wrote:
> > "Grumman-581" > writes:
> >
> > > And high enough that the sky was dark even when the sun was out -- at least
> > > from the photos that I've seen published...
> >
> > Yes, but the ANS could recognize stars even from the taxiway in broad
> > daylight. I still don't know how it managed that.
>
> Jupiter, Saturn, and Venus are visible to the naked eye in broad
> daylight at sea level, if you know exactly where to look. I've
> seen them all, at times when I knew their approximate position
> relative to the moon. You must look in exactly the right place --
> an error of a half degree or so puts them out of the central field
> of view of your eyes and renders them invisible against the
> glare of daylight.
>
I remember taking celestial shots of Venus and Jupiter in the daytime
but don't remember ever seeing Saturn. Pointing the sextant to the
right area of sky - not hard since I precomputed the shot - would put
them right in the field of view.

I would imagine the ANS could "see" just a bit better than I could.
:>)

--Walt

writes:

> Jupiter, Saturn, and Venus are visible to the naked eye in broad
> daylight at sea level, if you know exactly where to look.

Are these consistently above the horizon at all locations?

From what I've read, the ANS looked specifically at stars, not
planets, but I may be wrong.

I suppose that technically stars are visible, too, it's just that the
difference isn't perceptible to the naked eye.

> I've
> seen them all, at times when I knew their approximate position
> relative to the moon. You must look in exactly the right place --
> an error of a half degree or so puts them out of the central field
> of view of your eyes and renders them invisible against the
> glare of daylight.

Hmm ... I'll have to try it sometime.

> The brighter stars are just outside the ability of most people's
> naked eyes to see in broad daylight, but a small pair of
> binoculars will pick a few out nicely. Again, proper aim is
> crucial. Only a handful of the brightest stars will typically be
> visible at any given time, but you don't need very many for
> navigation.

The ANS required three, supposedly. It also required a very accurate
clock. With the clock setting, it could find its way. I guess it
just looked around at the sky until it found a few stars, then checked
it against its own computed ephemeris based on the time of day.

> It sounds like the optics of the SR-71's nav system are at
> least as good as a standard issue Mk 1 pair of eyeballs
> coupled with a 7x35 pair of binoculars. It may be that, for
> rapid startup, the system needs some hint of the location
> and time of day to figure out where to begin its search for
> stars, but I'm just guessing on that point.

It definitely needs very accurate time of day, but I don't think it
needs a hint of its location--although may it does, or maybe a general
hint speeds up acquisition (which usually took a matter of minutes, I
think).

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

Andrew Sarangan writes:

> I don't claim to know anything about navigation over the poles, but if
> it is as simple as you say it is, why do we continue using the
> magnetic compass for every-day navigation? My guess is that it must be
> complex, difficult, expensive or unreliable.

I think magnetic headings are still used because of the vast inertia
of the installed base of avionics and instruments, plus the inertia of
so many pilots who have been raised on that.

I certainly won't quarrel with using magnetic navigation as a back-up,
but I do question basing normal navigation on a compass, which is
relatively unreliable compared to more modern methods. If the SR-71
could navigate reliably by the stars half a century ago, I think most
aircraft could navigate reliably today using much more modern
satellite systems.

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

"Mxsmanic" > wrote in message
...
> Yes, but the ANS could recognize stars even from the taxiway in broad
> daylight. I still don't know how it managed that.

http://www.sr-71.org/blackbird/manual/4/4-3.php

"Mxsmanic" > wrote in message
...
> The leakage was trivial, and it rapidly warmed up enough to seal the
> leaks.

I once asked Mary Shafer ( SR-71 Chief Engineer NASA Dryden Flight Research
Center, Edwards, CA) about whether it was true that the SR-71 leaked like a
sieve... She replied something like, "to say that it leaks like a sieve
would be to insult all sieves" or maybe it was, "a sieve that leaked that
much would be pretty useless"...

Here's some interesting readings if you are so inclined:
http://www.netwrx1.com/skunk-works/v05.n129

In certain situations, 1200 lbs would leak off prior to takeoff...

Mxsmanic wrote:
> Andrew Sarangan writes:
>
> > So what instrument would you suggest we use for true headings?
>
> A combination of INS and GPS would work. It would be at least as
> accurate as a compass.

Accuracy isn't the problem. Would it be as reliable?
Would it be affordable and workable in airplanes that lack
electrical systems? And would it work when those
electrical systems failed?

If you're talking about high budget commercial aviation, any
nav system that has the processing power to decode the
GPS signals has the power to apply a local magnetic
deviation to its heading or course output. Updates to
the magnetic deviation can be distributed as needed
with the updates to the nav database. So for these
users, it's sort of arbitrary which reference is used,
as long as there is an agreed upon reference.

For the gliders, Piper Cubs, and other moderate budget
flyers, the price and reliability differences between a
compass and an INS weigh significantly in favor of the
compass.

There is the further issue of inertia. Every pilot flying today
learned to use magnetic headings. Every airplane cockpit
has an instrument (or several instruments) to prominently
display the magnetic heading to the pilot. To convert
wholesale would entail a period of minor confusion at
least.

Finally, what problem would it solve? The shifting of
the Earth's magnetic poles is slow, relatively
predictable, and something we have lived with for
awhile. While true headings may be more elegant
and stable over the very long term, that elegance
doesn't add much practical value.

--Rich

> wrote in message
oups.com...
> Finally, what problem would it solve? The shifting of
> the Earth's magnetic poles is slow, relatively
> predictable, and something we have lived with for
> awhile. While true headings may be more elegant
> and stable over the very long term, that elegance
> doesn't add much practical value.

It's the typical case of a solution in search of a problem...

Mxsmanic > wrote:
> I certainly won't quarrel with using magnetic navigation as a back-up,
> but I do question basing normal navigation on a compass, which is
> relatively unreliable compared to more modern methods.

Unreliable? The magnetic compass is about as reliable is it gets. There's
one moving part, no power source, and the Earth's magnetic field is good
for another few thousand years. What's unreliable about that? Of the
cannonical "watch and compass" navigation kit, the watch is by far the less
reliable of the two.

Roy Smith wrote:
> Mxsmanic > wrote:
>
>>I certainly won't quarrel with using magnetic navigation as a back-up,
>>but I do question basing normal navigation on a compass, which is
>>relatively unreliable compared to more modern methods.
>
>
> Unreliable? The magnetic compass is about as reliable is it gets. There's
> one moving part, no power source, and the Earth's magnetic field is good
> for another few thousand years. What's unreliable about that? Of the
> cannonical "watch and compass" navigation kit, the watch is by far the less
> reliable of the two.

I suspect he was talking about accuracy or precision more than
reliability. Although, if you are talking about finding a distance
point with a high degree of reliability, then that term might be
appropriate. The inherent lack of accuracy of dead reckoning as
compared to GPS means that you will be much less likely to find a
precise point in the distance, and thus you could consider the
reliability of consistently finding that point.

Matt

"Grumman-581" > wrote in message
...
> "Mxsmanic" > wrote in message
> ...
>> Yes, but the ANS could recognize stars even from the taxiway in broad
>> daylight. I still don't know how it managed that.
>
> http://www.sr-71.org/blackbird/manual/4/4-3.php
>
>

Did (or does) the U-2 employ a comparable ANS

Mxsmanic > wrote:
> From what I've read, the ANS looked specifically at stars, not
> planets, but I may be wrong.

Planet, star, it's all the same. It's a point of light in the sky. The
ephemeris calculations are a little more complicated for a planet, but
that's only something you'd notice if you were working it out with pencil
and paper.

Roy Smith wrote:
> Mxsmanic > wrote:
>> From what I've read, the ANS looked specifically at stars, not
>> planets, but I may be wrong.
>
> Planet, star, it's all the same. It's a point of light in the sky. The
> ephemeris calculations are a little more complicated for a planet, but
> that's only something you'd notice if you were working it out with pencil
> and paper.

But aren't the stars stuck to the celestial sphere so that their motion
is fairly simple and easy to predict. Planets are zipping around the
sun, as is the Earth, and the Earth is turning on its own axis. Much
more complicated.

"Chuck Peterson" <charles.petersonxxx@comcast(removethis and xxx).net>
writes:

> Did (or does) the U-2 employ a comparable ANS

The U-2 predates the ANS, I believe, and today I'd expect it to be
using GPS instead, which is much more accurate.

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

Roy Smith writes:

> Unreliable? The magnetic compass is about as reliable is it gets. There's
> one moving part, no power source, and the Earth's magnetic field is good
> for another few thousand years. What's unreliable about that?

Put a chunk of metal next to it, and you'll see. Turn the aircraft,
and see if the compass instantly changes position.

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

Roy Smith wrote:
> Mxsmanic > wrote:
>> I certainly won't quarrel with using magnetic navigation as a back-up,
>> but I do question basing normal navigation on a compass, which is
>> relatively unreliable compared to more modern methods.
>
> Unreliable? The magnetic compass is about as reliable is it gets. There's
> one moving part, no power source, and the Earth's magnetic field is good
> for another few thousand years. What's unreliable about that? Of the
> cannonical "watch and compass" navigation kit, the watch is by far the less
> reliable of the two.

I met a sea captain that piloted an old ship full of refugees from
Latvia to Nova Scotia in 1939 with only a sextant and magnetic compass.
And he said it was overcast most of the time.

writes:

> Accuracy isn't the problem. Would it be as reliable?
> Would it be affordable and workable in airplanes that lack
> electrical systems? And would it work when those
> electrical systems failed?

In modern aircraft, a failure of electrical systems brings a lot more
problems than mere navigation errors. No radio, no other navaids, no
control surfaces in some aircraft, no propulsion in some aircraft.

And while a compass shows magnetic north, that's all it shows. You
have no idea how far north or south you are, or which direction to fly
to your destination.

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

In article >,
Mxsmanic > wrote:

> Roy Smith writes:
>
> > Unreliable? The magnetic compass is about as reliable is it gets. There's
> > one moving part, no power source, and the Earth's magnetic field is good
> > for another few thousand years. What's unreliable about that?
>
> Put a chunk of metal next to it, and you'll see. Turn the aircraft,
> and see if the compass instantly changes position.

All devices have failure modes. Of course there are things which will
interfere with a magnetic compass, but I'll still stand by my statement
that it's about as reliable as a piece of technology can get.

In article >,
Stubby > wrote:

> Roy Smith wrote:
> > Mxsmanic > wrote:
> >> From what I've read, the ANS looked specifically at stars, not
> >> planets, but I may be wrong.
> >
> > Planet, star, it's all the same. It's a point of light in the sky. The
> > ephemeris calculations are a little more complicated for a planet, but
> > that's only something you'd notice if you were working it out with pencil
> > and paper.
>
> But aren't the stars stuck to the celestial sphere so that their motion
> is fairly simple and easy to predict. Planets are zipping around the
> sun, as is the Earth, and the Earth is turning on its own axis. Much
> more complicated.

Depends on your definition of "Much more complicated".

If you're doing it the traditional way, working from the Air (or Nautical)
Almanac with paper and pencil, reducing a planet sight is a couple more
table lookups and a couple more additions or subtractions. Some hulking
mainframe did all the really messy math for you a year or two earlier, in
plenty of time for the tables to be typeset, printed, and bound.

If you're doing it all from scratch with a computer, all the formulas you
need can be found in Jean Meeus's "Astronomical Formulae For Calculators"
(http://www.willbell.com/math/mc3.htm). The book was published in 1979,
and gave formulas usable on the popular hand calculators of the day to
achieve accuracies exceeding any practical navigational need.

In article >,
Stubby > wrote:

> Roy Smith wrote:
> > Mxsmanic > wrote:
> >> I certainly won't quarrel with using magnetic navigation as a back-up,
> >> but I do question basing normal navigation on a compass, which is
> >> relatively unreliable compared to more modern methods.
> >
> > Unreliable? The magnetic compass is about as reliable is it gets. There's
> > one moving part, no power source, and the Earth's magnetic field is good
> > for another few thousand years. What's unreliable about that? Of the
> > cannonical "watch and compass" navigation kit, the watch is by far the less
> > reliable of the two.
>
> I met a sea captain that piloted an old ship full of refugees from
> Latvia to Nova Scotia in 1939 with only a sextant and magnetic compass.
> And he said it was overcast most of the time.

Probably had a watch, too. And a taffrail log. In 1939, that would have
been a pretty standard navigational kit for an ocean-going ship.

On Sat, 02 Sep 2006 19:56:46 +0200, Mxsmanic wrote:

> And the poles occasionally
> reverse, which would also be somewhat of a disaster for
> magnetically-based aviation.

It's expected the poles will flip sometime over the next couple of
centuries. For those of you interested in this phenomenon.
http://www.pbs.org/wgbh/nova/magnetic

Grumman-581,

> It's the typical case of a solution in search of a problem...
>

You got that right.

--
Thomas Borchert (EDDH)

Mxsmanic,

> And while a compass shows magnetic north, that's all it shows. You
> have no idea how far north or south you are, or which direction to fly
> to your destination.
>

And having true heading (and only that) changes this problem how?

--
Thomas Borchert (EDDH)

Roy Smith wrote:
> In article >,
> Stubby > wrote:
>
>> Roy Smith wrote:
>>> Mxsmanic > wrote:
>>>> From what I've read, the ANS looked specifically at stars, not
>>>> planets, but I may be wrong.
>>> Planet, star, it's all the same. It's a point of light in the sky. The
>>> ephemeris calculations are a little more complicated for a planet, but
>>> that's only something you'd notice if you were working it out with pencil
>>> and paper.
>> But aren't the stars stuck to the celestial sphere so that their motion
>> is fairly simple and easy to predict. Planets are zipping around the
>> sun, as is the Earth, and the Earth is turning on its own axis. Much
>> more complicated.
>
> Depends on your definition of "Much more complicated".
>
> If you're doing it the traditional way, working from the Air (or Nautical)
> Almanac with paper and pencil, reducing a planet sight is a couple more
> table lookups and a couple more additions or subtractions. Some hulking
> mainframe did all the really messy math for you a year or two earlier, in
> plenty of time for the tables to be typeset, printed, and bound.
>
> If you're doing it all from scratch with a computer, all the formulas you
> need can be found in Jean Meeus's "Astronomical Formulae For Calculators"
> (http://www.willbell.com/math/mc3.htm). The book was published in 1979,
> and gave formulas usable on the popular hand calculators of the day to
> achieve accuracies exceeding any practical navigational need.

I would worry about running out of fuel while I'm trying to figure that
book out and fat-fingering the calculator.

I believe all U-2s have been retired. The satellite folks are winning
the high altitude intel game. Too bad the U-2 was a nice plane (glider?
rocket???).



Mxsmanic wrote:
> "Chuck Peterson" <charles.petersonxxx@comcast(removethis and xxx).net>
> writes:
>
>> Did (or does) the U-2 employ a comparable ANS
>
> The U-2 predates the ANS, I believe, and today I'd expect it to be
> using GPS instead, which is much more accurate.
>

Greg Copeland wrote:
> On Sat, 02 Sep 2006 19:56:46 +0200, Mxsmanic wrote:
>
>> And the poles occasionally
>> reverse, which would also be somewhat of a disaster for
>> magnetically-based aviation.
>
> It's expected the poles will flip sometime over the next couple of
> centuries. For those of you interested in this phenomenon.
> http://www.pbs.org/wgbh/nova/magnetic
>
>
Interesting, alarmist speculation.

"Walt" > wrote in message
ups.com...
>
> Bob Moore wrote:
>> Andrew Sarangan wrote
>> > So, I still don't agree that navigation systems have
>> > advanced to the point where we can abandon the
>> > magnetic based instruments.
>>
>> Hmmmm....I wonder how we used to navigate 'over-the-pole'
>> back before INS? Hint....Grid Navigation, an unslaved
>> DG referenced to true north.
>>
>> Bob Moore
>
> Way back when I was a navigator on a KC-135 using Grid Navigation we
> referenced the DG to Grid North, not True North. Big difference between
> the two, although I think I know what you're hinting at.
>
> And, I remember taking a celestial shot every 15-30 minutes or so to
> check for gyro precession. That would be hard to do in the Warrior I'm
> flying nowadays. :>)
>
> --Walt Weaver
> Bozeman, Montana

Yeah, Walt. During the Cuban crisis I flew B-52Hs out of Minot AFB, ND.
We flew the "North Country" route. From Minot fly East to the "Black Goat"
refueling area in the Atlantic just off the U.S. East coast.. North to the
Artic..SW to "Cold Coffee" refueling area in Alaska..out the Aleutian chain
to the periphery of the Soviet Union...back to Seatttle; Spokane, Minot and
land 24 hours after takeoff.

The Navigator had to convert Magnetic/True headings to/from Grid while also
observing celestial references for sextant shots. Not the time to have a
weak Navigator. Story was that one Navigator got it all screwed up and
actually penetrated Soviet airspace. Shots were fired in front of the
bomber by Soviet interceptors. The B-52 immediately reversed course and
nothing further happened. As with all B-52s in Airborne Alert it carried
nuclear weapons and could have been a disaster. Due to the sensitivity of
the crisis nothing was ever published about that situation that I know of.

Darrell R. Schmidt
B-58 Hustler Web Site URL (below)
http://members.cox.net/dschmidt1/

"Mxsmanic" > wrote in message
...
>
> From what I've read, the ANS looked specifically at stars, not
> planets, but I may be wrong.

When I was a tech in the B-2 program about 10 years ago I gained some
experience with its astro inertial navigation system. It was made by
Northrop, and word of mouth was that it was descended from the SR-71
system, but I don't know for sure.

The B-2 AINS had a catalog of 61 stars. No planets. The rapidity and
complexity of planetary motion would necessitate separate algorithms
for stars and planets.

Precise time came from an ATTU (airborne time transfer unit?) which we
synchronized to UTC on a lab time standard and installed in the
aircraft just before the crew arrived, to minimize clock drift.

The star tracker used a telescope of about 3 inch diameter on an
alt-azimuth mount. To find a star, it first aimed at the expected
point in the sky (based on the current nav solution), then did an
expanding square spiral search. After aquisition, it tracked for only
a short time before moving to the next star. If the search failed
(perhaps due to cloud), the tracker kept trying different stars. It
could shoot through holes in the clouds. And it worked just fine in
broad daylight.

I was able to verify that during a long ground test outdoors. The test
had nothing to do with the AINS, but there was enough slack time that
I could play around with it. First I aligned it to the GPS position,
then changed the AINS mode to pure inertial. Slowly its coordinates
drifted away from the GPS. Then I switched to stellar inertial mode,
and watched that star tracker drive the AINS position right back on
top of the GPS.

In those days the AINS accuracy was classified, and I'm not sure if
that's still the case, so I won't say exactly how well it did. But it
was impressive.

There was a period when we had trouble with star tracking during the
day, due to contamination on the inner surface of the window. (It
appears as a dark opening about the size of a dinner plate, a few feet
to the left of the cockpit in B-2 photos shot from above.) There was a
metallic grid that made the inside hard to clean. You couldn't just
wipe it off. I remember seeing some poor guy individually cleaning
several hundred tiny squares of glass with Q-Tips and solvent!


Getting back to the magnetic topic, the only magnetic compass on the
B-2 is the standby compass. It's made by Airpath and looks just like
one you'd see in a light plane. By default the glass cockpit heading
readouts show magnetic (you can select true), but that's synthesized
from gyro-derived true heading and a variation table in the aircraft
software.


Maybe someone else has already mentioned that VORs and TACANs are
aligned so their radials are close to the magnetic direction. Changing
them to true would be pretty expensive and disruptive.

--
Paul Hirose >
To reply by email remove INVALID

Stubby writes:

> But aren't the stars stuck to the celestial sphere so that their motion
> is fairly simple and easy to predict.

Yes, relatively speaking.

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

Paul Hirose writes:

> Maybe someone else has already mentioned that VORs and TACANs are
> aligned so their radials are close to the magnetic direction. Changing
> them to true would be pretty expensive and disruptive.

They have to be changed if the magnetic poles drift, too. In some
locations this may occur as often as once every few years, if an
accuracy of plus or minus half a degree is required.

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

Stubby writes:

> I believe all U-2s have been retired. The satellite folks are winning
> the high altitude intel game. Too bad the U-2 was a nice plane (glider?
> rocket???).

The U-2 is still used, oddly enough (whereas the SR-71 is not, at
least officially).

It's a conventional aircraft, but with some characteristics and uses
that make it extremely difficult to fly. It is an aircraft with a
distinctive "coffin corner," that is, in a typical mission cruise
configuration, its maximum speed is only a few knots higher than its
stall speed, and if the speed is not precisely held within those
narrow limits, trouble results.

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

Stubby writes:

> I met a sea captain that piloted an old ship full of refugees from
> Latvia to Nova Scotia in 1939 with only a sextant and magnetic compass.
> And he said it was overcast most of the time.

Lindbergh had only a compass and a maritime map (with his hand-drawn
route on it) that he had bought in a shop in San Diego to get him from
New York to Paris.

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

Thomas Borchert writes:

> And having true heading (and only that) changes this problem how?

It doesn't. But true north doesn't move, and it's right at the top of
standard maps.

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

Stubby writes:

> Interesting, alarmist speculation.

What is alarmist about it?

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

Grumman-581 wrote:
> > wrote in message
> oups.com...
> > Finally, what problem would it solve? The shifting of
> > the Earth's magnetic poles is slow, relatively
> > predictable, and something we have lived with for
> > awhile. While true headings may be more elegant
> > and stable over the very long term, that elegance
> > doesn't add much practical value.
>
> It's the typical case of a solution in search of a problem...

This is like the remark from non-aviators why we still use the archaic
units of nautical miles and knots. I have also had people comment why I
continue to use "clunky old Linux" instead of windows. The latter one
was from a highly educated person in Engineering. Clearly, these
types of remarks are due to misconceptions or lack of knowledge. I am
glad these people don't run the world (or may be they already do:-))

Mxsmanic,

> It doesn't. But true north doesn't move, and it's right at the top of
> standard maps.
>

Dodging and back pedaling again. You really ARE like this, are you?


--
Thomas Borchert (EDDH)

Andrew Sarangan writes:

> This is like the remark from non-aviators why we still use the archaic
> units of nautical miles and knots.

That is a different issue. Nautical miles and knots are stable and
need not be changed because aviation is effectively isolated from
other domains in which units of measure are required. In contrast,
magnetic poles move, and magnetic compasses depend on a magnetic field
that not only moves on its own throughout the planet but is also
distorted locally and regionally.

I have no problem with using nm and kts in aviation, or even with
using pounds for fuel, as long as everyone is on the same page.
Trying to switch units has sometimes had tragic results.

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

On Sat, 09 Sep 2006 00:09:20 +0200, Mxsmanic >
wrote:

>Thomas Borchert writes:
>
>> And having true heading (and only that) changes this problem how?
>
>It doesn't. But true north doesn't move, and it's right at the top of
>standard maps.

Except that apparently true north DOES move. The tsunami/earthquake of
a year and a half ago reportedly caused the north pole to shift about
an inch as well as decreasing the length of a day. Just goes to show,
you can't depend on anything.

RK Henry

RK Henry writes:

> Except that apparently true north DOES move. The tsunami/earthquake of
> a year and a half ago reportedly caused the north pole to shift about
> an inch as well as decreasing the length of a day. Just goes to show,
> you can't depend on anything.

All earthquakes cause such effects. However, if they produce changes
that are below the resolution threshold of avionics, they aren't a
problem. The magnetic pole, on the other hand, moves perceptibly over
time--enough to require new charts and new regulation of stations and
instruments.

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

Stefan wrote:

> Mxsmanic schrieb:
>
> > When will true headings be used?
>
> Never, I hope, as it would render the whisky compass as a reliable
> navigation aid near to useless.

>
> > Eventually, the magnetic poles will move so far that every station and
> > aircraft everywhere will have to be recalibrated to account for it,
> > and all charts will have to be changed.
>
> I'm hoping you fly with the newest maps.

Mxs doesn't fly except in the back of an Airbus or with a computer
monitor/Microsoft flight simulator. Take his remarks in that context.

>
>
> > And the poles occasionally reverse,
>
> Occasionally... :-)))
>
> Stefan

In article >,
RK Henry > wrote:

> On Sat, 09 Sep 2006 00:09:20 +0200, Mxsmanic >
> wrote:
>
> >Thomas Borchert writes:
> >
> >> And having true heading (and only that) changes this problem how?
> >
> >It doesn't. But true north doesn't move, and it's right at the top of
> >standard maps.
>
> Except that apparently true north DOES move. The tsunami/earthquake of
> a year and a half ago reportedly caused the north pole to shift about
> an inch as well as decreasing the length of a day. Just goes to show,
> you can't depend on anything.
>
> RK Henry

Not to mention that the pole itself moves around. See
http://en.wikipedia.org/wiki/Chandler_wobble

Mxsmanic wrote:
> Thomas Borchert writes:
>
>> And having true heading (and only that) changes this problem how?
>
> It doesn't. But true north doesn't move, and it's right at the top of
> standard maps.
>
Well, back in the 1400s or so, north was at the bottom of maps!

Stubby writes:

> Well, back in the 1400s or so, north was at the bottom of maps!

You need to buy some new charts.

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

On Sat, 09 Sep 2006 20:31:27 +0200, Mxsmanic >
wrote:

>RK Henry writes:
>
>> Except that apparently true north DOES move. The tsunami/earthquake of
>> a year and a half ago reportedly caused the north pole to shift about
>> an inch as well as decreasing the length of a day. Just goes to show,
>> you can't depend on anything.
>
>All earthquakes cause such effects. However, if they produce changes
>that are below the resolution threshold of avionics, they aren't a
>problem. The magnetic pole, on the other hand, moves perceptibly over
>time--enough to require new charts and new regulation of stations and
>instruments.

So does GPS. The system changes over intervals of hours, with such
factors as satellite outages or signal propagation, rather than the
months or years that it takes for magnetic variations. Generally, the
GPS computer applies corrections automatically. That makes it
transparent to the user, but it doesn't mean that the system is
inherently perfect. If GPS were inherently perfect, WAAS would be
unnecessary.

All instruments are inaccurate. In order to use them you have to
calibrate them.

RK Henry

Mxsmanic wrote:
> Stubby writes:
>
>> Well, back in the 1400s or so, north was at the bottom of maps!
>
> You need to buy some new charts.
>
Nah. They are on the walls of a museum somewhere. In Venice in the
Ducal Palace of the Doge, I believe. But "north at the bottom" was the
accepted convention. I don't know what made them change but that would
be interesting, too.

Stubby schrieb:

> Nah. They are on the walls of a museum somewhere. In Venice in the
> Ducal Palace of the Doge, I believe. But "north at the bottom" was the
> accepted convention. I don't know what made them change but that would
> be interesting, too.

Maybe the magnetic poles reversed? <:-P

Mxsmanic wrote:
> In modern aircraft, a failure of electrical systems brings a lot more
> problems than mere navigation errors. No radio, no other navaids, no
> control surfaces in some aircraft, no propulsion in some aircraft.
>
> And while a compass shows magnetic north, that's all it shows. You
> have no idea how far north or south you are, or which direction to fly
> to your destination.

You "fly" a PC flight simulator (game)... Even if the poles do shift,
it's not going to effect your game, so don't worry about it...

You are obviously on the wrong newsgroup... Perhaps you should go to
comp.pc.ibm.pc.games.flight-sim or rec.aviation.simulators and leave
this group for real pilots...