Why The Hell... (random rant)

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.

--
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Mxsmanic wrote:
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.


Not all planes have GPSes. In fact, most don't. Many of the haldheld
units fail. The failure rate for compasses is quite low. The FAA is
not likely to revise its requorements for a compass any time soon.
Thus, the reliance on magnetic north.


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.

Not really. It is unreliable. Its signals can be disrupted - rendering
them useless. I don;t want my only source of reference taken away at
anyone's whim.



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.


Not likely in most GA planes on most flights. Usually one is busy
flying and has no time for that stuff. Not possible on cloudy days.


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.

Bull****. Can you say piper cub (to name one counter example)
There is no need for electric power in a plane.



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.


Not in the real world. On a computer maybe...

compass is still the best, most reliable way to find north. (true or
magnetic)

Tim writes:

Not all planes have GPSes. In fact, most don't.

That depends on what category of aircraft you're looking at.

Many of the haldheld units fail.

How many? I've never seen one fail, although I'm sure it happens
occasionally. They don't even have any moving parts.

The failure rate for compasses is quite low.

So is their accuracy, even when they are functioning perfectly.

Not really. It is unreliable. Its signals can be disrupted - rendering
them useless.

Magnetic bearings are constantly disrupted, everywhere on Earth.

I don;t want my only source of reference taken away at
anyone's whim.

But a compass cannot give you the information that a GPS gives you. It can
hardly tell you anything at all.

Bull****. Can you say piper cub (to name one counter example)
There is no need for electric power in a plane.

You have an engine turning. That's power. And it can fail, just like
electrical power.

Not in the real world. On a computer maybe...

Even in the real world. The purpose of INS is to have a way of navigating
without any external references; it's a very advanced and accurate
implementation of dead reckoning.

compass is still the best, most reliable way to find north.

It's useless for truth north unless you have a chart _and_ you know where you
are. Even for magnetic north, it can be substantially off. And just knowing
which way is north doesn't help you much, anyway.

--
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Mxsmanic wrote:
Tim writes:


Not all planes have GPSes. In fact, most don't.


That depends on what category of aircraft you're looking at.


Many of the haldheld units fail.


How many? I've never seen one fail, although I'm sure it happens
occasionally. They don't even have any moving parts.


The failure rate for compasses is quite low.


So is their accuracy, even when they are functioning perfectly.


Not really. It is unreliable. Its signals can be disrupted - rendering
them useless.


Magnetic bearings are constantly disrupted, everywhere on Earth.


I don;t want my only source of reference taken away at
anyone's whim.


But a compass cannot give you the information that a GPS gives you. It can
hardly tell you anything at all.


Bull****. Can you say piper cub (to name one counter example)
There is no need for electric power in a plane.


You have an engine turning. That's power. And it can fail, just like
electrical power.


Not in the real world. On a computer maybe...


Even in the real world. The purpose of INS is to have a way of navigating
without any external references; it's a very advanced and accurate
implementation of dead reckoning.


compass is still the best, most reliable way to find north.


It's useless for truth north unless you have a chart _and_ you know where you
are. Even for magnetic north, it can be substantially off. And just knowing
which way is north doesn't help you much, anyway.



Tell that to Charlie Lindbergh.

Tim writes:

Tell that to Charlie Lindbergh.

Charles Lindbergh had not only multiple compasses but charts and a timekeeping
device. He never would have gotten anywhere with just a compass alone.

--
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In rec.aviation.piloting Mxsmanic wrote:
Tim writes:

Tell that to Charlie Lindbergh.

Charles Lindbergh had not only multiple compasses but charts and a timekeeping
device. He never would have gotten anywhere with just a compass alone.

A true enough statement, but one that shows how very little you know
about navigation.

--
Jim Pennino

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writes:

A true enough statement, but one that shows how very little you know
about navigation.

When did truth become evidence of ignorance?

--
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Mxsmanic wrote:
Tim writes:

Not all planes have GPSes. In fact, most don't.

That depends on what category of aircraft you're looking at.

Doesn't matter what category you are looking at. We've still
got transport aircraft with just steam gauges.


Many of the haldheld units fail.

How many? I've never seen one fail, although I'm sure it happens
occasionally. They don't even have any moving parts.

I've had them fail lots of times. All it takes is the battery to go doead.


The failure rate for compasses is quite low.

So is their accuracy, even when they are functioning perfectly.

Accurate enough. Reliable...never really have seen one fail.

Not really. It is unreliable. Its signals can be disrupted - rendering
them useless.

Magnetic bearings are constantly disrupted, everywhere on Earth.

Between your ears primarily.

You have an engine turning. That's power. And it can fail, just like
electrical power.

That power only propells the aircraft. There's no guarantee that it
provides electricity for avionics. I can tell you that I've been
in a number of aircraft where it did not, either by malfunction or
DESIGN.


Not in the real world. On a computer maybe...

Even in the real world. The purpose of INS is to have a way of navigating
without any external references; it's a very advanced and accurate
implementation of dead reckoning.

CHORTLE. Have you any experience with a real INS. A real INS can't
find squat without being told where it is starting from. This has
to be boostrapped from other navigational devices. It's long term
stability isn't any better than a compass. It needs additional
input.

It's useless for truth north unless you have a chart _and_ you know where you
are. Even for magnetic north, it can be substantially off. And just knowing
which way is north doesn't help you much, anyway.


Your GPS and INS are useless without a chart or their internal
electronic equivelent.

Ron Natalie writes:

CHORTLE. Have you any experience with a real INS. A real INS can't
find squat without being told where it is starting from. This has
to be boostrapped from other navigational devices. It's long term
stability isn't any better than a compass. It needs additional
input.

Not to find true north. It can find true north all on its own.

Your GPS and INS are useless without a chart or their internal
electronic equivelent.

I have a GPS with no chart and it's extremely useful.

--
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In rec.aviation.piloting Mxsmanic wrote:
Ron Natalie writes:

CHORTLE. Have you any experience with a real INS. A real INS can't
find squat without being told where it is starting from. This has
to be boostrapped from other navigational devices. It's long term
stability isn't any better than a compass. It needs additional
input.

Not to find true north. It can find true north all on its own.

Total, utter, nonsense.

You haven't the slightest clue how either a INS or a gyro compass
work.

snip rest

--
Jim Pennino

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