Earth's magnetic field

[Hardy Heinlin]

I'd like to share this nice sight of our Earth's isogonic lines before I remove this visualization from the map features (I was just testing if the field model works, it's actually just a part of the internal compass model).

Like PS1, PSX uses the magnetic field model by Ed Williams which is based on the IGRF and a few other models. Among other things, it allows to set a date and can even predict the near future to a certain limit.

Below are screenshots for the years 2010, 2015, 2020 and 2040. You can click on it to view the first shot in real size.



Regards,

|-|ardy

[Hardy Heinlin]

|-|

[Jeroen Hoppenbrouwers]

I know it serves no useful technical purpose, but these maps would certainly add oomph to PSX... if only you publish them in the manual.

[Hardy Heinlin]

In the manual, yes.

For the map it's of no big use as the lines are not labelled with digits, the lines just give an overall impression of the harmonic distribution. Secondly, it takes half a minute (on a fast computer) to compute the visualization.

[Richard McDonald Woods]

Wow Hardy!
I feel that I could almost touch the whisk(e)y compass, it's so realistic. Excellent!
Cheers, Richard

[Holger Wende]

Hi Hardy,

I searched airliners.net for 747-400 cockpit photos with visible standby compasses.
But independent of the location the photos were taken (Sydney, Hong Kong, Londin, over the Carrinean...), I could not find a single photo with a al least slightly tilted standby compass :roll:

My potentially naive assumtion is they are compensated for inclination effects :?

Or did I misinterprete your beautiful standby compass screen shot? Maybe that screen shot was produced during some aerobatic manoeuvers with significant lateral acceleration?

Gruss, Holger

[Mariano]

The glare on the plastic of the 'VERT SPD' and 'ALT' windows. Only you.

Mariano

PS: Is the date on the compass correction card indicative of a certain date looong awaited by many? Just kidding. Thanks for sharing!

[Hardy Heinlin]

Hi Holger,

the compass "bank" angle is level only at the ("magnetic") equator or at (magnetic) N/S headings.

At the magnetic poles the magnetic field lines are vertical and the compass is dipped so much that it is unusable.

The compass "pitch" angle is level only at the ("magnetic") equator or at E/W (magnetic) headings.

Further factors: Acceleration, climb, descent, slip/skid ...

If the lines of magnetic force were horizontal all over the  globe (no poles), we would have no compass turn errors and no acceleration errors.

The screenshot above was shot somewhere over Antarctica.

PSX models all compass errors:
- Variation (following isogonic lines all around the globe)
- Deviation (disturbance by electro-magnetic avionics)
- Turn error
- Acceleration error (incl. 180 deg reversal near the poles when bank angle steep)
- Oscillation error (inertia and dampening)

I don't know which photos you have seen, but if you take a close look, the compass is rarely levelled, even in mid latitudes like Frankfurt or Sydney. When parked in E/W you should see ca. 5 degree dip.

Cheers,

|-|ardy

[Hardy Heinlin]

My potentially naive assumtion is they are compensated for inclination effects :?

That may be the case for small local airplanes that never leave their home area. But on intercontinental flights, you can't put inclination compensation weights on the compass; it would work only in certain regions.

[Keith Maton]

Damnit, that's gorgeous

[Holger Wende]

I don't know which photos you have seen, but if you take a close look, the compass is rarely levelled

See e.g.
http://www.airliners.net/photo/Air-France/Boeing-747-228F-SCD/0847887/L/

Photo was taken over the Alps where I had expetced to see some tilt due to ~60 deg inclination?

Or this one from somewhere in Sweden heading east:
http://www.airliners.net/photo/Atlas-Air/Boeing-747-271C-SCD/0661286/L/
Is that stand by compass banked?

The turning errors will be visible, no doubt.

Anyway I trust your expertese, of course  
But it sounds so irritating to me, aircraft costs >200 mio$ but compass does not seem to be compensated for inclination. Some outdoor compasses offer a feature (German: "Reitergewicht") to compensate for inclination effects. But the Queen doesn't?

When parked in E/W you should see ca. 5 degree dip.

You should see or you do see?

Regards, Holger

[Hardy Heinlin]

I don't know what's going on there, Holger. It's hard to tell from the viewer's perspective.

Do we have 60 deg dip over the Alps? Sounds a bit too high.

Also note that the compass per se has a weight (the entire compass body) which forces a vertical attitude, so you will never see the full inclination as the magnetic force is not as strong as the gravity force of the compass body. That's why I said ca. 5, not 50 or so. It was just a guess. It may also be 2 or 3.

[Holger Wende]

Do we have 60 deg dip over the Alps? Sounds a bit too high.

According to  US/UK World Magnetic Model -- Epoch 2005.0 an inclination of 60 deg over the Alps is realistic.

But I agree a standby compass susceptable to magnetic inclination will show a significantly smaller dip.

I have just re-viewed my video "LTU9999 Sonderflug Norpol" (LTU special flight nothpole) conducted with an A330-200, but that bloddy standby compass is hardly visible  

Maybe some pilot/ground engineer out there is so kind to take a close-up photo of a standby compass, preferrable while being somewhere far north/south heading east or west :mrgreen:
Any aircraft type should be fine, I guess.

So long, Holger

P.S. While sufing the net I found this:
Inclination also can be compensated by a (non-magnetized) needle design that allows a cylindrical magnet to rotate and pivot on a jewel, while the needle pivots on the magnet so it stays horizontal. This allows the compass to read accurately at any latitude

[Matt Sheil]

If you stare long enough at Hardys PSX Earth's isogonic lines pictures, you can see the words
"YOU WILL BUY PSX"
Don't be fooled, it is all a trick  ;-)

[Hardy Heinlin]

P.S. While sufing the net I found this:
Inclination also can be compensated by a (non-magnetized) needle design that allows a cylindrical magnet to rotate and pivot on a jewel, while the needle pivots on the magnet so it stays horizontal. This allows the compass to read accurately at any latitude

Interesting.

While we're at it, that web site also mentions this (to compensate inclination):

"- a needle design featuring a low center of gravity"

I'm sure that design is used on every regular airliner.

My model doesn't show full inclination as the gravity pulls the body vertical. Only near the poles the inclination is vertical enough to pull the body at least by 18 degrees. Now I'm not sure anymore if this is still too much. Anyway, the first thing I checked was a comparison to a photo from Q showing a 744 compass parking in YSSY at heading 240. The compass "bank" is 5 deg "left wing" down. That agrees with my model.

Cheers,

|-|ardy

[Holger Wende]

Hi Hardy,

If you have seen a photo, that is proof enough.
I'll be quite now, no more word about whiskey :mrgreen:

Good night, Holger

[Hardy Heinlin]

Don't be quiet, Holger. I may be wrong. I'm here to learn.

Cheers,

|-|ardy

[Qavion]

The breakdown of the 744 compass shows straight magnets. Maybe circular magnets are later generation?

Also, local magnetic fields could be a factor. I don't recall which YSSY gate the photo was taken on. We have a list of gates and a maximum deviation limit for each gate.

Inclination is not unusual on the ground. You'll have to ask the pilots about in-flight ; )

Among other things, it allows to set a date and can even predict the near future to a certain limit.

Does it work with Lotto numbers?  :mrgreen:

[Peter Lang]

IThat's why I said ca. 5, not 50 or so. It was just a guess. It may also be 2 or 3.

Hi Hardy,

from my brain I can state, that the whiskey compass on small aircrafts or gliders are almost parallel to the horizon when on ground.  Perhaps a little bit tilted which is hardly noticable.

During flight we normally we use the gyros, but they have to be adjusted each 15 mins or so according the readings of the whiskey compass. The bigger problem in turbulent air is to see the exact indication. If you fly e.g. 90° the whiskey compass may vary from 80° to 100° while the gyro only makes from eg. 89 - 91°.

Here some glider pics.

http://www.airliners.net/photo/IAR-IS-28B2-Lark/1546367/L/&sid=53eb3dc8a46b587610a2dbde5355533a

http://www.airliners.net/photo/MBB-SG-Flugsportgruppe/Elan-DG-300/1526849/L/&sid=53eb3dc8a46b587610a2dbde5355533a

http://www.airliners.net/photo/Aero-Club-Mielec/PZL-Bielsko-SZD-9bis-Bocian/1411474/L/&sid=53eb3dc8a46b587610a2dbde5355533a

http://www.airliners.net/photo/Grob-G-103C-Twin/1380004/L/&sid=53eb3dc8a46b587610a2dbde5355533a

http://www.airliners.net/photo/Grob-G-103/1360749/L/&sid=53eb3dc8a46b587610a2dbde5355533a

for more pics simply search for gliders and flightdecks.  Hope this helps a little.

Peter

PS. I forgot: your pictures look great. They shout very loud: I want PSX  :mrgreen:

[paulstory]

You can see the Aurora Borealis leaving Minnesota for parts north.  Very cool.

paul