Slightly confused about Magnetic Variation

[ScatterbrainKid]

This thread convinces me I'd have never made a real-world pilot because no way could I have figgered out all that fancy maths stuff!
Even pro navigators sometimes get it wrong like in this excerpt from 'Strange Encounters' (Chaucer Press 1982) when an airliner ended up hundreds of miles off course over the Sahara-

A Handley Page Hermes

[JSkorna]

Adding and subtracting is a life skill. Maybe that is why we need the cash register at McDonalds to figure everything out for us?

[teson1]

Scatterbrainkid,
that's a very interesting story. Thanks for sharing.

Brainfarts happen easier than one might think. Been there...

[mgh]

Adding and subtracting is a life skill. Maybe that is why we need the cash register at McDonalds to figure everything out for us?

A girl at a checkout was heard explaining how to operate the cash register - "We press that button to find out how much change to give: if it doesn't work we just guess."

[scott967]

Back in my NROTC days in navigation301 what we learned was

True Virgins Make Dull Companions (At Weddings)
True - variation - magnetic - deviation - compass (add west)

Can Dead Men Vote Twice (At Elections)
Compass - deviation - magnetic - variation - true (add east)

On ship we have compass deviation cards which show the difference between what the compass shows and what "real" magnetic heading should be. I guess aviation doesn't do that.

scott s.
.

[LuckyBlundy]

Gee! There seems to be a lot of different ways to think about this. First off let me thank everybody for the help. I think teson nailed it. If I'm very tall and standing at LAX, I look northward and see the North Pole(true) and off to my right(eastward or clockwise) I see the Magnetic Pole toward which my compass points and it reads 360degs. The line to the north pole reads 346.

On the other hand; At JFK, if I look at the NP I see the Mag. Pole off the my left(westward or counter clockwise) and my compass points to it and reads 0 so the compass reading to the true NP would be 013 degs. It would appear that the magnetic pole lies somewhere in the very far northern reaches of Canada.

I would revise the "rule" to read West-Compass Best; East-Compass Least. Assuming counter clockwise is negative. This would simplify the mathematics because you could always subtract while taking east variations as negative. Subtracting a negative is adding.

This still leaves me with the logs from the Lindburg book. He added what he listed as W variations to his desired(true) course to get his compass heading.
Another question is: Do the airplanes in FS have deviation? I've always assumed they had perfect compasses.

[JSkorna]

If by deviation you mean drift, then yes there is that option in FS called gyro drift.

[ScatterbrainKid]

..Brainfarts happen easier than one might think. Been there...

Yes, when i feed the pigeons on my windowsill i say to them "come on guys, tell me the secret of how you navigate with pinpoint accuracy, or at least give me a little hint", but they never do, i suppose they want to keep it a secret (sniffle)
I still get red-faced thinking about the time I was travelling back on the motorway from Blackpool to Leicester on the coach late at night, just relaxing in my seat and watching the scenery go by like you do, and a big road sign flashed by reading someting like "KEGWORTH turnoff ahead".
I sat bolt upright thinking "Huh?? why the heck are we travelling north when we should be heading south??"
I was totally disoriented and actually on the verge of getting up to ask the driver what was going on, but my head cleared just in time and everything clicked into place, we were heading south and everything was fine!
I think my confusion was caused by tiredness.
Coincidentally an airliner had crashed on the motorway in that same spot some years previously when the pilot/co-pilot got mixed up between their left and right engines (google 'Kegworth air crash') on approach to East Midlands Airport. (it's on youtube too)
Just a thought, but i wonder if the assorted cocktail of frequencies from radars and beacons and stuff around airports can sometimes disorientate the human mind if we're tired and let our concentration wander?

[scott967]

If by deviation you mean drift, then yes there is that option in FS called gyro drift.

I think the reference is to the required compensated "magnetic direction indicator" aka Whiskey Compass. A deviation card must be placarded and installed near the compass (for "normal" category aircraft per FAR 25.1547) in the US.

scott s.
.

[LuckyBlundy]

If by deviation you mean drift, then yes there is that option in FS called gyro drift.

No, I don't think what was listed in the book (deviation) was gyro drift. I think (mostly because it's easier) it's the mechanical error in that particular compass. I stand to be corrected on this, but I don't think Lindburg had a gyro compass. He had an earth inductor compass and the standard, liquid filled, compass, both of which went haywire on him during part of the flight. He must have been doing something right because he hit Dingle Bay, Ireland three miles from his intended course.

I want to thank everybody again for their comments and the discussion.

Oops! I just looked up earth inductor compass and found out that it does have a gyroscopic component. There's no mention of any correction to it however.