Correction For Directional Gyro?

[334th_McSlash]

I'm new here, but I've done a bit of ocean navigation in real life.
A popular Guide to CLoD (Chuck's), and several people here say add 10 to Magnetic to get True . . .
To check this I simply went into ATAG #2, with its Open Pit.
In Closed Pit I set my Course Setter and got my read out, then went into O.P., where the Compass is True and Screenshot the comparison.

The result is clear, you must SUBTRACT 10 DEGREES from Magnetic to get True.

[uranor]

I'm new here, but I've done a bit of ocean navigation in real life.
A popular Guide to CLoD (Chuck's), and several people here say add 10 to Magnetic to get True . . .
To check this I simply went into ATAG #2, with its Open Pit.
In Closed Pit I set my Course Setter and got my read out, then went into O.P., where the Compass is True and Screenshot the comparison.

The result is clear, you must SUBTRACT 10 DEGREES from Magnetic to get True.

I see no contradiction there. It may be just a matter of precise naming convention. It seems (my perception, not sure) that some people in the forum use nomenclature imprecisely (not referring to you). The standard equation in this case is:

TC + VAR = MC

TC: True Course (i.e. referring to Geographic North, aka True North)

VAR: magnetic variation, to be accounted for algebraically: +W variation, -E variation. In CloD Var ~= +10W, so add.

MC: Magnetic Course, i.e. as shown on compass. Technically there are other things to consider in real life: wind correction angle, and compass errors, but in CloD these are not modeled (TF correct me if wrong); there is always very little wind and compasses are error-free.

One source of confusion, sometimes lost in the writer/reader assumptions, is that some pilots are trying to use the equation the other way around, like you are: TC = MC - VAR, so they change the sign to the Variation, subtracting, which is perfectly fine, as long as one states what is being calculated like you did.

[334th_McSlash]

One source of confusion, sometimes lost in the writer/reader assumptions, is that some pilots are trying to use the equation the other way around, like you are: TC = MC - VAR, so they change the sign to the Variation, subtracting, which is perfectly fine, as long as one states what is being calculated like you did.

Understood . . . however, while I really do appreciate the effort Chuck put into his PDF CLoD Guide, his Directional Gyro section got it wrong. I don't say this to critique, but to keep some from making a 20 degree error, I haven't seen it mentioned anywhere, I may have it wrong, but I don't think so. (declination 1)
Now, for Chuck's and any other's sake, I have found evidence that the game got it wrong, reversed, and that the declination for the English Channel was actually -10 in 1940. (Declination 1942a)

Just saying.

[1lokos]

Here say -9.574 for Dover area in 1940.

http://www.geomag.bgs.ac.uk/cgi-bin/igrfsynth

[334th_McSlash]

Here say -9.574 for Dover area in 1940.

Right, the game got it reversed, which is fueling all the confusion.

True bearing +10 = Mag. bearing
Mag bearing - 10 = true bearing
One way of remembering this on Clod could be "Magnetic is More" (than true bearing).
Hmm... "For True, trim ten"?

Right enough!

Add 10 for the directional gyro, course setter compass is -10 from true north.

Right in the Real 1940 world, wrong in the Game!

True north is 10 degrees more than magnetic. (In this map during 1940)

Again, right in the Real 1940 world, wrong in the Game!

Hmmm, four replies, 2 for plus ten, 2 for minus. You pays your money...Now I’m confused too.

You and me botyh, but I'm betting on a +10 game in a -10 world.

Just remember that Blitz is a +10 sim and you'll always remember to add that to your compass heading!

Right! But the English Channel in 1940 was -10

[Screamadelica]

Everyone confused at this point?

To keep it simple, you should only need to adjust the directional gyro to match the magnetic heading on the compass.
I am assuming that any vectors given by ATC, etc are magnetic headings with the deviation already taken into account.
You should only need to account for magnetic deviation when converting a heading from the map to the compass or vice versa.

Easy to memorise rule of thumb:
MGA = My Gran's Ace: Map (true) to Ground (magnetic) Add.
GMS = Grand Ma Sucks: Ground (magnetic) to Map (true) Subtract.

So, if you plot a course on the map to fly from point A to point B and the heading on the map is showing 360 degrees then, (MGA) 360 plus -10 = 350. Your heading to fly to point B is 350 degrees.
Set the Directional gyro to match the compass and when the gyro shows 350 degrees, off you go!

Please someone correct me if this is wrong, but this is what I remember from the navigation training I did many years ago.

Cheers, Scream.

[Tumbler]

Everyone confused at this point?

To keep it simple, you should only need to adjust the directional gyro to match the magnetic heading on the compass.
[...]

Correct indeed. But the silly thing is you can't read the compass directly. But you can read it indirectly by aligning your course setter to the compass needle and then you know your course and you can adjust your gyro. Just like in WW2, just look at your info window

[1lokos]

Just like in WW2, just look at your info window

If the in game compass has the "Lubber Line" - few pixels in 2D, we can adjust compass without forced to ready that silly "HUD" and can close the dam thing and their "brakes 80%, brakes 82%, brakes 84%..." Who in the "Dr.WhOMniverse" need this? Or that "Gunsight Light: ON". Duhhh"

BTW - This magnetic deviation matter for bomber pilots, for fighter pilots in the small "combat area" Dover - Calais this don't make difference.

[Baffin]

This thread is making a mountain out of a mole hill.

You never calculate TRUE course... There's no point to it unless you have a magic instrument like Inertial Navigation, GPS, etc. that can indicate TRUE headings. Instead, you plot true course from the aeronautical chart by using a plotter, or mathematically from a computer program.

To navigate a true course in an airplane with a magnetic compass or Directional gyro (DG), you must ADD WEST variation or SUBTRACT EAST variation from the true course. This derives a magnetic course. Make left or right corrections for enroute wind to derive the magnetic heading which you will fly by looking at the compass or DG..

This is not opinion... This is way it's done everywhere except a few places like Thule, Greenland where variation is extreme due to latitude. Such places will publish special instructions for their airports. SEE THIS:

http://www.gcmap.com/diagrams/archive/nga/BGTL.pdf

[Baffin]

For a Free Professional Explanation:

https://max.aero/flight-training/pri...avigation-log/

[MightyBouff]

so, if I want to (for some strange reason) have my DG reporting true (so I can compare it directly to the map), do I add +10 to my magnetic compass, or do I -10 from my magnetic compass?

[Baffin]

As far as I know, the only time a pilot would want to do this would be in compliance with local directives from tower because the runway is marked in degrees TRUE. (Thule) In that case, you would line up for takeoff, then set the DG to the published runway true heading, and take off. There are always exceptions for special circumstances, but in all my years of flying back in the "Whiskey Compass" days, I can remember only one... Thule.

It's a peculiar place because of its latitude. The asphalt runway is paved over perma-frost ground which would ordinarily cause it to heave and break up during the summer surface thaw. To prevent this, they paint the runway white and mark it with red stripes. That is one queer sight to see when you break out of the clouds at 200' AGL from a precision approach!

I realize that this is a video game and you can do whatever you like, but at some point I must draw the line at personally teaching universally unacceptable procedures. The DG, for all intensive purposes must read magnetic heading. Feel free to set it anyway you like in CLoD!

[334th_McSlash]

so, if I want to (for some strange reason) have my DG reporting true (so I can compare it directly to the map), do I add +10 to my magnetic compass, or do I -10 from my magnetic compass?

Subtract.

And besides the DG, knowing the Variation is a good idea if you are going to fly, say, a 109, with it's compass in front of your face. You're leaving Calais, your rendezvous is due West according to map grid lines, you need to fly 280, not 270.

[MightyBouff]

Subtract.

And besides the DG, knowing the Variation is a good idea if you are going to fly, say, a 109, with it's compass in front of your face. You're leaving Calais, your rendezvous is due West according to map grid lines, you need to fly 280, not 270.

Thanks. Given I've been adding 10 it's amazing that I've actually managed to navigate anywhere!

[334th_McSlash]

Thanks. Given I've been adding 10 it's amazing that I've actually managed to navigate anywhere!

Well, yeah, the RAF DG gets completely whacked with the first High G turn.
It's best, in this game to really know the map, and to learn the quick glance at the compass to confirm general direction.

[VO101_Mate]

Remember this and you'll always know it:

Variation west magnetic best, variation east magnetic least.

[Baffin]

Thanks. Given I've been adding 10 it's amazing that I've actually managed to navigate anywhere!

Don't beat yourself up about this. There is a lot of "Dip" error in the RAF mag compasses, especially the Blenheim's, so if you are not in level, unaccelerated flight, the heading is probably in error anyway.

Test this if you like, by pointing the Spitfire towards a distant landmark while trimmed at 240 MPH level flight after takeoff. Carefully check the heading. Then establish a trimmed climb at the best rate of climb speed (≈160 MPH in Spitfire) while visually flying to the same distant object. Check the heading again to observe the Dip error as the "North" pointer dips downward towards the north magnetic pole on the earth. Due to this, I find it necessary to pick up a coastal landmark as soon as possible and fly in visually. It's called VFR pilotage and is still a lot of fun. Blenheim's have as much as 30° of dip error because the 136 MPH climb calls for more pitch. On some climbing courses, I'm lucky just to hit France!

In CLoD, we can reliably use the Mag Compass for Low level dead reckoning navigation, and it's great fun. It's very rewarding to hit Dunkerque spot on after a channel crossing at 200' and you've not had a single landmark to look at along the way.

Makes you feel like Lindbergh!

[1lokos]

This image is from a topic in KG40 - Russian Bomber Squad who used play in CloD, about the Magnetic Deviation in "Dr. WhOM'niverse."



The (Google) translation add confusion to this confuse matter.

But is possible see in the Wind Rose (internal values) and graphical above - based in 36 different flights, that "Magnetic Deviation" in "Dr.WhOM'niverse" deviate a bit or RL conventions, measures. E.g. for 220 course is the correction 18.

That guys usually find their targets in SOW campaigns.

[334th_McSlash]

This image is from a topic in KG40 - Russian Bomber Squad who used play in CloD, about the Magnetic Deviation in "Dr. WhOM'niverse."

My head hurts . . .

[JimmyBlonde]

What a trainwreck...
Here: http://lmgtfy.com/?q=magnetic+declination

Was it really that bloody hard?

[1lokos]

Not about "magnetic declination", but "giroscopio" error and not due "G". I guess that "ind. giroscopio" is the Directional Gyro.

An test done by Escuadron69 guys in 2011 (text in Spanish), what interest is the "giroscopio" error - observed with the aircraft (He 111-H) stopped on the runway during ~24 hours (game time).

"El giroscopio tiene un error de unos 20º/hora=5º/15´"

"lo del error del giróscopo, es normal, tiene en cuenta la rotación de la tierra, por lo que se desajusta con ésta..."

Spoiler: 

Avión: HE-111 H
Mapa del canal
Base: Rosieres-en-Santerre
Meteo: default

Avión en cabecera 25, motores parados, rumbo magnético 251º.

Hora/QFE/Temp. ambiente/Temp. agua-aceite motor izq/Temp. agua-aceite motor derch/ind. giroscopio//

1200/984/15/16-15/20-18/-//
1300/984/13/15-15/19-18/-//
1400/984/12/15-14/19-17/-//
1500/984/11/14-14/18-17/-//
1600/984/9.4/14-13/18-16/-//
1610~1620 enciendo luces de cabina//
1700/984/7.5/13-13/17-15/101//
1800/984/5.6/13-12/16-15/120//
1900/984/3.5/12-12/15-14/140//
2000/984/1.2/11-11/15-13/161//
2005 puesta de sol//
2100/984/-1/11-10/14-13/181//
2200/984/-3.3/10-10/13-12/200//
Entre las 2200 y 2300 me doy cuenta de que se acabó la batería//
2300/984/-6.1/9-9/12-11/220//
2400/984/-9.1/8-8/11-10/244//
0100/984/-12/7-7/10-9/266//
Desde esta hora, hasta las 0345 imposible ver instrumentos por falta total de visibilidad//
0400/984/-24/4-4/5-5/324//
0410 amanece//
0500/984/-33/1-1/1-1/349//
0600/984/-40/0-0/0-0/011//
0700/984/-40/0-0/0-0/030//
0800/984/-40/0-0/0-0/051//
0900/984/-40/0-0/0-0/0/072//
0900 arranco motores pasando la temperatura ambiente a -12º//
1000/984/-5.5/0-0/-0-0/093//
1010/empiezan a parpadear las luces de cabina//
1020/las luces de cabina mantienen su luz//
1100/984/-4/0-0/0-0/114//
1105/paro motores//
1120/se acaban las baterias//
1200/984/-/0-0/0-0/135//
1215/arranco motores//
1225/vuelven las luces de cabina//

Comentarios:

La presión atmosférica no varía.

La temperatura ambiente si varía, aproximádamente 1º/hora.

Están contempladas la descarga y carga de baterías.

Cuando la batería se descarga, dejan de funcionar las luces de cabina, todos los indicadores de temperatura y el visor de bombardeo de manera inmediata. Los indicadores de fuel dejan de funcionar mas tarde.

Con batería de nuevo, todo vuelve a marcar lo que debe excepto los indicadores de temperatura de los motores, que no empezarán a marcar correctamente hasta que éstos no cojan temperatura.

Mola el efecto de las luces cuando quieren volver a encender, como una bombilla mal enroscada.
El giroscopio tiene un error de unos 20º/hora=5º/15´ ¡parado!

Si estamos en vuelo y vemos que no se nos encienden las luces de cabina, y/o la temperatura de los motores empieza a bajar, y no tenemos el visor de bombardeo, y si los indicadores de combustible marcan cero es que no tenemos electricidad. La única precaución que es que no nos podremos fiar de lo que nos digan los termómetros de agua/aceite de los motores, por lo que yo abriría un poco mas los radiadores y quitaría un punto de gas, por si las moscas.

Curioso, han modelado la carga de la batería.

El giroscopio tiene un error de unos 20º/hora=5º/15´ ¡parado!

El error del giroscopio se debe:

"Por cierto, lo del error del giróscopo, es normal, tiene en cuenta la rotación de la tierra, por lo que se desajusta con ésta..."

[334th_McSlash]

What a trainwreck...
Here: http://lmgtfy.com/?q=magnetic+declination

Was it really that bloody hard?

The Train Wreck is the Game reversed the real world declination.

[=FI=Murph]

And the upshot of all this seems to be that it doesn't matter which way the deviation is, we should be using magnetic North anyways? Okay, a good, simple, answer.

[1lokos]

And the upshot of all this seems to be that it doesn't matter which way the deviation is, we should be using magnetic North anyways? Okay, a good, simple, answer.

Because in British planes instruments the needle "+" pointing to magnetic North is the only indication that work correctly.

[JimmyBlonde]

The Train Wreck is the Game reversed the real world declination.

Really? Amazing, I never noticed. The joys of navigating by pilotage I guess.

[ATAG_kiwiflieger]

Cliffs has it correct, with the real world historical declination of between -9 to -11 degrees (WEST of north) for 1940. Diagram below:

Screenshot (49).png

Magnetic pole position in 1940:

[Baffin]

If you think there's only Magnetic north and True north, have a look at this brief article:

https://www.scientificamerican.com/a...ne-north-pole/

[334th_McSlash]

Cliffs has it correct, with the real world historical declination of between -9 to -11 degrees (WEST of north) for 1940.

I recant, you are correct, I was reading bad information, that the negative was taken from the True, not the Magnetic . . . however Chuck's Guide is still wrong.

[1lokos]

This scales came with 3rd part campaign for CloD.



At left left for use in fighters, with the with general 10 degrees of declination - with magnetic and true indications.

At right for an bomber campaign - notice that in this, due longer distances in bomber flights, the correction is not a fixed value - like the above KG.40 Squad scale.
Why? Rules of "Dr.WhOMniverse".

[334th_McSlash]

Why? Rules of "Dr.WhOMniverse".

Or is it the "Underverse"!?!?!?

underverse.jpg

Cuz this topic is killin' me!