investigating Compasses issues

[Bozon]

The Giro-compass:

Isn't it rotating the wrong way? I mean, the compasses I remember rotate the opposite of the plane - by this I mean that when you point northward, the dial should read (I think):

30---N---300

While in the mossie it shows:

300---N---30

 

It could be right, it is British after all, but seems odd to me.

 

The Magnetic compass and its remote indicator:

These seems to be off in their directions. I aligned myself with the Manston runway 112:

- The Magnetic compass Compass reads something like 080 (very hard to see due to its location).

- The remote indicator reads 135

So they don't agree with each other nor with the ground direction. I know about magnetic deviation, but over 20 degrees?

 

In addition, the axis of the remote indicator's needle seems off center. It is noticeable that the point of the needle and the butt of the needle don't indicate exact opposite azimuths. This may be a perspective illusion, but it persists when I move my head around.

 

[Nealius]

Gyro compass in all the Allied warbirds rotates the opposite direction from expected, so that's probably normal.

 

However, something is not right with the magnetic compass. On the Mossie, Mustang, and Jug, which all have the same magnetic compass, they are indicating +20 degrees compared to the gyro compass. Magnetic declination of Kent is +0.69 degrees. 

 

For navigation, the gyro compass is the only accurate device, and reliably gets me from Manston to Calais at 50ft over the water. 

[WolfhoundCH]

33 minutes ago, Nealius said:

Gyro compass in all the Allied warbirds rotates the opposite direction from expected, so that's probably normal.

 

However, something is not right with the magnetic compass. On the Mossie, Mustang, and Jug, which all have the same magnetic compass, they are indicating +20 degrees compared to the gyro compass. Magnetic declination of Kent is +0.69 degrees. 

 

For navigation, the gyro compass is the only accurate device, and reliably gets me from Manston to Calais at 50ft over the water. 

Weird, I don't have this issue, is it with coldstart or hotstart aircraft?
Also I think the gyro compass doesn't drift, which is understandable that it's not simulated, but would be cool.

[Frederf]

The difference is inherent of direct vs. indirect read compass designs.

This compass demonstrates both at the same time. The lower direct read part has east clockwise (left) of north. The flat scale has east clockwise (right) of north.

 

The item in the Mosquito cockpit is a directional gyro so it can work however it was designed being clockwork and not magnetic. But looking at photos I have only found instruments in the arrangement of increasing to the left. This would mimic a conventional direct-read magnetic compass.

[Nealius]

1 hour ago, Eteokles said:

Weird, I don't have this issue, is it with coldstart or hotstart aircraft?

 

Cold start. I haven't tested any hot starts. I'm thinking about compiling a track showing the issue later today. 

[Ramsay]

5 hours ago, Bozon said:

The Giro-compass:

Isn't it rotating the wrong way? I mean, the compasses I remember rotate the opposite of the plane - by this I mean that when you point northward, the dial should read (I think):

30---N---300

 

A quick browse on the internet suggests the current DCS implementation is wrong but I'm no SME, so perhaps I'm missing something

 

DCS (increasing to the right)

 

Real (increasing to the left)

 

 

Edited September 24, 2021 by Ramsay

[[ED]Ben]

the DI in our mossie is the 6A/1298 model - so correct as is

 

 

[Art-J]

43 minutes ago, [ED]Obi said:

the DI in our mossie is the 6A/1298 model - so correct as is

 

Thanks for the feedback, but unless I don't understand something, the picture you posted shows scale increasing to the left... which IS opposite to what we've got in DCS (?). 

Edited September 24, 2021 by Art-J

[[ED]Ben]

quite right. i clearly need more coffee.

[Ramsay]

Mechanics of an early air driven  DGI showing how/why the real scale is made increasing to the left.

 

The scale is attached to the gyro mechanism which is stabilised in space/direction by the gyro,  when the aircraft turns, the instrument window turns about the scale.

 

Directional Gyro Indicator DGI | Directional Gyro Indicator Operation And Errors | Lecture 27

 

 

https://youtu.be/H8HjjOOYthw?t=78

 

Edited September 24, 2021 by Ramsay

[Ramsay]

13 hours ago, Nealius said:

Gyro compass in all the Allied warbirds rotates the opposite direction from expected, so that's probably normal.

 

Not sure what you mean, the operation of other allied warbird DGI's are the same with the scale increasing to the left, only the DGI scale of the Early Access Mosquito is different.

 

 

Do you have an example of a WWII DGI that rotates in the direction you'd "expect" ?

[Nealius]

I just checked when looking for other compass errors and you're right. There was one warbird I flew before the Mossie came out where things were moving the opposite direction I expected them but maybe I confused that for a different plane.

 

EDIT: P-47 is the one that rotates opposite what I expect. With E off to my left, the compasses show E off to my right. 

Edited September 25, 2021 by Nealius