Hi Mates,

I'm flying the A2A C172 and here is what I do to set my Heading Indicator:

1. Pass the mouse over the Magnetic Compass

2. Thanks to the P3D tooltip function, read precisely the magnetic heading, in this case 196°

3. Set the Heading Indicator to 196°

In the real world, as the pilot is not exacly right in front of the Magnetic Compass, how can he read precisely the magnetic heading?

Is it possible to have a precision of 1%?

If the reading error is 2,3° or more, the consequence for the flight path can be amplified and dramatic with time and distance?

I would imagine in the real world you would select VFR reference points in your flight plan that are close enough together to minimize the impact of incorrectly reading the magnetic compass.

Magnetic compass like that one you showed are extremely basic. 

Speaking from PPL experience: They are only accurate during straight and level flight and constant airspeed (compass indication wanders north/south if you accelerate or decelerate while flying east or west headings, really interesting.)
it will also lag or lead the turn depending on turning from a north or south heading
And finally add local mag. variation + the specific compass deviation on the aircraft + wind drift and you will have your hands full flying intended tracks derived from flight planning earlier 😎.

You still use magnetic compass to realign the directional gyro though (due to gyro precession), so it has its purposes.

Edited July 18, 20196 yr by SAS443

5 hours ago, Simicro said:

Is it possible to have a precision of 1%?

If the reading error is 2,3° or more, the consequence for the flight path can be amplified and dramatic with time and distance?

Aviation is not an exact science.  If you are using only heading and time for navigation then you are going to have larger errors due to inaccurate wind predictions than from heading errors.  Simulation pilots often have difficulty identifying what things are important and what are not, exact heading is one of the not's.  If you are VFR your eyeballs, the world around you and your sectional charts are all you need to navigate.  Exact heading is irrelevant.  If you are IFR then you are navigating based on ground or satellite based navigation systems and using those navigation aids to get there.  Flight test for IFR rating requires a heading accuracy of +/- 5 deg.

5 hours ago, Simicro said:

If the reading error is 2,3° or more, the consequence for the flight path can be amplified and dramatic with time and distance?

As Dan says, if you can fly with sufficient accuracy to maintain heading to within 2 degrees on a long navigation leg in a C172 then you are a pretty superb pilot!

Trying to set the DI to within a fraction of a degree is like measuring with a micrometer when you know you are going to be marking with a chinagraph pencil and cutting with an axe... a few degrees error is not going to make any odds when you factor in all the other variables. As mentioned, the magnetic compass is subject to a great number of errors and it is pretty near on impossible to read with a great deal of accuracy when you are bumping around anyway.

TLAR (That Looks About Right) is quite sufficient :).

Thanks for your time and kind explanations everybody. Much appreciated.

I get the idea now!

🙂