Post by Major A
Just another question: I noticed that the different places in which
heading plays a role (the different indicators as well as the
autopilot) use magnetic and geographic heading at will. Are there any
plans to unify them and/or come up with a convention of what heading
is magnetic and what isn't?
Are you sure? Here's what you should find in the 172:
- The magnetic compass displays magnetic heading, but it is strongly
affected by acceleration and turning errors: it will be accurate
only in straight-and-level steady flight (or sitting flat on the
- The directional gyro is purely relative and doesn't care what it
displays: you can set it to true, magnetic, or anything in-between.
It will drift during flight, however, so you have to reset it from
time to time. Its starting point is fairly arbitrary -- make sure
you adjust it to what you want before you take off.
- The autopilot in the 172 tries to keep the orange heading bug at the
top of the directional gyro, period. If you set the DG to the true
heading (as you would in the Arctic), then the autopilot uses true
heading; if the DG has drifted, the AP will be off by the amount of
the drift. Bigger planes have more sophisticated flight-management
systems, but we're not modelling those properly yet.
- The ADF needle simply points to the ADF station (in real life, +/-10
degrees -- it's not all that accurate).
- The VOR indicators show (roughly) what radial the plane is on.
That's not necessarily the direction you're flying, or even exactly
the direction to the VOR.
The only place you can get the true heading directly is the HUD, which
isn't really meant to simulate anything you'll find in a small plane
-- it's just a (useful) developer's tool or a user's toy. Usually it
should be turned off.
All the best,
David Megginson, ***@megginson.com, http://www.megginson.com/