Bonanza and Baron: mag compass and HSI disagree.

[SadBucket]

Mag compass and HSI disagree by 5-10 degrees slaved all variants of baron and bonanza. no prop deice, AC, or wndshld heat on.

[Black Square]

How about the pitot heats, vent blowers, or heater? Absent those items, plus the ones you mention, and the obvious ones like the starters, flaps, and gear, they should be in perfect alignment.

[jmarkows]

I'm seeing the same in the Bonanza, actually. My HSI has me pointed at 150 and the compass is reading 156 or so.

The very tiny text around the compass says FOR 150 STEER 155, so if we're supposed to use the compass cards here I suppose it's right? This was with the aircraft running but no A/C, heaters, or avionics going, and after a full shut down nothing changed.

[jmarkows]

I did a flight in the Bonanza yesterday and noticed that while my observations above hold true on the ground, in flight they align very closely.

Could this be related to the aircraft attitude on the ground?