G'day
MyData,
Sounds like the DI in your HSI is "slaved", i.e. it is automatically aligned to magnetic North by being linked (“slaved”) to a flux valve (aka "magnetometer"). BTW, more modern aircraft / airliners may have something which is even better than a slaved-DI: solid-state laser-ring or MEMS-based gyros - see for example
http://www.xbow.com/Industry_solutio...uide.htm#solid
Anyway, if the aircraft does not have an electronic flux valve, then the gyroscopic DI has to be manually reset to the compass reading during straight and level flight from time to time to compensate for drift of the gyroscopic instrument.
So, you are very fortunate as it is a
great luxury to have a slaved-DI when learning! One of the aircraft I fly regularly (P28B Dakota
G-ODAK) has a slaved DI and it really makes a world of difference! Run of the mill PA38, PA28, C152, C172 etc rental aircraft typically wil lnot have a slaved-DI.
However, the challenge you may face if
learning on an aircraft with a slaved-DI is that when you come to rent a typical PA28 etc. after you have your license, you will typically find that there is no HSI certainly, and probably no slaved-DI so you might end up not sufficiently aware of the need to reset the DI to the mag compass.
Doing so is not too difficult - ensure you are straight and level (can be a bit difficult on bumpy days!), wait for the magnetic compass to settle down, and then rotate the small knob next to the DI to align the DI heading to be about the same as the mag compass indication. The main complication is the the DI and the mag compass rotate in opposite directions from each other, so you look at the mag compass and say "it's a bit to the left of 090" say, but you need to set the DI "a bit ot the right of 090" to get the same heading... this has often caught me out (small brain!)
Hope this helps!
Andy
