Dave Butler wrote:

Brenor Brophy wrote:

liberal snippage

This quote is from the Avionics West article at
http://avionicswest.com/articles/kno..._autopilot.htm
This HSI, slaved or not, MUST have BOTH vacuum and electrical inputs
in order to operate. In other words, if you lose vacuum or the
electrical system, this HSI compass card will quit!


Can anyone confirm the statement above from Avionics West? I consider
them a reliable source of information, but this seems counterintuitive
to me. In case of electrical failure, why is the heading information not
still available? Is the compass card not mechanically connected to the
gyro?

Obviously, I can see that the navigation information would not be
available in case of electric failure, but the quote specifically says
the compass card will quit.

Thanks,

Dave


The compass card is electrically connected to the gyro. Thats why either
a vacuum out or electrical out can kill it.

THe solution is pretty simple. Move the old DG over and keep it when installing
the new HSI.