The Royal Brunei Air Force certainly found the Sperry system to be superb. Unfortunately they (the Sperry systems...) are now obsolete. 3-axis and generally very reliable in the hot/humid Borneo conditions, they were better than the Chinook 4-axis system in use at the time. However, you wouldn't want the a/c in AP mode when doing any hover or lifting work (I think the min IAS was 40 kts anyway...).