Originally Posted by
70 Mustang
However you call them, they had similar functions, did they not? Terminology.
A "director" is a indication of the required correction and to be followed by whoever is in control.
A "deviation indicator" is an indication of the deviation in a certain point and time and has nothing to do with the correction required. Depending on situation the required correction could be big or small.
They have far from similar functions.
From memory (some can confirm or correct): on B737 classic non efis the standby attitude indicator had standard ILS deviation indicators (NAV 1). The B737 classis EFIS has standard ILS deviation indicators on the standby (NAV 1) if the captain EFIS is not connected to standby power. The B737 classic EFIS with captain EFIS on standby power has standby attitude indicators with the ILS deviation indicators (NAV 1) as an option.
Some people actually like this as the standby deviation indicators had a tendency to "come alive" slightly earlier than on the EFIS which sometimes helped to anticipate the turn on the localiser in raw data flying.