A question was raised on the PPRuNe site regarding the expanded Localizer scale on Boeing 737 EADI's. My notes are not clear on how the scale should behave on a 767 (or a 747-400) if the aircraft wanders off the Loc by more than one dot. Should it return to the four dot display or is it latched in the two dot display until, say the aircraft has reached a certain groundspeed? It does return to the 4 dot display in PIC if you wander off-beam, but I'd just like to confirm this with the experts ;-)Also, my notes tell me that the expanded scale appears only when the LOC deviation data is used by the "AFDS" and the deviation is less than 0.625 degrees. Does the A/P need to be engaged for the expanded display to appear, or will the Flight Director alone generate this display.Thanks.Cheers.Ian.P.S. I realize that on the 747-400, the expanded display only appears when the A/P is engaged, so the aircraft should not wander off the Localizer beam, but you can force it, in PS1, at least, with rudder trim and manual input.

Speaking from experience, not from bothering to look it up ;-)Anytime a LOC is tuned and you are within *about* 3/4 of a dot (may well be the 0.625 you mention?) it will go to expanded scale (regardless of A/P or F/D operation). The localiser will move in from the outside of the expanded scale indicating that one dot expanded scale is equal to half a dot normal scale. Anytime the localiser moves outside the expanded scale (1.25 dots expanded scale.. or 0.625 normal) is will revert to normal scale.

So, at least according to HPSOV here, PIC logic works OK :).Not a surprise though...Tero

Anytime a LOC is tuned and you are within *about* 3/4 of a dot (may well be the 0.625 you mention?) it will go to expanded scale (regardless of A/P or F/D operation). I find this surprising, HP.... This is both contrary to my notes and to PIC (In PIC you must have the FD on for the expanded scale to appear).According to my notes, one degree is approximately one dot on the normal scale, so it is about 3/4 of a dot that it should expand (or "5/8th" to be picky :-))."Speaking from experience, not from bothering to look it up ;-)"I'm just wondering how often you fly sans-FD on ILS approaches... and how often you fly 1.25 dots off scale to return the display to normal (grin).I might check the BMM when I get back to work to see if I can come up with a third or fourth variation :-)Cheers.Ian.