757 VOR lacking AUTO/MAN switch

[teropa]

Hi all,

I'm seeking for an explanation to this: http://www.airliners.net/open.file/0956858/L/

This UAL 757 does not have the AUTO/MAN switch on its VOR control panels. Thus, is one of these three possibilities the explanation to this:

1. The VOR Radios are tuned automatically and can't be switched to Manual. (not likely)

2. The VOR Radios are tuned manually and can't be switched to AUTO. (not likely)

3. The VOR Radios are tuned automatically with Manual remote tuning via the CDU.

This is the first and only of its kind I've ever seen, so any additional information would be good :).

cheers,
Tero

[Capt Pit Bull]

Couldn't say for sure, never flown a 75.

But the b737s I used to fly had various avionics fits.

Some had Manual / Auto boxs: Manual = Pilot controlled vor+dme, Auto = assigned by the FMC for FMC radio nav.

Others had the same as on you picture, which worked by having frequency agile DMEs, so VOR and DME permanantly under pilot control, with DME frequency hopping to tune other channels to derive a radio nav fix.

DMEs in use accessable via the NAV STATUS pages if I recall correctly, so you can see if the FMC is either (1) trying to tune the aid, or (2) successfully interrogating the aid, or (3) actually using it for a fix. (a combination of colours and / or inverse video being used to denote which, according to the vintage of the CDU). You can also inhibit the system from using specified DMEs (e.g. if it is notamed unreliable, or clearly pulling your radio fix off), so there is a degree of control over the auto tuning.

Hope that helps,

CPB

[Phil Squares]

Similar setup on the 744. You can manually tune the VOR in the NAv RAD page. Select VOR mode on the ND and off you go. Of course, the easier way is just direct to and then the inbound course.

[megapilot]

May be it's only manual mode for VOR/DME and only GPS updates for FMS. But our 757 Fleet has GPS and AUTO/MANUL mode for VOR/DME. First time I can see 757 VOR/DME control panel w/o this button. 757NG?

[ironbutt57]

Yeah...that's a strange one all right...never seen that before must have a nav/rad page in the FMC to select "man" mode...:confused: