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Using VOR2

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It is not clear to me how to make use of VOR2. In the 737NGX FCOMv2 it says:

 

While engaged in VOR or LOC modes:

•A autopilot and Captain’s F/D use information from Captain’s course selector and No. 1 VHF NAV receiver

• B autopilot and First Officer’s F/D use information from First Officer’s course selector and No. 2 VHF NAV receiver

different courses and/or frequencies for two VHF NAV receivers can cause disagreement between the Captain’s and First Officer’s F/D displays and affect A/P operation.

 

So does the highlighted line mean Nav1 and Nav2 should always be set to the same VOR freq when using the AP to track a VOR radial (and even if not using the B AP) ?

 

Related Theoretical queston: In a typical light GA a/c with two VORs/OBSs and nav receivers, you can use VOR1 to track along a radial, and use the other to identify your position along the tracked radial by identifying what VOR2 radial you are crossing (or said another way, identify an intersection using the two VORs). Can you use the two VORs in the 737NGX to do this? If so, how do you set up VOR2?

 

Thx,

Al

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So does the highlighted line mean Nav1 and Nav2 should always be set to the same VOR freq when using the AP to track a VOR radial (and even if not using the B AP) ?

 

You're overthinking this.  It's just saying that if the two pilots are referencing different VORs, then the displays will be showing different information.

 

 

 


Can you use the two VORs in the 737NGX to do this? If so, how do you set up VOR2?

 

Yes.  Put it in NAV2, and then use the switches above the ND.  The one for VOR2 is just under the BARO knob:

2011-12-27_17-32-54-355.jpg

 

Pushing that switch up will show VOR2 on the captain-side display.  The one on the left of that same panel (partially hidden in the picture, by the MINS knob) is for VOR1 and ADF1.

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You're overthinking this. It's just saying that if the two pilots are referencing different VORs, then the displays will be showing different information.

 

So if the displays are showing different info and you are in the VOR/LOC AP mode to track a radial, how does the system decide which VOR to use? Or can only one AP be on in this case?

 

 

Yes. Put it in NAV2, and then use the switches above the ND

 

I knew how to select VOR2, what I didn't get and suddenly realized while reading your response was I have to use the FO's Course Selector like I would the 2nd OBS in a light GA a/c. Seems so obvious now -- sigh.

 

Thanks very much for the help, Kyle.

Al

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So if the displays are showing different info and you are in the VOR/LOC AP mode to track a radial, how does the system decide which VOR to use?

 

You already answered this with the quoted text from your first post:

 

 


A autopilot and Captain’s F/D use information from Captain’s course selector and No. 1 VHF NAV receiver
B autopilot and First Officer’s F/D use information from First Officer’s course selector and No. 2 VHF NAV receiver
•different courses and/or frequencies for two VHF NAV receivers can cause disagreement between the Captain’s F/D display and First Officer’s F/D display and affect A/P operation (which will follow NAV1 if on CMD A, or NAV2 on CMD B).

 

 

 


I knew how to select VOR2, what I didn't get and suddenly realized while reading your response was I have to use the FO's Course Selector like I would the 2nd OBS in a light GA a/c. Seems so obvious now -- sigh.

 

haha - a lot of things do until it hits you.

 

For what it's worth, depending on the display mode, I believe it may only work like an RMI (just points towards the VOR without any specific course).

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which will follow NAV1 if on CMD A, or NAV2 on CMD B

Ah, that part wasn't included on page 4.10.13 of FCOMv2 where I got my quoted text.  ^_^

Thanks again for the info,

Al

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Ah, that part wasn't included on page 4.10.13 of FCOMv2 where I got my quoted text. ^_^

Thanks again for the info,

Al

You just quoted it - again - in your first post... ;)

 

Autopilot A is CMD A. Your very first post says "autopilot a gets it's info from the capt F/D, which gets info from Nav1 (VOR1)."

 

I certainly applaud the effort to go to the manuals, and clarification of the manuals is a better use of the forum, but sometimes all it takes is a little time to process what's read ;)

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If tracking inbound to a VOR using VOR/LOC and at the VOR you are to make, say, a 75 deg turn and then track outbound, is there a rule of thumb, perhaps based on ground speed and/or degrees of turn, to determine how far out from the VOR to change the VOR course heading to the outbound track (radial) so the AP can set up the intercept and track outbound on the proper course (radial)?

Thx,

Al

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If tracking inbound to a VOR using VOR/LOC and at the VOR you are to make, say, a 75 deg turn and then track outbound, is there a rule of thumb, perhaps based on ground speed and/or degrees of turn, to determine how far out from the VOR to change the VOR course heading to the outbound track (radial) so the AP can set up the intercept and track outbound on the proper course (radial)?

 

I was going to copy and paste things here, but I want to give these guys credit:

http://www.pprune.org/tech-log/439603-question-regarding-vor-intercepts-inbnd-outbnd.html

 

Have a look there.  Two guys posted two examples of things that'll help.

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