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JohanKotze
Posts: 52
This might be a silly question but as I am not a real pilot this do trigger me.

When flying I select VORLOCK and when descending for approach I select LNAV (when NAV1 signal is received) and when the <> on the vertical leg of PFD is centre I select APPROACH. When I select LNAV isn't VORLOCK supposed to deactivate?

I might be wrong.
2022-04-15 19:29
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pizman82
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From: ETSI, Germany
Posts: 5474
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iconJohanKotze:

This might be a silly question but as I am not a real pilot this do trigger me.



There is no silly question.... Only silly awnsers ! :P :thumbup:

iconJohanKotze:

This might be a silly question but as I am not a real pilot this do trigger me.
When flying I select VORLOCK and when descending for approach I select LNAV (when NAV1 signal is received) and when the <> on the vertical leg of PFD is centre I select APPROACH. When I select LNAV isn't VORLOCK supposed to deactivate?



The whole logic is strange .....

You will not select LNAV again.....

While Flight you have LNAV ( Means the FMC Flightplan (legs) controll the lateral Flight and you have VNAV active ( The FMC also control the vertical profile)

Normaly while aproach you get vectors from ATC.... So you already swap from LNAV to HDGSEL. But lets expect you fly the whole approach like in Flightplan...
So we remain LNAV until we make our base turn in the final.....

Shortly before ( e.g. when we are downwind some minutes before base) we "arm" one of the two modes VORLOC or APPR
BOTH will capture the Locator of the ILS and turn you onto Runway heading.
In that moment Lateral Mode change into LOC So lateral controll are done by AP/FD and follow the LOC.

The Difference between VORLOC and APPR.... APPR also capture the Glideslope. So it also will ARM the Vertical Mode for GS.
VORLOC will not do this. So if you use VORLOC to catch the Locater then you have to press APPR to capture the Glideslope.

As i know this is used in real if you just get a clearance like "DLH405 cleared Locator Rwr 25C ... Report when established ."
Means your cleared for final base turn on the Locator BUT your not cleared to descent !
So we just press VOR LOC but not APP.
After we get cleared for the ILS we press APP

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In easy words... "Arm" the Mode some time before you come to final....
VORLOC for the Lateral .... OR ... APP for Both ( App include VORLOC by itself).
So you not need to wait until Glidepath >< is there.
In theory you could press APP already 1 Hour before landing...: Whatever not realistic !
Good Luck !
2022-04-15 20:15
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JohanKotze
Posts: 52
Thank you for a clear explanation.
2022-04-16 07:32
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