Paul12

VOR question

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I need some assistance using a VOR approach.

First of all some terms ( see attached screen shot )

 a) what is the name and purpose of the green arrow on top of the ND pointing to 048 degrees.

b) what is the name and purpose of the dotted magenta line also pointing to 048 degrees.

How do I get the exact location of the VOR ?

Do I leave the A/P on ?

Can it be done with the VORLOC ?

I appreciate your help

Paul 12

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I do not see any reference to a specific VOR approach so I cannot walk you through how to fly one.

a) the green arrow is pointing to the station.  If the station were off a wing the pointer would be pointing to a wing.

b) the magenta line is the FMS rendering of the track as selected by the LEGs page.

c) the location of the VOR is 048 deg bearing at 9.7 nm DME.  The exact location is irrelevant, you are only interesting in the location with regards to the aircraft.  The DME distance is the slant range, it will never decrease to zero unless you are on the ground.  If you overfly the station at 16000 ft then the DME will decrease to about 2.6 nm.  It is the distance from the station to you.

Use of A/P and roll mode depends on what you are trying to do, which is the information you failed to provide.  By the way, all the symbols used in any display are tabulated in the FCOM.  I suggest learning how to find those.

Question in reverse:   Do you know how to fly a VOR approach regardless of aircraft type?  A good source is the free FAA Instrument Flying Handbook: https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/

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Paul the dotted (or dashed) line is the heading, it always points towards the heading bug, wherever it will be. it is there for your reverence if you want to fly to a certain point on your ND map with HDG mode. The solid magenta line is, as Dan said, your FMC calculated LNAV track.

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Regarding VOR LOC, according to SP.4.4 "VOR Navigation" in the FCOMpdf.

1. tune the radio and identify the VOR

2. set course

3. Push VOR LOC mode switch.

Note when changing localizer frequencies when captured on VOR LOC, disengage VOR LOC and repeat steps 1-3. 

Im guessing just hit heading select then tune your radios and course then hit VOR LOC. 

-Angelo Busato

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in the 737 the vor loc is used as part of your ILS approach. because you also need to manually tune the radio for this.

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8 hours ago, ph-cxz said:

in the 737 the vor loc is used as part of your ILS approach. because you also need to manually tune the radio for this.

Don‘t confuse an ILS with a VOR station. The set course during an ILS approach is only a visual reference and has nothing to do with flying the ILS itself. An ILS localizer sends two „beams“ next to each other and the airplane calculates the middle position.. it works even without any course information. (I‘m sure there are better words for this) a VOR sends 360 radials and choosing the course you will capture this radial.

there is absolutely no technical requirement to use the LOC mode during an ILS approach. Only it‘s saver to capture the localizer prior to the glide slope.

Edited by Ephedrin

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Gents,

Related to the original post, I see this a lot from simmers, and I'm not sure where it comes from.

When I see people write the modes like this, it seems that people think that it's a mode that "locks on" to a VOR (it's even clearer when people speak it as "VOR lock"). The mode is technically a VOR radial hold, or a LOCalizer hold. They both function on the same principle of tracking a lateral path, either a VOR or a LOCalizer, ergo the mode is called VOR/LOC. To be clearer, it is a VOR or a LOC tracking mode. It's a semantic point, but I think it's an important one: it's there to handle VORs or LOCs to track a signal, providing lateral deviation information, coming from a station in a fixed location on the ground.

1) The green arrow points to the VOR, and is called a bearing pointer (and in this case, a VOR pointer, since it points to a VOR and not an NDB).
2) The dashed magenta line is the heading leader. It runs from the nose of the plane symbol (the triangle) to the outer arc where the heading bug is currently set. In this case, it's actually 045 (see your MCP Heading window).
3) The location is shown on the ND as the hexagon with three boxes on the sides (and the dashed green line coming out of it, showing that your course is set to 135 on the MCP).
4) If you'd like, sure.
5) You can use VOR mode (VOR/LOC button) on the AP to track towards it, but you need to set the course first. In your case, you'd need to set the course to about 045, and then hit the VOR/LOC button.

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4 minutes ago, scandinavian13 said:

Related to the original post, I see this a lot from simmers, and I'm not sure where it comes from.

Oh my... I missed this.  I assumed he was asking how to shoot an approach when all he wanted to know was how to track a VOR radial. Interesting how I took the bait when he asked how to "use a VOR approach." 

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2 hours ago, Stearmandriver said:

To be fair, depending on your MCP, it may be labeled as he said. 

Right - I get it. Still...a lot of the cohort seem to even speak it as "vor lock" as if it "locks on" to VORs and not also LOCalizers. Pedantic, I get it, but misleads the person who is making the assumption (and perpetuating it).

Might not be fully relevant to this thread, specifically, but if you look around, you'll see it.

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5 hours ago, Ephedrin said:

The set course during an ILS approach is only a visual reference and has nothing to do with flying the ILS itself. An ILS localizer sends two „beams“ next to each other and the airplane calculates the middle position.. it works even without any course information.

That is true on many planes, however on the 737, the course is actually used by the flight control computer to calculate intercept and correction. If you have the wrong course in, the FCC can take you in the wrong direction.

 

A captain and I found this out the hard way flying in to Kodiak, Alaska. Not the best place for learning.

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36 minutes ago, Spin737 said:

That is true on many planes, however on the 737, the course is actually used by the flight control computer to calculate intercept and correction. If you have the wrong course in, the FCC can take you in the wrong direction.

 

When first getting into the PMDG NG, I also argued that all it set was compass rose on the OBI when ND is in APPR mode.... but I found out that indeed the automation uses it.  Of course the consequences in a simulator are not as dire.

As a comm engineer, I'd also avoid calling the localizer a pair of beams because I'm such a nerd. The antenna array creates one radiation pattern where one side of the lobe is amplitude modulated at 90 Hz and the other side at 150 Hz.  A simple 60 Hz detector, which is the difference frequency, is maximum when you are receiving both sides equally. No calculation necessary, just a filter and detector (diode). 

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2 hours ago, Spin737 said:

That is true on many planes, however on the 737, the course is actually used by the flight control computer to calculate intercept and correction. If you have the wrong course in, the FCC can take you in the wrong direction.

 

A captain and I found this out the hard way flying in to Kodiak, Alaska. Not the best place for learning.

oups, definitely not..

If you don't mind, could you specify this a bit? You say "the computer CAN take you in the wrong direction? 180°-wrong?

My technical english vocabulary lacks a bit but using Dan's words the airplane simply needs to follow the maximum amplitude with the detector. So actually no course is required. Even airplanes in the 40s could follow a localizer. 

If I understand you correctly, the 737 "only" needs the course to calculate the turn to capture the Loc and for higher precision corrections instead of being totally dependent on amplitude changes?

I think I've never had issues in the PMDG 737 following a localizer when I didn't set the course. I thought it was only mandatory for an autoland (and a VOR radial) 

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42 minutes ago, Ephedrin said:

oups, definitely not..

If you don't mind, could you specify this a bit? You say "the computer CAN take you in the wrong direction? 180°-wrong?

My technical english vocabulary lacks a bit but using Dan's words the airplane simply needs to follow the maximum amplitude with the detector. So actually no course is required. Even airplanes in the 40s could follow a localizer. 

If I understand you correctly, the 737 "only" needs the course to calculate the turn to capture the Loc and for higher precision corrections instead of being totally dependent on amplitude changes?

I think I've never had issues in the PMDG 737 following a localizer when I didn't set the course. I thought it was only mandatory for an autoland (and a VOR radial) 

Kodiak, Alaska ILS26. This was 10ish years ago, and I don't remember exactly the set-up. It was something along the lines of the CA left his course in the window from the departure, which would have been something like 330 or 070 out of Anchorage. We would have done the DME arc in LNAV and joined the final course. The plane was on final and then it started turning away from the course when we captured the LOC. I was very new and should have spoken up when he simply decided to do a 360 over the FAF to realign. Not comforting seeing large rocks out your window and you don't know where you're going.

 

The FCC looks at the course for intercept and correction and it got confused. It may have been that the CA had the wrong course in. It could also have been that our courses didn't agree, but I imagine that's more important on a dual-channel approach. The systems manual has a small mention of this. Our company had a memo about this at one point, but I can't find it anymore.

You might be able to twist the CRS selector and see what it does, but I'm not sure if the sim models this behavior.

 

Cheers

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Thanks Matt,

it sounds a bit strange to me that - on an armed precision approach - the airplane is being so easily to confuse by a pilot error (don't get me wrong) instead of following the hard facts of a dialed-in frequency and armed approach mode. I would have expected it to primarily follow the ILS instead of being dependent on something that can more or less easily be messed. So simple transposed digits could spool up an ILS approach although frequency and mode are correct.. Thanks for the explanation, I will definitely try this out!

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Hi Marc,

I can't speak to the specifics of the 737 but most modern aircraft use some inertial inputs (for which it is necessary to set the correct inbound course) alongside the raw localiser signal - the A320 for instance will do very odd things like S-turn down the approach if the course is not properly set.

The difference of course is that in most other aircraft apart from the 737 and 767 the ILS course is set automatically from the navigation database and so the likelihood of an error is much smaller!

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The Jurassic 737 was renowned for turning the wrong way on ILS LOC capture, so I was told by an old Skygod one day. The FlyJSim 737-200ADV simulates this really well when I try it in X-Plane. It's fun flying the relic sometimes. You can stick to Boeing SOP as per the NG and it works just fine too.

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