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Using the FMC to Intercept a VOR Radial

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If I was southeast of ABC VOR when ATC directed me to fly a heading of 60 degs to intercept and fly outbound on the ABC 90 deg radial, I think I understand how to do that "manually".  I would turn to a heading of 60 degs, set Nav1 to the ABC freq, set the MCP course window to 90 degs, use either the VOR or MAP display on the ND to identify the radial intercept, and then turn outbound on the 90 deg radial. Pretty much what you would do in a C172 except the MCP Course setting replaces the OBS setting in the 172.

What I don’t know how to do is to use the FMC and LNAV to accomplish the same thing, especially if this direction by ATC meant I would bypass one or more waypoints already programmed into the FMC. So there are two issues: how to set up the FMC to make the radial intercept with LNAV, and how to update the FMC since one or more flight plan waypoints would no longer be valid.

Thx for your advice,

Al

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What I don’t know how to do is to use the FMC and LNAV to accomplish the same thing, especially if this direction by ATC meant I would bypass one or more waypoints already programmed into the FMC. So there are two issues: how to set up the FMC to make the radial intercept with LNAV, and how to update the FMC since one or more flight plan waypoints would no longer be valid.

 

How to do this is explained in tutorial 2.

 

Regardless, when it comes to flying modern planes, there's this overwhelming want to adjust the magenta line to get the FMC to do something that - for it - is complex, but left to other devices is stupidly simple.  As such, it's honestly quicker probably to "go old school" and just do it like that.  When you get closer to that VOR in your flight plan, line select it to the top and go back into LNAV.

 

The FMC is a tool to help you.  If it's not helping, or something is going to be more complex done through it than done by other means, leave it out of the equation.

 

https://www.youtube.com/watch?v=R0rYX-Jn6o8


Kyle Rodgers

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OK. I did go through tutorial 1 and have been flying some short hops, learning how to use SIDs and STARS, etc. To this point the SIDs and STARS I've been flying have been RNAV, and part of the motivation for my original question was in preperation for dealing with a non-RNAV SID or STAR. I will defenitely take a look at tutorial 2.

 

I first saw that AA safety video a few years ago, which was before I got interested in flight simulation, and unfortunately my only RW flying experience had been (and is) a few hundered hours in a Piper Cherokee PA-28 (and that was over 30+ years ago ... sigh!).  As I recall, the Cherokee didn't have even a simple AP, but now that I can at least spell FMC, the video is even more interesing and meaningful.

 

Thx,

Al

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As I recall, the Cherokee didn't have even a simple AP, but now that I can at least spell FMC, the video is even more interesing and meaningful.

 

Yeah, I always end up re-watching it from time to time.  Good video.

 

I think I've used an autopilot while (real) flying - max - once or twice in my life.  Those in the Cessnas and Pipers aren't exactly the best.


Kyle Rodgers

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Regardless, when it comes to flying modern planes, there's this overwhelming want to adjust the magenta line to get the FMC to do something that - for it - is complex, but left to other devices is stupidly simple.

By stupidly simple, you mean VOR/LOC I presume? I didn't know until recently that 777 doesn't even have VOR/LOC so options become a bit more limited on the big bird!

 

Seriously, on the 737, VOR/LOC is stupidly easy to use, however in practical terms on departure clearances such as "right turn, inbound radial 280 to JJS, flight planned route." Given that LNAV is the general theme of the flight, it is often more practical to simply bring JJS to the top of the LEGS page, enter the radial into INTC CRS which will setup and infinate magenta line extending from JJS on the radial course. Then use HDG SEL to turn to intercept the radial at a sensible angle (30-45 deg usually) and once stable on that heading select LNAV, the aircraft with then follow that intercept heading and then automatically intercept the magenta line inbound to JJS.


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^^^ That's one way to do it. Last night I flew the Canarsie 13L at KJFK and intercepted CRI radial 223 on approach. How? Tune CRI, and put the magenta heading bug on the green arrow. Couldn't be simpler  :P 


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....... it is often more practical to simply bring JJS to the top of the LEGS page, enter the radial into INTC CRS which will setup and infinate magenta line extending from JJS on the radial course.

Could you please explain how you bring JJS to the top of the LEGS page (enter it via the scratchpad?), and where INTC CRS is found?

Thx,

Al

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Could you please explain how you bring JJS to the top of the LEGS page (enter it via the scratchpad?), and where INTC CRS is found?

Thx,

Al

Select or type JJS and select it into the first line on LEGS page, then enter the course you want in lower right, then hit EXEC.


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This is all fine if you're going to JJS. Not so much if you're going away from JJS.


Matt Cee

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Select or type JJS and select it into the first line on LEGS page, then enter the course you want in lower right, then hit EXEC.

Thanks.

Al

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This is all fine if you're going to JJS. Not so much if you're going away from JJS.

Interesting point. Now that I think about it, everything that I've learned so far about using the FMC with respect to a flight plan route always is in terms of "to" the next waypoint. So I guess that means if I wanted to fly outbound from JJS on a particular radial, I'd have to "translate" that to an inbound course to the next waypoint, and perhaps even have to define my own next waypoint?  For example, suppose I wanted to fly outbound from JJS on a particular radial a specific distance or time, and then turn back 180 degs to intercept an approach course (some type of procedure turn not in the FMC database, etc). As suggested above, maybe something like this is best done "the old fashion way" rather than trying to program it into the FMC.

Al

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Flying away from JJS at a radial is just as easy. If you want to depart JJS at 180 radial just type in JJS180/10 and select it into the first line. The "/10" is arbitrary and it'll make a fix 10 miles away from JJS at 180 radial. You can make it "/100" if you want a really long line.


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As suggested above, maybe something like this is best done "the old fashion way" rather than trying to program it into the FMC.

 

Definitely.  Again, so many simmers are obsessed with the box so much that they'll go out of their way to make it do something that's so incredibly simple to do any other way that it's mind boggling...

 

It's cool, sure, but there are points where it's just better to...well..."switch to guns," if you will.


Kyle Rodgers

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Flying away from JJS at a radial is just as easy. If you want to depart JJS at 180 radial just type in JJS180/10 and select it into the first line. The "/10" is arbitrary and it'll make a fix 10 miles away from JJS at 180 radial. You can make it "/100" if you want a really long line.

Well that's good to know, thanks!

Al

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This is all fine if you're going to JJS. Not so much if you're going away from JJ

Practically speaking, flying outbound JJS would be flying to something else, if not then you are probably being vectored for traffic in which case you're under radar control on a radar heading. If flying away from a navaid, the clearance could probably be "join the airway UL419" where the airway is the segment between the navaid and the next waypoint in which case you use the same intercept technique as I described above, or you could be cleared direct to the waypoint.

 

I'm not trying for an FMC solution to a problem, just that under some specific circumstances using a higher level of automation can reduce workload and it is up to the pilot to assess the most appropriate solution for the job which means being comfortable with any technique :)


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