workhorse
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Autopilot "Course" mode

Wed Mar 08, 2017 10:40 am

Dear commercial pilots and other knowledgeable people! Please, excuse me in advance for the naivety of the question, my experience with any airplane is limited to more or less realistic sim models.

The 737 has an autopilot mode where instead of setting a heading one can set a "course", which basically means telling the aircraft:

"fly along the line that crosses the VOR whose frequency has been selected on the NAV1 radio and that goes in the direction of the point of the compass selected on the Course knob".

It looks like Airbus aircraft as well as newer Boeings (such as the 777) do not have this feature. So, my question is: is this mode really used on the 737s? What is its use when you can just select a waypoint on the FMC?

Looking forward for your answers, thank you very much in advance!
 
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zeke
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Re: Autopilot "Course" mode

Wed Mar 08, 2017 12:40 pm

That is for flying a radial in or out of a VOR, on the Airbus you would just select direct to the VOR, and on the right hand side insert the inbound or outbound radial you wish to intercept.
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gloom
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Re: Autopilot "Course" mode

Wed Mar 08, 2017 12:43 pm

workhorse wrote:
It looks like Airbus aircraft as well as newer Boeings (such as the 777) do not have this feature. So, my question is: is this mode really used on the 737s? What is its use when you can just select a waypoint on the FMC?


1. You can fly on radial (course from/to VOR, or in fact any other radio aid, like NDBs as well, or even intersections if required) on any plane. Most (if not any) current airliners will allow it on autopilot, plus some more (like arc flight etc). It's just realized differently.
2. Yes it is. Less and less, but it is. One particular, best known case is VOR (or NDB) approach, but it's not the only one.
3. Sometimes it's important not only to reach a specified point, but also on specified course (as you call it). Approach is the case again, when you reach the airport, you want to be aligned with its runway when making approach, right?

Cheers,
Adam
 
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SaveFerris
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Re: Autopilot "Course" mode

Wed Mar 08, 2017 1:22 pm

workhorse wrote:

It looks like Airbus aircraft as well as newer Boeings (such as the 777) do not have this feature. So, my question is: is this mode really used on the 737s? What is its use when you can just select a waypoint on the FMC?

Looking forward for your answers, thank you very much in advance!


The newer Boeings (my knowledge is limited to the 747 but I'm assuming the other planes are similar) have a system very similar to what zeke described, you enter the VOR into the FMC and then you are able to select an inbound or outbound course with which to track. Once you have that set up you then use LNAV to track the course, so it's not exactly as you described with using a "course" mode specifically to track the VOR. There really is no way to track to or from a VOR the old fashioned way, even with a VOR approach it is loaded in the FMC and the course is flown using LNAV.
 
workhorse
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Re: Autopilot "Course" mode

Wed Mar 08, 2017 1:38 pm

Thank you Zeke (I knew you would help!) and Gloom!

So, if I understand well, on aircraft other than the 737, if I need to fly a specific "course" aka radial in or out of a VOR (or NDB or intersection...) I set this via the FMC and than just let the airplane fly in "LAT" or "LNAV" mode, right?
 
workhorse
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Re: Autopilot "Course" mode

Wed Mar 08, 2017 1:42 pm

workhorse wrote:
So, if I understand well, on aircraft other than the 737, if I need to fly a specific "course" aka radial in or out of a VOR (or NDB or intersection...) I set this via the FMC and than just let the airplane fly in "LAT" or "LNAV" mode, right?


SaveFerris wrote:
The newer Boeings (my knowledge is limited to the 747 but I'm assuming the other planes are similar) have a system very similar to what zeke described, you enter the VOR into the FMC and then you are able to select an inbound or outbound course with which to track. Once you have that set up you then use LNAV to track the course, so it's not exactly as you described with using a "course" mode specifically to track the VOR. There really is no way to track to or from a VOR the old fashioned way, even with a VOR approach it is loaded in the FMC and the course is flown using LNAV.


Posted at the same time. :)

So I have my answer, thank you SaveFerris!
 
Woodreau
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Re: Autopilot "Course" mode

Wed Mar 08, 2017 6:25 pm

At least on the Airbus, there is no way to track any ground navaid other than an ILS.
Tracking a VOR/NDB is all virtual, all done using the FMGC.
Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
 
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SaveFerris
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Re: Autopilot "Course" mode

Wed Mar 08, 2017 6:31 pm

workhorse wrote:
workhorse wrote:
So, if I understand well, on aircraft other than the 737, if I need to fly a specific "course" aka radial in or out of a VOR (or NDB or intersection...) I set this via the FMC and than just let the airplane fly in "LAT" or "LNAV" mode, right?


SaveFerris wrote:
The newer Boeings (my knowledge is limited to the 747 but I'm assuming the other planes are similar) have a system very similar to what zeke described, you enter the VOR into the FMC and then you are able to select an inbound or outbound course with which to track. Once you have that set up you then use LNAV to track the course, so it's not exactly as you described with using a "course" mode specifically to track the VOR. There really is no way to track to or from a VOR the old fashioned way, even with a VOR approach it is loaded in the FMC and the course is flown using LNAV.


Posted at the same time. :)

So I have my answer, thank you SaveFerris!


No problem, more than happy to try and share my limited aviation knowledge...
 
BoeingGuy
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Re: Autopilot "Course" mode

Wed Mar 08, 2017 9:22 pm

SaveFerris wrote:
workhorse wrote:

It looks like Airbus aircraft as well as newer Boeings (such as the 777) do not have this feature. So, my question is: is this mode really used on the 737s? What is its use when you can just select a waypoint on the FMC?

Looking forward for your answers, thank you very much in advance!


The newer Boeings (my knowledge is limited to the 747 but I'm assuming the other planes are similar) have a system very similar to what zeke described, you enter the VOR into the FMC and then you are able to select an inbound or outbound course with which to track. Once you have that set up you then use LNAV to track the course, so it's not exactly as you described with using a "course" mode specifically to track the VOR. There really is no way to track to or from a VOR the old fashioned way, even with a VOR approach it is loaded in the FMC and the course is flown using LNAV.


The 757, 767, 747-400/-8, 777 and 787 all work as you described. There is no direct Autopilot Mode to follow a VOR course like on the 737. You'd use the FMC and LNAV.
 
Alias1024
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Re: Autopilot "Course" mode

Thu Mar 09, 2017 12:00 am

717 is the same as well. Bearing pointers can be displayed to verify you are on course but it would be selected in the FMC and NAV used.
It is a mistake to think you can solve any major problems with just potatoes.
 
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Starlionblue
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Re: Autopilot "Course" mode

Thu Mar 09, 2017 1:37 am

workhorse wrote:
Thank you Zeke (I knew you would help!) and Gloom!

So, if I understand well, on aircraft other than the 737, if I need to fly a specific "course" aka radial in or out of a VOR (or NDB or intersection...) I set this via the FMC and than just let the airplane fly in "LAT" or "LNAV" mode, right?


Indeed. Same on Airbus. You'd be in HDG or TRK mode until intercept, with NAV armed. Once you intercept the radial, NAV becomes active and the aircraft follows that radial.

The advantage is that it works for any fix. Often used to intercept the runway heading if you're not following the full procedural arrival, by inserting a radial in from the final or intermediate fix.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
BoeingGuy
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Re: Autopilot "Course" mode

Thu Mar 09, 2017 5:37 am

Starlionblue wrote:
workhorse wrote:
Thank you Zeke (I knew you would help!) and Gloom!

So, if I understand well, on aircraft other than the 737, if I need to fly a specific "course" aka radial in or out of a VOR (or NDB or intersection...) I set this via the FMC and than just let the airplane fly in "LAT" or "LNAV" mode, right?


Indeed. Same on Airbus. You'd be in HDG or TRK mode until intercept, with NAV armed. Once you intercept the radial, NAV becomes active and the aircraft follows that radial.

The advantage is that it works for any fix. Often used to intercept the runway heading if you're not following the full procedural arrival, by inserting a radial in from the final or intermediate fix.


It's not exactly what the OP asked, but I'll mention that all Boeing models have Heading select and hold modes - HDG SEL and HDG HOLD. The 777 and 787 also allows you to select Track - TRK SEL and TRK HOLD. Do all Airbus models have Track Select in addition to Heading?
 
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Starlionblue
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Re: Autopilot "Course" mode

Thu Mar 09, 2017 7:25 am

BoeingGuy wrote:
Starlionblue wrote:
workhorse wrote:
Thank you Zeke (I knew you would help!) and Gloom!

So, if I understand well, on aircraft other than the 737, if I need to fly a specific "course" aka radial in or out of a VOR (or NDB or intersection...) I set this via the FMC and than just let the airplane fly in "LAT" or "LNAV" mode, right?


Indeed. Same on Airbus. You'd be in HDG or TRK mode until intercept, with NAV armed. Once you intercept the radial, NAV becomes active and the aircraft follows that radial.

The advantage is that it works for any fix. Often used to intercept the runway heading if you're not following the full procedural arrival, by inserting a radial in from the final or intermediate fix.


It's not exactly what the OP asked, but I'll mention that all Boeing models have Heading select and hold modes - HDG SEL and HDG HOLD. The 777 and 787 also allows you to select Track - TRK SEL and TRK HOLD. Do all Airbus models have Track Select in addition to Heading?


Airbus* has TRK select as well as HDG select. You toggle between HDG/VS and TRK/FPA with the round push button in middle of the FCU (Airbus-speak for MCP).

Image

As mentioned aboce you cannot track a radial with FCU inputs. You enter the course in the MCDU ("FMS"). Then it just becomes another input from the FM so you'll be in NAV mode.

The 350 gets the same end result but with a drop down menu and radio buttons on the screen.

Image

The backup method is using the radio control panel to manually tune a navaid and set a course.

Image

* FBW models. I don't know the 300/310 systems.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
workhorse
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Re: Autopilot "Course" mode

Thu Mar 09, 2017 1:08 pm

Wow, a lot of great information here, thank you very much to all contributors!

Starlionblue wrote:
You'd be in HDG or TRK mode until intercept, with NAV armed


How do you arm the NAV mode? Select a heading and then pull the HDG knob?

BoeingGuy wrote:
all Boeing models have Heading select and hold modes - HDG SEL and HDG HOLD.


What is the difference between these two modes?
 
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zeke
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Re: Autopilot "Course" mode

Thu Mar 09, 2017 4:58 pm

BoeingGuy wrote:
The 777 and 787 also allows you to select Track - TRK SEL and TRK HOLD. Do all Airbus models have Track Select in addition to Heading?


All the FBW Airbus models have track in the vertical (flight path angle) and horizontal sense.

Have to adjust the heading bug all the time while following an LNAV path used to drive me nuts on the 74.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
Woodreau
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Re: Autopilot "Course" mode

Thu Mar 09, 2017 6:04 pm

workhorse wrote:
How do you arm the NAV mode? Select a heading and then pull the HDG knob?


Push.

Pulling will keep you in heading mode flying through the course line on heading in perpetuity. Or at least until you change the mode
Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
 
BoeingGuy
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Re: Autopilot "Course" mode

Thu Mar 09, 2017 9:24 pm

workhorse wrote:
Wow, a lot of great information here, thank you very much to all contributors!

Starlionblue wrote:
You'd be in HDG or TRK mode until intercept, with NAV armed


How do you arm the NAV mode? Select a heading and then pull the HDG knob?

BoeingGuy wrote:
all Boeing models have Heading select and hold modes - HDG SEL and HDG HOLD.


What is the difference between these two modes?


Heading and Track may be two different things. Heading is the direction the airplane is pointing. Track is the path it's following over the ground. On the ground or no wind, Heading and Track are the same. If the airplane is flying in a crosswind, Heading and Track could be substantially different.

The 777 and 787 also work as described above for Airbus. You have a smaller switch to toggle between HDG and Track; and another small switch to toggle between V/S and FPA.
 
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Starlionblue
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Re: Autopilot "Course" mode

Fri Mar 10, 2017 12:39 am

workhorse wrote:

How do you arm the NAV mode? Select a heading and then pull the HDG knob?


As mentioned, you'd push the knob. This would give you HDG active with NAV under it in blue (armed) until such time as you intercept the NAV track, at which point NAV becomes active.

The rule on Airbus is that pushing an FCU knob (speed, heading or altitude) "gives control to the plane", as in activates or arms modes where guidance comes from the FM. These are known as "managed modes". Pulling a knob (speed, heading, altitude or V/S) on the other hand "takes control from the plane", as in the pilot now commands the autopilot with the FCU knobs. These are known as "selected modes".

Following this logic, NAV is a managed lateral mode since the FM is guiding, while HDG and TRK are selected lateral modes since the pilot is directly inputting a specific heading or track on the FCU.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
workhorse
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Re: Autopilot "Course" mode

Fri Mar 10, 2017 10:15 am

Workhorse wrote:
What is the difference between these two modes?


BoeingGuy wrote:
Heading and Track may be two different things. Heading is the direction the airplane is pointing. Track is the path it's following over the ground.


This, I knew, but what is the difference between HDG SEL and HDG HOLD? Thank you!
 
workhorse
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Re: Autopilot "Course" mode

Fri Mar 10, 2017 10:20 am

Starlionblue wrote:
The rule on Airbus is that pushing an FCU knob (speed, heading or altitude) "gives control to the plane", as in activates or arms modes where guidance comes from the FM. These are known as "managed modes". Pulling a knob (speed, heading, altitude or V/S) on the other hand "takes control from the plane", as in the pilot now commands the autopilot with the FCU knobs. These are known as "selected modes".

Following this logic, NAV is a managed lateral mode since the FM is guiding, while HDG and TRK are selected lateral modes since the pilot is directly inputting a specific heading or track on the FCU.


This is very clear, thank you for the explanation! I know it works with the Speed knob too (have seen it done), does it work with Altitude too?
 
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Starlionblue
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Re: Autopilot "Course" mode

Fri Mar 10, 2017 10:48 am

workhorse wrote:
Starlionblue wrote:
The rule on Airbus is that pushing an FCU knob (speed, heading or altitude) "gives control to the plane", as in activates or arms modes where guidance comes from the FM. These are known as "managed modes". Pulling a knob (speed, heading, altitude or V/S) on the other hand "takes control from the plane", as in the pilot now commands the autopilot with the FCU knobs. These are known as "selected modes".

Following this logic, NAV is a managed lateral mode since the FM is guiding, while HDG and TRK are selected lateral modes since the pilot is directly inputting a specific heading or track on the FCU.


This is very clear, thank you for the explanation! I know it works with the Speed knob too (have seen it done), does it work with Altitude too?


Speed, heading and altitude knobs are all pull for selected vs push for managed. The V/S knob is slightly different. Pull gives you selected V/S while push gives you immediate level off, same as the ALT pushbutton.

Another quirk is that if you're in a selected lateral mode such as HDG, pushing the altitude knob does nothing. You can't have CLB or DES, which are managed vertical modes, without being on the flight plan path. You have to pull the altitude knob to get OPEN CLB or OPEN DES, which are selected modes. I could say that no one ever pushes the altitude knob while in HDG, but I won't.... ;) And that's why we read the modes and cross check; to ensure our actions produce the desired result.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

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