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AF330

Heading/Course difference

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Hi,

 

A strange question....what is the difference between course and heading?

I learnt that there were 2 types of course:

- One with a VOR or a LOC

- The "route" over the ground.

A HDG is where the aircraft is pointing.

 

So when we enter HDG 30, it just means that the nose of the plane should be pointing 30°? But it means that the plane can be flying in another direction than HDG 30° over the ground???????

 

Dangerous!

 

Thanks to help! :)

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MUST CONSIDER WIND DIRECTION AND SPEED. DO SOME RESEARCH ON THE FOLLOWING: TRUE COURSE, TRUE HEADING, MAGNETIC COURSE,MAGNETIC HEADING. 

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Hmmm....thanks.

 

Magnetic HDG = Angle between magnetic north and your HDG

 

Magnetic CRS = Angle between magnetic north and your CRS

 

True HDG = Angle between true North and your HDG

 

True CRS = Angle between true north and your CRS.

 

If there is wind, the CRS of the aircraft can change . If you enter a HDG, it will point to that HDG but if there is wind, CRS is not equal to HDG. Isn't it dangerous or am I missing something? Basically thr plane is no more going where it should!!!

 

Thanks

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It isn't dangerous, although I can see where it might seem so if you aren't familiar with it.

 

The difference between heading and course that you see while in cruise is due to your wind correction angle. When you fly a constant heading, the nose of the airplane stays pointed in the same direction, but the actual track of the airplane across the ground can be altered by wind. So if you want to travel along a straight line (radial) on a heading of 270, and the wind is from 340, you will actually end up flying a HEADING of greater than 270 (probably close to 277 if my mental math is somewhat accurate). This heading will compensate for the wind that is blowing you "off course" so to speak. The nose of the airplane will be to the right of course, but the airplane will be tracking on course of 270.

 

 

Make sense?

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adding to the excellent answer above.......

 

Any flightplan you fly, you will be expected to fly as a magnetic track(or Course). If you are hand flying, you will need to adjust for the wind manually. If using a modern AP, it will do this automatically.

 

If you then are being vectored by ATC with magnetic headings, they will have factored in the wind.

 

So the aircraft is always going where it should.

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Hmmmm....yes makes sense!

 

Read something about a triangle....

So if we enter in the FCU HDG 70, it will try to fly CRS 70?

 

Thanks

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I should have said "if using a modern FMC, it will fly the magnetic track between two waypoints". The glareshield AP controls, when using HDG SEL, will give you the option to fly a HDG or a TRK.

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Hmmmm.....

 

But the A/P in HDG selective mode will basically try to do this: CRS = HDG (but the HDG now, can be different.)

 

Do you agree?

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Hmmmm.....

 

But the A/P in HDG selective mode will basically try to do this: CRS = HDG (but the HDG now, can be different.)

 

Do you agree?

 

No

 

HDG SEL will fly a HDG ...ie nose pointed at whatever degree magnetic you have dialed in. If there is wind you will be flying a different track to that heading.

 

There will be a selector on a modern AP to change the HDG SEL to fly a track. If you select that, you will be flying the magnetic track you have dialed in.

 

CRS does not = HDG.  CRS is a magnetic track to/from a VOR or ILS

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But the A/P in HDG selective mode will basically try to do this: CRS = HDG

You lack basic understanding what is CRS and what is HDG. People suggested to you long time ago that you should get a sim and experiment and see what it does under different inputs instead you ask endless questions and I can tell you aren't learning anything.

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Yes....Will answer this evening!

 

@ michal: I will get a sim and a book explaining basics for christmas!

 

Thanks

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No

 

HDG SEL will fly a HDG ...ie nose pointed at whatever degree magnetic you have dialed in. If there is wind you will be flying a different track to that heading.

 

There will be a selector on a modern AP to change the HDG SEL to fly a track. If you select that, you will be flying the magnetic track you have dialed in.

 

CRS does not = HDG. CRS is a magnetic track to/from a VOR or ILS

Thanks a lot,

 

Ok....

 

1) In managed mode, the plane uses only tracks to fly. It doesn't use HDG, do you agree?

 

2) Wiki: " In an aircraft, to correct for these difference between "heading" and "course"a navigator uses the wind triangle."

 

Does the FMGC use the wind triangle in selective heading so that track = heading?

 

Thanks a lot,

A.Roy

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1) In managed mode, the plane uses only tracks to fly. It doesn't use HDG, do you agree?

2) Wiki: " In an aircraft, to correct for these difference between "heading" and "course"a navigator uses the wind triangle."

Does the FMGC use the wind triangle in selective heading so that track = heading?

 

1. If by "managed mode" you mean a FMC/FMS LNAV navigation function....then the aircraft will fly tracks, not headings

 

2. The FMC has no need to use a wind triangle. The FMC has access to Satellite positioning and inertial navigation equipment. This tells it precisely where it is and what track it is flying.

 

If you are flying where there is crosswind then track will never = heading.

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2. The FMC has no need to use a wind triangle.

I disagree, the AP/FD has to compute 'first guess' wind correction angle and for this it needs some basic trigonometry. Plus there is a ton of great-circle formulas that FMC must know how to compute so it is in fact quite loaded with all kinds of formulas.

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Ok....thanks a lot....

 

1) So the track we enter on the FCU, is it the angle between the track and magnetic north?

 

2) Well...michal give another answer....

 

A simple question: In selective HDG mode, does the FMGC use the wind triangle to try to match HDG and TRAK?

 

Thanks

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In selective HDG mode, does the FMGC use the wind triangle to try to match HDG and TRAK?

No.

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Hi.

 

A strange question....what is the difference between course and heading?
 

 

In a nutshell, course is the direction your plane is moving and heading is the direction in which the nose is pointing.

 

...

 

Your track is just the (imaginary) line the plane is following - it doesn't even have to be straight.

 

As so many others have already told you, you need to learn some fundamental stuff. The way you are going about things is a bit like trying to understand calculus before you can do simple sums. If you keep asking about the complex stuff, some of the basics will come along with the answers but people will probably misunderstand you as you don't have the knowledge to describe what you want to know.

 

Regards,

D

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I disagree, the AP/FD has to compute 'first guess' wind correction angle and for this it needs some basic trigonometry. Plus there is a ton of great-circle formulas that FMC must know how to compute so it is in fact quite loaded with all kinds of formulas.

Yes of course! I am going to get a book explaining basics of flight for christmas!! ;)

 

But when does the plane use tge wind triangle? In managed mode, it already uses TRK so no need to use the wind triangle. In selective mode, it uses HDG only...

 

So CRS is basically more "important" and should be respected. That's why, ILS has got a CRS and not a HDG because the plane should remain in the correct direction....Right?

Well, ATC will include wind factor while giving a HDG....

 

Thanks

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Try this analogy. You're in a boat and want to cross a mile wide river to reach the marina. The river has a current of 5 knots, the cross wind. Take a compass reading from your beginning point toward the marina, this is your True Course.

 

Now begin your trip to the marina. If you follow the compass heading you initially took and the boat is moving at 5 knots on the speedometer you are making 5 knots ground speed. At the same time the river current is pushing you down stream also at 5 kts. The point you will reach while maintaining the initial heading will be one mile down stream of the marina, because you are going 5 kts down stream and 5 kts along your compass heading. Trigonometry will tell you how far you actually travel thanks to good old Pythagorus (sp?).

 

The path the boat actually makes to reach the down stream point is your track, also called course over ground or COG. If you want to go directly to the marina, you'll have to add a correction factor to your magnetic heading to compensate for the current. The correction factor can be found by doing the math, using a computer (paper or electronic) or letting the autopilot do it for you. In this simplification you would take compass reading of a point one mile upstream. The initial heading to your destination plus the correction factor for the drift. This will result in COG=Initial Heading=True Course.

 

Of course actual aeronautical navigation is more complex because of the greater distances travelled and the fact that the world is round, but the theory is the same. All of this is better explained in any book on navigation or even Wiki it's called vector arithmetic.

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Thanks a lot!  :wink:

 

But when does the A/P use it? When we our in NAV, the plane uses tracks, so no calculation to do. It knows which CRS to go. In selective mode, the plane doesn't use the triangle...we enter a HDG, it points the plane to that HDG. So when does A/P calculate how to equal HDG and TRACK (or COG)? In which situation?

 

In manage mode, when we enter an airway, it knows the track to keep. So it doesn't use HDG. So no need to calculate the triangle. In selective mode, it only uses HDG...

 

So it gives:

 

Managed mode: Tracks only - to follow the right CRS.

Selective mode: HDG only.

 

Hope you understand my question,

 

Thanks a lot,

A.Roy

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So when does A/P calculate how to equal HDG and TRACK

 

HDG is HDG

 

TRK is TRK

 

TRK and HDG will only be the same in a zero crosswind situation. The AP cannot make them equal each other if there is crosswind. The AP is either flying a HDG or it is flying a TRK.

 

I am afraid your question makes no sense.

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Hi.

 

So CRS is basically more "important" and should be respected. That's why, ILS has got a CRS and not a HDG because the plane should remain in the correct direction....Right?
 

 

Your question about ILS illustrates what I posted earlier but if you are referring to ILS approaches rather than the hardware, then the answer is yes. If you set a heading rather than flying the course you'd be doing the same as the plane on the right in this animation:

 

http://www.physicsclassroom.com/mmedia/vectors/plane.cfm

 

 

Here's one from the real world. Watch the crosswind landings in this clip. You can see the planes travelling parallel with the runway (course) but pointing well off to one side (heading), just like swimming across a river. If they were using an ILS localiser, it would be pointing out from the end of the runway in the direction they'd just come from.

 

https://www.youtube.com/watch?v=la-hSjKP2TU

 

Cheers,

Dave

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Thanks a lot....

Hmmm.... Let me ask my question this way:

 

We we enter an airway in the MCDU, what does the FMGC know? It's track, isn't it?

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Thanks a lot....

Hmmm.... Let me ask my question this way:

 

We we enter an airway in the MCDU, what does the FMGC know? It's track, isn't it?

Yes

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Great....

 

So what else does the plane know?

Does the plame know our current track? Our current HDG? How? With IRS qnd GPS isn't it?

 

Thanks

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