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Captain Caveman

Heading and Track

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When flying the 737 i often get a diffrent track than the heading i have selected.f.ex: heading 180 and track 190. this means that the aircraft flys a little wideways cause of the wind right? with the nose 10 degrees of the direction of the aircraft is flying?and now for the real question:when flying in LNAV the aircraft always flys on the route track, but does it change heading accoring too the wind or is the heading and track the same in LNAV?


Thorbjørn Henriksen

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Heading is always the direction the plane is pointing. Track is always the lateral track over the ground. It matters not which mode you are in.Do this little experiment. Fly with a strong crosswind. In LNAV with the map display you will be able to see the track you are flying (straight ahead). At the top of the map display you can see a pointer which shows your heading- it will be off centre towards the direction the wind is coming from.Now switch to VOR/ILS mode display. Your straight ahead view is now your heading. The pointer at the top of the display will now show your track- which should be off centre away from the wind direction.Peter


Peter Schluter

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Guest Ray51

When you fly in LNAV the FMC will adjust the aircraft heading to follow the planned track. It uses the IRS and GPS data to determine the course correction. In heading select or when hand flying you have to adjust your heading to maintain the planned track. The small triangle is the course offset due to the current wind. So if the triangle is 5 degress to the right and you input fly a heading of 180 degress into the MCP, you will be flying a track of 175 degress over the ground. You would correct 5 degress right to get a track of 180 degress over the ground.Ray

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In LNAV the route track displayed on the ND is an "anticipated" rte track. It proceeds to the next active wpt regardless of the magenta line's position and or the plane's position in regards to the magenta line displayed on the ND. So, in reality it IS flying the track if LNAV is engaged. Why the discrepancy with the map? Well for one, the information needed to process variations within the sim greatly limit the continual updating needed to keep the line correctly displayed. The real one does a better job at this but even it is not perfect in this regard. The line "could" be made to perform very realistically but in turn would mean that you fly with your frame rates in the single digits all the time simply because of the processor time needed to calculate the line perfectly. More directly to your question - I don't believe the orientation of the airplane symbol on the ND is greatly affected (i.e. the aircraft's nose direction) and the ND is used primarily for situational awareness and not a direct heading per se. All said it still does a great job and the minor variations are a limitation that we will have to deal with until our computers play catch up.. Best,Randy J. Smith<<>>


Randy J Smith

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But why does the aircraft let you set hdg on the mcp and not track? andwhy does atc operate with hdg? it makes much more sence to use track since thatsthe direction the aircraft acctualy is going...


Thorbjørn Henriksen

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ATC vectors are headings, not tracks. There are still lots of aircraft without fancy computers that manage wind correction. Without the fancy stuff, there's no practical way to fly a track.


Dan Downs KCRP

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when atc plan the traffic do they know the track of the aircraft before giving the heading ?i would assume this is quite important for traffic planing. if a plane has a 15 degrees track off the heading i assume they would wanna know about it...before it happens.


Thorbjørn Henriksen

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Torbj


Mats Johansson
PMDG Flight Test Dept
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