Hello to all fellow simmers, I've been flying the 737 for a while now but just noticed that while flying from LIMF to LIRF (more specificly on downwind to rnwy 16L) at one point the plane wasn't following the correct HDG dialed in (340hdg instead of 344hdg as you can see from the picture).A little while after I noticed that the aircraft did correct it's HDG and everything else was perfect as usual from then on.I honestly can't recall when this happened in the past but now I remembered to take a pic (excuse me for the very bad quality) and send it to you guys.What could have caused that to occur?Thanks,David http://forums.avsim.net/user_files/68049.jpg

That should be because of the wind...The aircraft is Actually flying on heading 340, but it has to head 344 in order to go 340. It's all because of the wind, and probably no bug...--------------------Hopefully the first person to buy the PMDG 737-800 :D

In Map mode, the triangle on the heading scale indicates which direction the nose of the aircraft is pointing. In this case you will notice that your heading bug is set at 340 and it has a triangle in its notch.The line that your plane is flying (and that is indicated in the center of the display) is referred to as the aircraft track. In this case, track and heading are different because you have a crosswing from the west.Hope this helps!Jeff

Actually, I think you described it backwards. The heading is 340 above, but because of the wind from the left, the track is 344.Some of the ND modes are heading up, and some are track up.Lee Hetherington, PP-ASEL (KBED)

Everything looks fine. Your heading is indeed 340 but your track (TRK) is 344.

The deviation is due to the 255 degree / 12 knot wind. Actually, you can calculate this deviation or wind correction angle (WCA) with an E6B flight computer or the following,WCA = ArcTan ( ( Wind Speed / TAS ) x Sin ( Wind Angle - Heading ) ) x 180 / PI In your case, Wind Speed = 12 knots, TAS = 184 knots, Wing Angle = 255 degrees, and Heading = 340, PI ~ 3.1415926Plug these numbers into the formula, the wind correction angle = 3.717 or ~ 4 degrees. Note 340 + 4 = 344, your magnetic heading in degrees!Ain't math wonderful ... :-wave

Thanks for the answer guys but forgive me if I still can't see things that clear.Is the wind blowing from 225 or is it blowing from it's reciprocal of 045?If it is blowing from 225 shouldn't track be a little less than 340 instead of 344 to compensate for the crosswind from the west?To me, according to the correction the aircraft is making the wind seems to be blowing from the est instead of the west.Please correct me if I'm wrong.My best to you all,Davidhttp://forums.avsim.net/user_files/68150.jpg

Hi David, If my understanding is correct, and forgive me, I some times too get confused about wind directions, the wind in your case is blowing from 225 degrees to the reciprocal (45 degrees). The nice thing is that wind directions are given in the direction in which they originate. That means that when landing or taking off, you will have to find the runway matches the wind direction most (guess this is done so that pilots under stress will not have to subtract 180 from the wind direction ;-)). Still, with cross wind components, the calculations become difficult enough :-) Alternatively, look at the wind arrow in the ND. The arrow will display the wind relative to your path of flight. Hope this helps,BoazEKCH

In layman's terms the wind follow's the arrow's direction, which mean's (in Fab 5 terms) it's blowing against your left tail uh..ha ;)which means that although your heading is 344, you will end up a little skewed (or screwed, depending on what your doing) off to the right a little.Better?

Better?Not really, my question is:" if the wind is blowing from the left towards the reciprocal souldn't the aircraft steer left (and not 344 which is right like picture) in an attempt to correct the drift created to the right since a wind is blowing against my left tail as you also say (225 in my case)"?Thanks...Davidhttp://forums.avsim.net/user_files/68163.jpg

Hi David, It does! As you can see in your picture, your heading is set to 340 degrees, but due to the wind coming from your left side, your track (that is the path your aircraft is making over ground) is 344 degrees. It is more evident if you look at the partial compass rose in the PFD. Here you will see your heading as being straight up, but the track line veering off to the right. This means that your nose is pointing to 340, but due to wind your path is actually 4 degrees off. Also, you are in HDG SEL, so the autopilot will only make sure that your nose is pointing in the right direction. If you fly in LNAV, you will sometimes notice that the heading bug is offset from the path line. Here, the FMC will make sure your track, as opposed to the heading, will match what the current route prescribes. I am not sure if any Boeings have the feature, but Airbusses have the option to select track vs heading on their MCP (can't remember the proper Airbus term -- I mean the autopilot). This will ensure that the heading put in their MCP is actually the track that the plane will follow.BoazEKCH

Hi David,The airplane will not perform any corrective actions to counter the effects of the wind itself. Your picture above is correct for the situation. If you set 340 in the heading box of the MCP the autopilot will point the nose at 340 (as above). It will not correct for wind i.e. it won't add the 4 degree (in this situation) WCA for you. The white line shows the resultant ground track as does the 'heading' box on the top of the ND. This box doesn't show your actual heading, rather the ground track you're flying.This can be confusing as many other aircraft display this in a complete polar opposite way i.e. they show your aircraft heading in the 'heading' box as most peoples logic would suggest is the natural way to display it.If you want to fly a parallel downwind you have to adjust the heading in the MCP manually to correct for the wind, in other words you want the white line on the ND to point straight up and the heading box to read 340. The easiest way to do this is to set the heading you want in the MCP window first (I'll use the above situation as an example), so you put in your downwind heading (340

Thanks a lot David, that was the kind of answer I was looking for.I never fly using fs9 atc unless occasionally but it is much more clear to me why I was beeing always vectored left and right while coming in for a landing.With your precious suggestions I'll be learning a whole new way of flying the 737 and other aircraft in windy conditions.Thanks again,Davidhttp://forums.avsim.net/user_files/68190.jpg

Hey David,I'm glad I could help :)CheersDavid