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Guest Erups

Sidewind reaction????

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Guest Erups

I noticed that in case of heavy sidewind, the PMDG although following correctly the plan with no lateral deviation, maintains a heading in favor of the wind.I mean that if you're flying 270, with 360/50 wind, the pmdg will not maintain a heading higher of 270 (say 278) but lower instead (so something like 262).That's against physics laws :DAlso i just noticed (while taxiing at small airports like LOWI... :D)that, even if i have the correct assignements for the differential brakes (F11 and F12) only left seems to work, right have no effect.Anyone can confirm this?BRClaudio

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Hi Claudio,The display is working fine. I believe you are looking at the ground track and not the heading. In your example your heading is 270 but your ground track will be 278 due to the cross wind. There is a better explanation of this in the manual or you can do a search. There are a few good threads out there explaining this.

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Guest Erups

I have to clarify my statement a bit.What i described has to be referred to the ND display, and the HDG numbers i gave should be referred to the TRK of the ND display.To rephrase it:what i saw is that, when haveing sidewind from my right, my TRK was left of the magenta line, instead of right.BrClaudio

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Guest Erups

I didn't write it clear enough, so i reposted below.But probably it was a one time only thing, because i tried to have this phenomenon show again without success... :-hmmm

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Guest Erups

Unfortunately i wasn't seeing phantoms here, look at the screenshothttp://forums.avsim.net/user_files/78764.jpgAt the moment i have a 60/40 wind and the situation is the same.For this shot i was in hdg mode, but yesterday it happened in LNAV mode.I may add that i can see this phenomen visually:if i set a tower view to the near left of the airplane, during the view the plane translates to the left, and the view comes to be on the right of the airplane.BRClaudio

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"For this shot i was in hdg mode, but yesterday it happened in LNAV mode."For HDG mode, these indications are normal. You are maintaining a heading of 290 and you are being blown sideways along a ground track of 286. Heading is where your aircraft nose is pointing, track is where your aircraft is actually going.Hope this makes sense.Cheers.Ian.P.S. (Edit) Or to put it another way, if YOU were a pedestrian walking NORTH across a pedestrian crossing and a large truck came racing down the road from your right (the EAST) at 60mph... if it hit you, which way would you go? Eastwards? (I don't think so) ;-)

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>came racing down the road from your right (the EAST) at>60mph... if it hit you, which way would you go? Eastwards? (I>don't think so) ;-) :-xxrotflmao

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>Or to put it another way, if YOU were a pedestrian walking NORTH >across a pedestrian crossing and a large truck came racing down the >road from your right (the EAST) at 60mph... if it hit you, which way >would you go? Eastwards? (I don't think so) ;-) A very good and informative simile. ;-)But Ian, now suppose this pedestrian were in LNAV mode and the truck hit from the east at 60 mph. Now what happens?Cheers,

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I understand the fact that the wind is pushing the nose left but shouldn't the aircraft be pointing more to the right to maintain the track? I.E. pointing the engines in to the wind instead of with the wind? I would think that with a heading to the left the aircraft would go off track but with a heading to the right it would stay on track. I'm confused :( Edit:Spelling

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Guest Erups

>But Ian, now suppose this pedestrian were in LNAV mode and the>truck hit from the east at 60 mph. Now what happens?I think i have earned this :)

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JeremyWhen in HDG mode the plane will only try to keep the heading selected on the MCP. Any wind will blow it off any intended path. The A/P is in fact not trying to keep a path.Now, in LNAV mode the A/P will try to keep the path or TRacK and will therefore adjust its HeaDinG to compensate for any wind.Got it? Or did I just confuse it even more? ;-)Cheers,

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No Matt I understand what you are saying but what is confusing me is that when in LNAV it seems that the A/P turns the aircraft with the wind to correct instead of into the wind to correct. If the wind is blowing from the right the nose is turned to the left of the intended track, instead of to the right.

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Guest Erups

>No Matt I understand what you are saying but what is>confusing me is that when in LNAV it seems that the A/P turns>the aircraft with the wind to correct instead of into the wind>to correct. If the wind is blowing from the right the nose is>turned to the left of the intended track, instead of to the>right. That's exactly what i was saying :-roll BRClaudio

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Ok guysTwo small bed time stories ;-)The story of LNAV:AP -I have to keep this TRACK that is headed 270

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Guest Erups

>PIC -Why is the aircraft HEADING south of my TRACK ?Actually it's the TRACK which is south of the HEADING ;)Story part #2:wind - Hi again airplane, this is wind blowing on you as usualap - hi wind, how do you do today?wind - fine thanks, blowing as usual, and you?ap - fine, following my lnavwind - you sure?ap - ya, why?wind - cause i am blowing on youap - as usual, and as usual i am correcting, can't you see? you're blowing from my right, i have to keep a track of 270, and i'm pointing 262.... mhhh.... huston i'll call you back!How does this one sound?:DBRClaudio

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No way, Claudio, take a look at this:http://forums.avsim.net/user_files/78805.jpgI'm tracking 287 in LNAV, wind coming more or less from the north. In order to compensate, the autopilot has correctly turned the a/c to a heding of approx. 293, i.e. into the wind. Look at the down-pointing arrowhead above the compass arc, THAT is where the a/c nose is pointing.This is also confirmed by glancing on the good old compass on the window post.

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But Claudio You are in HDG SEL for crying out loud! :-)When in HDG SEL the A/P doesn't give a darn about the TRACK!And you will never ever see this while in LNAV. I won't believe that you did until you prove me wrong with some screenies. ;-)TGIF :-beerchugHow does that sound? ;-)

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Ok well here is another example that I have seen. When on APP on final if the wind is from the right the nose of the aircraft is pointed left of RNW heading. I know the aircraft is flying a path because it is locked on the localizer why after I disconect A/P do I have to apply right rudder just prior to touchdown to correct to RNW heading? Shouldn't this be nose right of RNW hdg and correct left prior to touchdown? Note: I just want to make sure everyone else is as confused as I am now lol

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>>Ok well here is another example that I have seen. When on APP on final if the wind is from the right the nose of the aircraft is pointed left of RNW heading. I know the aircraft is flying a path because it is locked on the localizer why after I disconect A/P do I have to apply right rudder just prior to touchdown to correct to RNW heading? Shouldn't this be nose right of RNW hdg and correct left prior to touchdown? <

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Now that we talking about HDG and TRK (drift angle) how do you calculate the exact headwind component. For Example: I'm flying at a "TRK" of 270 degrees and there is a wind of 290/45. Then wat is my exact headwind component? VREF calculations are: VREF30/40 + the steady headwind and then add half the figure of the total "gust"Thats how it is in the performance pages. How do you calc. the gust?Thanks people,

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RamonThis is a simple trigonometric problem.If you are flying with your nose pointing to 270

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thanks, but I mean TRACK 270 so the drift angle should be a HDG of about 278.Thanks anyway.PS do you mean the PROG. page 2??

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Guest ChristophIllmer

Sinus and Cosinus values of the according angles...

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YesThanks Ramon, I do mean PERF page 2 :-)Cheers,

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