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martinlest2

HDG or TRK mode?

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After take-off and Auto Flight mode is engaged, ATC at some point turns me towards my flight route. I am a bit confused though, because if I am in HDG mode, the a/c will not turn towards the heading I have selected, in fact it turns in the opposite direction. The a/c only responds 'normally', arriving at the heading value I have entered, if I select TRK (pulling the HDG/TRK knob in all cases)

 

I don't understand this. Is it me or the a/c that is at fault here? Shouldn't the a/c turn and then maintain the heading shown in the instruments when I am in HDG mode?

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n fact it turns in the opposite direction.

 

Pay attention to the direction in which you turn the knob. This is why it's considered a good habit to keep the heading bug on your nose at all times. From there, it's pretty easy to know which way you need to turn it to turn in the correct direction for the ATC instruction.

 

 

 


Is it me or the a/c that is at fault here?

 

To be honest - and a little blunt - given the number of posts I'm seeing in the MD-11 section of the forum, one has to start thinking about the commonality: the operator.

 

In this case, I'm guessing you're not fully understanding the difference between heading and track:

  • Heading: The direction the nose is pointed. Does not account for wind.
  • Track: The direction the aircraft is tracking across the ground. Accounts for, or is the result of wind.

If you're responding to an ATC direction, you will nearly always fly a heading. Only fly a track if it is specified (note that a lot of departure procedures specify runway heading, so you should not attempt to correct for wind).

 

 

 


Shouldn't the a/c turn and then maintain the heading shown in the instruments when I am in HDG mode?

 

If you are in heading mode, yes. In this case, the aircraft will point in the direction of the heading, and the track will be askew if there is any cross wind.

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Thanks for the reply - I do understand the difference. Your comment about the 'operator' being the issue is quite possibly true in many of the posts though: but that's fine, surely? I haven't pretended otherwise: I mostly post here to learn correct procedure that I haven't been able to work out from either the manuals or practice, I'm not automatically assuming anything that goes wrong is the software's fault. The reason for all the posts at the moment is that I have only been flying the MD-11 for some days now, in order to 'master' as many of the details as I can. My posts in this forum will die away, fear not, as I assimilate details like this - most of the plane's fairly complex operation I have no problem with..

 

As for the HDG/TRK question, I should have been more specific. On my last flight, say I was heading 360. I needed to turn, again let's say 270 to intercept my flight path. When I engage the HDG knob by setting the correct value and pulling, the aircraft turned right, not left, as long as I had the selector on HDG. When I turned it to TRK, then we turned left to 270, as shown on the instruments. Back to HDG and we turned away to the right again. A long way to the right, not accountable for by wind or whatever.

 

That is what I was asking about. Did the a/c have a temporary brainstorm, or is there an explanation (from which I can learn)? I am not new to this a/c, I bought it a long time ago, but haven't flown it for a few years for one reason or another, so am very rusty..

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As for the HDG/TRK question, I should have been more specific. On my last flight, say I was heading 360. I needed to turn, again let's say 270 to intercept my flight path. When I engage the HDG knob by setting the correct value and pulling, the aircraft turned right, not left, as long as I had the selector on HDG. When I turned it to TRK, then we turned left to 270, as shown on the instruments. Back to HDG and we turned away to the right again. A long way to the right, not accountable for by wind or whatever.

 

You seemed to be discussing two concepts, so I addressed both.

 

Again - when in a single mode, the aircraft keeps track of your relative direction to the HDG bug. Look around the outside of the ND. There will be a dotted line. Does that dotted line go to the right or to the left between your nose and the bug?

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I'll check when I next have the problem - I don't recall for the flight in question. I am flying the a/c on the other PC at the moment and it is responding fine in HDG mode.

 

Thanks..

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I believe that when you asking your aircraft to return to the Lnav mode, you need to be clicking on the 'nav' button.


If your keen on the MD11 I respectfully suggest you consider the MD11 course at 'Angle of Attack'. I found it was the only way to get to know this aircraft completely.

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No, this is before I engage LNAV, just using the heading controls with autopilot on. I only engage LNAV when  I line up with the flight path.

 

Thanks for the suggestion - I feel that I am 99% OK (well, 95%!) with this a/c now - but will certainly have a look at the "Angle of Attack' (rings a bell -  maybe I have looked before, but would be a long time ago if so)./

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