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When I started searching for Heading Bug (other bugs like altitude, speed bugs), I didn't get much clear idea about it. Usually this is displayed on Horizontal Situation Indicator display on the direction of wind (calculated based on wind direction, speed?). This heading bug can be selected to a value by pilots during flight.

  1. What is the use of heading bug?
  2. how heading bug is calculated?
  3. what's the significance of heading bug?
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Bugs simply make instruments easier to read with a very quick glance.

If I need to steer exactly 162 degrees, which is easier? To read where the needle is pointing or just see if the needle is pointing to the bug which I manually set to 162 degrees?

The bugs are set by rotating knobs on the gauges. Here, the heading bug knob is in the lower right corner.

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The way I often use it is to turn onto the next heading required according to my plan, then set the bug to that heading so that I can simply glance at the needle (still pointing to the bug, good) to keep me on course.

Other uses:

  • If ATC gives you a "next heading", you will read back the instruction, then you can set the bug to that next heading so that a), you don't forget it and need to call back and b) can simply turn onto the bug when it's time to turn.

  • Set it to the departure runway heading on take off. To "fly runway heading", just keep the bug at the top of the gauge.

  • On arrival, set it to the landing runway heading.

  • As a "gross error" check. You would not believe how many inexperienced pilots set off in entirely the wrong direction. As well as setting the heading bug to "first leg of the plan", you check this along with "and the road should be on my left with the river on my right".

On some simple autopilot systems, the autopilot follows the altitude and heading bugs rather than having controls for these settings on the autopilot itself.

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  • $\begingroup$ @Simon why would I set bug when I know which direction I wants go? I can directly use the Heading instead of bug. $\endgroup$ – Lucky Nov 26 '15 at 9:01
  • $\begingroup$ @Lucky As I said, it's just easier to see if the needle points to the bug rather than to read the value. If I don't set the bug, then everything still works, I just need to read a little more carefully to make sure I stay on track. $\endgroup$ – Simon Nov 26 '15 at 9:06
  • $\begingroup$ @Simon would you do some math for calculating the Bug? will this be used when cross wind is applied? How this will be used in Autopilot mode to steer the plane? or just as you said pilot will monitor heading w.r.t bug even when it is under autopilot control? Also same logic applies to other Bugs too? $\endgroup$ – Lucky Nov 26 '15 at 9:23
  • $\begingroup$ This is a very good answer. Just marked it up. When you are piloting an aircraft you have lots of things to think about. The heading bug is good to remember the heading you are supposed to be flying especially as you don't want to go in the wrong direction or look bad in front of ATC. When you have a lot to think about is very easy to make a mistake. So if you always set the bug its one less thing to remember. There are many reasons why you would set it, although it sounds to me that how you arrive at your heading yourself might be a whole new question about VFR navigation. Hope this helps. $\endgroup$ – Philip Johnson Nov 26 '15 at 9:47
  • $\begingroup$ @Lucky Those are good questions but, I think you are better asking a new question for that. This question is "what is it", a new good question would be "how to use it, especially when thinking about wind. The short answer is that heading is the direction that the aircraft is pointing. "Track" is the direction that the aircraft moves across the ground. If you are taking wind ("drift") into account, then the heading bug will not be set to the direction you want to move across the ground. This topic is more about VFR navigation than the heading bug itself. $\endgroup$ – Simon Nov 26 '15 at 11:50

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