Compass Turns

9 Answers

1. 
   

   
   

   ccwebb on Jul 24, 2013

   You can use a picture like this I found on google:
   http://www.compassadjustment.com/attachments/Image/earth_magnetic_field.jpg

   Be sure to emphasis that the compass does NOT point to North, but it aligns itself with the magnetic lines. Since the lines begin to ‘dip’ back into the earth near the north pole, the compass will try to dip with them, thus causing dip errors.

   The instrument Flying Handbook has some good explanation and diagrams in Chapter 5.

   +2 Votes 2 Votes  0 Votes

2. 
   

   
   

   Lucas on Jul 26, 2013

   ANDS
   UNOS

   I know many of the instructors in this forum hate acronyms but in 14 years of teaching I find that for some of my students this is the easiest way to digest concepts that they are unable to understand.

   Not everyone is born a pilot but most can surely become one if they have the right instructor following them.

   Acronyms make sure students follow the right procedures, so they can still fly safely and enjoy their experiences.

   Acronyms help until the student understands the concepts fully.

   Heck most checklists are full of acronyms.

   ANDS:

   When on a heading of East or West If you:
   Accelerate the compass will show a turn towards the North
   Decelerate and it will show a turn towards the South.

   UNOS:

   Undershoot North
   Overshoot South

   The amount depends on the latitude and other factors. If you tried to explain this to a new student, who has no knowledge of physics and/or any mathematical logic he would probably give up flying.

   So keep it simple.Unless the examiner asks you to teach at the ATP level. (BTW if you are going for an instructor rating you are probably not an ATP yet, and you should “carefully” explain that to your examiner).

   Keep Flying a Fun Experience

   +3 Votes 3 Votes  0 Votes

3. 
   

   
   

   Brian on Jul 26, 2013

   The rote explanation, which Lucas already covered, is great. For me though, showing how it can be understood and applied is equally beneficial and I rarely see it covered.

   To do this take a piece of paper and draw a large circle to depict a compass. On your compass mark 360, 030, 060, 090, 120, 150, 180, 210, 240, 270, 300, and 330. Next 270 and 090 put the number 0. Next to 060, 120, 240, and 300 put the number 10. Next to 030, 150, 210, and 330 put the number 20. FInally, next to 360 and 180 put the number 30.

   The numbers 0, 10, 20, and 30 are there to note the lead and lag necessary to make effective compass turns assuming you make standard rate turns. For example, using UNOS we know that turning north means we must under shoot: Undershoot North. Let’s take our numbers we have and start from a west heading to turn north to 360. To do this make a right turn, when the compass reads 330 (360-30) roll out. Did it work? I think you’ll find it quite accurate.

   Let’s try another, how about starting from a southeast heading of 115 and turning to a northeast heading of 030. We have to undershoot again since our target heading is to the north, but this time by only 20 degrees. Start your left turn from 115 and when you hit 050 rollout. Did it work? Again I believe you’ll find it to be quite accurate.

   Repeat this for some turns to the south and overshooting. Do them from both left and right. What I do is draw this out on paper for the student and let him or her come up with some experiments. What heading should we start from? Ok, what heading will we turn to? Great, now what heading should we roll out on to make it work? Talk through a half dozen of these during the brief, write them down, and then go up and try them out.

   Memorizing an acronym is one thing, understanding and being able to apply it so you can realize how it works, however, is far more beneficial. Not to mention helping to clear up much of the common confusion with this topic.

   +23 Votes 23 Votes  0 Votes

4. 
   

   
   

   Mark Kolber on Jul 28, 2013

   I’m one of those who hates acronyms. ANDS and UNOS have always confused me. Not that what they stand for is confusing, but I never quite understood the need for two acronyms when one will do.

   ANDS works for both types of compass errors.

   Accelerate North, Decelerate South.
   Anticipate North, Delay South.

   But I guess the acronym lobby would be out of business without adding all the extra ones.

   Disclaimer: this is intended to be somewhat tongue in cheek. But it is accurate.

   +2 Votes 2 Votes  0 Votes

5. 
   

   
   

   Brian on Jul 28, 2013

   “ANDS works for both types of compass errors.”

   I personally don’t see a point at all in this acronym existing. You cannot easily quantify the rate of change of velocity to the degree of inaccuracy in heading. So what is the point? Would it not be simpler to just leave it as “don’t read your compass as accurate unless you’re in level, unaccelerated, flight.” ..? Vuala, no need for an acronym.

   +1 Votes 1 Votes  0 Votes

6. 
   

   
   

   Fly92020 on Aug 05, 2013

   Brian – if only it were that simple; if on the check ride you could just tell the examiner “the compass is only accurate in level, unaccelerated flight…”.

   You will need to demonstrate Compass Turns (no gyros) on the Instrument ride. When the DPE asks you to “turn to a heading of 170-degrees”; if you don’t know whether to roll out at 140 or 200, you’re gonna fail that task.

   +1 Votes 1 Votes  0 Votes

7. 
   

   
   

   Brian on Aug 05, 2013

   Sorry fly, I poorly presented my point there. I teach it because I have to. However, since acceleration errors cannot be easily quantified I see no logical reason for teaching it. Simply knowing the compass isn’t accurate during acceleration or deceleration would suffice. Knowing which way that in accuracy occurs, since not quantifiable, is moot.

   As far as the level part, this is why I say I poorly represented my viewpoint above. As my first post depicts, you can easily quantify, and thus plan for, the inaccuracies associated with banking. So in that instance I see it being useful knowledge.

   0 Votes 0 Votes  0 Votes

8. 
   

   
   

   ccwebb on Aug 05, 2013

   Compass turns have too many errors and too many variables to be successful in learning unless rote teaching is used (ie: acronyms.) and you spend the rest of your flying career in the same ‘zip code’. You also have a student staring at compass for nearly a minute as they try to figure out if they should undershoot or overshoot, or they need a post-it note with a double compass drawn on it. (BTW-I used to teach this way. Then introduce them to a vertical swing compass… ugh.

   Simply teach time turns. At standard rate, the circle (360 degrees) becomes very easy math. Every 30 degree painted number is 10 seconds. Start your turn, hit the timer, and roll out. All you have to do is compensate for a quick or slow ‘roller’. Teach the student there are compass errors because of _______________, then use time turns.

   This knowledge can be transferred to any part of instrument flying, as oppose to, only partial panel flying.

   Since the PTS does not state “you must use compass turns or timed turns”, pick the one without acronyms, and uses simple math-by-10’s.

   There’s my two cents.

   +2 Votes 2 Votes  0 Votes

9. 
   

   
   

   Mackey on May 08, 2020

   Brian, I like your answer. What latitude are you using for your turns?
   I’m in Idaho where the latitude is 43 degrees.
   Here are the formulas I have….360 (N) – 43 (Lat) -8 (1/2 standard rate) =309 for a right turn to 360 degrees.

   For a left turn to the north….360+43-8=51
   For a left turn to 180 degrees 180+43-8 = 215
   For a right turn to 180 degrees 180-43+8 =145
   I haven’t tried this yet but I will tomorrow. I’m not really sure I need to use 1/2 Standard rate yet. It seems that if I use the same roll rate in & out of the turn then I could use 16 degrees as the factor(?) in my formula.

   0 Votes 0 Votes  0 Votes