Compass turns

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mxalix258

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mxalix258
I've heard about the trick when turning to compass headings where you split up the rose in 10 degree increments with 0 being on 90* and 270*. So if you are turning to 360 from a heading you would undershoot 30 degrees (plus presumably half your rate of turn). While this isn't exact, I suppose it gets you in the ballpark.

When does this trick actually come in to play? when you are more than 30 degrees off heading? 45? Because if you are at 330 and want to turn to 360 this trick doesn't really do much help.

And in this case, do you just resort to a timed turn of 10 seconds for every 30 degrees?

Thanks!
 
Sounds like you learned a bad version of the turning error system. The actual numbers are that the error is zero going through E/W and your latitude going through N/S. So, if I'm in Maryland (Lat 38N), the error is about 40 degrees through N/S. Further, since the South leads and the North lags (easy for those south of the Mason-Dixon to remember, the War of Northern Aggression notwithstanding), if I'm trying to turn left to 360, I know that the compass will be lagging 40 degrees when I get there, so I stop the turn when it reads 040. You can interpolate this, too, so if I'm turning left to 045, the compass will be lagging about 20 degrees when I get there, so I roll out when it reads 065. And, of course, if I'm turning to 090 or 270, the error is zero, so I just roll out on the heading per the mag compass. Just remember to look at your chart so you know what latitude you're at -- your 30-degree method will work pretty well in Florida or Texas, but not in Maine or Washington where the turning error is much larger.

Of course, a lot of pilots find doing those computations in their head harder than using the timed turns method, so not a lot of us use the system. From a practical standpoint, just like primary/supporting vs control/performance, the FAA doesn't care how you do it, as long as you can, if you're down to your mag compass for heading, turn to and roll out on or within 10 degrees of any desired heading.
 
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Ron Levy said:
Sounds like you learned a bad version of the turning error system. The actual numbers are that the error is zero going through E/W and your latitude going through N/S. So, if I'm in Maryland (Lat 38N), the error is about 40 degrees through N/S. Further, since the South leads and the North lags (easy for those south of the Mason-Dixon to remember, the War of Northern Aggression notwithstanding), if I'm trying to turn left to 360, I know that the compass will be lagging 40 degrees when I get there, so I stop the turn when it reads 040. You can interpolate this, too, so if I'm turning left to 045, the compass will be lagging about 20 degrees when I get there, so I roll out when it reads 065. And, of course, if I'm turning to 090 or 270, the error is zero, so I just roll out on the heading per the mag compass. Just remember to look at your chart so you know what latitude you're at -- your 30-degree method will work pretty well in Florida or Texas, but not in Maine or Washington where the turning error is much larger.

Of course, a lot of pilots find doing those computations in their head harder than using the timed turns method, so not a lot of us use the system. From a practical standpoint, just like primary/supporting vs control/performance, the FAA doesn't care how you do it, as long as you can, if you're down to your mag compass for heading, turn to and roll out on or within 10 degrees of any desired heading.
Click to expand...

Yup, the US/Canadian border for much of the US is 48 degrees. We're close, so a 50 degree lead/lag is closer to reality for us.

Timed turns work better for me, too.

And I've heard that conflict referred to as the War for Southern Independence. :D
 
Ron Levy said:
Sounds like you learned a bad version of the turning error system. The actual numbers are that the error is zero going through E/W and your latitude going through N/S. So, if I'm in Maryland (Lat 38N), the error is about 40 degrees through N/S. Further, since the South leads and the North lags (easy for those south of the Mason-Dixon to remember, the War of Northern Aggression notwithstanding), if I'm trying to turn left to 360, I know that the compass will be lagging 40 degrees when I get there, so I stop the turn when it reads 040. You can interpolate this, too, so if I'm turning left to 045, the compass will be lagging about 20 degrees when I get there, so I roll out when it reads 065. And, of course, if I'm turning to 090 or 270, the error is zero, so I just roll out on the heading per the mag compass. Just remember to look at your chart so you know what latitude you're at -- your 30-degree method will work pretty well in Florida or Texas, but not in Maine or Washington where the turning error is much larger.

Of course, a lot of pilots find doing those computations in their head harder than using the timed turns method, so not a lot of us use the system. From a practical standpoint, just like primary/supporting vs control/performance, the FAA doesn't care how you do it, as long as you can, if you're down to your mag compass for heading, turn to and roll out on or within 10 degrees of any desired heading.
Click to expand...

"East is least. West is best." :rofl:
 
Well, since I consider myself a 'Northerner' my saying to remember how to do it is "Fly Through the South"...as in don't stop keep going.
 
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