smartt1982
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Difference Between Runway And Departure

Tue Apr 24, 2012 12:50 pm

Any ideas on the reason why the R/W heading is 259 but then on the SIDs it says follow runway track buts states 260?
 
PapaChuck
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RE: Difference Between Runway And Departure

Tue Apr 24, 2012 1:14 pm

Terrain or other factors permitting, why not just round it off one degree to make it a nice even number? It would make the procedure a little easier if you were flying by hand.

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Mir
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RE: Difference Between Runway And Departure

Tue Apr 24, 2012 3:56 pm

Probably took the data from two different sources. One had the runway at 259 when it should have been 260, and one had the departure track at 260 when it should have been 259 (or vice versa). The runway heading is probably 259.5 or something like that.

-Mir
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Longhornmaniac
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RE: Difference Between Runway And Departure

Tue Apr 24, 2012 5:50 pm

Quoting PapaChuck (Reply 1):

While I generally agree with your premise (if that is, indeed, the case), there's nothing about a round number that makes it any easier to hand fly than an odd number. It's still one degree, either way.

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Cameron
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bond007
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RE: Difference Between Runway And Departure

Tue Apr 24, 2012 9:42 pm

Quoting Longhornmaniac (Reply 3):
there's nothing about a round number that makes it any easier to hand fly than an odd number. It's still one degree, either way.

Sure it is, if you're using steam gauges. My HSI/Compass doesn't have markings at one degree intervals, so it has to be easier to get set on a round number ... in fact even if it did have one degree tick markings, it would still be easier since I don't want to mentally count tick marks, when I can just fly to where it says 260.... OK, or next big tick mark between 24 and W (see what I mean).

Quoting smartt1982 (Thread starter):
Any ideas on the reason why the R/W heading is 259 but then on the SIDs it says follow runway track buts states 260?

Well, this may have little or nothing to do with it, but in some parts of the world when they say fly runway heading (I know this says track), they mean fly the numbered runway heading, not the actual specific degrees. So, if runway is 26, you fly 260 even though actual runway magnetic heading may be different. This is not true in the US of course, where I understand the phrase "fly runway heading" is being phased out (?) in preference to a given heading by ATC. I think the FAA say specifically to not fly the numbers, but the actual heading.


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asqx
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RE: Difference Between Runway And Departure

Tue Apr 24, 2012 10:17 pm

Quoting bond007 (Reply 4):
Well, this may have little or nothing to do with it, but in some parts of the world when they say fly runway heading (I know this says track), they mean fly the numbered runway heading, not the actual specific degrees. So, if runway is 26, you fly 260 even though actual runway magnetic heading may be different. This is not true in the US of course, where I understand the phrase "fly runway heading" is being phased out (?) in preference to a given heading by ATC. I think the FAA say specifically to not fly the numbers, but the actual heading.

From the FAA Pilot/Controller Glossary: http://www.faa.gov/air_traffic/publications/atpubs/pcg/R.HTM

"RUNWAY HEADING- The magnetic direction that corresponds with the runway centerline extended, not the painted runway number. When cleared to "fly or maintain runway heading," pilots are expected to fly or maintain the heading that corresponds with the extended centerline of the departure runway. Drift correction shall not be applied; e.g., Runway 4, actual magnetic heading of the runway centerline 044, fly 044."
 
FlyboyOz
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RE: Difference Between Runway And Departure

Wed Apr 25, 2012 4:17 am

Im not a pilot...i guess it depends on the wind direction.... maybe change to +/- 0.5 degree sightly
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Jeff G
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RE: Difference Between Runway And Departure

Wed Apr 25, 2012 3:33 pm

There's another possible explanation. The Earth's magnetic field isn't static, it drifts. The surveyed runway heading could have been recently updated, but when was the last time the VOR was calibrated to magnetic north? VOR radials are referenced to magnetic north to make navigation easier, but it's just an electrical signal, not a true compass. As the field drifts between VOR calibrations, there is an increasing difference between the calibrated north reference and the actual field, so that you have to dial in the calibrated radial to make good your track, but the compass heading doesn't quite match it even in a calm wind. This is acceptable because plus or minus a degree or two of heading just isn't operationally significant. The important thing is that the surveyed and flight checked ground track formed by the VOR radial is accurate.
 
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zeke
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RE: Difference Between Runway And Departure

Wed Apr 25, 2012 3:54 pm

Looks like it is just a Jepp issue, the local AIP has the runway as being 260 degrees

http://www.kaunas-airport.lt/images/apiemus/aerodrome_chart.pdf
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Mir
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RE: Difference Between Runway And Departure

Wed Apr 25, 2012 4:03 pm

Quoting zeke (Reply 8):
Looks like it is just a Jepp issue, the local AIP has the runway as being 260 degrees

The true heading of the runway is listed as 265.08 degrees, with a variation of -5 for the magnetic heading of 260. And if you look at the Jepp chart, they've got variation of -6, for a magnetic heading of 259.08. So there's the discrepancy (the departure chart is going to come straight from the government, and will use their specific instructions).

This sort of thing isn't uncommon - we see differences of a degree or two in courses between charts and FMS databases all the time. It's only when the difference becomes more than a few degrees that one has to worry about it. Often times it is due to differences in the data that different providers use to calculate magnetic variation.

-Mir
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