PapaChuck From United States of America, joined Aug 2010, 134 posts, RR: 0 Reply 1, posted (1 year 1 month 1 day 11 hours ago) and read 1999 times:
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.
Mir From United States of America, joined Jan 2004, 19722 posts, RR: 56 Reply 2, posted (1 year 1 month 1 day 9 hours ago) and read 1935 times:
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
7 billion, one nation, imagination...it's a beautiful day
Longhornmaniac From United States of America, joined Jun 2005, 3095 posts, RR: 48 Reply 3, posted (1 year 1 month 1 day 7 hours ago) and read 1865 times:
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.
bond007 From United States of America, joined Mar 2005, 5098 posts, RR: 8 Reply 4, posted (1 year 1 month 1 day 3 hours ago) and read 1762 times:
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.
Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
asqx From United States of America, joined Jun 1999, 589 posts, RR: 0 Reply 5, posted (1 year 1 month 1 day 2 hours ago) and read 1737 times:
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.
"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."
Jeff G From United States of America, joined Jan 2002, 431 posts, RR: 1 Reply 7, posted (1 year 1 month 9 hours ago) and read 1475 times:
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.
Mir From United States of America, joined Jan 2004, 19722 posts, RR: 56 Reply 9, posted (1 year 1 month 9 hours ago) and read 1453 times:
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
7 billion, one nation, imagination...it's a beautiful day
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