Significance of variation in airport chart
Thread Starter
Join Date: Jun 2010
Location: Salians, USA
Posts: 48
Likes: 0
Received 0 Likes
on
0 Posts
Significance of variation in airport chart
Typically in Jeppessen Airport Chart (10-9) the variation is depicted in the form of one arrow with complete arrowhead and one with half arrow head. I know this is depiction of Variation of the place. But what is significance of this? How would it help a pilot in either takeoff or landing or ground ops?
1. As the TAF and METAR always give wind direction in degrees true, the variation is needed to convert this into a magnetic value to calculate cross-wind components relative to the (magnetic) runway directions.
2. ATIS broadcasts and 'tower' winds given over the Radio are in degrees magnetic, but you wouldn't normally hear these until you were in the cockpit, so the variation is supplied for pre-flight planning purposes.
Other than that, I agree that a knowledge of the variation plays little part in take-off, landing and ground operations; it's more of an aid to planning.
Hope this helps
Eck
2. ATIS broadcasts and 'tower' winds given over the Radio are in degrees magnetic, but you wouldn't normally hear these until you were in the cockpit, so the variation is supplied for pre-flight planning purposes.
Other than that, I agree that a knowledge of the variation plays little part in take-off, landing and ground operations; it's more of an aid to planning.
Hope this helps
Eck
Probably because they are forecast by the Met office using meta data, so it saves them adjusting the variation for all of the different airports out there. A bit of a historical inertia as well, as it's easier to measure true off a chart, so true winds in the "old days" were easier to work with for planning.
Join Date: Feb 1998
Location: Formerly of Nam
Posts: 1,595
Likes: 0
Received 0 Likes
on
0 Posts
Fair enough and thanks Checks, but one would think with all
the modern software available to forecasters these days that
the wind could be auto adjusted for magnetic variation by the
program as soon as its inserted into the database.
the modern software available to forecasters these days that
the wind could be auto adjusted for magnetic variation by the
program as soon as its inserted into the database.
Thread Starter
Join Date: Jun 2010
Location: Salians, USA
Posts: 48
Likes: 0
Received 0 Likes
on
0 Posts
Jeppessen enroute tracks and tracks on b737 FMCs
Taking this discussion further what are the airway tracks shown on Jepp enroute charts True or Magnetic? What about tracks shown on B737 FMCS, true or magnetic? And tracks shown on computerized flight plans of any airlines?
Join Date: Aug 2000
Location: S Warwickshire
Posts: 1,214
Likes: 0
Received 0 Likes
on
0 Posts
Their all Magnetic.
Then there's the polar grid.......
Join Date: Apr 2002
Location: Bohol, Philippines
Posts: 150
Likes: 0
Received 0 Likes
on
0 Posts
Also in a Head Up Display in order for the system to paint the synthetic runway display it needs the localiser track in degrees true. This is normally done automatically by the software but having the variation allows the crew to calculate this value.