Robert Woodhouse
21st Dec 2007, 00:46
I have a 1941 UK ATC course sylabus in which it clearly states that "the direction in which an aircraft is heading is called its course". This links with the labels on the old Dalton compter. It is also what I learnt on my pilot course in 1950. It also matches the US navy definition " the angle which the centreline of the vessel makes with the meridian, "American Practical Navigator" (Hydrographic Department), US Navy, Bowditch, 1938.
However - recently trained US trained aircrew, GPS manufacturers, and the navigation database coders have a different definition. For them course does not equal heading. For them, course is the intended track. The very opposite meaning!
Hence a CA leg (course to altitude) used in some SIDs where the start is undefined (wherever you are at FMC engagement) and the end is undefined (wherever you reach the specified altitude) - but at least your track (course?) will be between the two in the right direction. This leg is often used for parallel departures, where it frightens all if the aircraft banks towards the other runway (which can happen if the other option FA - fix to altitude leg, is coded).
Problem comes when the procedure designer promulgates the words ("climb straight ahead" or "track extended centreline" as per ICAO Doc 4444). The word "course' is not in the ICAO lexicon at all. So the database coders see the word track and code the FA leg. Result is conplaints all round.
At present it is not an international requirement for the procedure designer to specify the coding (which anyway has to be massaged by the database coders to suite the limitations of the various makes and models of FMS).
To help sort this muddle out, it would help a lot to hear from some European trained pilots (hopefuly trained later than I) whether they believe course is the direction the aircraft is pointing or whether it is the intended track. Your advice would be very useful to in resolving this issue.
However - recently trained US trained aircrew, GPS manufacturers, and the navigation database coders have a different definition. For them course does not equal heading. For them, course is the intended track. The very opposite meaning!
Hence a CA leg (course to altitude) used in some SIDs where the start is undefined (wherever you are at FMC engagement) and the end is undefined (wherever you reach the specified altitude) - but at least your track (course?) will be between the two in the right direction. This leg is often used for parallel departures, where it frightens all if the aircraft banks towards the other runway (which can happen if the other option FA - fix to altitude leg, is coded).
Problem comes when the procedure designer promulgates the words ("climb straight ahead" or "track extended centreline" as per ICAO Doc 4444). The word "course' is not in the ICAO lexicon at all. So the database coders see the word track and code the FA leg. Result is conplaints all round.
At present it is not an international requirement for the procedure designer to specify the coding (which anyway has to be massaged by the database coders to suite the limitations of the various makes and models of FMS).
To help sort this muddle out, it would help a lot to hear from some European trained pilots (hopefuly trained later than I) whether they believe course is the direction the aircraft is pointing or whether it is the intended track. Your advice would be very useful to in resolving this issue.