A Complete Manual for Conducting International Flight Operations
Figure 2 code7700
AIRINC 424 is a great tool for simplifying FMS Latitude and Longitude inputs. It is, however, very important that flight crews understand the significance of the shorthand and double check that AIRINC 424 inputs match the expected distance and heading in the filed ICAO flight plan. It is also important to note that half-degree separation has been implemented in 2014. This half degree of separation has led to a high level of gross navigational errors. It is recommended that crewmembers advise their flight planner to NOT file half-degree fixes unless absolutely necessary.
From an operational standpoint, all clearances shall be read back using the standard full format, for example 5150N shall be read back as 51N50W. (Five One North, Five Zero West)
Flight Plan usage of AIRINC 424
In the example below, fixes are displayed in the flight plan in AIRINC 424 shorthand which makes for straightforward flight plan entry into the FMS. The challenge occurs when the aircraft is re-routed, or the initial clearance given over radio communications differs from the flight planed route. It is therefore recommended that both crewmembers be monitoring the frequency when receiving an initial clearance or oceanic reroute. A read back of the above clearance would be: N74GG cleared direct ELSIR, 50N50W, 50N40W, 49N30W, 47N20W, PASAS Mach .80 FL410.
It is also recommended that waypoints are recorded in the journey log in standard format to aide in position reporting, i.e. 49N30W as opposed to ARINC 424 format of 4930N.
If a half degree has been filed in the flight plan, such as 50.30N 040W, the shorthand ARINC 424 naming condition would be N5040. You can probably understand why this causes confusion. In this example the latitude has been moved half a degree to the North. For additional questions, crewmembers should consult their aircraft specific FMS operating manual.
Revision date: July 29, 2015
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