If you get a re-clearance that is significantly different than what is on your master document, you will need to update the master document, get a new one sent to you, or you will have to compute a new one on your own. The math isn't that hard, but you are likely to be in a rush when this happens and that means you will be prone to making math errors. You should carry a supply of blank navigation worksheets on every oceanic flight. You can download a blank copy: Navigation Worksheet (Blank). Now that you have the worksheet, here are your options.
I've only had to do this a few times and each time it was with the plotter and circular slide rule. It was tedious and it was not as easy as I remember from my lieutenant days. The next time I will pick up the phone. Why bother? There are reports every month of a crew that got a re-clearance and ended up flying into the wrong airspace. It is nice having an accurate master document to check the electrons flying the jet.
Everything here is from the references shown below, with a few comments in an alternate color.
[AC 91-70B, ¶D.2.5.7]
[AC 91-70B, ¶184.108.40.206.1] The majority of today’s GNEs arise from pilots flying a very precise track to the wrong position because they failed to properly update their FMS to reflect their currently effective route clearance. This can also result from a clearance or reclearance that was incorrectly entered, misread, or misunderstood. Procedures to follow in the event of a reclearance are included in paragraph 220.127.116.11. Examples of scenarios that have led to GNEs are:
Note: Waypoints entered via full latitude and longitude can produce misleading display names, where minutes are truncated or rounded and/or generic names are generated.
[AC 91-70B, ¶18.104.22.168.6]
Note 1: If you “accept” a clearance via CPDLC, the FAA recommends you also “execute” the new clearance in your FMS. Some crews have accepted, but not executed, a CPDLC clearance to avoid losing wind data or to preserve meaningful waypoint labels. Failure to “execute” the new clearance in the FMS could result in a navigation error and/or pilot deviation.
Note 2: Reclearance via CPDLC has also been a factor in navigation errors associated with a route change. Operators should be cognizant of this when designing operating procedures for the use of CPDLC.
Note: We highly recommend that the relief pilot(s) also cross-check the FMS against the master document to ensure complete understanding of the new clearance.
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