You must include a UTC time check and re-synchronization of the master clock — Page 144, Lesson 226

Let’s start with a list of three common failures that have been identified in real operations. First, failure to observe the principles of checking waypoints to be inserted into the navigation systems against the ATC cleared route. That means when you type a waypoint into the flight management system, you must verify it matches exactly what air traffic control cleared you to fly — not just a similar name or a nearby fix. Second, failure to load waypoint information carefully — a simple typo or mis-selection can take you off the cleared track. Third, failure to cross-check on-board navigation systems — you cannot assume one system is correct without comparing it against another. Now, for a NAT MNPS flight — that’s a North Atlantic Track Minimum Navigation Performance Specification flight — the pre-flight procedures are very specific. You must include a UTC time check and re-synchronization of the master clock. UTC is Coordinated Universal Time, the standard time reference used in aviation. The master clock is the primary time source in the cockpit, and it must be set precisely to UTC before departure. Operators must ensure that flight crew are familiar with the concept of cross-checking route inputs into the FMS — the Flight Management System. Ideally, the route would be loaded independently. That means each pilot loads his own FMS, if the aircraft is equipped with two independent systems. Then, the route is cross-checked by the other pilot. The correct method is to note the position shown in the system, then compare it to the Master Document — the official source of the cleared route — rather than the other way around. So you read the system first, then check the document, not the document first and then the system. Alignment of the IRS — Inertial Reference System — must be ensured. For flights using GNSS — Global Navigation Satellite System — you must also run a Satellite Availability Prediction Programme, which tells you whether enough satellites will be in view for the planned route. An altimeter cross-check must be conducted as well. Prior to entering the NAT OCA — that’s the North Atlantic Oceanic Control Area — you must perform a check of the SELCAL, the master clock, and another altimeter cross-check. SELCAL stands for Selective Calling, a system that alerts the crew when ATC wants to communicate over high-frequency radio without the crew having to monitor the frequency continuously. The altimeters must be within 200 feet of each other. The standby altimeter difference should be noted, so that the error can be applied should there be a failure of the primary systems. In other words, if the primary altimeters fail, you know how much to add or subtract from the standby reading to get an accurate altitude. Finally, the altimeters are to be compared at each subsequent waypoint. Any disagreement in excess of 200 feet must be reported — presumably to ATC, because it indicates a potential system error that could affect separation.