ENR 7.7 North Atlantic (NAT) Timekeeping Procedures

1.. Prior to entry into NAT High Level Airspace, the time reference system(s) to be used during the flight for ­calculation of waypoint estimated times of arrival (ETAs) and waypoint actual times of arrival (ATAs) must be ­synchronized to universal coordinated time (UTC). All ETAs and ATAs passed to air traffic control must be based ­on a time reference that has been synchronized to UTC or equivalent. Acceptable sources of UTC include:

1. WWV * National Institute of Standards and Technology (Fort Collins, Colorado). WWV operates 24 hours ­a day on 2500, 5000, 10000, 15000, 20000 kHz (AM/single sideband (SSB)) and provides UTC voice every ­minute.
2. GPS (corrected to UTC) * Available 24 hours a day to those pilots who can access the time signal over their ­shipboard GPS equipment.
3. CHU * National Research Council (NRC) *Available 24 hours a day on 3330, 7335, and 14670 kHz ­(SSB). In the final 10*second period of each minute, a bilingual station identification and time announcement ­is made. Since April 1990, the announced time is UTC.
4. BBC * British Broadcasting Corporation (United Kingdom). The BBC transmits on a number of domestic ­and worldwide frequencies and transmits the Greenwich time signal (referenced to UTC) once every hour on ­most frequencies, although there are some exceptions.
5. Any other source shown to the State of Registry or State of Operator, as appropriate, to be an equivalent ­source of UTC.