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crosscheck against ETAs computed by the LRNS.
Prior to oceanic entry
Gross error accuracy check
Before oceanic entry, the accuracy of the LRNS should be checked against a ground-based NAVAID.
The results of the accuracy check should be recorded with the time and position. A large
difference between the ground-based NAV-AID and the LRNS may require immediate corrective
action. Operators should establish a gross error check tolerance based on the type LRNS. It is not
advisable for crews to attempt to correct an error by doing an air alignment or by manually updating
the LRNS since this has often contributed to a Gross Navigation Error.
HF checks
If the crew was unable to accomplish the HF and SELCAL checks on the ground, these checks must
be accomplished before oceanic entry.
Log on to CPDLC or ADS
Operators approved to use Controller Pilot Data Link Communications (CPDLC) or Automatic
Dependent Surveillance (ADS) should log on to the appropriate FIR 15 to 45 minutes prior to the
boundary.
Obtain oceanic clearance
Both pilots must obtain oceanic clearance from the appropriate clearance delivery. (Clearance via
voice should be at least 40 minutes prior to oceanic entry and via data link should be 30 to 90
minutes prior to oceanic entry). It is important that both pilots confirm and enter the ocean at the
altitude assigned in the oceanic clearance (this may be different than the domestic cleared flight
level). An oceanic clearance typically includes a route, flight level and assigned MACH. Crews
should include their requested flight level in their initial clearance request. Some oceanic centers
require pilots to advise them at the time of their oceanic clearance “When Able Higher” (WAH).
Crews should be confident that they are able to maintain requested flight levels based on aircraft
performance capabilities.
Re-clearance
A re-clearance (that is different from the oceanic route requested with the filed flight plan) is the
number one scenario which leads to a Gross Navigation Error. Crews must be particularly cautious
when receiving a re-clearance. Both pilots should receive and confirm the new routing and conduct
independent crosschecks after the LRNS, Master CFP and Plotting Chart are updated. It is critical
that crews check the magnetic course and distance between the new waypoints as noted in
PREFLIGHT under the paragraph “LRNS Programming”.
Altimeter checks
Crews are required to check the two primary altimeters which must be within 200 ft of each other.
This check is conducted while at level flight. The stand-by altimeter should also be noted. The
altimeter readings should be recorded along with the time.
NORTH ATLANTIC MNPSA OPERATIONS MANUAL CHAPTER 12
NAT MNPS 74 Edition 2008
Compass heading check
It is recommended to conduct a compass heading check and record the results. This check is
particularly helpful with inertial systems. The check can also aid in determining the most accurate
compass if a problem develops over water.
After oceanic entry
Squawk 2000
Thirty minutes after oceanic entry crews should Squawk 2000, if applicable. There may be regional
differences such as maintaining last assigned Squawk in the West Atlantic Route System (WATRS).
Crews transiting Reykjavik’s airspace must maintain last assigned Squawk.
Maintain assigned Mach
Some oceanic clearances include a specific Mach. There is no tolerance for this assigned Mach. The
increased emphasis on longitudinal separation requires crew vigilance in a separation based on
assigned Mach. The requirement is to maintain the true Mach which has been assigned by ATC. In
most cases, the true Mach is the indicated Mach. Some aircraft, however, require a correction factor.
VHF Frequency Monitoring.
After going beyond the range of the assigned VHF frequency, crews should set their radios to
interpilot (123.45 Mhz) and emergency frequencies (121.5 Mhz).
Strategic Lateral Offset Procedures (SLOP)
The SLOP should be Standard Operating Procedure (SOP) for all oceanic crossings. This procedure
was developed to reduce the risk from highly accurate navigation systems or operational errors
involving the ATC clearance. SLOP also replaced the contingency procedure developed for aircraft
encountering wake turbulence. Depending upon winds aloft, coordination between aircraft to avoid
wake turbulence may be necessary. This procedure of flying centerline, 1 NM or 2 NM right of
centerline, greatly reduces the risk to the airspace by the nature of the randomness. Aircraft that do
not have an automatic offset capability (that can be programmed in the LRNS) should fly the
centerline only. SLOP was not developed to be used only in contingency situations.
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