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Revised Estimate
Example: “Revised Estimate, Speedbird 212 on 3476, 57 North 040 West at 0305”
Miscellaneous
Plain language – free format
Data link communications are gradually being introduced into the NAT environment for position reporting. On first contact with the initial aeradio stations crews of participating aircraft should expect to receive the instruction “VOICE POSITION REPORTS NOT REQUIRED”. Above 70N the position reports are made at intervals of 20° of longitude.
Radio Failure in the North Atlantic Area
In the case of radio failure prior to exiting the NAT region, the pilot shall maintain the last received and acknowledged oceanic clearance, including level and speed, to the last specified oceanic route point, normally landfall, then:
•Cleared On Filed Flight Plan Route: Continue on the filed flight plan route. The pilot shall maintain the last assigned oceanic level and speed to landfall, and after passing the last specified oceanic route point; the pilot shall conform to the relevant state procedures/ regulations.
•Cleared Other Than Filed Flight Plan Route: After passing this point, the pilot shall conform to the relevant state procedures/regulations and rejoin the filed plan route by proceeding via the published ATC route structure where possible to the next significant point ahead as contained in the filed flight plan.
Initial Clearance
At least 40 minutes before entering the NAT airspace (above FL55) pilots are required to obtain an oceanic clearance directly from the initial OACC. The clearance request should include requested FL, and maximum acceptable FL at the entry to the OCA. As all the entry points to the OTS are within 250 NM of the coast, the aircraft should be able to obtain the clearance by VHF. Within the states concerned, the OACCs have remote VHF transmitter sites on discrete frequencies for this purpose. If direct communications are not possible, HF can be used through the air-ground station. Alternatively, a request could be made through the domestic ACC on the airways/UIR frequency in use. Recent advances in technology have made data link available for use with ATC and this is another possible source of obtaining the clearance. If the aerodrome of departure is less than 40 minutes flying time from the entry point to the OTS, the oceanic clearance will have to be obtained on the ground. Where this is normal procedure, the OACC has a local transmitter site close by i.e. Dublin, Shannon, and Prestwick.
The clearance will include the limit of clearance (normally the destination), the track identifier, the entry point, the initial FL, the Mach number required and any specific instructions. This must be read back, but an abbreviated read back is permitted replacing the route details with the track identifier plus the TMI. This indicates that the pilot has the route details in accordance with the TM for the current OTS. If the pilot does not include the track identifier and TMI, the OACC will then read the route details and the pilot will have to read this back. Any misunderstanding concerning clearances and re-clearances not picked up by the OACC is known as ‘an ATC loop error’.
If an aircraft encounters, whilst en route to the NAT Oceanic Airspace, a critical in-flight equipment failure, or at dispatch is unable to meet the MEL requirements for RVSM or MNPS
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approval on the flight, then the pilot must advise ATC at initial contact when requesting oceanic clearance. After obtaining and reading back the clearance, the pilot should monitor the forward estimate for oceanic entry, and if this changes by 3 minutes or more, should pass a revised estimate to ATC.
Pilots should pay particular attention when the issued clearance differs from the flight plan as a significant proportion of navigation errors investigated in the NAT involve an aircraft which has followed its flight plan rather than its differing clearance.
If the entry point of the oceanic route on which the flight is cleared differs from that originally requested and/or the oceanic flight level differs from the current flight level, the pilot is responsible for requesting and obtaining the necessary domestic reclearance. There are three elements to an oceanic clearance: route, Mach number and flight level. These elements serve to provide for the three basic elements of separation: lateral, longitudinal and vertical.
Transition
Because the OTS uses all the available FLs as ‘one way streets’ when an aircraft leaves the OTS and joins the domestic route system an adjustment in FL may be required. In order to make sure this is only conducted where there is no loss of separation, special areas known as transition areas have been established for this purpose. At the eastern side of the NAT region, the Shannon Oceanic Transition Area (SOTA), west of Ireland to 15W, and in the Bay of Biscay the Brest Oceanic Transition Area (BOTA), have been established. These are ostensibly special rules areas where the normal rules of the air are not complied with.
SSR
When flying in the NAT region, the last assigned SSR code by a domestic ATCU is to be maintained for a period of 30 minutes after entering the OCA. After that, mode A2000 plus C is to be set and maintained. In the event of emergency, radio failure or unlawful interference, the appropriate code should be squawked even though the aircraft is well out of range of a ground radar station.
Meteorological Reports
With effect from 18 November 2010 aircraft are no longer required to provide voice reports of MET observations of wind speed and direction nor outside air temperature. Nevertheless any turbulence or other significant meteorological conditions encountered should be reported to ATC. The format to be used for the reporting of such observations should, where appropriate, be by reference to geographical co-ordinates.
When a ground unit establishes an event contract with an aircraft to provide ADS position reports, it may also establish an additional periodic report contract (e.g. with a 30 min interval). Such ADS-C periodic reports, unlike event reports, contain wind and temperature data and thereby satisfy the MET authorities requirements for the provision of MET data. Similarly, “FMC waypoint position reports” sent via data link also include wind and temperature data and aircraft participating in such a data link programme are deemed to meet the MET authorities requirements. However, it must be appreciated that any such automated MET reports do not include information on any turbulence or any other unusual meteorological phenomena. Therefore any pilot providing position reports via data link, who encounters turbulence, etc. should report this information via voice or, if appropriate, via a CPDLC free text downlink message.
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Special Contingencies and Procedures
The inability to maintain level, navigate accurately or communicate, when flying in the MNPSA, can have serious results. At the first indication that things are ‘not normal’ pilots are advised to communicate the problem to the OACC. Loss of HF communications may be overcome by asking an adjacent aircraft on VHF to relay. Remember all aircraft flying in the MNPSA are required to monitor 123.45 MHz and 121.5 MHz. Pressurization failure will require the aircraft to descend rapidly to a safe level and pilots are required to broadcast safety information (altitude passing) on 121.5.
Strategic Lateral Offset Procedure (SLOP)
If an aeroplane flying in the NAT MNPSA encounters wake turbulence and the pilot considers it necessary, a procedure has been established to allow the aeroplane track to be offset from that of the aeroplane causing the turbulence. The procedure is called the Strategic Lateral Offset Procedure (SLOP) and offers three options. The first allows the aeroplane to be flown along the cleared track centre line, the second to offset by 1 NM right, and the third to offset by 2 NM to the right only. If neither of the offset options are upwind of the other aeroplane, the pilot should contact the other aeroplane on 123.45 MHz and request that that aeroplane adopts an allowable alternate downwind (SLOP) offset.
If wake turbulence is encountered whilst flying in the NAT MNPS airspace, a report is to be submitted to the NAT Central Monitoring Agency.
Deviation Around Severe Weather
If the aircraft is required to deviate laterally from track to avoid weather (e.g. thunderstorms), the pilot should request a revised clearance from ATC and obtain essential traffic information prior to deviating. This is the case even when a pilot expects to have to deviate by a relatively small distance (e.g. less than 10 NM). However, if for any reason such prior revised ATC clearance cannot be obtained, the contingency procedures described below should be adopted. (Efforts should be continued to obtain an appropriate revised ATC clearance.)
a)If possible, deviate away from the organized track or route system;
b)Establish communications with and alert nearby aircraft broadcasting, at suitable intervals: aircraft identification, flight level, aircraft position (including ATS route designator or the track code) and intentions, on the frequency in use (when VHF) and on frequency 121.5 MHz (or, as a back-up, on the VHF inter-pilot air-to-air frequency 123.45 MHz);
c)Watch for conflicting traffic both visually and by reference to ACAS/TCAS (if equipped);
d)Turn on all aircraft exterior lights;
e)For deviations of less than 10 NM, aircraft should remain at the level assigned by ATC;
f)For deviations of greater than 10 NM, when the aircraft is approximately 10 NM from track, initiate a level change of +/-300 ft.
(Climb/descent depends on direction of flight and deviation)
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Unable to Obtain Revised Clearance
If it is not possible to obtain a revised clearance immediately, it is to be obtained at the earliest possible time. In the meantime, the pilot shall:
•Broadcast position and intentions on 121.5 MHz at suitable intervals until a revised clearance can be obtained.
•Make maximum use of the aircraft lights to make the aircraft visible.
•Maintain a watch for conflicting traffic.
•Initiate such action as necessary to ensure the safety of the aeroplane.
If a pilot of an aeroplane is unable to obtain a revised ATC clearance, the aeroplane should leave its assigned route or track by turning at least 45° to the right or left whenever this is possible. The direction of the turn should, where possible, be determined by the position of the aircraft relative to any organized route or track system. Other factors may be the direction to an alternate aerodrome, terrain clearance and levels allocated to adjacent routes or tracks. Subsequent actions are determined by the ability of the aeroplane with respect to height keeping. When able to maintain assigned flight level:
•Turn to acquire and maintain in either direction a track laterally separated by 15 NM from its assigned route or track, and
•If above FL410, climb or descend 300 m (1000 ft), or
•If below FL410, climb or descend 150 m (500 ft), or
•If at FL410, climb 300 m (1000 ft) or descend 150 m (500 ft).
An aeroplane unable to maintain its assigned flight level should:
•Initially minimize its descent rate to the extent that it is operationally feasible.
•Turn while descending to acquire and maintain in either direction a track laterally separated by 15 NM from its assigned route or track, and
•For the subsequent level flight, a level should be selected which differs from those normally used by 300 m (1000 ft) if above FL410 or by 150 m (500 ft) if below FL410.
Navigation System Failure
If a failure occurs before entering the MNPSA the pilot should attempt to resolve the problem (determine that the system is useable) or land (or delay the take-off) and get the system repaired. Under no circumstances should an aircraft enter the MNPSA with unresolved navigation errors. Alternatively, the pilot may consider obtaining a clearance to remain outside MNPSA, e.g. below FL290, or re-file for one of the special routes designed for non-compliant aircraft. If however, the aircraft has triple LRNSs, the MNPSA requirement for two LRNSs would be met with one unserviceable, and the flight could proceed as planned. If an aircraft with only two LRNSs suffers a system failure after entering the MNPSA, the flight is to be continued in accordance with the clearance received. In this case the pilot should:
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