The OCC position is responsible for maintaining required separation within the Oceanic Control area by using the position reports and oceanic clearances.
Flights planned through Oceanic airspace must obtain a separate Oceanic Clearance. The request is made atleast 30 minutes prior to the ETA of the OEP (Oceanic Entry Point) via Voice or Text. It is the responsibility of the Oceanic Controller to ensure that all aircraft enter oceanic airspace properly spaced and remain spaced throughout the crossing.
At airports situated close to oceanic boundaries or within the NAT Region, it may be necessary to obtain the Oceanic Clearance before departure. These procedures are detailed in relevant State AIPs. On the east side of the NAT, this will apply to departures from all Irish airfields, all UK airfields west of 2° 30'W and all French Airfields west of zero degrees longitude. Aircraft departing from Canadian airfields such as Goose Bay, Deer Lake, Gander and St. Johns must also obtain their Oceanic Clearance prior to departure. Oceanic Clearances are issued by the relevant ATS unit or on specified oceanic delivery frequencies. The clearance request will include an estimate for the OEP expressed in terms of Takeoff + xx minutes as well as altitude and speed. Note that the aircraft must be capable of entering Oceanic airspace at both the level and speed assigned by the ATC clearance.
Here is a summary:
|Oceanic Clearance||Time Frame|
|From Coastal Airports||30-45 mins prior to departure|
|Long-range aircraft flying Eastbound||40-60 mins prior to Oceanic Boundary|
|Via Datalink||40-90 mins prior to Oceanic Boundary|
|Westbound - SHANWICK||45-90 mins prior to Oceanic entry point ETA|
|REYKJAVIK (from Scottish/Stavanger areas)||20 mins prior to Oceanic entry point ETA|
|General||40 mins prior to Oceanic Boundary|
Before issuing clearance the controller confirm positive spacing exists and will be maintained throughout the crossing. It is the OCC controller’s responsibility to coordinate routing and/or altitude changes with domestic units. A time limitation is only given if the aircraft's ETA at the NAT needs to be altered
There are three elements to an Oceanic Clearance:
These three items serve to provide for the three basic criteria of separation:
The clearance format is dependant upon whether the aircraft is flying on an Organised Track or following a random route.
Air Traffic Services will issue an abbreviated clearance when clearing an aircraft to fly along the entire length of an Organised Track. An abbreviated clearance will include:
Pilot: Requesting clearance to Toronto via track Delta, estimating LIMRI at 1235z, mach .81, FL360, TMI 034.
ATC: Cleared to Toronto via Track Delta, from LIMRI maintain FL360, Mach .80
In general, for aircraft cleared via a random route in NAT airspace, Air Traffic Services will issue:
A typical random route clearance is as follows:
Pilot: Requesting clearance to Boston via DOGAL 54N20W 54N30W 53N40W 52N50W 51N60W ALLRY, estimating DOGAL at 1235z, mach .82, FL360.
ATC: Cleared to Boston via DOGAL 54N20W 54N30W 53N40W 52N50W 51N60W ALLRY, from DOGAL maintain FL360, mach .82.
Both Gander and Reykjavik OACs may, however, issue clearances for random routings which specify “via flight plan route” instead of providing the entry point, the route coordinates and the exit point.
Pilot: Requesting clearance to Boston via random routing, estimating DOGAL at 1235z, mach .82, FL360.
ATC: Cleared to Boston via flight plan route, from DOGAL maintain FL360, mach .82.
An abbreviated clearance for an organised track can be confirmed using an abbreviated readback which contains the Track Message Identification (TMI) number for the current NAT Track Message. The abbreviated OTS track clearance from the previous section could be acknowledged as follows:
Pilot: Cleared to Toronto via Track Bravo, from PIKIL maintain FL360, mach .82, TMI 032.
If the TMI is not available or incorrect, Air Traffic Services will issue a full route clearance and will require a full readback.
For random route traffic, a full route readback is required in all cases, even when ATS has cleared the aircraft via "flight planned route".
Pilot: Cleared to Boston via DOGAL 54N20W 54N30W 53N40W 52N50W 51N60W ALLRY, from DOGAL maintain FL360, mach .82
A position report consists of:
actual time, flight level
FL, mach decimal
mach number, estimating
estimated waypoint at
Pilot: "Gander, hello, Speedbird 172 heavy, position report."
ATC: "Speedbird172, pass your message."
Pilot: "Speedbird 172 passed 47 north 50 west at 0246, FL 330, Mach decimal 83, 49 North 40 West at 03:29, next 51 North 30 West"
ATC: "Speedbird 172 has passed 47 north 50 west at 0246, FL 330, Mach decimal 83, 49 North 40 West at 03:29, next 51 North 30 West"
Pilot: "Speedbird 172 heavy, readback correct."
The same principle applies at every waypoint the aircraft passes, or latest 45 minutes after the last position report. Especially on random routings the fixes may be further apart than 45 minutes.
Minimum vertical separation within HLA airspace is 1000 feet up to and including FL410, and 2000 feet above that.
Supersonic flights require 4,000 feet vertical separation from all other traffic if no other form of separation exists. This applies at any level for aircraft at supersonic speeds
Minimum lateral separation is 60nm and for Reduced Lateral Separation Minimum (RLatSM) tracks 25nm
Parallel tracks which are spaced apart by 1 degree, and which change latitude by no more than 2 degrees over a longitude of 10 degrees are deemed to be separated.
NATs are normally defined so that they do not change latitude by more than 2 degrees for each 10 degrees longitude difference thereby ensuring separation.
Minimum longitudinal separation for aircraft on the same track is 10 minutes flying time
Aircraft on crossing tracks at the same level must be 15 minutes apart at the point where their tracks cross
Example: An aircraft passing 49N040W at FL380 must not be followed by another at the same level on the same track until ten minutes have elapsed after the first one passed that point
Aircraft with different speeds on the same track/FL will gradually get closer or further apart. It is imperative to monitor this change of spacing closely for loss of separation. Aircrafts are requested to maintain the cleared speed given with the oceanic clearance
When calculating initial spacing use the following formula: Slow followed by fast: Add 1 minute to the standard for every increase of 0.01 Mach number of the second aircraft
Example: M0.80 followed by M0.84 requires FOURTEEN minutes at ocean entry same track same level.
Fast followed by slow. Subtract one (1) minute from the standard for every decrease of 0.02 Mach number of the second aircraft. The minimum is 5 minutes at Oceanic entry
Example: M0.84 followed by M0.80 requires a minimum of EIGHT minutes separation at ocean entry same track same level.
If two aircraft at different speeds are entering Oceanic Airspace at the same point but following tracks which will be separated by no less than 60 nautical miles, or 10 degrees of longitude after entry the increase above is not required. The reduction above may still be applied. If this situation occurs inside Oceanic Airspace (as opposed to at entry) then they are considered to be on crossing tracks and the 15 minute rule applies. There is no reduction to the fifteen minute rule for fast followed by slow on crossing tracks
The following is included in order to determine the separation requirement for aircraft wishing to climb/descend through the level of another aircraft opposite direction, whether on the same track or crossing tracks opposite direction
Vertical separation must be established by a position calculated to be 30 minutes flying time before the position/time at which it is estimated that they will pass one another, and must continue to exist until 30 minutes after they are estimated to have passed. If it can be positively established that they have passed, by both having reported passing the same Oceanic Reporting Point then the separation may be reduced to 10 minutes after they are known to have passed each other
Example: Two aircrafts, A: routing 55N010W 56N020W 57N030W estimates 56N020W at 1234Z and 57N030W at 1304Z B: routing 56N030W 56N020W 56N010W. estimates 56N030W at 1224Z and 56N020W at 1254Z. Inspection and calculation indicates that they will both be approximately one third of the way from 20W to 30W (or two thirds of the way from 30W to 20W) at approximately the same time (1244Z). So vertical separation must exist from 1214Z until 1314Z. Once (B) has reported coordinate 20W the pass will have been established and one or other may climb/descend through the other aircraft's level after 1304 (ten minutes after they are known to have passed)
SELCAL shall be used whenever aircraft are equipped. On initial call-up SELCAL should be verified. Subsequent communications shall always be initiated with a SELCAL signal. If the SELCAL check fails the aircraft should be advised to monitor the frequency continuously
Following remark is required in th FP for SELCAL to be used SEL/(code)
To send a SELCAL right click the aircraft, select SELCAL, select SEND RX