ATI Blog

The following is from the IBAC Bulletin 08-1:

Shanwick Oceanic still has a very high proportion of Interventions to prevent GNEs.

The total number of Interventions since the beginning of this calendar year was 74.

Although an Intervention is a safety net that seems to be successful for most of the time there are always holes (3 GNEs were not prevented this year).It is vital that we do not allow these holes in the safety nets to line up. One of the first safety nets has to rest with the crew ensuring that their Oceanic clearances are correct. The majority of these Interventions are as a result of following the flight plan and not the clearance.

Even within that there appears to be another common thread. Attached you will find an Oceanic map for your reference. A large proportion of these Interventions are happening in the airspace east of 15W. For example an Oceanic clearance might be via MALOT – BURAK but the flight plan is MALOT – DOLIP.
The airspace between 15W and Landfall is still Shanwick Oceanic and a safe procedural clearance must be provided in the event of RT failure, Shannon radar failure etc. Although flights will usually be in contact with Shannon Radar after 15W and Shannon may well take them off the original Oceanic clearance (which Shannon is allowed to do) the flight must still anticipate following Oceanic clearances.

Consequently the awareness of crews is drawn to the issue of proper adherence to oceanic navigation procedures and its importance to flight safety.
Crews are urged to uphold the following practices:

• Question clearances if in doubt
• Cross check understanding of clearance
• Cross check FMS and clearance
• Follow clearance to clearance limit
• Follow clearance – not the flight plan

There is research into the possibility of reducing separation standards on the North Atlantic which could provide operators with more opportunity to request optimum routes and levels. It may be that navigation errors such as these interventions may delay that introduction.
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Prepared by Peter R. Ingleton
IBAC Director, ICAO Liaison
21 October 2008