Interpretation 28

Document Change Proposals have been initiated to amend the language in FAA Order JO 7110.65, Paragraph 2-6-4, AIM, Paragraph 7-1-14, and AIP, Paragraph 10.2. The phrase “lateral deviation area” will be removed and the new language will align with this interpretation.

When an aircraft is issued the clearance “Deviation 20 degrees left approved, when able proceed direct ONL”, what can a controller expect the lateral deviation area to be?

The deviation was approved in reference to the original route. Direct ONL is only relevant when the deviation is complete. Therefore the aircraft may deviate left or right between the original course and the limits specified in the clearance.

Are aircraft capable of displaying the original course while concurrently showing a 20 degree deviation wedge based off their current location, allowing pilots to freely navigate within this defined airspace?

This office cannot definitively answer the question of aircraft route display capabilities; however, controllers should expect possible left and right deviations between the original course and the limits specified in the clearance, while recognizing that weather deviations are fluid situations that require close monitoring.

Does adherence to FAA Order JO 7110.65, 13-1-10, require an immediate update to the route of flight upon approval of a weather deviation?

No, an immediate update to the route of flight is not required upon approval of a weather deviation. FAA Order JO 7110.65, Paragraph 13-1-10, states automation entries shall be performed in a timely manner. The reason for conducting the route amendment entry in a timely manner is to maintain the accuracy of the conflict probe function of ERAM. The FAA Initial En Route Qualification Training ERAM Lab Procedures and SOP, Section V, Paragraph 103, Weather Reroutes and Side Stream Handoffs states that route amendments for aircraft on approved weather deviations must be accomplished after “completion of the deviation.” Updating a route of flight before completion of weather deviation is counterproductive for several reasons:

• Original route is no longer displayable.
• Entering route amendments before resumption of normal flight does not provide accurate trajectory information.
• Routing entered before completion of deviation would generate inaccurate conflict probe data because the aircraft is not yet actively flying the new clearance.

During weather deviations pilots do not have an assigned course but are cleared to operate within a General area with a route to follow after the deviation is completed. When a pilot advises resumed navigation of the assigned route, only then does updating the flight plan provide accurate trajectory information. An amendment conducted in a timely manner is one that is accomplished as soon as the course flown by the aircraft matches the assigned route of flight.