JO 7110.65 5-1-6

Inform an aircraft when it is observed in a position and on a track which will obviously cause the aircraft to deviate from its protected airspace area. If necessary, help the aircraft to return to the assigned protected airspace.

NOTE-

RNAV ATS routes have a width of 8 miles and laterally protected airspace of 4 miles on each side of the route centerline

Navigation system performance requirements for operations on RNAV ATS routes require the aircraft system be capable of remaining within 2 miles of the route centerline. Aircraft approaching this limit may be experiencing a navigation system error or failure.

REFERENCE-

FAA Order JO 7110.65, Para 4-2-5 , Route or Altitude Amendments.

FAA Order JO 7110.65, Para 7-9-3 , Methods.

FAA Order JO 7400.2, Para 20-5-2, RNAV Route Criteria.

AC 90-100A, U.S. Terminal and En Route Area Navigation (RNAV) Operations, Para 8a. Navigation System Accuracy.