Required Navigation Performance


  • Required Navigation Performance (RNP) is RNAV with on-board navigation monitoring and alerting
  • RNP is also a statement of navigation performance necessary for operation within a defined airspace
  • A critical component of RNP is the ability of the aircraft navigation system to monitor its achieved navigation performance, and to identify for the pilot whether the operational requirement is, or is not being met during an operation
  • This on-board performance monitoring and alerting capability therefore allows a lessened reliance on air traffic control intervention (via radar monitoring, automatic dependent surveillance (ADS), multilateration, communications), and/or route separation to achieve the overall safety of the operation
  • RNP capability of the aircraft is a major component in determining the separation criteria to ensure that the overall containment of the operation is met
  • The RNP capability of an aircraft will vary depending upon the aircraft equipment and the navigation infrastructure
    • For example, an aircraft may be equipped and certified for RNP 1.0, but may not be capable of RNP 1.0 operations due to limited NAVAID coverage

RNP Operations:

  • Lateral Accuracy Values:

    • Lateral Accuracy values are applicable to a selected airspace, route, or procedure
    • The lateral accuracy value is a value typically expressed as a distance in nautical miles from the intended centerline of a procedure, route, or path
    • RNP applications also account for potential errors at some multiple of lateral accuracy value (for example, twice the RNP lateral accuracy values)
    • Nav Specs and Standard Lateral Accuracy Values:

      • U.S. standard values supporting typical RNP airspace are as specified below. Other lateral accuracy values as identified by ICAO, other states, and the FAA may also be used [Figure 1]
        • RNP Approach (APCH):
          • RNP APCH procedures are titled RNAV (GPS) and offer several lines of minima to accommodate varying levels of aircraft equipage: either lateral navigation (LNAV), LNAV/vertical navigation (LNAV/VNAV), and Localizer Performance with Vertical Guidance (LPV), or LNAV, and Localizer Performance (LP). GPS or WAAS can provide the lateral information to support LNAV minima
          • LNAV/VNAV incorporates LNAV lateral with vertical path guidance for systems and operators capable of either barometric or WAAS vertical
          • Pilots are required to use WAAS to fly to the LPV or LP minima. RNP APCH has a lateral accuracy value of 1 in the terminal and missed approach segments and essentially scales to RNP 0.3 in the final approach. (See paragraph 1-1-18)
        • RNP AR APCH:
          • RNP AR APCH procedures are titled RNAV (RNP)
          • RNP AR APCH vertical navigation performance is based upon barometric VNAV or WAAS
          • RNP AR is intended to provide specific benefits at specific locations
          • It is not intended for every operator or aircraft
          • RNP AR capability requires specific aircraft performance, design, operational processes, training, and specific procedure design criteria to achieve the required target level of safety
          • RNP AR APCH has lateral accuracy values that can range below 1 in the terminal and missed approach segments and essentially scale to RNP 0.3 or lower in the final approach
          • Operators conducting these approaches should refer to AC 90­101A, Approval Guidance for RNP Procedures with AR. (See paragraph 5-4-18)
        • Advanced RNP (A­RNP):
          • Advanced RNP includes a lateral accuracy value of 2 for oceanic and remote operations but not planned for U.S. implementation and may have a 2 or 1 lateral accuracy value for domestic enroute segments
          • Except for the final approach, A­RNP allows for scalable RNP lateral navigation accuracies
          • Its applications in the U.S. are still in progress
        • RNP 1:
          • RNP 1 requires a lateral accuracy value of 1 for arrival and departure in the terminal area and the initial and intermediate approach phase
        • RNP 2:
          • RNP 2 will apply to both domestic and oceanic/remote operations with a lateral accuracy value of 2
        • RNP 4:
          • RNP 4 will apply to oceanic and remote operations only with a lateral accuracy value of 4
        • RNP 0.3:
          • RNP 0.3 will apply to rotorcraft only. This Nav Spec requires a lateral accuracy value of 0.3 for all phases of flight except for oceanic and remote and the final approach segment
  • Application of Standard Lateral Accuracy Values

    • U.S. standard lateral accuracy values typically used for various routes and procedures supporting RNAV operations may be based on use of a specific navigational system or sensor such as GPS, or on multi-sensor RNAV systems having suitable performance
  • Depiction of Lateral Accuracy Values:

    • The applicable lateral accuracy values will be depicted on affected charts and procedures
  • Other RNP Applications Outside the U.S.

    • The FAA and ICAO member states have led initiatives in implementing the RNP concept to oceanic operations
    • For example, RNP−10 routes have been established in the northern Pacific (NOPAC) which has increased capacity and efficiency by reducing the distance between tracks to 50 NM (See paragraph 4−7−1)
  • Aircraft and Airborne Equipment Eligibility for RNP Operations:

    • Aircraft meeting RNP criteria will have an appropriate entry including special conditions and limitations in its Aircraft Flight Manual (AFM), or supplement. Operators of aircraft not having specific AFM−RNP certification may be issued operational approval including special conditions and limitations for specific RNP lateral accuracy values
    • Some airborne systems use Estimated Position Uncertainty (EPU) as a measure of the current estimated navigational performance. EPU may also be referred to as Actual Navigation Performance (ANP) or Estimated Position Error (EPE)
U.S. Standard RNP Levels
U.S. Standard RNP Levels