Gulf of Mexico Flight Operations


  • On 20 October 2011 at 0900 UTC, the Federal Aviation Administration (FAA), Serviciós a la Navegacion en el Espacio Aéreo Mexicano (SENEAM) and the Direccion General de Aeronautica Civil (DGAC) Mexico implemented 50 Nautical Mile (NM) lateral separation between aircraft authorized Required Navigation Performance 10 (RNP 10) or RNP 4 operating in the Gulf of Mexico (GoMex) Oceanic Control Areas (CTA). Existing Air Traffic Services (ATS) routes and route operating policies did not change for this implementation
  • RNP 10 Versus RNAV 10 Terminology:

    • "RNP 10" has the same meaning and application as "RNAV 10". The ICAO Performance-based Navigation (PBN) Manual (ICAO Doc 9613), Volume II, Part B, Chapter 1 (Implementing RNAV 10, Designated and Authorized as RNP 10) explains that the term "RNP 10" was in use before the publication of the ICAO PBN Manual and the manual has "grandfathered in" its continued use when implementing an "RNAV 10" navigation specification
  • Background:

    • 50 NM lateral separation was first applied between aircraft authorized for RNP 10 operations on the North Pacific Route System in April 1998. Since that time, 50 NM lateral separation has been expanded throughout the Pacific Flight Information Regions (FIRs) and is currently applied in other airspaces, including, starting in June 2008, the West Atlantic Route System. GoMex 50 NM lateral separation implementation will apply the experience gained in those operations
  • Control Areas (CTA) Affected:

    • 50 NM lateral separation is implemented in the following CTAs/FIRs/Upper Control Areas (UTA)
      • The Houston Oceanic CTA/FIR and the Gulf of Mexico portion of the Miami Oceanic CTA/FIR
        • The Monterrey CTA and Merida High CTA within the Mexico FIR/UTA
  • Reference Material:

    • Information useful for flight planning and operations within the Gulf of Mexico under this 50 NM lateral separation initiative can be found in the West Atlantic Route System, Gulf of Mexico, and Caribbean Resource Guide for U.S. Operators located at headquarters_offices/avs/offices/afs/afs400/afs470/ media/WATRS.pdf. The Guide can also be found through a web search for "WATRS, GOMEX, Caribbean Resource Guide"

Lateral Separation Minima Applied:

  • 50 NM lateral separation is applied in the GoMex CTA’s between aircraft authorized RNP 10 or RNP 4 at all altitudes above the floor of controlled airspace
  • The current lateral separation minima of 100 NM in the Houston, Monterrey and Merida CTAs, and 90 NM in the Miami Oceanic CTA will continues to be applied between aircraft not authorized RNP 10 or RNP 4

Operation on Routes on the periphery of the Gulf of Mexico CTAs:

  • Operations on certain routes that fall within the boundaries of affected CTAs are not affected by the introduction of 50 NM lateral separation. Operation on the following routes is not affected:
    • Routes that are flown by reference to ICAO standard ground-based navigation aids (VOR, VOR/DME, NDB)
    • Special Area Navigation (RNAV) routes Q100, Q102 and Q105 in the Houston, Jacksonville and Miami CTAs

Provisions for Accommodation of Non-RNP10 Aircraft (Aircraft Not Authorized RNP 10 or RNP 4):

  • Operators of aircraft not authorized RNP 10 (or RNP 4) must annotate their ICAO flight plan for Gulf of Mexico operations as follows:
    • Item 18: "STS/NON−RNP10" (no space between letters and numbers
  • Pilots of Non-RNP10 aircraft that operate in GoMex CTA’s must report the lack of authorization by stating "Negative RNP 10:"
    • On initial call to ATC in a GoMex CTA;
    • In read back of a clearance to climb to or descend from cruise altitude. (See paragraph 4−7−5 e); and
    • When approval status is requested by the controller. (See paragraph 4−7−9 e)
  • Operators of NonRNP10 aircraft must not annotate ICAO flight plan Item 18 (Other Information) with "PBN/A1" or "PBN/L1" if they have not obtained RNP 10 or RNP 4 authorization
  • NonRNP10 operators/aircraft may file any route at any altitude in a GoMex CTA. They will be cleared to operate on their preferred routes and altitudes as traffic permits. 50 NM lateral separation will not be applied to NonRNP10 aircraft
  • NonRNP10 aircraft are encouraged to operate at altitudes above those where traffic is most dense (i.e., at/above FL 380), if possible. NonRNP10 aircraft should plan on completing their climb to or descent from higher FLs within radar coverage, if possible

Operator Action:

  • In order to maximize operational flexibility provided by 50 NM lateral separation, operators capable of meeting RNP 10 or RNP 4 that operate on oceanic routes or areas in the GoMex CTA’s should obtain authorization for RNP 10 or RNP 4 and annotate the ICAO flight plan accordingly
    • RNP 10 is the minimum "Navigation Specification (NavSpec)" required for the application of 50 NM lateral separation. RNP 4 is an operator option. Operators/aircraft authorized RNP 4 are not required to also obtain RNP 10 authorization
    • "RNP navigation specification" (e.g., RNP 10) is the term adopted in the ICAO Performance-based Navigation (PBN) Manual (Doc 9613). It replaces the term "RNP type"

RNP 10 or RNP 4 Authorization: Policy and Procedures for Aircraft and Operators:

  • RNP NavSpecs Applicable To Oceanic Operations:

    • In accordance with ICAO guidance, RNP 10 and RNP 4 are the only NavSpecs applicable to oceanic and remote area operations. Other RNAV and RNP NavSpecs are applicable to continental en route, terminal area and approach operations
  • FAA Documents:

    • The guidance and direction of FAA Order 8400.12 (as amended) (RNP 10 Operational Authorization) is used to grant RNP 10 authorization to operators and aircraft for which the FAA is responsible. FAA Order 8400.33 (as amended) (Procedures for Obtaining Authorization for RNP 4 Oceanic/Remote Area Operations) is used to authorize RNP 4. The FAA RNP 10 and RNP 4 orders are consistent with the ICAO PBN Manual guidance discussed below. Pertinent FAA and ICAO documents are posted online in the West Atlantic Route System, Gulf of Mexico and Caribbean Resource Guide for U.S. Operators described in paragraph 4−7−1
  • ICAO Performance-based Navigation (PBN) Manual (ICAO Doc 9613):

    • Guidance for authorization of RNP 10 and RNP 4 is provided in ICAO Doc 9613. RNP 10 is addressed in Volume II, Part B; Chapter 1. RNP 4 is addressed in Volume II, Part C; Chapter 1
  • RNP 10 and RNP 4 Job Aids:

    • Operators and authorities are encouraged to use the RNP 10 or RNP 4 Job Aids posted on the FAA Gulf of Mexico 50 NM Lateral Separation Initiative Web Page. For U.S. operators, one set of RNP 10 and RNP 4 Job Aids provides references to FAA documents. For international operators, a second set of Job Aids provide references to the ICAO PBN Manual. These Job Aids address the operational and airworthiness elements of aircraft and operator authorization and provide references to appropriate document paragraphs. The Job Aids provide a method for operators to develop and authorities to track the operator/aircraft program elements required for RNP 10 or RNP 4 authorization
  • Qualification of Aircraft Equipped With a Single Long-Range Navigation System (S-LRNS) For RNP 10 Operations In GoMex CTA's

    • Background:

      • S-LRNS operations in the Gulf of Mexico, the Caribbean Sea and the other designated areas have been conducted for at least 25 years. Provisions allowing aircraft equipage with a S-LRNS for operations in specified oceanic and off-shore areas are contained in the following sections of 14 Code of Federal Regulations (CFR): 91.511, 121.351, 125.203 and 135.165
    • ICAO PBN Manual Reference:

      • In reference to RNP 10 authorization, the ICAO PBN Manual, Volume II, Part B, Chapter 1, paragraph states that: "A State authority may approve the use of a single LRNS in specific circumstances (e.g., North Atlantic MNPS and 14 CFR 121.351 (c) refer). An RNP 10 approval is still required"
    • Policy Development:

      • The FAA worked with the ICAO NACC Office (North American, Central American and Caribbean), State regulators and ATS providers in the GoMex and Caribbean areas to implement a policy for S-LRNS equipped aircraft to qualify for RNP 10 for GoMex operations. Allowing S-LRNS equipped aircraft to qualify for RNP 10 enables more operator aircraft to be authorized RNP 10, thereby creating a more uniform operating environment for the application of 50 NM lateral separation. The factors considered were: the shortness of the legs outside the range of ground navigation aids, the availability of radar and VHF coverage in a large portion of GoMex airspace and the absence of events attributed to S-LRNS in GoMex operations
    • Single LRNS/RNP 10 Authorization Limited to Gulf of Mexico:

      • At this time, qualification for RNP 10 based on use of a single long-range navigation system (LRNS) only applies to Gulf of Mexico operations. Any expansion of this provision will require assessment and agreement by the appropriate State authorities
  • RNP 10 Time Limit for INS or IRU Only Operators should review their Airplane Flight Manual (AFM), AFM Supplement or other appropriate documents and/or contact the airplane or avionics manufacturer to determine the RNP 10 time limit applicable to their aircraft. They will then need to determine its effect, if any, on their operation. Unless otherwise approved, the basic RNP 10 time limit is 6.2 hours between position updates for aircraft on which Inertial Navigation Systems (INS) or Inertial Reference Units (IRU) provide the only source of long range navigation. Extended RNP 10 time limits of 10 hours and greater are already approved for many IRU systems. FAA Advisory Circular 90−105 contains provisions for extending RNP 10 time limits

Flight Planning Requirements:

  • Operators must make ICAO flight plan annotations in accordance with this paragraph and, if applicable, Paragraph 4−7−4, Provisions for Non−RNP 10 Aircraft (Not Authorized RNP 10 or RNP 4)
  • ICAO Flight Plan Requirement:

    • ICAO flight plans must be filed for operation on oceanic routes and areas in the Houston Oceanic CTA/FIR, the Gulf of Mexico portion of the Miami CTA/FIR, the Monterrey CTA and Merida High CTA
  • To inform ATC that they have obtained RNP 10 or RNP 4 authorization and are eligible for 50 NM lateral separation, operators must:
    • Annotate ICAO Flight Plan Item 10 (Equipment) with the letters "R," and
    • Annotate Item 18 (Other Information) with, as appropriate, "PBN/A1" (for RNP10) or "PBN/L1" (for RNP4)
      • See paragraph 4−7−8e. It provides recommended filing practices for domestic U.S. RNAV operations and filing with EUROCONTROL
      • On the ICAO Flight Plan, the letter "R" in Item 10 indicates that the flight is authorized for PBN operations. Item 18 PBN/ indicates the types of PBN capabilities that are authorized
  • 50 NM lateral separation will only be applied to operators/aircraft that annotate the ICAO flight plan in accordance with this policy. (See 4−7−8 b)
  • Operators that have not obtained RNP 10 or RNP 4 authorization must not annotate ICAO flight plan Item 18 (Other information) with "PBN/A1" or "PBN/L1", but must follow the practices detailed in paragraph 4−7−4

Pilot and Dispatcher Procedures: Basic and In-flight Contingency Procedures:

  • Basic Pilot Procedures:

    • The RNP 10 and RNP 4 Job Aids contain references to pilot and, if applicable, dispatcher procedures contained in:
      • Advisory Circular 90−105
      • ICAO PBN Manual, Volume II, Parts B and C, Chapter 1
  • ICAO Doc 4444, In-Flight Contingency Procedures:

    • Chapter 15 of ICAO Doc 4444 (Procedures for Air Navigation Services – Air Traffic Management (PANS-ATM)) contains important guidance for pilot training programs. Chapter 15 includes Special Procedures for In-flight Contingencies in Oceanic Airspace, as well as Weather Deviation Procedures. Chapter 15 covers in-flight diversion and turn-back scenarios, loss of navigation capability, and procedures to follow for weather avoidance. This critical guidance is reprinted in the Oceanic Operations section of the U.S. Aeronautical Information Publication (AIP), the International section of the Notices to Airmen Publication, and FAA Advisory Circular 91-70, Oceanic and Remote Continental Airspace Operations
  • Strategic Lateral Offset Procedures (SLOP):

    • Pilots should use SLOP procedures in the course of regular oceanic operations. Guidance regarding SLOP, including how to perform the procedures, is provided in the Oceanic Operations section of the U.S. AIP
  • Pilot Report of Non−RNP 10 Status:

    • The pilot must report the lack of RNP 10 or RNP 4 status in accordance with the following: 1. When the operator/aircraft is not authorized RNP 10 or RNP 4 - see paragraph 4−7−4. 2. If approval status is requested by the controller - see paragraph 4−7−8 e
  • Pilot Statement of RNP 10 or RNP 4 Approval Status, If Requested:

    • If requested by the controller, the pilot must communicate approval status using the following phraseology:
      • Controller Request:
        • (Call sign) confirm RNP 10 or 4 approved
      • Pilot Response:
        • "Affirm RNP 10 approved" or "Affirm RNP 4 approved," as appropriate, or
        • "Negative RNP 10" (See paragraph 4−7−4 for Non−RNP 10 aircraft procedures)
  • Pilot action when navigation system malfunctions:

    • In addition to the actions addressed in the Oceanic Operations section of the U.S. AIP, when pilots suspect a navigation system malfunction, the following actions should be taken:
      • Immediately inform ATC of navigation system malfunction or failure
      • Accounting for wind drift, fly magnetic compass heading to maintain track
      • Request radar vectors from ATC, when available