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Operational Policy/Procedures for the Gulf of Mexico 50 NM Lateral Separation Initiative

AC 90

−105 to evaluate an operator’s application for

RNP 10 or RNP 4 authorization. Authorization to
conduct RNP operations in oceanic airspace is
provided to all U.S. operators through issuance of
Operations Specification (OpSpec), Management
Specification (MSpec), or Letter of Authorization
(LOA) B036, as applicable to the nature of the
operation; for example, Part 121, Part 91, etc.
Operators may wish to review FAA Order 8900.1,
Flight Standards Information Management System,
volume 3, chapter 18, section 4, to understand the
specific criteria for issuing OpSpec, MSpec, and/or
LOA B036.


The operator’s RNP 10 or RNP 4 authorization

should include any equipment requirements and
RNP 10 time limits (if operating solely inertial

based navigation systems), which must be observed
when conducting RNP operations. RNP 4 requires
tighter navigation and track maintenance accuracy
than RNP 10.


−7−4. Authority for Operations with a

Single Long

−Range Navigation System

Operators may be authorized to take advantage of
50 NM lateral separation in the Gulf of Mexico CTAs
when equipped with only a single long


navigation system. RNP 10 with a single long


navigation system is authorized via OpSpec, MSpec,
or LOA B054. Operators should contact their FSDO
or CMO to obtain information on the specific
requirements for obtaining B054. Volume 3, chapter
18, section 4 of FAA Order 8900.1 provides the
qualification criteria to be used by FAA aviation
safety inspectors in issuing B054.


−7−5. Flight Plan Requirements


In order for an operator with RNP 10 or RNP 4

authorization to obtain 50 NM lateral separation in

the Gulf of Mexico CTAs, and therefore obtain
preferred routing available to RNP authorized
aircraft, the international flight plan form (FAA

−4) must be annotated as follows:


Item 10a (Equipment) must include the letter



Item 18 must include either “PBN/A1” for

RNP 10 authorization or “PBN/L1” for RNP 4


Indication of RNP 4 authorization implies the

aircraft and pilots are also authorized RNP 10.


Chapter 5, section 1, of this manual includes

information on all flight plan codes. RNP 10 has the
same meaning and application as RNAV 10. They
share the same code.


−7−6. Contingency Procedures

Pilots operating under reduced lateral separation
must be particularly familiar with, and prepared to
rapidly implement, the standard contingency proce-
dures specifically written for operations when
outside ATC surveillance and direct VHF communi-
cations (for example, the oceanic environment).
Specific procedures have been developed for weather
deviations. Operators should ensure all flight crews
operating in this type of environment have been
provided the standard contingency procedures in a
readily accessible format. The margin for error when
operating at reduced separation mandates correct and
expeditious application of the standard contingency
procedures. These internationally accepted proce-
dures are published in ICAO Document 4444,
chapter 15. The procedures are also reprinted in the
U.S. Aeronautical Information Publication (AIP),
En Route (ENR) Section 7.3, Special Procedures for

−flight  Contingencies in Oceanic Airspace; and

AC 91



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