AIM
12/2/21
1.
The large number (over 300) of waypoints in
the grid system makes it difficult to assign
phonetically pronounceable names to the waypoints
that would be meaningful to pilots and controllers. A
unique naming system was adopted that enables
pilots and controllers to derive the fix position from
the name. The five
−
letter names are derived as
follows:
(a)
The waypoints are divided into sets of
3 columns each. A three
−
letter identifier, identifying
a geographical area or a NAVAID to the north,
represents each set.
(b)
Each column in a set is named after its
position, i.e., left (L), center (C), and right (R).
(c)
The rows of the grid are named
alphabetically from north to south, starting with A for
the northern most row.
EXAMPLE
−
LCHRC would be pronounced “Lake Charles Romeo
Charlie.” The waypoint is in the right
−
hand column of the
Lake Charles VOR set, in row C (third south from the
northern most row).
2.
In December 2009, significant improvements
to the Gulf of Mexico grid system were realized with
the introduction of ATC separation services using
ADS
−
B. In cooperation with the oil and gas services
industry, HSAC and Helicopter Association Interna-
tional (HAI), the FAA installed an infrastructure of
ADS
−
B ground stations, weather stations (AWOS)
and VHF remote communication outlets (RCO)
throughout a large area of the Gulf of Mexico. This
infrastructure allows the FAA’s Houston ARTCC to
provide “domestic
−
like” air traffic control service in
the offshore area beyond 12nm from the coastline to
hundreds of miles offshore to aircraft equipped with
ADS
−
B. Properly equipped aircraft can now be
authorized to receive more direct routing, domestic
en route separation minima and real time flight
following. Operators who do not have authorization
to receive ATC separation services using ADS
−
B,
will continue to use the low altitude grid system and
receive procedural separation from Houston ARTCC.
Non
−
ADS
−
B equipped aircraft also benefit from
improved VHF communication and expanded
weather information coverage.
3.
Three requirements must be met for operators
to file IFR flight plans utilizing the grid:
(a)
The helicopter must be equipped for IFR
operations and equipped with IFR approved GPS
navigational units.
(b)
The operator must obtain prior written
approval from the appropriate Flight Standards
District Office through a Letter of Authorization or
Operations Specification, as appropriate.
(c)
The operator must be a signatory to the
Houston ARTCC Letter of Agreement.
4.
Operators who wish to benefit from ADS
−
B
based ATC separation services must meet the
following additional requirements:
(a)
The Operator’s installed ADS
−
B Out
equipment must meet the performance requirements
of one of the following FAA Technical Standard
Orders (TSO), or later revisions: TSO
−
C154c,
Universal Access Transceiver (UAT) Automatic
Dependent Surveillance
−
Broadcast (ADS
−
B) Equip-
ment, or TSO
−
C166b, Extended Squitter Automatic
Dependent Surveillance
−
Broadcast (ADS
−
B) and
Traffic Information.
(b)
Flight crews must comply with the
procedures prescribed in the Houston ARTCC Letter
of Agreement dated December 17, 2009, or later.
NOTE
−
The unique ADS
−
B architecture in the Gulf of Mexico
depends upon reception of an aircraft’s Mode C in addition
to the other message elements described in 14 CFR 91.227.
Flight crews must be made aware that loss of Mode C also
means that ATC will not receive the aircraft’s ADS
−
B
signal.
5.
FAA/AIS publishes the grid system way-
points on the IFR Gulf of Mexico Vertical Flight
Reference Chart. A commercial equivalent is also
available. The chart is updated annually and is
available from an FAA approved print
provider
or
FAA
directly, website address:
http://www.faa.gov/air_traffic/flight_info/aeronav.
10
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1
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5. Departure Procedures
a.
When departing from a location on a point
−
in
−
space (PinS) SID
with a visual segment
indicated and the departure instruction describes the
visual segment the aircraft must cross the initial
departure fix (IDF) outbound at
−
or
−
above the
altitude depicted on the chart. The helicopter will
initially establish a hover at or above the heliport
crossing height (HCH) specified on the chart.
10
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1
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6
Helicopter IFR Operations