Use of GPS in Lieu of DME

Use of Suitable Area Navigation (RNAV) Systems on Conventional Routes and Procedures.

For complete details refer to: Advisory Circular 90-10 Date: 3/3/11  This circular provides guidance regarding the suitability and use of RNAV systems while operating on, or transitioning to, conventional, i.e., non-RNAV, routes and procedures  within the United States (U.S.) National Airspace System (NAS) 

1. Use of a suitable RNAV system as a substitute means of navigation when a: VOR, DME, TACAN, VORTAC, VOR/DME, NDB, LOC),
— is out of service
— the NAVAID information is not available
— an aircraft is not equipped with an ADF or DME
— or the installed ADF or DME is not operational. 
 
EXAMPLE: If equiped with a suitable RNAV system,
a pilot may hold over an out-of-service NDB.
 
2. Use of a suitable RNAV system as an Alternate Means of Navigation when a (VOR, DME, TACAN, VORTAC, VOR/DME, NDB, LOC),
— is operational
— the aircraft is equipped with operational navigation equipment that is compatible with conventional NAVAIDs. 
 
EXAMPLE: If equipped with a suitable RNAV system,
a pilot may fly a procedure or route based on
operational VOR using the RNAV system without monitoring the VOR.
 
3. Suitable RNAV system are installed in accordance with appropriate airworthiness installation requirements:
— TSO-C129/-C145/-C146 equipment … authorized for IFR en route and terminal operations (including those systems previously qualified for “GPS in lieu of ADF or DME” operations.
 
4. Usage of Suitable RNAV systems:
— Determine aircraft position relative to or distance from a VOR, TACAN, NDB, compass locator, DME fix, or named fix defined by a VOR radial, TACAN course, NDB bearing, or compass locator bearing intersecting a VOR or Localizer (LOC) course.
–Navigate to/from a VOR, TACAN, NDB, or compass locator.
–Hold over a VOR, TACAN, NDB, compass locator, or DME fix.
–Fly an arc based upon DME.
 
5. Usage of Suitable RNAV systems NOT ALLOWED:
— Unless otherwise specified, navigation on procedures that are identified as not authorized (“NA”) without exception by a NOTAM. For example, an operator may not use a RNAV system to navigate on a procedure affected by an expired or unsatisfactory flight inspection, or a procedure that is based upon  a recently decommissioned NAVAID.
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