RNG PULL SCAN PUSH ON BRT PROC CRSR MSG OBS ALT NRST CLR ENT D MENU AMERICAS AERO Database Expires 15 FEB 2006 AMERICAS LAND Database  Created 06 OCT 2004 Acknowledge? Check the expiration data for the navigation database when the RNAV powers up. Figure 3-7. Checking the navigation database. FMS/RNAV Approval for IFR Operations NOTAMs Relevant to GPS GPS Signal Availability Navigation Database Currency Alternative Means of Navigation a check of these same requirements before operating under  visual flight rules (VFR) enhances safety and enforces good  habit patterns, which have been proven to greatly enhance  aviation safety. Only some FMS/RNAV units are approved for IFR navigation,  and it is important to make this determination before flying  with any particular unit. Sometimes, this limitation is based  on the installation (i.e., method of installation, qualifications  of installer), aircraft approval, availability of approved  maintenance, and geographic location. No hand‑held GPS  unit is approved for IFR navigation, and many panel‑mounted  units are restricted to VFR use only. The avionics operations manual/handbook should state the  certification status of the installed system. The supplements  to the AFM should state the status of the installed equipment, including the installed avionics. Most systems require that the  advanced avionics manuals be on board as a limitation of use. Even when an FMS is approved for IFR, the installation of  the system in that specific aircraft must also be approved.  Even if you have an IFR‑approved FMS unit, you may not  use it for IFR navigation unless the installation is approved  as well. This approval process usually requires a test flight  to ensure that there are no interfering inputs, signals or  static emanating from the aircraft in flight. RNAV units that  do not meet all of these requirements may still be used as  situation enhancing navigation resources when operating  under instrument flight rules. There are numerous notices to airmen (NOTAMs) that  apply specifically to users of navigation aids. For example,  when anomalies are observed in the behavior of the global  positioning system, or when tests are performed, a GPS  UNRELIABLE NOTAM is issued. Similarly, published  instrument procedures that rely on RNAV equipment  sometimes become “Not Available” when safety concerns  arise, such as ground‑based interference. It is important to  check all NOTAMs prior to IFR flights and, especially,  GPS and WAAS NOTAMs before flying. Remember, when  talking to a flight service station (FSS)/automated flight  service station (AFSS) briefer, you must specifically request  GPS/WAAS NOTAMs. The first place to check when determining IFR certification  for an FMS is the Pilot’s Operating Handbook (POH) or  Aircraft Flight Manual (AFM). For every aircraft with an  IFR approved FMS/RNAV unit, the AFM explicitly states  that the unit has been approved for IFR navigation and what  IFR operations are specifically authorized for that installation. The navigation database contained in the FMS must be  current if the system is to be used for IFR navigation and  approaches. Some units allow en route IFR operations if the  navigation waypoints are manually verified by the pilot and  accepted. The effective dates for the navigation database  are shown on a start‑up screen that is displayed as the FMS  cycles through its startup self‑test. Check these dates to ensure  that the navigation database is current.  Figure 3-7  shows the  start‑up screen and effective dates for one popular FMS. GPS‑based RNAV equipment that uses the DOD GPS relies  on adequate signal reception throughout the course of a  flight. Signal reception becomes especially critical during  instrument approaches when signal reception criteria become  more stringent. Signal reception is generally predictable, and  you can request information on likely signal reception for  the destination airport in the preflight briefing from Flight  Service. Many GPS RNAV units include a feature called  receiver autonomous integrity monitoring (RAIM) that  allows you to view predictions about future signal reception  at specific locations. WAAS-enabled receivers do not have  this restriction or limitation due to the error corrections  available from the WAAS. WAAS is a form of differential  GPS (DGPS) providing enhanced position accuracy. Each  Wide Area Reference Station (WRS) provides correction  data to a Wide Area Master Station (WMS), which computes  a grid of correction data to be uplinked to a geostationary  satellite (GEO) from a Ground Earth Station (GES). The  geostationary satellite transmits the correction data (and  also navigation data) to the user on the L1 GPS navigation  To use some GPS-based RNAV units (those certified under  Technical Standard Order (TSO) 129) for IFR flight, an  aircraft must also be equipped with an approved and alternate  means of IFR navigation (e.g., VOR receiver) appropriate  to the flight. Ensure that this equipment is onboard and  operational, and that all required checks have been performed  (e.g., 30‑day VOR check). 3-6