Aviation Theory

From AIM 1-1-8. NAVAID SERVICE VOLUMES

1. Most air navigation radio aids which provide positive course guidance have a designated standard service volume (SSV). The SSV defines the reception limits of unrestricted NAVAIDs which are usable for random/unpublished route navigation.
    
2. A NAVAID will be classified as restricted if it does not conform to flight inspection signal strength and course quality standards throughout the published SSV. However, the NAVAID should not be considered usable at altitudes below that which could be flown while operating under random route IFR conditions (FAR Part 91.177), even though these altitudes may lie within the designated SSV. Service volume restrictions are first published in the Notices to Airmen (NOTAM) and then with the alphabetical listing of the NAVAIDs in the A/FD.
    
3. Standard Service Volume limitations do not apply to published IFR routes or procedures.
    
4. VOR/DME/TACAN STANDARD SERVICE VOLUMES (SSV)
1. Standard service volumes (SSVs) are graphically shown in Figure 1-1-1, Figure 1-1-2, Figure 1-1-3, Figure 1-1-4, and Figure 1-1-5. The SSV of a station is indicated by using the class designator as a prefix to the station type designation.

Figure 1-1-1
Figure 1-1-2	Figure 1-1-3

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Figure 1-1-4


Figure 1-1-5

EXAMPLE: TVOR, LDME, AND HVORTAC

2. Within 25 NM, the bottom of the T service volume is defined by the curve in Figure 1-1-4. Within 40 NM, the bottoms of the L and H service volumes are defined by the curve in Figure 1-1-5.
    
5. NONDIRECTIONAL RADIO BEACON (NDB)
1. NDBs are classified according to their intended use.
2. The ranges of NDB service volumes are shown in Table 1-1-2. The distances (radius) are the same at all altitudes.

  Table 1-1-2 - NDB Service Volumes
  ----------------------------------
     Class         Distance (Radius)
  ----------------------------------
   Compass Locator   15 NM
    MH               25 NM
    H                50 NM*
    HH               75 NM
  ----------------------------------

* Service ranges of individual facilities may be less than 50 nautical miles (NM).
Restrictions to service volume are first published in the Notice to Airmen and then with the alphabetical listing of the NAVAID in the Airport/Facilities Directory.

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