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VOR receiver against the radial designated on the sign. Listed below are the steps to use at a VOR checkpoint: 

1. Tune the proper VOR frequency. 

2. Identify the VOR frequency. 

3. Set the published radial on the course deviation indicator (CDI). 

4. Confirm that the TB is centered. 

5. Check the needle sensitivity by changing the omnibearing select (OBS) 10° each way. 

6. Set the reciprocal of the radial and check the TO FROM flag change. ­ 

7. The maximum permissible difference between aircraft equipment and the designated radial is 4° and 0.5 NM of the posted distance. 

## Dual VOR Check 

If a VOT or VOR checkpoint is not available and the aircraft is equipped with dual VORs, the equipment may be checked against one another by tuning both sets to the VOR facility at the same time and noting the indicated bearings to that station. [Figure 2-52] A difference greater than 4° between 

the two VORs indicates that one of the receivers may be out of tolerance. 

## Airborne VOR Check 

V fl r t o OR equipment can also be checked for accuracy while in ight by flying over a fix or landmark located on a published adial and noting the indicated radial. Variances of more han 6° from the published radial should be considered out f tolerance and not be used for IFR navigation. 

## NDB Accuracy Check 

T n f i s he pilot must identify an NDB before using it for avigation, and continuously monitor it while using it or an instrument approach. The lack of an IDENT may ndicate that the NDB is out of service, even though it may till be transmitting (for instance for maintenance or test purposes). If an incorrect IDENT is heard, then the NDB should not be used. 

## RNAV Accuracy Check 

RNAV accuracy checks may differ depending on the different type of equipment and manufacturer. When available, all written procedures should be followed. 

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