Final answer:
VOR receiver checks specified in Federal Aviation Regulations 91.171 involve a series of tests such as ground checkpoint test, airborne checkpoint test, dual VOR comparison, and VOT test to ensure VOR system accuracy for navigation.
Step-by-step explanation:
According to Federal Aviation Regulations (FAR), specifically 91.171, certain VOR receiver checks must be performed to ensure the accuracy of the equipment used for navigation. These checks are essential for aircraft that rely on VHF Omnidirectional Range (VOR) systems for navigation.
The VOR receiver checks required under 91.171 include:
- A ground checkpoint test, which should be done at a designated location on the airport, and the VOR receiver should indicate within plus or minus four degrees of the published radial.
- Airborne checkpoint test, which involves checking the VOR receiver accuracy at a designated airborne checkpoint location within plus or minus six degrees of the published radial.
- Dual VOR check comparing two VOR receivers against each other. The indicated bearings to a VOR ground station should not differ by more than four degrees.
- A VOT test using the FAA's VOR Test Facility, where the receiver should read 0 degrees when on the radial aligned with the course selector set to the TO position, or 180 degrees when to the FROM position, with a tolerance of plus or minus four degrees.
- If no ground or airborne checkpoints are available, a selected radial from a VOR ground station received at a known ground point more than 20 nautical miles from the station can be used with a maximum allowable deviation of plus or minus six degrees.
These periodic checks are necessary to maintain the reliability and safety of instrument navigation. Pilots must ensure these checks are recorded as described by the regulations.