At what altitude is the VOR service volume 100 nautical miles valid?

The correct answer is based on the service volume specifications of VHF Omnidirectional Range (VOR) navigational aids. The VOR service volume is determined by the altitude at which the VOR can provide reliable navigation signal coverage. For a VOR, the range within which it can be expected to provide reliable service is 100 nautical miles when the aircraft is at altitudes between 1,000 and 14,500 feet AGL (Above Ground Level).

This altitude range reflects the operational design of VOR systems, which are most effective in lower altitudes where obstructions and terrain interference are less of a factor. At higher altitudes, although VOR signals can still be received, the service range can extend beyond 100 nautical miles for VORs, but the specific question asks for the valid range at which the 100 nautical mile service volume applies directly.

Therefore, this altitude range is crucial knowledge for pilots operating under IFR conditions, as it helps determine how far away they can rely on a VOR for navigation. Understanding this ensures that pilots can effectively use VORs for their navigation, particularly during approaches and en route phases of flight.