Ground Based Navigation Aids (Private Pilot)
Beginner pilots should become familiar with both VFR ground based navigation systems and ground reference points when learning to fly in case of a radio failure or failure of the navigation systems.
There are three types of radio navigation systems that can be used for VFR flight.
VOR - VHF Omnidirectional Range
NDB - Nondirectional Radio Beacon (NDB)
GPS - Global Positioning System
VHF Omnidirectional Range or VOR is designed in three different types of navigation aids (NAVAIDs).
VOR - Is a VOR by itself.
VORDME - VOR/DME (Distance Measuring Equipment)
VORTAC - VOR/TAC (TAC short for TACAN -Tactical Air Navigation for military use)
On all types of aeronautical sectional charts, such as VFR sectional or IFR sectionals, every VOR will have an information box.
The Omnidirectional means a VHF radio transmitting a straight line courses, known as radials from a ground based station and the "Omni" means all VOR stations.
Each radial transmission from the station is projected as a magnetic bearing from 001 or 1° east in a circle to 360° representing a compass rose on a aeronautical sectional chart.
VOR's transmit a VHF frequency that has a line-of-sight restriction. The reception range is generally about 40 - 45 miles depending on the type of VOR, starting at an altitude of 1,000 feet AGL. There are three different types of VOR and VORTAC stations, they are:
T - (Terminal) with a range of 25 miles and 12,000ft and below.
L - (Low altitude) with a range of 40 miles and 18,000ft and below.
H - (High altitude) with a range from 130 - 40 miles and 60,000ft to 14,500ft.
The accuracy of VOR radials is excellent, within +-1°, but there are a few internal parts of VOR instruments that can affect the accuracy. To be sure that the VOR instruments in the aircraft are reading accurate pilots should do a VOR check, even though the check is not required for VFR flight. There are three types of checks that can be done, they are:
FAA VOR test facility (VOT)
Certified airborne checkpoints
Certified ground checkpoints, located on the airport surface
If the aircraft has two VOR instruments installed a dual VOR check can be accomplished. To check this simple tune both receivers to the VOR frequency. Maximum variation between both VOR receivers is 4°.
Identify the VOR inflight
If a VOR station is out of service or undergoing maintenance, the Mores code identification is removed from the transmission. Pilots should not use the station for navigation purposes.
Identify the station first by listening for the Morse code identifier.
Remember, The VOR signal is line-of-sight.
When using a VOR for navigation, determine the inbound radial.
Many GA aircraft have an ADF radio receiver installed in them that use the radio signal form a Nondirectional Radio Beacons (NDB). NDB is another ground based navigation system used for navigation. Although it is an old system it is still used in few parts of the U.S and in many locations around the world.
NDB's do have an advantage over VOR's; the signal from an NDB does follow the curve of the earth unlike VOR's.
The standard radio broadcast station, the same one's used in your car to listen to music, etc. can also be used as an NDB for the ADF receiver in the airplane.
Global Positioning System (GPS)is a satellite-based navigation system. The GPS system is accompanied by the RNAV guidance which makes it a worldwide navigation system.
There are no symbols to identify a GPS on any aeronautical charts since the GPS satellites are a space based system.
The GPS satellites are operated by the Department of Defense (DOD).
To get status information for the satellites:
U.S Coast Guard navigation information service, 703-313-5907 or www.navcen.uscg.gov.
Also, satellite status will be available via a NOTAM.
There are 24 GPS satellites orbiting the earth on six different planes.
The GPS uses four satellites, three to give you an accurate location of your position, and the fourth one is used as a backup to the first three.
Student Pilots should not use GPS during flight training, recommended that Private Pilots and more experienced pilots use it.
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