NDBs and VORs are both radio beacons, but function very differently.
The VOR is a beacon that projects 360 separate radio beams, one in every compass degree. Each beam is called a radial. The bearing indicator in the cockpit can differentiate between the radials and tell you which one you are currently on. For example, let's say that you started over the VOR and flew directly north. If you had the bearing indicator in the cockpit tuned to receive the 360 degree radial, then the dial would remain in the center of the instrument. However, if you then changed and began to fly at a heading of 005 degrees, the needle in the instrument would move to the left because the 360 degree radial would be to your left (imagine the radials as painted lines on the ground radiating from the VOR in every direction). Often planes navigate from VOR to VOR, but there are also thousands of imaginary navigational fixes that planes may use as waypoints in their flight plan. Each of these imaginary points is the meeting point between certain VOR radials. For example, the waypoint "CYPER" in New York does not have a VOR or NDB, but it is defined as the meeting point between the 222 degree radial of the Albany VOR and the 127 degree radial of the Rockdale VOR. Therefore, if a pilot has both of the VHF receivers tuned to those VORs and one of his bearing indicators tuned to the right radials, when the needles are centered he or she knows that they are at the CYPER waypoint. In addition, most VORs are equipped with distance measuring equipment. That means that if you have the right system in your plane, the VOR can tell you how far you are from it. VORs also have substantially more range that NDBs.
NDBs are much simpler. The NDB dial in most planes looks just like a compass. When you tune in to an NDB frequency, the needle points toward the NDB. All you have to do is make sure the needle is pointing straight up and your know you are flying right toward the NDB. NDBs do not have radials or anything complicated like that. Also, few NDBs are equipped to provide distance information.
Most airliners usually use VORs or imaginary waypoints to navigate. If a plane has GPS or an inertial navigation system, it doesn't even need to tune in to the VORs to pick up their radial beams, since it already knows where it is in space and what direction it needs to fly to get there. Some older airliners, like old DC-9s or 737s do not have inertial navigation systems and still need to use the radio beams to navigate, but few airliners like that are still flying. Really, the only time that an airliner might use an NDB is when landing. Most runways with ILS have an NDB positioned about 5 miles away, in line with the runway. You can fly toward that NDB to pick up the ILS.
The FAA has already began taking down some of the more useless NDBs, and they will likely all dissapear within a few year. The VORs are still more valuable, but useless to planes with GPS or inertial navigation systems. They, too, will likely be taken down by the FAA as soon as GPS becomes the primary mode of navigation for most pilots.
NDBs และ VORs มีเบคอนทั้งวิทยุ แต่ฟังก์ชันแตกต่างกันมาก The VOR is a beacon that projects 360 separate radio beams, one in every compass degree. Each beam is called a radial. The bearing indicator in the cockpit can differentiate between the radials and tell you which one you are currently on. For example, let's say that you started over the VOR and flew directly north. If you had the bearing indicator in the cockpit tuned to receive the 360 degree radial, then the dial would remain in the center of the instrument. However, if you then changed and began to fly at a heading of 005 degrees, the needle in the instrument would move to the left because the 360 degree radial would be to your left (imagine the radials as painted lines on the ground radiating from the VOR in every direction). Often planes navigate from VOR to VOR, but there are also thousands of imaginary navigational fixes that planes may use as waypoints in their flight plan. Each of these imaginary points is the meeting point between certain VOR radials. For example, the waypoint "CYPER" in New York does not have a VOR or NDB, but it is defined as the meeting point between the 222 degree radial of the Albany VOR and the 127 degree radial of the Rockdale VOR. Therefore, if a pilot has both of the VHF receivers tuned to those VORs and one of his bearing indicators tuned to the right radials, when the needles are centered he or she knows that they are at the CYPER waypoint. In addition, most VORs are equipped with distance measuring equipment. That means that if you have the right system in your plane, the VOR can tell you how far you are from it. VORs also have substantially more range that NDBs. NDBs are much simpler. The NDB dial in most planes looks just like a compass. When you tune in to an NDB frequency, the needle points toward the NDB. All you have to do is make sure the needle is pointing straight up and your know you are flying right toward the NDB. NDBs do not have radials or anything complicated like that. Also, few NDBs are equipped to provide distance information. Most airliners usually use VORs or imaginary waypoints to navigate. If a plane has GPS or an inertial navigation system, it doesn't even need to tune in to the VORs to pick up their radial beams, since it already knows where it is in space and what direction it needs to fly to get there. Some older airliners, like old DC-9s or 737s do not have inertial navigation systems and still need to use the radio beams to navigate, but few airliners like that are still flying. Really, the only time that an airliner might use an NDB is when landing. Most runways with ILS have an NDB positioned about 5 miles away, in line with the runway. You can fly toward that NDB to pick up the ILS. The FAA has already began taking down some of the more useless NDBs, and they will likely all dissapear within a few year. The VORs are still more valuable, but useless to planes with GPS or inertial navigation systems. They, too, will likely be taken down by the FAA as soon as GPS becomes the primary mode of navigation for most pilots.
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