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Radio Navigation NDB Radio Beacons So far I have taught you to fly an aeroplane correctly and to navigate across country without using any radio navigation equipment. The next part of the course will teach you how to use the radio navigation instruments, when we get into the air we can then fly in clouds or bad weather, and know where we are without seeing the ground. If you want to just go and fly for an hour, you do not have to worry about flying on instruments. If the weather had closed in you would not go up anyway. Perhaps though you would like to fly from England to France for the day, going in the morning and coming back in the evening. You could not guarantee the weather will be suitable for your return flight. Then you may find yourself stranded for days until it improves. By learning to fly on instruments and radio navigate you could then guarantee to return unless the weather is really severe. Remember for you to be able to fly in controlled airspace you require an instrument rating. NDB The first type of radio beacon used is a Non Directional Beacon known for short as NDB I will now explain what an NDB is, and how it works . There are some things you need to know about NDB s for your safety. The NDB is a ground base radio transmitter that transmits a signal in all directions thus given it its name. The aircraft is fitted with Automatic Direction Finding Equipment known as ADF. The pilot can look at an air chart and find these beacons and the frequency . Each beacon transmits on a different frequency . The pilot then tunes his ADF equipment into the beacon. The needle on the ADF gauge will point to the beacon if it is in range and a signal is received. The ADF equipment consists of a moveable needle that points to the beacon tuned. The gauge has a compass clock background underneath the needle. From this the pilot can work out the heading he has to fly to the beacon. The early form was the compass did not move and maths were required to work out the heading by adding or subtracting the distortion angle of the needle to the heading being flown. Now days the pilot sets the the compass card up like the DI. this type of instrument is known now as the RMI Radio Magnetic Indicator this gives an instant heading reading. it is alson known as a slaved gyro.
Remember the needle always points to the beacon. SO all the pilot has to do to fly to the beacon is make sure the needle is pointing to Twelve O Clock on the instrument and you will get to the beacon the pilot has to turn the aircraft in the direction of the needle until it becomes at 12 o clock which is then pointing over the nose of the aircraft. That said beware below ADF equipment can be affected by lightening in the area and give a false reading by the needle swinging towards the storm. Distorted signals can also be received due to Mountains and Coastal effects. Also other nearby NDBs can affect it. Dawn and Dusk are the worst times for this. Each beacon transmits a Morse code identity so the pilot can check he or she is tuned to the correct beacon. If no Morse code is received the beacon should not be used even though it may be transmitting. Range The range of a NDB varies, in the Pacific for example it could be 400 miles. Around the UK it could be 100 miles or less. Sometimes these NDBs have only a few miles and are part of an instrument approach procedure to an airfield. An NDB on an airfield approach between 3 to 4 miles out is often called a Locator. These beacons have a very low range. As the aircraft crosses over these type of beacons directly above it, it sets off the Blue light and a tone is heard. This tells the pilot to start his stop watch for a final approach. This is often called the Outer Marker a similar beacon goes off about 2 miles out called the Middle Marker and a tone is heard. The inner marker beacon is being phased out. Airways and Airport Approaches Airways can be defined using an NDB. The pilot has to then work out how to position the aircraft so that he stays on the centre line. This may mean initially the pilot will fly 30 degrees off course. As the needle moves around eventually to the heading required the pilot then turns the aircraft to the heading required. The needle will either point to twelve O clock if going to the NDB or six O clock if flying away from the NDB.. If you are getting wind drift this will be corrected for by the pilot the needle now will point to the degrees wind drift from the 12 or 6 O clock position.
Let us say that the runway we are going to land on is runway 02. The approach heading to fly down the runway is 018. The pilot would therefore aim off from the beacon until the heading to the beacon is 018 as shown on the top gauge. The pilot would then turn the aircraft onto a heading of 018. He would then be able to line up on the runway centre line, (even in cloud as he let down to land) If the pilot has done it correctly as the aircraft comes out the bottom of the cloud the runway should be directly in front. The needle would have started in the 1 O clock position and gradually moved clockwise as the aircraft moved along. You now know what an NDB is You now know how to use the ADF You now have had an introduction to an NDB Approach for landing This will be learnt later in full detail
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