Radio Navigation And On Route Procedures     Lesson 5

We left the last lecture approaching Southampton VOR. This lecture will teach you about the VOR and Radio Navigation. The Pilots en route procedures are also covered . Firstly I will discuss what a VOR is. I will then discuss what an  NDB beacon is.  I will discuss what the ILS is in the landing lecture later in the series.


The VOR is a radio beacon with a range of about 200 miles. VOR stands for omni directional radio range equipment . If it has a distance measuring facility then it is known as a VOR/DME. They are accurate to about 2 degrees. Terrain can distort the signal . There are various types but I am not going to confuse you. The beacon works on VHF frequencies  between 108 and 118mhz . Voice for ATC then starts at 118 to 136Mhz.

The VOR is put in various locations around the world. Lines are then drawn  between the VORS and that is how the centre line of an airway becomes established. The lines that come from a VOR are known as radials. Equipment on the aircraft can detect which radial it is on . If it is a VOR DME it can also give you a distance to the VOR tuned. As we know the compass has 360 degrees so therefore a VOR has 360 degrees of radials. The easy way to picture this is a bicycle wheel  with the VOR being in the middle with all the spokes going out. These spokes being the radials. If you are flying towards a VOR then it is on the inbound radial.  If flying away from the VOR it is known as the Outbound radial .

 The inbound radial heading is therefore 180 degrees to the radial. you are on, so if you was told to track inbound to a VOR on the 180 radial and you were flying from the South  you would therefore be flying a heading of 360 degrees. If you was told to fly inbound from the North to on the 360 radial to the VOR then your heading is 180 degrees. If you was told to leave a VOR outbound on the 330 Radial then your heading would be 330 degrees.

Taking this a step further, we talk about reporting points on route. If the VOR has a triangle on the chart then that is a reporting point . The pilot should tell Air Traffic Control when he is over it. Sometimes these reporting points are not on a VOR but in the middle of nowhere. ORTAC is one of those waypoints. VOR identity is always a 3 letter identity.  Waypoints are 5 letters identity. ORTAC  is on a track from Southampton VOR  outbound on the Southampton 208 radial at 63 dme (distance measuring equipment)  Once the pilot has set the VOR instrument up correctly to the track and the moving needle is in the centre when he has got to 63 DME he has got to ORTAC. In Some cases the waypoint is reached by having a radial cross your outbound track from another VOR. (The crossing point being the waypoint.)

I will now discuss how we set up the VOR to track the correct radial and how the instrument works. Firstly you need to find the frequency of the beacon by looking in the flight plan log. You should have  this printed out . In this case Southampton is 113.35 so this needs to be set up in the radio box number 1 our next point after ORTAC is Guernsey VOR we can set that up into radio box number 2. The frequency is 109.40. If we are in range the needle on Nav 2 which is the bottom left  instrument will swing and point towards Guernsey and if it is a VOR/DME will give out the distance to it. All the pilot would have to do is turn the aircraft so the needle is pointing to 12 O clock and the pilot will fly the correct course to the beacon. 

The track to Guernsey from ORTAC is 220 degrees the pilot can monitor this instrument and can read the heading to Guernsey at anytime. Going back to the 2nd bottom left instrument we need to set the instrument up ready for the track on leaving Southampton VOR . What you need to do then is turn the heading bug on the autopilot until the little heading bug on your compass is facing Twelve o clock and switch from  GPS to NAV and disconnect the white NAV button and engage the heading bug. Now set your course to 208 on the course indicator of the autopilot by clicking on it. As we get to 2 miles DME from Southampton start a left turn with 25 degrees maximum bank until the aircraft settles onto a track of 208  outbound from the Southampton VOR . Reset your heading bug to 208. Disconnect the heading bug in the turn, only reselect  it when rolled out on the 208 heading.

A good tip is to start rolling the aircraft level about 5 degrees before the heading required to stop at.  If not you will have to go the other way and zig zag . Hopefully the needle in the middle of the compass will be in the centre of the instrument . You will notice that in the middle of the compass is a little white arrow this should be now pointing down to indicate the VOR is behind you. If the needle is over to the right then you may have to alter to a heading of 213 to get the needle back into the centre. You will  then turn back onto 208 as the needle centres . You can then switch back to NAV mode again. The dots to the left or right of the centre of the compass indicate 2 degrees each. Therefore from far left to far right of the instrument is 10 degrees. All the time the needle is in the centre you are on course. If of course turn in the direction of the needle to correct it.

As you get to about 40 miles from SAM VOR change your radio nav frequencies round so that frequency 2 is in 1 box etc and one is in 2. Now go to heading mode again on the autopilot whilst you do this. Now set the VOR course indicator to 220 ready for tracking into Guernsey. You will note the needle is over to the left as the needle starts to move ,turn right and fly a heading of 220 to Guernsey. Again correcting five degrees to get the needle in the centre. You always turn in the direction of the needle. Note the closer you are to the VOR the faster the needle moves. We then fly into the Guernsey VOR and repeat the whole process of tracking outbound to the next VOR . This happens for the whole route.

I will touch on NDB beacons here. This stands for Non Directional Beacon they work on the principle of the instrument in the bottom left hand corner the needle always pointing to the beacon. They are affected by lightning and also if near the coast water as well. Both VOR and NDB can be affected at night. as well so you have to be aware of that.

The  NDB receiving ranges varies but maximum would be about 100 DME.  These are found on airfields or approaches to airfields . The ones on approaches are often called locators indicated by L on the chart .

 If a runway was on a track out from a NDB of  220 degrees, you would try and get the  to the opposite side of the beacon from the airport at an angle of 45 degrees . As the needle indicated the heading  of 220  you would turn and fly inbound  to the beacon on a 220 degrees heading.  After over flying the beacon you would keep on the heading of 220  straight onto the runway . 

The NDB is normally about 4 miles away from the runway . The blue light will go off as you cross the beacon. If it is an ILS approach at this point the pilot would start the stop watch if he was in cloud and fly for the elapsed time, descending to decision height. If the pilot could not see the airport the pilot  would have to go around for another attempt or divert to an airfield with better weather. More on this aspect later in the course.

 The Maximum Bank you ever need to do in turns  with an airliner is 25 degrees indicated here.
The lines on the top indicate 10 degrees  of the bank angle. The pitch angle is 5 degrees here.
You will soon learn the skill of anticipating when to turn onto the correct radial.

The picture above shows the Guernsey VOR 10 degrees off to the right on the RMI instrument  ( left  instrument of the picture) It also shows that we are to the right of track leaving Southampton VOR  7. 5 miles behind us on the right hand instrument.We need to steer left to get the needle in the middle we are therefore heading 202 degrees until the needle centres we then turn back to 208 degrees.

This picture above  shows we are on course to ORTAC 

As we get near ORTAC we can tune both VOR radios  to Guernsey VOR 109.4 set the course from ORTAC to Guernsey which is 220  then when the needle settles in the centre we turn heading 220 inbound to Guernsey 2 miles from Guernsey we repeat the whole process whole again and again until we arrive at destination. As we cross  ORTAC the GPS Screen on the right will change to Guernsey automatically.  If we were using GPS the aircraft would turn itself and fly to GUR VOR.  We can check the distance to ORTAC on the GPS instrument.

We are well onto the route now  so we  can now look into the routine of the pilots.

 One pilot is deemed pilot flying the other non pilot flying this role will change on the return flight . The non pilot deals with the paper work, handles and assists the flying pilot by changing the radio frequencies and talking to Air Traffic Control . Both pilots monitor each other. At this point I will bring in about Safety Heights. This will be known to the pilots from the start of the flight. For the take off phase they also will be aware where high ground is in case of a forced landing. Also  what obstructions  are in the airport vicinity. 

Obviously flying across the Bay of Biscay safety height is 1000 ft above sea level .  When flying over the coast of Northern Spain it will become mountainous all the way down the flight path to Malaga.  Pilots need to be aware of the safety height at all times, especially if it was bad weather and the mountain tops are hidden in full cloud. 

The  757 cruises at Mach .82 normally. The pilots on route will be monitoring the weather from ATIS or Volmet  weather  broadcasts for all the airports on route.  Pilots watch the weather radar for thunderstorms or heavy build ups to avoid.. At some point they will plan their descend point and look at the Standard Arrival charts for Malaga. They also maintain a time log over waypoints.

The Descent Point  

The descent point  would be about 150 miles out from the destination airport for  the descent from FL350 . It is about  20 minutes out at a rate of descent of 2000ft per minute.  Obviously Air Traffic Control may start descending the aircraft early to fit in with the traffic situation . At some point the pilots will speak to their handling agents at Malaga giving the agent arrival information . Advice of ETA and any problems or wheelchair passengers .  The agent gives the stand number to park on to the pilots . The pilots would also have contacted their ops base after take off on a company radio frequency and given them a progress report  . A lot of this can be done by the ACARS reporting system by satellite and computer on the aircraft and ground.
 
Most Aircraft are fitted with TCAS  collision warning system and pilots monitor that throughout the route . It is not uncommon to see aircraft passing below or above you at 1000 ft intervals, that is why it is important not to deviate in height . At this time we will end the lecture and carry on in the next one with the approach and landing. 

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