By the way, Mark, I've been doing a lot of flights with VOR navigation and I've discovered that the closer you get to the VOR, the closer the reading is to the GPS. I'm not sure of the exact distance-to-offset ratio, though.

The VOR!




vans...you can do this, but only if you want!  

Each radial has width. As you fly out from the station the one degree of arc gets wider.
At 60 miles from the station a degree is one mile wide. At 120 miles it grows to 2 miles wide.
Adding to any error is the OBS knob. If you are a bit sloppy in putting in the exact degree of
selected radial or there is a bit of slop in the knob itself you can see how the accuracy of navigation begins to slip.  



Flying from VOR to VOR or VOR to an intersection is pretty easy, and was all we had back in the 60's.

If you think using the VOR is hard, you should try flying a radio range!   No sissy pilots here!



Lou

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Quick look at ADF

The most under used instrument in the modern day cockpit is the ADF. Back in the days of the early jets, the ADF (automatic direction finder) was a very valuable navigation tool.
Now in the days of moving maps, IRS and GPS the term NDB leaves some pilots with a blank stare.
NDB stands for non directional beacon. Another term pilots of the early jets used was "bird dog" since on a fixed card instrument the needle shows only relative bearing.
Even the term fixed card is not exact since the card with the printed compass can be turned by the pilot.
It wasn't until the addition of a remote driven compass card that the instrument was called the ADF.

This is a fixed card DF (direction finder) or "bird dog." The knob allows the pilot to move the non-north seeking compass card to the planes current heading.
By moving the card to the current heading it makes the math a bit easier.


A true ADF has a feed from a compass source that automatically turns the card to the correct heading making it an automatic direction finder.  
This is the ADF instrument in the CS 707-300. There are two needles and two source selections so the pilot can display either NDB or VOR information from the left or right set of radios.


In the above picture the two lower knobs are selected to the ADF position. When there is no signal the needles go to a parked three o'clock position on the instrument.

In the 707 the control head for the ADF is located on the pilots overhead position. The 727 has the control head down on the center pedestal.
The control head for the ADF consist of several knobs and switches.



The selector knob on the lower left is the main ON-OFF switch.
First position is ADF. This allows the unit to display the bearing to the station.
The next position is ANT (antenna). This position is used to listen to a radio station without bearing information.
Last is the LOOP position, used in conjunction with the LOOP knob to electronically turn the loop antenna for non automatic bearing information. Next to the LOOP control is the BFO (beat frequency oscillator). This is used when the signal strength is weak or there is a lot of noise. The BFO acts as a whistle tuner to help get the station on frequency.

The window displays the selected frequency under the lubber line. Later units with digital tuning were much easier to tune.

The tune knob is all the way on the right side of the control head. It has 3 bands that can be selected by moving the lower collar. The upper knob moves the numbers in the window. In FSX tuning the ADF can be a bit of a chore, so use the mouse, as I show above, to show what exact frequency you have dialed in. Just float the mouse cursor over the TUNE knob and a window will appear with the selected frequency.



Next I want to show a map with multiple plane positions during vectoring for an approach to KIAD RW1R.



This is the map in FSX. By mousing over items on the map you can identify all the items and frequencies and courses for various approach aids in the area.






Using the ADF to display the TILLY LOM/NDB as the plane flies the pattern, the relative magnetic position is displayed in the ADF instrument.



Position 1 shows the plane on a west heading entering the traffic pattern at KIAD.
The ADF needle is pointing at the LOM/NDB called TILLY and identified by the two letter code IA - frequency 346.0 in red on the map.

In each position, you will see the airceaft heading and the relative bearing of the LOM/NDB. (Low frequency Outer Marker)  

The ADF is a great tool to use to keep track of where you are in the area of the airport. Sure, there is no DME, but the relative bearing to the outer marker in this case gives the pilot a ton of information and improves situational awareness in the pre-moving map days.

Use the numbered positions of each plane to see what the instrument would display using the outer marker. As you turn base in Fig. 5 you can see how close to the final turn you are by the bearing change as you fly west. Using the ADF you can vector yourself because you know where you are relative to the marker.

Between plane 6 & 7 I show a display with the ADF needle pointing a bit to the right. This shows wind drift. Even though the planes heading is still lined up to the north the plane is drifting to the west because of an east wind. All the pilot need to do is make a correction to the right to counter the wind and get back on course as is shown in position 7.

As you pass the station (marker) the needle will point to the tail of the plane since it is showing the relative position of the marker.

Practice a bit with the ADF and if you like to fly the old planes as they were flown in the past, you will find the ADF to be invaluable.



Lou

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