ADF Flashcards
Automatic Direction Finder. They are slowly being phased out but still come up on the exam
What does an ADF do?
The ADF points you toward an NDB (non-directional beacon)
What is an NDB?
- Non-Directional Beacon
- A physical station on the ground that the ADF LF/MF tunes into
- Accurate to +-5° for approaches and +-10° for en route
In what frequency range do NDBs opperate?
- 190-415-510-535 Khz band
- Operate close to the AM radio band and your ADF can sometimes pick up AM radio stations
- Unlike VHF and UHF, NDB signals have both line of sight and a significant groundwave component. This allows reception at low altitudes and at long distances
How are non-directional beacons classed?
L: beacon has a power of less than 50W
M: 50 - 2000W
H: 2000W and higher
What are the limitations NDBs have?
- Night Effect
- Mountains
- Shorelines
- Electrical Storms
- Bank Error
- Ore Deposits
- Fading Effect
What is the Night Effect on NDBs?
Greatest at one hour either side of sunrise or sunset and at distances of more than 30NM from the station. The farther from the station, the greater the effect of Night Effect.
Minimize this effect by everaging the needle’s fluctuation, by flying at a higher altitude, or by selecting a station with a lower freqency.
How do mountains affect NDB signals?
How can shorelines affect NDBs?
Shorelines can refract or bend low-frequency radio waves as they pass from land to water. A pilot flying over the water should not use an NDB signal that crosses over a shoreline at an angle of less than 30°. Anything greater than 30° has little effect
How can an electrical storm (thundrstorm) or precipitation affect DNBs?
Your ADF will point towards bursts of lightning
What is Bank Error?
What are the advantages of ADFs?
- Low cost of installing an NDB (gives airports that otherwise wouldn’t be able to afford an instrument approach the ability to have one)
- Require low maintenance compared to ILS
- Provide greater range than VORs
Note: GPS is even cheaper
Diagram of typical newer ADF
What is the Bearing Indicator on your ADF and what does it do?
It displays the bearing to the NDB relative to the nose of the aircraft. It has nothing to do with my magnetic heading.
This means if I am flying directly to the station, my bearing indicator should read 0/360°.
If I am flying directly away from the station, my bearing indicator would read 180°
Where will the pointer on the ADF always point to?
It will always point to the beacon/station/NDB
How do you figure out what heading to fly to the NDB?
Add the bearing indicated on the ADF to whatver heading you are currently flying.
If the aircraft is flying 040° and the ADF is showing a relative bearing of 210°, then the heading to fly to the station is 250°
If you want to track outbound from an NDB, then you would use the reciprocal of the magnetic bearing to the station (BTS) that you just calculated.
If you add your MH and RB and get a number greater than 360, what do you do?
Subtract 360 from whatever the answer was.
In cases of no wind, keeping your ADF on the 0° heading will take you directly to the station. But what should you remember for real life where there is always winds?
You will kind of spiral around and take a potentially very long time to get there.
General procedure for using an ADF
How to get a time check and distance to station using your ADF
