Navigation by ADF
and information on the aircraft compass
Navigation by ADF using NDBs
This section covers the basics of navigation by ADF (the instrument in the aircraft) using non-diirectional beacons (NDBs - the navigational aid transmitter on the ground) - everything you need to know can be found here: Navigation by ADF
You may also find the Elite Premair video series on navigation by ADF helpful - you can view each of the videos in the series here: Video Series - NDB Navigation Note that videos ONE and TWO are the SAME as those two videos in the VOR navigation series so if you have already viewed those for the Navigation by VOR lesson then you can skip them.
Much of the ADF navigation in the US today is limited to NDB approaches and other near-facility uses. NDBs have little use for cross-country navigation in the US but there are still some high power stations in the western US and Alaska. In other countries there are a good number of high-powered stations remaining and NDB approaches are quite common in some areas. So, it may be of interest to you to view this video of a non-precision approach using NDB - NDB Approach The ADF needle is the blue needle in the Lear 45 PFD / EHSI - the green needle is the heading indicator is used as a reference and is set to the actual runway magnetic heading (a nice trick to provide you some information that will help keep you oriented). NOTE: You will NOT be tested on anything in this video outside the basics for the lesson outlined in the document.
PAY VERY CLOSE ATTENTION to the fixed-card display that is used in the Cessna 172 shown on pages 5 and 12 of the Navigation by ADF document. This DOES NOT have a compass card that rotates to the actual heading so YOU have to rotate this to coincide with your current or desired compass heading (or do the math in your head to understand the actual bearing to the NDB).
This section provides some basic information that all pilots should know (along with how to navigate and pilot an aircraft using basic instruments alone) about how to use the magnetic compass in an aircraft. The key principles to understand are:
How to correct for magnetic declination - or, how to determine the magnetic heading that will result in a desired true heading
How a compass behaves when you make a turn or when you accelerate or decelerate
Compass deviation due to all the metal and electronic stuff in your aircraft
Understanding #2, above, why you reset your gyro compass only in straight and level flight
A word about gyro compasses:
Larger, more sophisticated aircraft have a device called a flux gate compass which can provide information to the heading indicator (AKA gyro compass, although this is somewhat of a misnomer) to keep it set to the proper magnetic heading. A flux gate can also be found in some smaller aircraft as part of the heading indicator itself. Without this correction the heading indicator drifts from the correct heading. This occurs due to two primary factors - the earth's rotation (about 15 degrees per hour) and internal friction and other mechanical factors. So, in the absence of a flux gate to correct the heading indicator for these factors periodic resetting of the heading indicator (recommended to be done every 10 to 15 minutes) is required. The pilot does this by referencing the reading from the magnetic compass (and can incorporate the compass deviation correction for the direction of flight) to reset the heading indicator to the correct heading.
Read and understand at least one of the two articles shown below, These cover the same information and are both from reliable sites that contain other valuable information.
You might also find this article from AOPA interesting (and, AOPA is another excellent source of aviation information and eduation) that gives some insight into the value of understanding compass navigation - like we said: Can you get home if all your electronic systems fail??