by Jonathan M. Stern
Like the VOR approach, the NDB approach is a non-precision approach. No electronic glidepath information is provided. In fact, the NDB is generally the least precise approach procedure in terms of its course guidance. Some airlines consider it an emergency-use only procedure. Nonetheless, at many smaller airports, it provides the only IAP available.
One of the problems with NDB navigation is that its accuracy is completely dependent upon the accuracy of the aircraft's heading indicator. Moreover, the NDB's signals are subject to disturbance from weather, terrain, and other phenomena. Because there is no flag to indicate a loss of reception of the NDB's signal, pilots should continuously monitor the aural station identifier for the NDB during an approach in IMC. Unfortunately, Flight Simulator does not provide the means to check aural identifiers of NAVAIDS.