by Jonathan M. Stern
Instrument Approach Procedures
In a case I defended in western Texas, a pilot claimed that he crashed after an encounter with severe turbulence of which he had no warning. He was flying on a dark night over desolate terrain. I still believe that he misread his altimeter, hit the rough terrain below the approach path, and simply had a rough ride as his plane bounced along the ground.
There are three basic types of instrument approach procedures (IAPs): VOR, NDB, and ILS approaches. Additionally, the back course of the ILS's localizer can be used for a localizer back course approach. There are also several variations of ILS approaches, including LDA and SDF approaches.
Air traffic control, when providing clearance to an aircraft to fly an IAP, may say cleared for approach, which gives the pilot the choice of any published IAP at the destination airport, or may clear the aircraft for a specific IAP at the airport (e.g., cleared for the VOR runway two-four approach). After receiving clearance for the approach, you are required to maintain the last assigned altitude until established on a published route with a lower specified minimum altitude or until established on the instrument approach procedure.