ILS provides dedicated ground-based guidance
An instrument landing system transmits lateral and vertical signals that lead toward a specific runway. It has long been the standard precision-approach technology at major airports.
RNAV approaches use onboard area navigation
Satellite navigation and certified aircraft systems can guide flights along flexible paths without a dedicated radio transmitter beside the runway. Some procedures add vertical guidance comparable in use to a precision approach.
Non-precision approaches may provide only lateral guidance
Older VOR, NDB or some localizer procedures require crews to manage descent using published altitude steps or calculated vertical paths. Minimums are generally higher than on the best precision approaches.
Minimums protect terrain and obstacle clearance
The procedure designer evaluates terrain, towers and navigation accuracy. Crews cannot simply descend below the published minimum because they believe the runway should be nearby.
The missed approach is part of the procedure
If the required visual references are not obtained, pilots climb and follow a published route away from terrain and conflicting traffic. A missed approach is a planned option, not a failure.
Aircraft and crew approval determine what can be flown
A runway may publish several approaches, but the operator, aircraft equipment and crew qualification determine which ones are available on a given flight.
An approach procedure organizes the descent to an airport
Published routes define altitudes, tracks and fixes that guide aircraft from the en-route environment toward a runway.
Not every instrument approach provides vertical guidance
Some procedures guide only lateral position, requiring crews to manage descent using published altitude steps or calculated paths.
Precision-like capability now comes from several technologies
ILS remains important, while satellite navigation and augmentation systems can support accurate lateral and vertical guidance at many airports.
Minimums depend on more than the aircraft
Runway lighting, obstacles, navigation equipment, crew authorization and weather all affect how low the procedure can be flown.
A missed approach is designed into the procedure
If the runway is not visible or the approach becomes unstable, pilots follow a published escape path rather than improvising near terrain.
Briefing the procedure reduces surprises
Crews review frequencies, altitudes, descent profile, weather, runway conditions and missed-approach instructions before beginning.
More aviation guides
Explore more aircraft, pilot, airport and aviation guides on SY.com.
Explore aviation