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Instrument Approach Procedure (IAP)
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Instrument approach procedure (IAP). A series of predetermined manoeuvres by reference to flight instruments with specified protection from obstacles from the initial approach fix, or where applicable, from the beginning of a defined arrival route to a point from which a landing can be completed and thereafter, if a landing is not completed, to a position at which holding or en-route obstacle clearance criteria apply. Instrument approach procedures are classified as follows:
- Non-precision approach (NPA) procedure
- Approach procedure with vertical guidance (APV)
- Precision approach (PA) procedure
Source: ICAO Doc 8168 PANS-OPS
An instrument approach procedure may have five separate segments:
- Arrival segment - this segment is a transition from the en-route phase to the approach phase of the flight.
- Initial approach segment - this segment begins at the initial approach fix (IAF) and ends at the intermediate fix.
- Intermediate approach segment - this segment usually begins at the intermediate fix (IF) and ends at the final approach fix (FAF) or final approach point (FAP). Here the aircraft speed and configuration should be adjusted to prepare for the final approach. For this reason, the descent gradient is kept as shallow as possible.
- Final approach segment - this segment usually begins at the FAF/FAP and ends at the missed approach point (MAPt). Here the alignment and descent for landing are made. Final approach may be made to a runway for a straight-in landing, or to an aerodrome for a visual manoeuvre. Some aerodromes are not equipped with a facility to serve as FAF. If this is the case, descent to MDA/H is made once the aircraft is established inbound on the final approach track. Four types of final approach are defined:
- Non-precision approach (NPA) with FAF.
- NPA without FAF. Sometimes an aerodrome is served by a single facility located on or near the aerodrome, and no other facility is suitably situated to form a FAF. In this case, a procedure may be designed where the facility is both the IAF and the MAPt.
- Approach with vertical guidance (APV). It utilizes lateral and vertical guidance but does not meet the requirements established for precision approach and landing operations.
- Precision approach, e.g. ILS. The segment begins at the FAP, i.e. the point where the intermediate approach altitude/height intercepts the nominal glide path.
- Missed approach segment - this segment starts at the MAPt. It is designed to provide protection from obstacles throughout the Missed Approach manoeuvre. It specifies a point where the missed approach begins, and a point or an altitude/height where it ends. Only one missed approach procedure is established for each IAP and its design is been kept as simple as possible due to the high pilot workload associated with such situations. If a missed approach is initiated before arriving at MAPt, the pilot will normally proceed to the MAPt and then follow the missed approach procedure in order to remain within the protected airspace.
Note: Not all approach procedures include all of these segments.
The instrument approach procedures are published in the AD section of the AIP. The arrival segment is described in the standard arrival (STAR) charts and the other segments are described in the instrument approach charts. While usually more than one STAR is placed on a single chart (e.g. all STARs for a particular runway), in most cases each IAP is explained on a separate chart sheet, although it is possible, to have e.g. all ILS approaches on a single chart.
- Precision Approach
- Non-Precision Approach
- Instrument Landing System (ILS)
- Visual Approach
- Stabilised Approach
- Continuous Descent Final Approach (CDFA)
- Approach Speed Categorisation
- ICAO Doc 8168 PANS-OPS