APPROACH TERMS AND DEFINITIONS
For Virtual Flying Only

GLIDESLOPE INTERCEPT ALTITUDE -- The minimum altitude to intercept the glideslope/path on a precision approach. The intersection of the published intercept altitude with the glideslope/path, designated on Government charts by the lightning bolt symbol, is the precision FAF, however, when ATC directs a lower altitude, the resultant lower intercept position is then the FAF.

DECISION HEIGHT (DH) -- With respect to the operation of aircraft, means the height at which a decision must be made during an ILS, MLS, or PAR instrument approach to either continue the approach or to execute a missed approach.

MINIMUM DESCENT ALTITUDE (MDA) -- The lowest altitude, expressed in feet above mean sea lvel to which descent is authorized on final approach or during circle-to-land maneuvering in execution of a standard instrument approach procedure where no electronic glideslope is provided. (See Nonprecision Approach Procedure)

HEIGHT ABOVE TOUCHDOWN (HAT) --The height of the Decision Height or Minimum Descent Altitude above the highest runway elevation in the touchdown zone (first 3,000 feet of the runway). HAT published on instrument approach charts in conjunction with all straight-in minimums.

HEIGHT ABOVE AIRPORT (HAA) -- The height of the Minimum Descent Altitude above the published port elevation. This is published in conjunction with circling minimums.

MINIMUM SAFE ALTITUDE (MSA) -- 1. The minimum altitude specified in FAR 91 for various aircraft operations. 2. Altitudes depicted on approach charts which provide at least 1,000 feet of obstacle clearance for emergency use within a specified distance from the navigation facility upon which a procedure is predicated. These altitudes will be identified as Minimum Sector Altitudes or Emergency Safe Altitudes and are established as follows

Minimum Sector Altitudes. Altitudes depicted on approach charts which provide at least 1,000 feet of obstacle clearance within a 25-mile radius of the navigation facility upon which the procedure is predicated. Sectors depicted on approach charts must be at least 90 degrees in scope. These altitudes are for emergency use only and do not necessarily assure acceptable navigational sign coverage.

[ICAO] Minimum Sector Altitude. The lowest altitude which may be used under emergency conditions which will provide a minimum clearance of 300 m (1,00 feet) above all obstacles located in an area contained within a sector of a circle of 46 km (25 NM) radius centered on a radio aid navigation.

VISUAL DESCENT POINT (VDP) -- A defined point on the final approach course of a nonprecision straight-in approach procedure from which normal descent from the MDA to the runway touchdown point may be commenced, provided the approach threshold of that runway, or approach lights or other markings identifiable with the approach end of that runway are clearly visible to the pilot.

MISSED APPROACH POINT (MAP) -- A point prescribed in each instrument approach procedure at which a missed approach procedure shall be executed if the required visual reference does not exist.

Category A. Speed less than 91 knots.

Category B. Speed 91 knots or more but less than 121 knots.

Category C. Speed 121 knots or more but less than 141 knots.

Category D. Speed 141 knots or more but less than 166 knots.

Category E. Speed 166 knots or more. (Refer to FAR 1) (Refer to FAR 97)

IFR TAKEOFF MINIMUMS AND DEPARTURE PROCEDURES -- FAR, Part 91, prescribes standard take-off rules for certain civil users. At some airports, obstructions or other factors require the establishment of nonstandard takeoff minimums, departure procedures, or both to assist pilots in avoiding obstacles during climb to the minimum en route altitude. Those airports are listed in NOS/DOD Instrument Approach Charts (IAP's) under a section entitled "IFR Takeoff Minimums and Departure Procedures." The NOS/DOD IAP chart legend illustrates the symbol used to alert the pilot to nonstandard takeoff minimums and departure procedures. When departing IFR from such airports or from any airports where there are no departure procedures, SID's, or ATC facilities available, pilots should advise ATC of any departure limitations. Controllers may query a pilot to determine acceptable departure directions, turns, or headings after takeoff. Pilots should be familiar with the departure procedures and must assure that their aircraft can meet or exceed any specified climb gradients.

VISIBILITY -- The ability, as determined by atmospheric conditions and expressed in units of distance, to see and identify prominent unlighted objects by day and prominent lighted objects by night. Visibility is reported as statute miles, hundreds of feet or meters. (Refer to FAR 91) (See AIM).

INITIAL APPROACH FIX (IAF) -- The fixes depicted on instrument approach procedure charts that identify the beginning of the initial approach segment(s). (See Fix) (See Segments of an Instrument Approach Procedure)

FINAL APPROACH FIX (FAF) -- The fix from which the final approach (IFR) to an airport is executed and which identifies the beginning of the final approach segment. It is designated on Government charts by the Maltese Cross symbol for nonprecision approaches and the lightning bolt symbol for precision approaches, or when ATC directs a lower-than-published Glideslope/path Intercept Altitude, it is the resultant actual point of the glideslope/path intercept. (See final Approach Point) (See Glideslope/path Intercept Altitude) (See Segments of an Instrument Approach Procedure)

FINAL APPROACH POINT (FAP) -- The point, applicable only to a nonprecision approach with no depicted FAF (such as an on-airport VOR), where the aircraft is established inbound on the final approach course from the procedure turn and where the final approach descent may be commenced. The FAP serves as the FAF and identifies the beginning of the final approach segment.

1. Plan View. This is a bird's eye view of the entire procedure. Information pertaining to the initial approach segment, including procedure turn, minimum safe altitude for each sector, courses prescribed for the final approach segment and obstructions, is portrayed in this section. Navigation and communication frequencies are also listed on the plan view.
   1. Format. Normally, all information within the plan view is shown to scale. Data shown within the 10 NM distance circle is always shown to scale. The dashed circles, called concentric rings, are used when all information necessary to the procedure will not fit to scale within the limits of the plan view area. These circles then serve as a means to systematically arrange this information in their relative position outside and beyond the 10 NM distance circle. These concentric rings are labeled Enroute Facilities and Feeder Facilities.
   2. Enroute Facilities Ring. Radio aids to navigation, fixes and intersections that are part of the Enroute Low Altitude Airway structure and used in the approach procedure are shown in their relative position on this Enroute Facilities Ring.
   3. Feeder Facilities Ring. Radio aids to navigation, fixes and intersections used by the air traffic controller to direct aircraft to intervening facilites/fixes between the enroute structure and the initial approach fix are shown in their relative position on this Feeder Facilities Ring.
      
       
2. 

3.		Alternate minimums not standard
4.		Alternate minimums are not authorized due to unmonitored facility or absence of weather reporting
5.		Takeoff minimums not standard and/or published departure procedures
6	Altitudes	Mandatory Minimum Maximum Recommended

7. THRESHOLD CROSSING HEIGHT (TCH) -- The theoretical height above the runway threshold at which the aircraft's glideslope antenna would be if the aircraft maintains the trajectory established by mean ILS glideslope or MLS glidepath.
   
    
8. TOUCHDONE ZONE -- The first 3,000 feet of the runway beginning at the threshold. The area is used for determination of Touchdown Zone Elevation in the development of straight-in landing minimums for instrument approaches.
   
    
9. TOUCHDOWN ZONE ELEVATION (TDZE) -- The highest elevation in the first 3,000 feet of the landing surface. TDZE is indicated on the instrument approach procedure chart when straight-in landing minimums are authorized. (See Touchdown Zone)
   
    
10. RUNWAY GRADIENT -- The average slope, measured in percent, between two ends or points on a runway. Runway gradient is depicted on Government aerodrome sketches when total runway gradient exceeds 0.3%.
    
     
11. FEEDER FIX -- The fix depicted on Instrument Approach Procedure Charts which establishes the starting point of the feeder route.
    
     
12. FEEDER ROUTE -- A route depicted on instrument approach procedure charts to designate routes for aircraft to proceed from the en route structure to the initial approach fix (IAF).