VATUSA
Virtual Air Traffic Simulation - USA Division
Vectoring to the Final Approach Course
The second way to vector for an Instrument Approach Procedures (IAP) is vectoring to the final approach course. This is most commonly used when vectoring for a Instrument Landing System (ILS), Localizer, or Localizer-Backcourse approach, but can be done to any approach. Let's begin by reviewing the PTAC acronym and how it will relate when vectoring to the final approach course.
- P (Position) - Remember that the "P" stands for the aircraft's position relative to a fix on the approach. This is required when vectoring to the final approach course.
- T (Turn) - This is a turn given to the aircraft that will get it on a heading to intercept the localizer/final approach course. If you remember from the section Introduction to Vectoring, you must have the aircraft established on an intercept heading of 30 degrees or less for fixed-winged aircraft or 45 degrees or less for helicopters. If the aircraft is less than one mile from the approach gate, the turn to final cannot exceed 20 degrees. We will cover more detail on this later on in this lesson.
- A (Altitude) - This is the altitude that the aircraft is to maintain until established on the localizer/final approach course. The reason why we issue this is to ensure appropriate terrain/obstacle separation.
- C (Clearance) - This is the clearance for the approach.
Introduction to the ILS
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Definitions
ILS - Instrument Landing System. It is a precision approach since it provides both vertical and lateral guidance to the aircraft. It consists of four elements: Localizer, Glideslope, Marker Beacons, and Approach Lights.
Localizer - The localizer is a radio signal that provides lateral guidance to the aircraft on an approach.
Established - When an aircraft is straight and level, and tracking the localizer (and/or final approach course), it is said to be "established".
Glideslope - The Glideslope provides vertical guidance to the aircraft. Most glideslopes provide a three degree descent angle, though this can vary slightly from airport to airport. Always be sure to assign altitude in your approach clearance that will allow the aircraft to capture the glideslope from below. You never want the aircraft to capture the glideslope from above as it will require steep descents and may be uncomfortable to our virtual passengers.
Marker Beacons - Marker Beacons comprise the third element of the ILS system. They exist to provide position updates to the pilot conducting the approach. If the pilot is flying a localizer only approach, then the marker beacons allow the pilot to judge if he/she is descending at the correct rate. There are three types of marker beacons.
- Outer Marker - The outer marker is located normally 4-7 miles from the runway threshold.
- Middle Marker - Some ILS systems have a middle marker, which is located roughly 3,500 feet from the runway threshold.
- Inner Marker - Some ILS systems have an inner marker as well, which is located between the Middle Marker and the runway threshold, usually 1,000 feet from the runway threshold.
Approach Lights - The final element of the ILS system is the approach lights, which aid the pilot when transferring from instrument flight conditions, into visual fligh conditions.
Approach Gate - The approach gate is defined as an area two miles from the final approach fix. The final approach fix for a precision approach is the point in which the aircraft is going to begin to descend via the glideslope. For a non-precision approach, it is depicted as a maltese cross. When vectoring to final, the aircraft must be established one mile from the approach gate (or three miles) from the Final Approach Fix.
Types of Approaches and Approach Clearance Phraseology
ILS Approach
An ILS Approach is one that contains an operating localizer and glideslope, thus making it a precision approach. There are three different categories of ILS approach, each offering a different level of precision. The following information is courtesy of Wikipedia
.- Category I (CAT I) - A precision instrument approach and landing with a decision height not lower than 200 feet (61 m) above touchdown zone elevation and with either a visibility not less than 800 meters (2,625 ft) or a runway visual range not less than 550 meters (1,804 ft).
- Category II (CAT II) - Category II operation: A precision instrument approach and landing with a decision height lower than 200 feet (61 m) above touchdown zone elevation but not lower than 100 feet (30 m), and a runway visual range not less than 300 meters (984 ft) for aircraft category A, B, C and not less than 350 meters (1,148 ft) for aircraft category D.
- Category III (CAT III) is further subdivided
- Category III A - A precision instrument approach and landing with:
- a decision height lower than 100 feet (30 m) above touchdown zone elevation, or no decision height; and
- a runway visual range not less than 200 meters (656 ft).
- Category III B - A precision instrument approach and landing with:
- a decision height lower than 50 feet (15 m) above touchdown zone elevation, or no decision height; and
- a runway visual range less than 200 meters (656 ft) but not less than 75 meters (246 ft).
- Category III C - A precision instrument approach and landing with no decision height and no runway visual range limitations. A Category III C system is capable of using an aircraft's autopilot to land the aircraft and can also provide guidance along the runway surface.
Localizer Approach
A localizer approach is one in which there is no glideslope to provide vertical guidance to the aircraft. Due to there being no vertical guidance provided, the pilot will descend in a "stair-step" type of pattern down to their decision height.
Localizer-Backcourse Approach
A Localizer-Backcourse Approach is similar to the localizer approach. There is no vertical guidance provided to the aircraft, thus the approach is non-precision. A big difference for pilots with this approach is that the localizer signal is reversed.
Phraseology for Issuance an Approach Clearance When Vectoring to Final
Now that you have a better understanding of some of the more common approaches that you'll use when vectoring to final, let's look at the phraseology that you'll use.
- P - "(aircraft) YOU ARE (miles) FROM (fix)"
- T - "(turn left,right/fly) HEADING (heading)"
- A - "MAINTAIN (altitude) UNTIL ESTABLISHED ON THE.....
- LOCALIZER - if flying an ILS/Localizer Approach
- LOCALIZER BACKCOURSE - if flying a Localizer Backcourse Approach
- FINAL APPROACH COURSE - if flying something other than the above (such as VOR/NDB/etc)
- C - "CLEARED APPROACH"
- If you wish a particular type of approach to be flown, then you must state the type of approach. "CLEARED (type) APPROACH"
- If there is more than one approach of any particular type (such as ILS23 and ILS14) then you will need to specify which approach you would like the pilot to fly. "CLEARED (type)(designator) APPROACH"
- Finally if they are going into a satellite or uncontrolled field, you will need to state the airport in which the procedure is located. "CLEARED (optional: Type/designator) APPROACH INTO (airport)"
