Monday, July 6, 2009

The ILS or LOC Rwy 12R

Hi, this is a NACO (National Aeronautical Charting Office) Chart:
When I saw a NACO chart for the first time , I was overwehlmed. There is just too much information in the chart! But no worries :) I'll explain it step by step.

Top left part, the city: San Antonio, Texas. Top right, the approach and airport: ILS or LOC RWY 12R, San Antonio INTL (SAT). Left from it, a small box with the ILS identifier (LOC/DME I-ANT and the frequency 110.90 Mhz), the approach course is 124º. Runway 12R landing distance is 5519 feet (1672m), touch-down zone elevation is 797 feet and airport elevation is 809 feet ASL.

The A symbol means: Alternate Minimums not standard. Civil users refer to tabulation. USA/USN/USAF pilots refer to appropiate regulations.
The T symbols means: Takeoff Minimums not standard and/or Departure Procedures are published. Refer to tabulation (The Tabulation is a page in the approaches booklet where the Alternate and Takeoff Minimums of the airports are published. Take-off minimums in KSAT for example, in page 7).
The missed approach procedure is to climb to 3100ft via the heading 124º and intercept the SAT 160º Radial outbound to EMBOW intersection and hold. EMBOW int is abeam the SAT 160º Rdl and the SSF 097º Rdl, so it's a bit difficult to know where it is if you don't have a GPS. The box below is the communication frequencies.

In the PLAN section, they've included the MSA. The IAF navaid (Navigation Aid) for this approach and the reference point for the MSA, is the ALAMO NDB (AN with frequency 368). So, how do we fly this approach? The San Antonio ATC will give us radar vectors to REUBE (another IAF). If there is no radar for some reason, we will have to fly direct to the AN NDB and follow the ILS backcourse. We will have to tune the ILS frequency (I-ANT 110.90) and proceed with the backcourse approach:

"When you fly a "conventional" Localizer Approach, or any approach for that matter, a needle deflection to the left means that your desired course is to the left, and that you as the pilot must correct the plane's heading to the left to recapture the approach course. The opposite applies for right deflection of course.

However, in a Localizer Back Course, if the needle deflects to the left it means that your desired course is to the right, and that you must correct in the opposite direction to recapture the desired approach course. In other words, left is right and right is left."

As we fly on the 124º backcourse (heading 304), we will have to make a procedure turn over HASDO (13.7 from I-ANT=The ILS' DME) so that we intercept the normal approach course of the ILS. The PT is shown as a thick line with a 259 and a 079. The 259º is the outbound leg of the procedure turn and the 079º is the inbound leg of the procedure turn. As we see in the PROFILE section, we must maintain 3200ft in the PT and when reaching HASDO, we must descend to 2800ft. As we fly over AN, we capture the Glideslope and descend to our minimums.

In the MINIMUMS Section of this format, we see the different types of categories divided in columns. For a Straight-In (S-) ILS approach to Rwy 12R, we need to see the runway by 1009 feet ASL or 200ft Decision Height. The 1009/18 means that 1009 is our Decision Altitude and 18 is 1800ft RVR. The 200 is our DH. What is in brackets is for military use.
If the GS is unserviceable, we would have to refer to the S-LOC 12R (Straight-In LOC approach) minimums. Our MDA would be 1440ft and RVR 2400ft. Minimum Descent Height is 631ft.
If we want to make a sidestep to the parallel runway (12L), our minimums would be 1600ft and with a visibility of 1 mile. 803ft above airport elevation.

On the left side of the Minimums section, we can see an airport diagram. This small diagram shows the runway lengths, the tower location, etc. The booklet also gives us an Airport Diagram page. It is very important to see the location of the taxiways, terminals, hangars, etc.
You can get a bit confused with this chart format and it takes a while to fully understand the content.

Most of the NACO charts are sold in booklets and they issue a new cycle every 56 days (for Terminal Procedures Publication and Airport/Facility Directory). You can find the Terminal Procedures Publications HERE and the Airport/Facility Directory HERE.

Taken from the National Aeronautical Charting Office - NACO (USA ONLY)

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