8
$\begingroup$

More precisely, in the case when a straight-in approach is present, what is the maximum angle between the final approach course and the runway heading for a straight-in minimum apply?

I had thought it is 15° for GPS IAP and 30° for others. However, when I looked at RNAV (GPS) RWY 28L @ KMRY, the angle is |279.4° - 261°| = 18.4° > 15°. Is there any other rule that applies, or is this simply an exception?

Note that on IAP runway diagram (bottom-left), there is usually an arrow with a distance from FAF to MAP and course direction, and they are omitted here.

RNAV (GPS) RWY 28L @ KMRY

Improve this question
$\endgroup$
2
  • 1
    $\begingroup$ According to the FAA Instrument Procedures Handbook, Chapter 4, p 4-63: For a non-vertically guided straight-in RNAV (GPS) approach, the final approach course must be aligned within 15° of the extended runway centerline. That doesn't conclusively answer the question, but does lead me to wonder if the LP approach is considered straight in here, but the LNAV approach is essentially considered a circling approach. But then why have the LNAV option at all? $\endgroup$
    – J W
    Commented Apr 19, 2016 at 10:52
  • $\begingroup$ Also I noticed that on G1000/GFC700 WAAS-equipped database, there is no procedure for LP approach, only LNAV. $\endgroup$
    – CrepuscularV
    Commented Apr 19, 2016 at 20:36

1 Answer 1

Reset to default
8
$\begingroup$

This is an interesting question because it turns out that RNAV approach criteria aren't defined in the TERPS as you would expect. Instead, there's a separate FAA order 8260.58 for RNAV approaches.

The TERPS does indeed give 30° as the maximum offset for most approaches (e.g. section 4-2-4) and 15° for VOR/DME RNAV approaches (section 13-3-4), but VOR/DME RNAV approaches are still based on ground stations (section 13-1):

VOR/DME RNAV systems use signals based solely upon a VOR/DME, VORTAC, or TACAN reference facility. These systems use radials and distances from a reference facility to compute position and flight track information

On the other hand, the criteria for 'true' RNAV approaches not based on ground stations are defined in 8260.58 and they allow for offsets up to 30° for approaches without vertical guidance (section 3-2-2):

a. Offset. When the final course must be offset, it may be offset up to 30 degrees (published separately from vertically guided) when the following conditions are met:

(1) Offset ≤ 5 degrees. Align the course through LTP.

(2) Offset > 5 degrees and 10 ≤ degrees. The course must cross the runway centerline extended at least 1500 feet prior to LTP (5200 feet maximum).

(3) Offset > 10 degrees and ≤ 20 degrees. The course must cross the runway centerline extended at least 3000 feet prior to LTP (5200 feet maximum). For offsets > 15 degrees, CAT C/D minimum published visibility 1 SM, minimum HAT of 300 feet.

(4) Offset 20 to 30 degrees (CAT A/B only). The course must cross the runway centerline extended at least 4500 feet prior to the LTP (5200 feet maximum).

Since the approach you showed doesn't have vertical guidance, it would fall under this section and therefore the offset of 16.76° marked on the plate is normal.

Improve this answer
$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .