ILS Course vs RWY CenteLine

[bucks_raj]

Some ICAO Doc some where gives a number for the ILS course to be within the mag rwy crs so that it is considered Published Precision app for that particular rwy.

Vaguely form memory i think it is 6 Degrees..

Any references would be much appreciated.

FAA/JAA/CAA/CASA??

[rudderrudderrat]

Hi bucks_raj,

Your 6 degrees rings a bell with TriStar Auto Land procedures. At 350 radio, we ensured the ILS Course was set to the runway QDM (max 6 degs difference). But I can't find any reference to that figure anywhere.

aterpster is probably your best bet. Please see:
Offset ILS Cat 2 [Archive] - PPRuNe Forums (http://www.pprune.org/archive/index.php/t-464058.html)

[underfire]

Depends on the CAT level.

Many, many variables....

"TERPs criteria permit ILS approach procedures to be offset as much as 3 degrees from the precise runway centerline, yet the procedure is still considered to be a precision instrument approach procedure. The FAA is currently proposing that pseudo-precision approach procedures, such as Baro VNAV, be permitted to be offset from runway centerline by as much as 5 degrees. GPS non-precision approach procedures can be offset by as much as 30 degrees (original criteria limit was 15 degrees).

The “precision” in precision IAPs means not only a precise electronic glidepath, but precise alignment with the exact centerline of the runway. In this way, the properly flown approach will require no maneuvering in either the vertical or lateral planes to effect a landing within the target touchdown zone. This is significant to the safe operation of transport category jet aircraft, especially during low visibility (RVR-enabled) visibility conditions.

As to non-precision IAPs, some have RVR authorizations as low as normal Category I IAP’s - RVR 2400. Yet where there are significant offsets to the runway centerline, it is impossible for the pilot to make safe alignment with the runway during low-visibility conditions.

The requirement to chart “offset localizer” or “offset final approach course” lacks standard application. "