A Bit Over Ninety

It started with a reader question about the RNAV (GPS) Y Rwy 28L at Monterey, CA (KMRY). The question seems simple on the surface: There is a feeder from the SNS VOR to HIXAR on a heading of 146 degrees. The inbound course is 235, meaning an 89-degree turn is required. Are you required to fly the HILPT? AIM 5-4-9 (5) and (6) seem to say yes, but 5-4-5 (8) seems to say a turn from the feeder of less than 90 degrees is implicitly NoPT.

jwanwest

Tuesday, August 01, 2017 at 12:00 AM ET

Verified

Key Takeaways:

RNAV approaches are restricted to turns of 90 degrees or less (compared to 120 degrees for conventional navigation) due to GPS turn anticipation and the need to maintain protected airspace, particularly for faster aircraft.
Apparent discrepancies where turns less than 90 degrees still require a Hold-in-Lieu-of-Procedure-Turn (HILPT) often stem from fractional magnetic variation differences, approach designers' precise calculations, or critically short intermediate legs that prevent aircraft from properly establishing on course.
Pilots can often avoid unnecessary HILPTs by requesting vectors onto the approach course or asking for a "straight-in" clearance from a specific fix, as Air Traffic Control (ATC) may be able to accommodate or not track to the same granular detail as approach design.

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There’s little that’s more essential to an instrument pilot than the approach clearance. We controllers issue them all day long. I fully expect much of my frequency time to be spent issuing approach clearances for either training flights or weather-related needs. Approach Clearance, ATC Notebook, Tarrance Kramer, TAA, PTAC, IFR Magazine, The Terminal Arrival Area makes approach clearances simpler. Intercept vectors that are closer to the FAF have to be shallower. With no associated runway, this approach has only circling minimums. Tarrance Kramer

It started with a reader question about the RNAV (GPS) Y Rwy 28L at Monterey, CA (KMRY). The question seems simple on the surface: “There is a feeder from the SNS VOR to HIXAR on a heading of 146 degrees. The inbound course is 235, meaning an 89-degree turn is required. Are you required to fly the HILPT? AIM 5-4-9 (5) and (6) seem to say yes, but 5-4-5 (8) seems to say a turn from the feeder of less than 90 degrees is implicitly NoPT.”