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 (GPS) approaches are subject to a strict 90-degree turn limitation, unlike conventional navigation which allows up to 120 degrees, primarily because RNAV systems anticipate turns into protected airspace before a fix.
Even turns seemingly less than 90 degrees may still require a Hold-in-Lieu-of-Procedure-Turn (HILPT) due to fractional degree differences in magnetic variation calculations or insufficient leg length between fly-by waypoints for anticipated turns.
Pilots can often bypass unnecessary HILPTs by requesting ATC vectors or explicitly asking for a "straight-in" approach clearance, acknowledging that procedural rules sometimes lag behind aircraft capabilities and practical safety.

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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.”