Routing Puzzles

In the December 2014 issue, I answered a question from Tim, a reader, regarding filing an IFR flight plan. DUATS flight planner computer accepted the flight plan but the FSS planner rejected it. That was disconcerting, so we dug into it. This article will explain whats happening and Ill illustrate how different flight planning tools can behave differently with some less common routing elements.

ATC offered Tim a clearance that read KAGC AGC073 HOMEE JST300 JST SEG. ATCs intent was to have Tim depart Allegheny County, PA, join the AGC VORs 073 radial and fly it to HOMEE. Then he would fly southeast on the JST VOR 300 radial to JST. Neither route is an airway and this was not a preferred route. Tim has only VOR and DME (with a VFR GPS) aboard and filed accordingly.

Good intentions notwithstanding, ATC gave Tim a flyable clearance but not one that FSS or Center would accept if you were to file it. A clearance you cant file isnt worth much, and this one fails in two respects.

Fred Simonds

Tuesday, February 10, 2015 at 12:00 AM ET

Verified

Key Takeaways:

ATC may issue clearances that are flyable but contain elements (like bare radials or unnamed airway junctions) that are often unfileable or misinterpreted by standard flight planning tools.
Flight planning software varies in its acceptance and processing of ambiguous route information; pilots must understand their specific tool's behavior, as some (like DUATS) might pass unexamined data that others reject.
The Fix/Radial/Distance (FRD) format is essential for precisely defining fixes for filing, especially for airborne departures/arrivals or unlisted airports, and is generally well-understood by FAA systems.
Pilots should file using named fixes and airways, supplementing with FRD details in their navigation logs for VOR-only segments, and be prepared to manage dynamic route changes efficiently, noting that raw VOR/DME editing can sometimes be faster than GPS for quick reroutes.

See a mistake? Contact us.

In the December 2014 issue, I answered a question from Tim, a reader, regarding filing an IFR flight plan. DUATS’ flight planner computer accepted the flight plan but the FSS planner rejected it. That was disconcerting, so we dug into it. This article will explain what’s happening and I’ll illustrate how different flight planning tools can behave differently with some less common routing elements.

ATC offered Tim a clearance that read KAGC AGC073 HOMEE JST300 JST SEG. ATC’s intent was to have Tim depart Allegheny County, PA, join the AGC VOR’s 073 radial and fly it to HOMEE. Then he would fly southeast on the JST VOR 300 radial to JST. Neither route is an airway and this was not a preferred route. Tim has only VOR and DME (with a VFR GPS) aboard and filed accordingly.