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 clearances may include elements (like a radial without a distance) that are "flyable" but not "fileable" due to ambiguities, often leading to flight plan rejections by ATC centers despite initial acceptance by some planning tools.
Flight planning tools vary significantly in how they interpret and process ambiguous routing elements, such as standalone radials or unspecified airway junctions, making it critical for pilots to understand their chosen planner's specific logic.
For successful IFR flight planning, pilots should prioritize using specific, named fixes, Fix/Radial/Distance (FRD) formats, or clearly identified intersections to ensure clarity and acceptance, especially when navigating by VOR/DME rather than GPS.

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.