Narrative:

While at 10,500' heading south of the gcn VOR (grand canyon) on 341 degree right, at about 10-15 NM north I had to deviate to the right off of the V257 airway centerline to avoid entering the 'free flight zone, no flight below 14,500'.' however nowhere on the chart proper (las vegas sectional 41ST edition) does it state or indicate that you must do this. If this is of such a high safety priority (and it obviously is) it should be indicated in print or some indication made, on the chart itself, that this deviation is required. Having this vital and critical information listed only on an inset (where someone may miss it) is very inadequate and in my opinion inviting the kind of ambiguity that causes critical incidents. Most pilots are going to assume that by staying on the centerline of an established airway they would be proceeding properly.

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Original NASA ASRS Text

Title: PLT OF SMA AT 10,500 IN GRAND CANYON SPECIAL FLT RULES AREA ALLEGEDLY THREADED CORRIDOR.

Narrative: WHILE AT 10,500' HDG S OF THE GCN VOR (GRAND CANYON) ON 341 DEG R, AT ABOUT 10-15 NM N I HAD TO DEVIATE TO THE RIGHT OFF OF THE V257 AIRWAY CENTERLINE TO AVOID ENTERING THE 'FREE FLT ZONE, NO FLT BELOW 14,500'.' HOWEVER NOWHERE ON THE CHART PROPER (LAS VEGAS SECTIONAL 41ST EDITION) DOES IT STATE OR INDICATE THAT YOU MUST DO THIS. IF THIS IS OF SUCH A HIGH SAFETY PRIORITY (AND IT OBVIOUSLY IS) IT SHOULD BE INDICATED IN PRINT OR SOME INDICATION MADE, ON THE CHART ITSELF, THAT THIS DEVIATION IS REQUIRED. HAVING THIS VITAL AND CRITICAL INFORMATION LISTED ONLY ON AN INSET (WHERE SOMEONE MAY MISS IT) IS VERY INADEQUATE AND IN MY OPINION INVITING THE KIND OF AMBIGUITY THAT CAUSES CRITICAL INCIDENTS. MOST PLTS ARE GOING TO ASSUME THAT BY STAYING ON THE CENTERLINE OF AN ESTABLISHED AIRWAY THEY WOULD BE PROCEEDING PROPERLY.

Data retrieved from NASA's ASRS site as of August 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.