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SNot Authorized
afe and successful instrument flight is in the details. What does it mean when a procedure is marked as “not authorized?” Doesn’t the controller protect you by refusing to clear you for an unauthorized procedure?
It’s your responsibility as pilot-in-command to be aware of the limitations on approach procedures, to avoid asking for an unauthorized approach, and to refuse a clearance if it includes a procedure that’s not authorized. Air Traffic Control’s guidance is to clear you for any procedure you request as long as there is no conflict with other IFR aircraft. What sorts of procedures may be “not authorized” for an instrument approach? How will you find out a procedure is not authorized, so you’ll know not to request it or attempt to fly the procedure?
Symbology
Most “not authorized” instrument procedures are identified in textual notes on the approach chart. There is no specific symbol to jump out and alert you. You must read the notes at the top of the chart and look for the notation “NA” – for example, “Circling to Rwy 5-23 NA at night.”
Here are some limitations that may apply to an instrument approach.
NA at Night
“Occasionally, operations at an airport may be limited at night,” wrote James E. Terpstra, now retired Senior Corporate Vice President at Jeppesen. “Because runway lighting is required for approval of night instru- ment operations, some approaches are authorized only during the day. In some cases, the mountainous terrain around an airport is so significant that some night operations may be limited or not authorized at night.”
4 • TWIN & TURBINE / January 2023
Circling NA
If terrain or obstacles are near the airport, straight-in approaches may be authorized but circle-to-land procedures may not. A variation on this theme is when an obstacle exists on one side of the airport but not oth- ers, and circling is not authorized if it takes the airplane near that obstacle. In this case, you may see a note that says, “Circling NW NA,” for example, if any circling maneuver that would take the airplane northwest of the airport puts it in conflict with the obstacle. Or “Circling to Rwy 15 NA” if maneuvering from the final approach course for the procedures being f lown cannot safely end with a circle-to-land maneuver to Rwy 15.
Circling NA at Night
It may be that obstacles or terrain permit circling in daylight conditions (even in poor weather that requires a circle-to-land maneuver), but the
obstruction is not lighted, so attempt- ing the circle maneuver at night is hazardous. In this case, a note such as “Circling to Rwy 5-23 NA at night” provides you with this warning.
Straight-In Minimums NA at Night
At first glance, this may seem odd. It sounds like it means straight-in procedures are not authorized, but circling maneuvers are. That seems backwards. What this notation is re- ally saying, however, is that you must use the circling minimums value to define MDA, DH or DA even if you’re f lying a straight-in approach – a straight-in procedure is authorized, but you must use the higher circling minimums. This is usually because the runway has limited lighting that does not completely prevent the use of the procedure at night but that re- quires you to be more conservative about flying it after dark.
by Thomas P. Turner