Discussing Aircraft Navigation: Arc or Procedure Turn, Which Fares Better?

Discussing Aircraft Navigation: Arc or Procedure Turn, Which Fares Better?

In the skies above Durango, Colorado, IFR pilots facing a partial panel scenario are presented with a crucial decision when approaching Runway 3 – whether to opt for the procedure turn or fly the arc.

When the Rattlesnake VOR is out of service, as is currently the case, the arc becomes a more suitable choice for pilots limited by their instruments. The Rattlesnake VOR's absence means the published procedure turn may not be available or advisable for partial panel conditions, as it requires reliable VOR navigation.

Flying the arc around a navigation aid or using an RNAV system to join the final approach course is a standard method to transition to the final approach fix, especially when certain navaids are inoperative. This approach can provide a more continuous and smoother path to the final approach fix without requiring a course reversal, which can be challenging under partial panel conditions.

GPS or RNAV systems can substitute for DME or VOR navigation, allowing a pilot to fly a DME arc or an RNAV lateral path even when the VOR is out. This simplifies navigation and reduces workload in partial panel situations.

Minimising maneuver complexity is prudent in partial panel flying, and flying an arc instead of a procedure turn reduces the risk of spatial disorientation and workload by avoiding a course reversal.

However, it's important to note that flying the arc requires flying several small turns, which can be difficult to time. In a non-GPS equipped plane, the procedure turn might be a better option. Additionally, managing a 1,200' descent during a procedure turn in IMC, partial panel conditions can be challenging.

The author suggests considering equipment availability when deciding between the arc and the procedure turn. If equipped with GPS or RMI, the author would choose to fly the arc for a slower, more paced approach. Having an RMI also makes flying an arc easier.

The aircraft, currently in a partial panel state, has been cleared direct to the Durango VOR. The aircraft will fly the ILS to runway 3, with the choice between the procedure turn or the arc. If flying with GPS, the "turn 10, twist 10" method of flying through radials is not necessary, as the GPS navigates along the arc and gives a heading leg to intercept the localizer.

In conclusion, when the Rattlesnake VOR is out of service, a partial panel IFR pilot should prefer flying the arc (using RNAV/GPS as applicable) to join the final approach course for the ILS approach to Runway 3 at Durango, Colorado, instead of flying the procedure turn. This approach maintains situational awareness and reduces complexity during a partial panel approach. Always confirm with the latest approach chart notes and ATC instructions before the approach.

1. Despite the Rattlesnake VOR being out of service, IFR pilots can still approach Runway 3, opting for the arc as a more suitable choice for pilots limited by their instruments.
2. Flying the arc, pilots can transition to the final approach course, avoiding a course reversal which can be challenging under partial panel conditions.
3. GPS or RNAV systems can substitute for DME or VOR navigation, allowing a pilot to fly a DME arc or an RNAV lateral path even when the VOR is out.
4. Minimising maneuver complexity is crucial in partial panel flying, and flying an arc reduces the risk of spatial disorientation and workload by avoiding a course reversal.
5. However, flying the arc requires flying several small turns, which can be difficult to time, especially in a non-GPS equipped plane.
6. The author suggests considering equipment availability when deciding between the arc and the procedure turn; they would choose to fly the arc if equipped with GPS or RMI.
7. The aircraft, currently in a partial panel state, has been cleared direct to the Durango VOR, and will fly the ILS to runway 3, with the choice between the procedure turn or the arc. If flying with GPS, the "turn 10, twist 10" method of flying through radials is not necessary, as the GPS navigates along the arc and gives a heading leg to intercept the localizer.

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