Instrument Approaches Harnessing the CAAS Vectors Function  

To simplify automation management, the Coast Guard H-60 community created a norm that harnessed “direct to” Common Avionics Architecture System (CAAS) functionality for advancing the flight plan during vectors to instrument approaches. In early 2024, the fleet began to encounter some anomalies relating to this technique. I had years of experience using the CAAS vectors function, as it was designed, to transition FMS guidance from vectors to final without anomalies. Through hundreds of repetitions, civilian sim instructors at the Coast Guard’s Aviation Training Center further validated the vectors functionality and they have significantly advanced fleet knowledge regarding this best practice.

In this post, we will review how to harness the CAAS vectors function, as it was engineered, to efficiently transition from ATC-assigned radar vectors to a final approach segment, while ensuring the flight management system (FMS) is properly primed to provide guidance for both the approach and a possible missed approach. The process is applicable for vectors to any approach type and centers around managing flight plan discontinuities and mode selections to prepare the system for automatic sequencing while becoming established on the approach. Using CAAS in this way eliminates anomalies, enhances automation management, and reduces pilot workload. 

Process for Vectors to Final with Discontinuity 

Set-Up: 

• Dep/Arrival Page (Arrival Side): 
  • Input:
    • Arrival Airport ID
    • Initial Altitude (FAF altitude recommended)
    • Minimum Safe Altitude (MSA – published or assigned)
    • Minimum Descent Altitude (MDA – published)
  • Choose expected or assigned approach
  • Select Transition > Vectors

Once ATC begins issuing vectors: 

• Set the Flight Director (FD) cues to match assigned heading (HDG), barometric altitude (BALT), and airspeed (ASPD). 
  • Select CDI source appropriate for the expected approach
• Bring the discontinuity to the top of the flight plan in magenta.
  •  This will: 
    • Change FPLN sequence mode from Auto to Man 
    • Display the discontinuity in magenta in the FPLN and under the scratchpad 
    • Highlight ACP in red on the CDI if ACP is selected 
  • At this point, the FPLN is armed for vectors 
  • Continue to comply with ATC headings and altitudes using FD-selected modes 

On the final vector and cleared for the approach: 

• Verify the CDI nav source is correct (Source) 
• Select FD NAV mode for the approach (NAV) 
• Change FPLN mode from Man to Auto (Auto) 

At this point, the FMS will calculate which leg of the final approach course to intercept based on the aircraft’s current heading and will automatically advance to the correct waypoint. Do not manually advance the FPLN to a future waypoint—doing so bypasses the internal navigation logic needed for proper approach activation and guidance. 

Note – Our sim instructors at ATC created the SNA acronym for easy memorization of “source, nav, auto.” If you put an “H” in front for “heading, source, nav, auto” the acronym HSNA (helicopter student naval aviator) provides the step-by-step process to methodically switch flight director cues from one FD NAV guidance source to another FD NAV guidance source (e.g., flying an ILS then using the FMS to fly the missed approach using RNAV). 

HSNA replaces the old “around the horn” memory aid previously used to methodically switch from one FD NAV guidance source to another FD NAV guidance source.  

I have tremendous gratitude for our civilian instructors at the training center and their contribution to our community’s operational effectiveness.  

By following this structured technique, pilots can effectively manage CAAS during vector-to-final scenarios, ensuring the system is correctly configured to support a smooth transition onto the final approach course. This process minimizes workload, prevents common errors, and ensures the flight plan is ready to execute the approach and missed approach as conditions dictate. Understanding and applying these procedures improves consistency and efficiency when harnessing CAAS during instrument flight operations.