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Approach Procedures

APPROACH PROCEDURES

Ensure the approach has been entered into the FMS flight plan, and that it is currently active in the IFD. An approach can be selected and flown as a full published procedure or as a Vectors-to-Final – the choice is made on the Transitions dropdown menu in the FMS. When an approach is selected from the FMS drop down list, the Transition dropdown menu is presented. “Vectors” is the first choice in the list and if it is selected, an “Activate Approach” button is presented in the LSK L4 along the left side of the page. Until the “Activate Approach” button is pressed, "Vectors to Final – Inactive” is displayed just above the FMS leg into the FAF. As soon as the Activate Approach button is pressed, the leg into FAF becomes active (magenta) and “Vectors to Final” is displayed just above that leg. NOTE Displayed Inbound Course Due to mathematical rounding, it is possible that course being sent to an EFIS for digital display may be 1 degree off from the published approach chart.

NOTE FOR THE IFD510/545 ONLY VHF based Approaches Although the IFD510 and IFD545 have no VHF radio, ILS, LOC and VOR approaches will still be displayed in the dropdown list of available approaches at your destination. Though the unit will allow the user to select those approaches, it will only give GPS overlaid lateral guidance. The unit will provide no vertical guidance on an ILS approach. Any guidance is advisory only as these types of approaches should be flown with the NAV radio and not the IFD.

TIPS AND TECHNIQUES

Discontinuities During Approaches Before you insert an approach at an airport, the FMS is being told to fly a leg directly to the airport (i.e. the reference point) and the legs on the map reflect that. However, when you insert an approach, the FMS is being told to fly the legs of the approach to the airport (actually to the runway) and not fly a leg to the airport reference point. After the approach has been entered, you'll notice a "discontinuity" before the first leg of the approach. A discontinuity is an indication that the FMS doesn't know how to get from the leg before the discontinuity to the leg after. In other words, there's a gap in the flight plan. The gap can be closed via a number of means to include using the L4 LSK hook, activating a leg of the approach, or Direct-To the leg to the FAF. Verify the system will do as you expect by examining the depiction on the map.

AUTOMATIC MODE SWITCHING

† Automatic mode switching to VLOC (e.g. GPSVLOC transition) including automatically setting the inbound course, will occur if the capture criteria defined above are met and the primary nav frequency can be auto-identified. If auto tuning has not been enabled on the setup pages, or a station cannot be identified, automatic mode switching will not occur.

TIPS AND TECHNIQUES

Exception to Automatic Nav Mode Switching If VLOC mode had been previously manually selected to be the nav mode (e.g. cross-tuning a VOR) and then an approach is activated in the flight plan that would have normally resulted in a GPSVLOC nav mode indication, the nav mode will NOT toggle to GPSVLOC. Instead, it will stay at VLOC since it is assumed the pilot intended to keep using the previous function. Likewise, the approach nav frequency will be inserted into the #1 standby nav frequency slot but not the active nav frequency position. Both the nav mode transition and the swapping of the nav frequencies will have to be manually performed by the pilot. With the proper inbound course set, including on localizer or ILS approaches where the course pointer is just for reference, the course and glide slope deviation data will be transmitted as appropriate from the IFD for display on compatible cockpit thirdparty devices such as CDIs, HSIs, EFISs, etc. In the ILS/Localizer case, the CDI deflection will be driven by the localizer signal itself, regardless of the course setting. PRECISION APPROACHES VHF Based Precision Approaches † On ILS/LOC approaches (Vectors-to-Final transition or the full published procedure), the IFD will automatically toggle the nav mode to VLOC when all of the following conditions have been met for 5 consecutive seconds:  The next leg or the active leg terminates at the FAF  The aircraft is on the front side of the approach  The aircraft course is within 15 degrees of the final approach course  Cross track deviation is less than half a dot  The correct station is tuned and identified.

Lateral and vertical deviation data will be transmitted by the IFD for use by any integrated autopilot and external indicators. Conversely, the IFD will toggle the nav source from VLOC back to GPS when executing the missed approach at the Missed Approach Point. GPS Based Precision Approaches Lateral and vertical deviation data will be transmitted by the IFD for use by any integrated autopilot and external indicators. For all models except IFD510, precision WAAS approaches are flown with the nav source knob set to GPS (which will automatically change to the GPS approach type). For IFD510, precision WAAS approaches are flown when OBS has not been selected using the nav source button. NON-PRECISION APPROACHES As with the case in precision approaches, as long as the published approach is entered into the FMS as part of the active flight plan, the inbound course is done automatically. All switching between GPS and VLOC (if appropriate) is also done automatically.† Procedure turns and holds-in-lieu-of-procedure-turn, when part of a published procedure, appear as normal legs in the flight plan and therefore have no special or different procedures – just fly them as part of the flight plan. DME arc legs and approaches are supported by the system.

TIPS AND TECHNIQUES CDI Deflection During VOR Approaches When VOR and GPS inbound courses are not coaligned, a large CDI deflection may occur when the Nav Source transitions from GPS to VLOC.

For additional reference, please view our training videos here:

https://www.youtube.com/c/AvidyneAvionics/videos

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  • 04-Feb-2021
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