GTN750 Load Procedure

One does not need to activate the approach to fly the approach. Many instructors, including myself recommend not using the activate approach method because it is poorly understood and doesn’t always accomplish what the pilot wants. Activate the approach causes the navigator to perform a direct-to the first waypoint of the approach procedure, as it was originally loaded. So if an IAF is the first waypoint, then activating the approach is the same as a direct-to the IAF. If a feeder waypoint is the first waypoint, then it will be the equivalent of a direct-to the initial feeder waypoint, and so on. If an approach is repeated because of a missed approach, the version in the flightplan may not include a required course reversal, or the IAF may be different for the redo. Activating the approach still starts the approach back at the original IAF/IF with the original course reversal regardless if it is appropriate for the redo. A better method, in my opinion is to load the approach and at the appropriate time select the specific waypoint needed to join the approach. Here in the US, we teach the student to avoid using the VTF function until the pilot is absolutely sure it is the method to be used to join the approach, always load the full procedure. Switching to VTF is a very simple operation later in the approach, but going the other way, from VTF to direct to another fix in the approach procedure involves reloading the approach. So, if you want to avoid the question, what is it doing now, proactively select where you want to navigate to rather than using the activate approach function.

In general, the flightplan is divided into four sections: The SID, Enroute, STAR, and Approach sections. If you start loading the sections by adding the departure airport, enroute waypoints, and destination airport. These initially together are the Enroute section of the flightplan. If you add a SID, the departure airport is removed from the Enroute section and the SID starting from the runway is inserted before the remaining enroute section. If you add a STAR, it is inserted after the enroute section that still includes the destination airport waypoint. The STAR also ends with a duplicate copy waypoint of the destination airport. Regardless if there is a STAR or not, the flightplan ends at the destination airport. If you then load an approach, the destination airport remains in the Enroute section, but the destination airport is replaced in the end of the STAR by the approach procedure. If no STAR is loaded, then the approach procedure is added after the enroute portion that includes the destination airport.

Because the destination airport is included in the Enroute section, navigation will be to the destination airport and then to the STAR if one is loaded or the approach first fix if a STAR is not loaded. In most cases, the aircraft clearance limit is the airport. When they are cleared for the STAR, the pilot is expected to load the flightplan and select the first waypoint of the STAR, rather than navigating to the destination airport. When the pilot is cleared for the approach, with or without a STAR, they are expected to select the first waypoint in the Approach section to navigate to (this will occur if one activates the approach or does a direct to the first waypoint in the procedure). In the case of lost communications, in the US, we are required to fly to our clearance limit and then to the IAF to commence the approach. Since the clearance limit is typically the destination airport and the Enroute section ends at the destination airport, the GPS will automatically sequence to the IAF and fly the approach. Even when expecting vectors, navigation is typically to the destination airport waypoint until vectors are provided.

Regardless, there is never a need to delete the airport waypoint from the enroute section to transition to the approach, as all the pilot needs to do is to either activate the approach when cleared for the approach, or select an appropriate fix within the approach procedure to navigate to, or select VTF.

Vectors To Final ?

Many instructors, including myself recommend not using the activate approach method….

A better method, in my opinion, is to load the approach and at the appropriate time select the specific waypoint needed to join the approach….

I am sorry NCYankee but I do not understand the exact procedural differences
(i.e. when and what do you do differently to and with your friendly GPS navigator?! )
in the two methods – the one you refer to as “the active approach method”
and “the other one”?

He means load the approach and then do a direct to the fix you want to go to. I also do not use activate approach.

At the moment you do a direct to any of the fixes of a loaded approch the approach IS activated

I am sorry NCYankee but I do not understand the exact procedural differences
(i.e. when and what do you do differently to and with your friendly GPS navigator?! )
in the two methods – the one you refer to as “the active approach method”
and “the other one”?

Using the activate approach function is an implied direct-to the first waypoint in the approach procedure that is currently loaded into the flightplan.

I prefer not to use the implied direct-to “activate approach”, but rather use an explicit selection of the waypoint within the approach procedure that is currently loaded into the flightplan. This allows the approach to be joined at any fix within the approach procedure that is currently loaded into the flightplan, with the exception of the FAF. Here in the US, controllers are permitted to clear an aircraft direct to a fix within the approach procedure including an IF or a stepdown fix between the IF and the FAF. These fixes are not choices in the load approach dialog as it only provides choices for various IAF or initial feeder fixes. If cleared to the IF that is not an IAF, activating the approach will take you to a fix that you are not cleared to and in fact may be behind you.

I do understand that using the DIRECT-TO command will allow me to proceed without delay to any waypoint (with exception of the FAF) of the pre-LOADED approach sequence, while use of the ACTIVATE command will guide me to the first waypoint in the SELECTED (not yet LOADED) or the already pre-LOADED approach sequence.

What I still fail to appreciate is the apparent preference of many here (if I understood your comments in this thread correctly) to use the DIRECT-TO command rather than the ACTIVATE command under ALL CIRCUMSTANCES, including
(1) when the clearance for the approach
(including the entry point into the procedure via one of the “standard” commencement/entry choices offered to you by your helpful GPS navigator just after you had decided which of the available approaches you are going to embark on today),
is received BEFORE any approach has been pre-LOADED by you in anticipation of clearance; or
(2) when the clearance finally received specifies the approach that you have already correctly pre-LOADED
BUT via a different entry point – the occurrence not uncommon in my experience, and requiring ab initio re-programming as per (1); or
(3) when the selection of the entry waypoint (one of the “standard” ones as in 1) into an approach is done by the pilot alone (an everyday occurrence for many un-towered airfields located within Australia’s vast G-class airspace. If still in controlled airspace when ready for descent, the pilot usually requests clearance to descent into uncontrolled airspace below tracking from the present position directly to the selected-by-him/her entry point of the chosen-by-him/her approach procedure).
In all these cases I would use the ACTIVATE command rather than the LOAD followed immediately by the DIRECT-TO command…….

My 2 Australian cents = (at the current exchange rate) = 5.41 Polish groszy