Garmin Tips and Tricks #20
The new GTN 650/750 software
Keith Thomassen, PhD, CFII
www.avionicswest.com

 

In the last Tip we discussed how the latest software (v6.11) for the GTN 6XX/7XX lets you add holds to your flight plan.  It also added other features, like adding +V to LP approaches, recognizing when a VI leg needs to sequence at the intercept (no leg suspension), and other features.  One of the new additions described here is the change in the way Approach (and Arrival) legs are added into your flight plan.
Garmin has always added the Approach and Arrival legs after your Enroute flight plan, that is, after your destination waypoint.  This began with the 430/530 and continued with the 650/750 and G1000.  In contrast, in the year 2000 time frame, the Apollo CNX 80 (now Garmin 480) and Chelton added these legs in place of your last leg to your destination. The new Avidyne 440/540 does the same thing. This creates issues when you add the approach if you are currently flying on that leg to your (clearance limit) destination. Namely, your current (active) leg goes away – swept out from under you!
With the new software Garmin has gone over to the dark side, and done the same thing.  Here in Fig 1 is a flight plan from Clovis, NM to Lubbock TX, through Muleshoe (2T1). The RNAV (GPS) Y 17R with Vectors was added.  The screen shot on the left a shows our map on the 750 before adding the approach, while that on the right shows the map after adding the approach.


Figure 1.  Flight Plan to Lubbock, TX;  KCVN, 2T1, KLBB with an RNAV approach.

Clearly, your last leg was wiped out, and if your clearance is to Lubbock and you add this approach early, you don’t have flight guidance after Muleshoe.  Worse, suppose you add the approach while on the leg to Lubbock from Muleshoe, and you haven’t yet been cleared for the approach (don’t do that!).  So the lesson is, wait until cleared for the approach and are directed to your iaf or have been given vectors off of your course.  You can use HDG mode on the autopilot to fly this while you add the approach.
Imagine the problem you have if you only had one leg in your flight plan.  Let’s eliminate 2T1 and make a simple plan from Clovis to Lubbock.  Now, there is only one flight leg, shown on the left of Fig 2. Adding an approach should wipe out your entire plan, right? On the right is the plan after adding the Approach. But, “Alors”, it’s now added after your destination?  ¿Que´ pasa?
Both the Avidyne and 750 make exceptions for the leg insertion of Arrivals and on Approaches if there is only one leg in your flight plan. [Actually, there are two legs here because your departing waypoint is an IF leg, or point leg, as are initial transition waypoints to Approaches and Arrivals.]


Figure 2.  A “one-leg” Flight plan with an Approach added – after Destination.

There are also interesting differences in adding Arrivals to one-leg plans, which you can explore in my new manual “GPS for Pilots” on my website (www.avionicswest.com).  This manual is all about the problems pilots typically encounter with their GPS, and what to do about them.  I see the same set of problems – over and over - with all of my students so the manual uses the Garmin, Chelton, and Avidyne to illustrate the different ways of dealing with the same issue.

 

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