GARMIN TIPS AND TRICKS Programming and Flying Departures and Arrivals

A flight plan that contains departures (SID) or arrivals (STAR) can present challenges if you don’t commonly fly these procedures. They contain features that can complicate an otherwise routine flight plan, so let’s explore some of the potential issues.

First, when you add either procedure into the box, the flight legs that represent them are inserted into your flight plan. Where are they inserted, and with what consequences? Departures are inserted into a flight plan in place of the starting leg, while arrivals might be inserted just before your destination (in place of the last flight leg in your plan) or after it, depending on the GPS you have. These insertions have various consequences. In addition, departures often contain a variety of strange legs that you don’t usually encounter except in a missed approach. To illustrate, let’s start by looking at an interesting departure from Medford, Oregon. For those who need a refresher on the 23 flight legs specified in the ARINC 424 standards, see my article on Flight Legs.

Departures

On a flight south from Medford to Sacramento Metro via the RBL VOR, you anticipate the BRUTE7.TALEM departure from Runway 32. You can either make the flight plan without a departure and add it when you get your clearance, or anticipate one and begin your flight plan with it and add waypoints after the chosen transition. In the first case, the leg from MFR to RBL would be eliminated by adding the departure, which ends at the transition waypoint TALEM.

Figure 1. The RW32.BRUTE7.TALEM Departure from Medford, Oregon. It’s represented by seven flight legs, and several are a bit unusual. It starts at the departure end of Runway 32 and ends at the TALEM transition.

 

Since we anticipate that departure in our clearance, let’s first create a flight plan consisting solely of the departure as in Figure 1, showing the preview on a GTN 750. Here is how this is done using any recent Garmin GPS (300 series through G1000, excluding the GNS 430/530 and 480). With an empty flight plan, select PROC, then departure, then put in KMFR, RW32, and TALEM.

The first leg is a point leg, the point in question being the departure end of Runway 32. Had we made the plan KMFR-RBL-KSMF, without a departure, there would instead be a leg at KMFR (a point about halfway down and a little offset from Runway 32) followed by a TF leg (track-to-fix) to RBL. Here, the initial leg changes to the takeoff end of RW32, the leg to RBL is eliminated, and a leg from TALUM to RBL is created. If this isn’t your clearance you need to edit the plan to get to RBL by your cleared route.

Turning to the departure, the second leg, a CA leg (course-to-altitude), follows the runway course (323 degrees) and ends at an altitude of 1,735 feet. This could also have been a VA leg (heading-to-altitude) on the runway heading. Remember, a flight leg is described by the path it takes and how it ends, so the difference between the two is following a course over the ground or a heading.

The first question is whether your GPS will recognize this leg-ending altitude. In general, a leg will sequence to the next one if your GPS knows when the active leg ends. In this case, it depends on whether your unit receives baro-corrected altitude data. Of course, if sequencing is suspended you will know it because the SUSP light comes on and you need to push the SUSP button to sequence when you’re ready. (Avidyne GPS receivers don’t have a SUSP button so there you need to activate the next leg if it doesn’t sequence.)

The next leg is a VI leg (heading-to-intercept) and it does sequence automatically on modern Garmin receivers, but does not on the GNS480 (the 430/530 doesn’t even create this leg). The intercept point depends on where you sequenced from the CA leg, and on the wind on the VI leg, which then determines where this intercept happens. So, your GPS must have software to recognize when you are about to intercept the CF leg (course-to-fix) to BRUTE. Some GPS navigators can recognize this intercept point, and some cannot.

The DME arc is an AF leg (arc-to-fix). It differs from an RF leg (radius-to-fix) which is also an arc, but on the latter the entry and exit to the arc are along a tangent. On this AF leg you are in a constant turn, and hand flying this arc can be a little challenging. Unlike an RF leg, it ends with a 90-degree turn. The remaining legs are conventional straight legs ending in a waypoint.

Another question is, what signals does your GPS create on each leg for autopilot tracking? Two types of signals are possible; one is an analog signal to your CDI or HSI to deflect the course needle so that your autopilot (in an analog mode) can react to zero-out the tracking error. The other signals are digital pitch or roll commands the autopilot uses regardless of the CDI tracking error, which it ignores. Roll commands are tracked by engaging the GPSS mode on the autopilot, while pitch commands are tracked in GPSV mode. Figure 2 shows these two modes on an STEC-31 digital autopilot.

Figure 2. Pitch and Roll modes on the STEC-3100 digital autopilot. The lateral mode is APR (Approach mode), tracking the roll command on approach. Instead of GPSS, as is normal, their terminology is GPS Lateral for approaches (GPSL). The vertical mode is Altitude Hold, but the GPSV mode is armed and will become active upon intercepting the GPS glidepath.

 

In the display, lateral modes are on the left and vertical modes on the right. Active modes are on the top and armed modes are on the bottom. In this case we have selected APR as the lateral mode and since we’re on the approach, GPS Lateral (rather than GPSS) is announced. Vertically, we’re in the altitude hold mode, but GPSV is armed and will automatically become active when the glidepath is intercepted.

On our departure, analog signals for all but the VI leg (and IF leg) are sent to your CDI or HSI. Roll commands are sent on all legs (except the IF leg). So, if you have an analog autopilot, you can track all but the VI leg. On the VI leg you’ll get roll commands if your GPS knows your heading from an interfaced magnetometer, which all modern units have. This is generally not true for legacy GPS units. For example, the 430/530 units don’t even create VI legs. The GNS 480 does, but it doesn’t receive a magnetometer input to compare your heading with the one specified for the leg, so it doesn’t issue roll commands.

If you don’t have a digital autopilot, GPSS convertors will create heading commands for your analog autopilot that can be flown in heading mode after selecting (with a GPSS switch) these signals over those from a heading bug. With that setup you can track the VI leg.

In summary, adding a departure makes several changes to your flight plan; it shifts the first IF leg, eliminates the leg after that, and creates a new leg after the transition. The leg types in the departure are somewhat unusual. It’s important to know which ones will sequence automatically by your GPS, and whether (and in what mode) your autopilot can track them.

Arrivals

Unlike departures, arrivals generally contain the usual IF leg at the initial fix and TF legs thereafter except at the end, when an Arrival often ends in a vector, which is a FM leg (fix-to-manual termination). As we’ll see, even though there is no end to this leg, there is one important circumstance in which you will sequence automatically from that vector leg; when joining a vector-to-final for an approach added to your plan.

A common issue with arrivals stems from the geographic length of the procedure, with the transition often starting a considerable distance from your destination. If your flight plan has fixes between that transition and your destination you will automatically sequence to these and pass the transition and subsequent arrival legs. In some cases, the arrival path and your flight plan path may cover common ground. In general, you will need to intervene to avoid backtracking.

Specifically, you’ll likely need to leave your enroute flight plan to join the arrival, whose legs are further down your flight plan list, skipping any legs in between. There are two options for leaving your flight plan. One is to go direct to the transition or a fix at the end of one of the arrival legs, skipping all the legs in between. Another option is, if you’re tracking an enroute leg and it’s overlapping a later arrival leg (which sometimes happens), you can activate that arrival leg to bypass everything in between. The good news here is that ATC will tell you what to do and when, so you simply need to follow directions.

To illustrate these points on a flight plan to Salt Lake City from Twin Falls, Idaho. The plan is to pick up V142 from TWF to SHEAR, joining V101 there to the Wasatch VOR (TCH), then KSLC. Adding an arrival to this plan in the GTN 750 will eliminate the leg from TCH to KSLC and insert the arrival legs in its place. On the way to SHEAR we’re advised that KSLC is using Runway 32, and we should expect the BEARR5 arrival (BYI.BEARR5.RW32). Figure 3 shows that BEARR5 arrival with a transition at the Burley VOR (BYI), which is about 130 miles from KSLC, while TCH is very close. If we sequence normally on our enroute plan we’d go all the way to TCH, then go backwards to BYI. Interrupting the enroute flight plan will be required.

Figure 3. The BYI.BEAR5.RW32 arrival into Salt Lake City. Here, BLIDA AND BEARR are waypoints on V101, as is SHEAR which is in our flight plan and is the unnamed waypoint before BLIDA here.

 

We note from our map that the first leg on V101 beyond SHEAR is BLIDA, followed by BEARR. Both TF legs are part of the BEARR5 arrival. A likely possibility is that after reaching SHEAR we may be cleared to join the arrival. However, while our active enroute leg is from SHEAR to BLIDA, we are also flying the path of the arrival leg to BLIDA, but our GPS doesn’t know it. You have to fix that. Simply scroll down the flight plan list, into the arrival portion, and activate the arrival leg you’re now on. You could at this time go direct to BLIDA, but this creates a DF leg that technically is not the same as activating the arrival leg. Remember, BLIDA appears twice in our flight plan, first on the enroute portion and next in the arrival sequence, as in Figure 3.

Now that you’re on the arrival you may need to program an approach into your plan.  How will you transition from the last arrival leg to the approach? If the arrival ends in a vector as it does here, it’s usually designed to send you on a path that makes it easy to transition. For example, the vector could intercept the final approach course, or send you on a downwind leg as is done here, so you can be vectored towards final. Other arrivals might end at a fix, which is an initial approach fix for the approach. Each case is different, and you simply need to study this transition so you can plan to execute it smoothly.

For our case of a vector leg after DYANN, sequencing is suspended but roll commands are available (it’s a VM leg, or a heading vector) for a digital autopilot or an analog autopilot with a GPSS convertor. We have added an approach (ILS or RNAV) to RW 32 using VTF as the transition, and this vector is taking us downwind (south) on the west side of the airport. As we’re being vectored off the 160 degree heading from DYANN (heading mode on our autopilot) our heading instructions should be turning us east, then north to join the vector-to-final course for the approach. When within a 45-degree intercept of the course, sequencing will automatically be restored and the VTF leg of the approach becomes active. At this time, select the APR mode on your autopilot to fly the approach.

Dr. Thomassen has a PhD from Stanford and had a career in teaching (MIT, Stanford, UC Berkeley) and research in fusion energy (National Labs at Los Alamos and Livermore). He has been flying for 64 years, has the Wright Brothers Master Pilot Award, and is a current CFII. See his website (www.avionicswest.com) on all his manuals plus numerous articles on GPS and other aviation topics.