Tips and Tricks #31
Using your Flight Plan

Keith Thomassen, PhD, CFII
www.avionicswest.com

A flight plan can be viewed as a structure that you create/use for specific flight purposes. It can be as simple as two waypoints, the origin and destination. Or it can be a more extensive plan, perhaps with airways, and to which procedures have been added. In either case, the emphasis in this article is how to create/use a plan advantageously. I'll illustrate this shortly. Let's start first with a VFR plan (no procedures).

You depart Sacramento Executive and want a simple plan direct to John Wayne Airport (KSAC to KSNA). There are two ways to do this; go D-> KSNA or make a flight plan by entering both waypoints. To go direct, push the D-> button and enter KSNA, then select D-> Activate, as shown in Fig 1 (left). If you want to delete any D-> operation in your flight plan push the Direct button then select Remove, as shown in the figure on the right.

Figure 1

Figure 1. Going D-> KSNA creates the flight plan page on the left, which has no flight legs in the list. The way to remove this operation is on the right; push the D-> button then Remove.

Is this a "real" flight plan? In some sense, it's not. No flight legs are listed there, but you did create a CF leg (Course-to-Fix), and that operation is listed above the area where flight legs would be listed. In contrast, you could make a plan from KSAC to KSNA as in Fig 2 (left). Now, after takeoff you could "re-center" on course by selecting KSNA and go Direct, giving the screen on the right. Note that the Direct operation is indicated there by the short arrow. The difference between these two ways to go Direct to KSNA is not simply how they are displayed.

Suppose you want to add two intermediate points on the plan, Lemore (KNLC) and Bakersfield (KBFL). You can't do that in Fig 1, as that would create a plan between those two waypoints while going D-> KSNA. Now, to go to KNLC you have to select D-> KNLC. The plan then ends at KBFL and it's no longer a plan to KSNA. So to edit a plan, make a "real" one.

Figure 2

Figure 2. A simple flight plan to KSNA (left) altered before takeoff by going D->KSNA.

If you insert those waypoints into the plan in Fig 2 (right), you're still going D-> KSNA but would then have 4 waypoints in the plan. This makes it easier to get information at these 4 Fixes, such as TAF's and METAR's, frequencies, and NOTAM's. Just touch one of the waypoints and select Waypoint Info. This is a quick way to get to the ATIS frequency and select it to find surface winds, temperatures, and other data. This example illustrates the point of this article, how to use your flight plan - here by adding extra waypoints where you may want Enroute information (without actually flying through those waypoints).

Let's turn to more complex situations. When you add IFR procedures to your flight plan you complicate what was otherwise a simple plan with point-to-point flight legs that automatically sequence when you get to the end of each one. You may have added a Departure, or perhaps an Arrival followed by an Approach. Each of these has the potential to disrupt the orderly flow of the original flight plan. In addition, it may add flight legs that no longer end at a fix, but may end in an altitude, intercept, DME distance, etc. This can complicate the normal sequencing of flight legs, if some of those legs don't sequence. When suspended, you have to intervene. Some of these legs may not provide autopilot guidance, depending on which GPS you have, and on other assisting devices (AHARS, ADC, and magnetometers, for example).

Adding a procedure generally leaves you with a plan that has extra legs you won't fly. For example, departing your airport, your flight plan goes to a nearby VOR then onto an airway towards your destination. But the Departure can overlap these legs. A specific example is a flight from Salt Lake City to Boise; we file for KSLC to TCH, V484 to TWF, V253 to BOI, KBOI. Clearance Delivery gives us the CGULL1 departure to TWF, which we enter into the plan. These legs are inserted after KSLC, before the Wasatch VOR (TCH) that's 4 nm north of KSLC. From TCH its 149 nm to TWF, so after reaching TWF on the Departure the next leg is back to TCH where we pick up V484 to TWF. So we need to eliminate lots of legs, but not by editing.

After several Departure legs we are on V484, so after joining it we could select a leg from our Enroute plan on V484 that overlaps the one we're on, and Activate it. This will skip many legs in the plan, namely, the remainder of the Departure legs and the first several Airway legs of our Enroute plan. Let's be specific; here are the Departure Legs.

KSLC to CORVR, CGULL, MOFER, SCOVL, DRYAD and TWF

From TWF we go back to TCH to join V484 whose legs are;

TCH to JOSIF, RIDEN, CAUSE, HOGUP, SWITZ, DRYAD, CEEDY, WODEN, FERUD, TWF

Since DRYAD is on both of these lists, one clear option is to Activate the airway leg from DRYAD to CEEDY as soon as you reach DRYAD on the Departure, skipping the remainder of the Departure to TWF and skipping ahead of all the V484 legs from TCH to DRYAD.

Here's another example. On the return flight from Boise we file the above plan in reverse, on V253 and V484. After climb out we're cleared direct Burley (BYI) for the BEARR5 Arrival into KSLC to runway 34B (both). There is an Arrival Transition at BYI that we select. The flight plan with the Arrival is shown in Fig 3 (left). A portion of our flight plan is shown on the right, where the leg to TCH on V484 is shown followed by the Arrival legs. On the map you can see our airway plan through TWF to TCH, followed by a leg back to BYI. Here, when cleared to Burley, a simple D-> BYI operation from our present position skips everything remaining on the airways and the leg back to BYI. There we join the arrival and everything sequences normally.

Figure 3

Figure 3. The BEARR5 Arrival into KSLC with the BYI Transition, shown on the map (left) and in a portion of the flight plan (right).

If you look carefully at the map, above CAUSE, you'll see a Top-of-Descent (TOD) mark where you start a VNAV slope to hit a crossing altitude of 11,000' at the DYANN waypoint. To couple the autopilot to fly this slope you need a digital autopilot like the Garmin GFC 500. Arming the VNAV mode prior to the TOD will make it active there.

We could pick endless examples to illustrate a variety of situations that require manipulation of your flight plan, which are geometry dependent. If you add an Approach, where does it go in relationship to your flight plan legs? Are the legs added in place of the last Enroute leg or after the Destination. The key is to examine the flight plan after adding the procedure, study the geometry, and make a plan for the transition from Enroute to Approach, just as you do for Departures and Arrivals.

 

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