Sunday, June 24, 2007

The Case of the Disappearing Waypoint

T. is one of many customers who does a monthly sim session with me. He flies a Mooney, equipped with a Garmin 430W and is proficient on its use. His June sim session brought up an interesting scenario which is well worth sharing with you.

In the sim session, T. was flying an IFR flight from Anoka (KANE) to Rochester, Minnesota (KRST). For this particular flight, I had selected strong winds from the southeast. Playing the part of ATC, I directed T. to fly directly to CORDY intersection to start the GPS-13/RST.

T. loaded the approach into the Garmin 430 in the sim and activated it, with CORDY as the IAF. Unfortunately none of the Garmin 400/500 series downloadable simulators have a database current enough to contain the GPS-13/RST approach, so I will have to instead describe as best I can what happened. After T. loaded and activated the approach, FPL0 looked like this.

Approach GPS 13
RWY 13 (MA)

I had thoughtfully set the ceiling so he would be forced to fly the missed approach, holding at the Rochester VOR (RST). As usual, T. flew it perfectly, executing the missed approach and entering the hold at the Rochester VOR, using the SUSP feature of the Garmin 430 to bring up the holding waypoint, RST in this case.

What happened next caught both of us by surprise. I told him to anticipate the ILS-13 approach into Rochester and was planning on having him do the transition from the VOR to ELLIE.

While still in the hold at the Rochester VOR, T. decided to load the ILS-13/RST approach. So he loaded it, using ELLIE as the IAF, but did not activate it since he was still holding around RST. As soon as he did this, RST disappeared as the active waypoint. This left him in a hold without an active holding waypoint.

In discussing it later, he explained his logic was to simply load the ILS approach, the logic being that he would not activate it since he was still in the hold at RST. However, as soon as he loaded the ILS approach in the Garmin, all of the waypoints from the previous approach promptly disappeared. Since RST was not a waypoint in the loaded approach, T. was left without his holding waypoint. Had he chosen RST as the starting point when he loaded the approach, he would have still had RST in the set of FPL waypoints.

It was an unexpected scenario to both of us. The bottom line is that you should not replace an approach in the Garmin 430 if you are depending on a waypoint in the current approach for navigation. Unless you are very careful, doing so can cause you to suddenly be navigating to an unintended waypoint. I think this would be a case of being up the well known creek without a proper waypoint!

Sunday, June 10, 2007

Back to Basics - Holding 101

Probably one of the weakest areas I see in working with both instrument students and instrument-rated pilots is holding. Granted, you don’t do it too often in the real world of IFR flying, but holds do come along on occasion.

In a previous article, Creating Holding Clearances, I talked about entries into holding patterns. But in this article, let’s step back even further and talk about how to draw a hold, given a holding clearance. Surprisingly, it’s an area that experience has shown me is lacking in basic understanding.

There are two broad categories of holds – published and unpublished. Published holds are drawn out for you on either an instrument approach plate or an enroute low chart. Unpublished holds are not depicted. They start with a holding clearance, and from there you are expected to translate that into the holding pattern. A holding clearance has a very definite form.

Hold [direction] of [waypoint] on the [radial or bearing] [direction of turns] [EFC]

So a hold around Gopher (GEP) VOR could be given as:

Hold northeast of Gopher on the 060° radial right-hand turns EFC

EFC is shorthand for “expect further clearance” and is a time limit, given in the event of loss of communications.

Once the holding clearance has been given, there is often a fair amount of confusion about the correct way to translate that into a graphic holding pattern. This is what I often see. The pilot will draw a line outbound from the VOR, hesitate, then draw the right hand turn at the “end” of the outbound leg. Then they will complete the pattern, which results in a left-hand holding pattern. This is how the incorrect holding pattern looks.

This all too common mistake results from confusion about where the “right hand” turn is defined. Here are the steps to drawing it correctly. Start at the VOR and draw a line outbound on the radial. Next reverse course and draw over the same line back in towards the VOR. Once you are back to the VOR, now draw the right-hand turn, and complete the holding pattern. It should look like this.

If you will follow this procedure, your holding pattern will be correct. The key point to remember is that the direction of turn, right or left, is drawn at the VOR, not out on the radial. Another key to help you get it right is to remember that when you track inbound, you want to be tracking inbound on the specified radial, with a heading that is the reciprocal of the given radial. Your outbound track is in the same direction as the given radial, but you are offset from the radial.