Vectors to final with the Garmin 420/430

There recently was a blog on the COPA web site about whether or not to use the “vectors to final” selection when pushing the PROC button on the GARMIN. The VTF selection is the easy way to set up once approach puts you on a vector. You’ve dialed up ATIS so you know what approach to expect. Then you are handed off to approach control and provided directions to “fly heading 030 degrees and expect the ILS 25 approach”. You select heading on the autopilot, push the PROC button, select "vectors to final" and then “activate”. So you're all set, correct? When you select VTF the pointy end of your HSI will turn to the inbound heading for the approach. Check out the ILS 25 for KPHF (Newport News International, VA). Your course deviation indicator (CDI) would be pointing to 247 degrees and the map view would show a nice green line with STEVE INT as the final approach fix. But the problem with this approach is that the approach fixes outside of STEVE disappear.


This can become a problem when approach then decides to send you to HASBA INT which is currently not displayed on your map view or MFD (if you have one) and is not listed on the your Garmin flight plan page. An option to solve this delima is to load the approach by selecting one of the feeder fixes instead of VTF. For the ILS 25 at PHF we could select the CCV transition and then load (not activate) the approach. The COPA article uses the following technique. Go to the flight plan page, activate the cursor, and scroll down until the final approach fix (STEVE) is highlighted. The next step is to activate this leg by pressing the menu button and selecting "Active leg Hasba to Steve". This will now turn the leg from HASBA to STEVE green on your GARMIN map page and leave all the other waypoints visible. So you have CCV, HASBA, and STEVE right there in front of you for situational awareness. Another way to get to this same point is to load the approach as discussed above and then push the Direct To button. Activate the cursor and scroll to the Flight plan waypoints option. Turn the little knob and you'll get a drop down screen with all your flight plan waypoints. Select STEVE and the press the Direct To key again. The will pop up the "Activate leg HASBA to STEVE" window. Enter, activate, and you're on your way.
Usually you push the Direct To key once and then the Enter key twice to activate a direct to waypoint leg. Pushing the direct to key two times and then the enter key will activate the route from one waypoint to another. Ever been on a vector and been told to intercept an airway? Enter the begining waypoint (let's say a VOR) and the end waypoint in your flight plan (it always helps if they are already there). Highlight the end waypoint, push Direct To two times and your set up. Your HSI will swing to the leg heading with CDI slewed off depending on your distance from the course. Sweet.

Riding the Wave

Recently I’ve been flying around the Lake Tahoe area of California/Nevada. I had a student performing the GPS A approach into Minden Airport (KMEV). Minden is known as a haven for glider pilots because of the “wave” that forms when conditions are right. A standing mountain wave forms as the wind drives in from the west, rises over the mountains, and then plummets down to the desert valley floor. It’s actually a little more complicated than that; you can learn more here.

We were flying in from the southwest to intercept HOYJO intersection. The winds in the Minden valley were out of the southwest at 16 gusting to 28 but the ride at 11,000 was not bad. This flight was in a rather well equipped helicopter complete with a 4-axis autopilot. The pilot was new to autopilots in general and we were coupled in 3-axis mode. The ability to hold heading and/or the navigation course line as well as altitude is a 2-axis autopilot. The ability to descend/climb and capture an altitude is the 3rd axis. The ability to capture and hold speed (think power) would be the 4th axis. Our indicated airspeed was 100 knots, but we weren’t in a hurry and the VNE of helicopters is limited at higher altitudes (another discussion). Our groundspeed was about equal to our airspeed. At HUYJO we turned east on course to OZEDU and descended to 10,300 feet. We had just leveled at 10,300 when the airspeed jumped to 140 knots! The power (torque in a helicopter) was still set to maintain 100 knots. A quick look at the groundspeed indicated 168 knots. What’s happening here? The initial reaction from my student was that the wind was “pushing” us so we were “faster”. But we know that ground speed (read tail wind) and indicated airspeed really have nothing to do with each other. The answer was the wave. We were caught in the up flow of the wave and the autopilot was doing exactly what it was being told to do, maintain altitude. How does the autopilot maintain altitude? By pitching down and because we had the power set the airspeed increased dramatically.

The autopilot in a Cirrus works exactly the same way, it pitches to altitude. The pilot could reduce power to fix the sudden increase in airspeed. But avoid excessive power changes with the autopilot engaged. In this case (and many others) the best solution may be to disconnect the autopilot, level the wings, and ride the wave out. Contact approach and inform them of your predicament. We were in the “up flow” of the wave; the “down flow” of a mountain wave can be extreme. In the case of down flow a TAWS/CFIT escape could be warranted. In the Cirrus a TAWS escape would be to level the wings, apply full power, and pitch to 15 degrees; then flaps up (check airspeed) and adjust to Vx. To let “George the autopilot” handle the situation is to ask a little much of old George. One other item of note before we end this post. The GPS A at KMEV is a circling approach. That’s what the “A” denotes. But a perusal of the approach plate shows a straight in approach. The approach heading is 160 degrees with a runway heading of 16. What gives? Look at the MDA. This approach only gets you down to 1502 feet above the runway. So, the only way to land from that altitude at the missed approach point would be to circle. Unless, of course, you have a helicopter;)

First Post

Well, this is my first foray into the world of blogging. My goal is to provide antidotes and information about flying. Some posts will be about operating TAA equipment. Basically I’ll attempt to post unusual stuff that you might not encounter everyday. Other posts will cover procedures and also just some of my flying experiences around the country. Since I fly both airplanes and helicopters you can expect some of both. So, I hope any viewers will be patient as I learn how to do this blogging thing.