Thursday, March 08, 2007

The 4 NM Hold

Holding patterns based on distance rather than timed legs are becoming increasingly common, particularly for GPS approaches. Whether it is a turn around holding in lieu of a procedure turn or holding at the missed approach waypoint, 4 nm legs are becoming quite common.

The traditional method for making a teardrop entry into a hold is to turn approximately 30° away from the outbound heading, making the turn so as to stay inside the protected area of the hold, and fly for approximately one minute before turning back to intercept the inbound course. (See "A Eureka Moment".) This time honored technique works quite well for holds based on one-minute inbound legs, but it doesn’t work so well for the 4 nm holds. If you make the conventional turn for a teardrop entry and fly until you are 4 nm away from the holding waypoint, you might be far enough away from the inbound course to make intercepting it problematic.

So consider a variation on the teardrop entry. In this method, after crossing the holding waypoint, turn to the heading for the teardrop entry and fly for one minute. At the end of one minute, turn to the outbound heading and parallel the inbound course until 4 nm from the holding fix. Then turn to intercept the inbound course.

Below is shown the track of a turn around holding for a procedure turn at NOVSY, from the GPS-12/OWA. The turn around holding was flown by one of the instructors at Sim Flite Minnesota, who wanted to do some sim work to keep her instrument skills sharp.

I would say from the track, that her skills are quite good. Try this technique for a hold with 4 nm legs. It works quite well.

Sunday, March 04, 2007

Little Things That Can Ruin a Flight

In Right Airport, Wrong Approach, I described a short instrument training flight from Anoka (KANE) to New Richmond (KRNH) to Osceola (KOEO) and back to Anoka, with an approach planned at each airport. The article describes how to get the Garmin 430 to display the approaches for the next airport in the route (KRNH) rather than the final airport (KANE).

Once that was taken care of, we proceeded to New Richmond, where my student did the GPS approach. The plan was to then go to Osceola and do the GPS approach there. New Richmond and Osceola are relatively close together, which does not leave the pilot much time to troubleshoot any problem that might occur.

At New Richmond, once again we employ the MENU trick in order to bring up the approaches for Osceola. There are only two, a traditional NDB approach and a GPS approach, both for runway 28. But now there is a nasty little surprise waiting for the unwary. The 430 database only shows the traditional NDB approach.

But your trusty Jepp or NOS instrument approaches distinctly show two approaches for Osceola. Time is short, and you quickly reload the approaches for Osceola. But the 430 stubbornly insists there is only the one approach. The MSP approach controller is getting a little more insistent – what do you want to do, fly the full approach or take vectors. Perhaps the easiest way to handle this is to select the full approach, which makes the NDB at OEO a waypoint.

With the OEO NDB as the active waypoint, the GPS can then be put into OBS mode and the HSI or OBS course selector set for the final approach course. Then the approach can be flown, using the 430 to make a virtual VOR out of the NDB.

Things to double check – OEO is the active waypoint, the VOR display or HSI is being driven by the GPS (CDI is set to GPS) and the unit is in OBS mode. You can now fly an intercept course, and life is good again. MSP approach is happy again too, which is always a good thing.

But why was there no GPS approach into Osceola? You have an approach plate for it, but it was not in the GPS database. The answer is one of those little things that can jump up and bite you at the most inappropriate of times – Notams.


Yep, the GPS-28 approach into Osceola is not authorized. In questioning Jeppesen about the mismatch between the printed approach procedures and the GPS database, it appears that it is much easier to remove it from the database than to remove it from the printing process. So in order to comply with the FDC Notam, the approach was removed from the database. The object lesson here is that it is all too easy to become complacent, particularly when dealing with airports and approaches that are very familiar.

Our last planned approach was the ILS-27 back into Anoka (KANE). The wind was out of the northwest, so a straight-in approach was planned. But what if you had planned on doing the VOR-DME-27 approach into Anoka?

Once again, those pesky Notams could jump up and bite the unwary.


Because of the FDC Notam, you can only descend to the circling minimum of 1400 feet. Those extra 60 feet, if you weren’t aware of them, could certainly result in a pink slip on an instrument checkride.

The bottom line is to check those Notams. Use the Find function in Notepad or whatever you use to search for everything relevant to your flight. Don’t let complacency ruin a perfectly nice flight.