The Very Inaccurate VOR Approach!
It’s no surprise this is a non-precision approach. They might as well call this an obstacle clearing procedure rather than an Instrument Approach Procedure. In my experience with the reliability of the VOR stations in the USA the way it is and the condition of most VOR receivers in today’s GA airplanes, you are more likely to find the cell phone tower 1 mile right of the final approach course as you turn your Cessna into a shish kabob, rather than find the actual runway.
In any case, let’s take a quick review of VOR approach plates and how we would fly a VOR approach.
If you need to reference the FAA approach plate LEGEND, you can do so by clicking this link: Approach Chart Legend
VOR to KARB
The VOR approaches into KARB are different from the example in the video above, given for an airport with a VOR located directly on the field. During a VOR approach, there is one KEY THING TO REMEMBER.
YOU’RE USING A VOR, JUST AS IF YOU’RE FLYING ALONG AN AIRWAY
People often forget that and treat a VOR approach like an ILS or LOCALIZER approach. The most fatal error here is just spinning the OBS knob “close” to what your inbound course will be, which you can get away with on a localizer. That will not work on a VOR, as you will be tuned to a different radial, and could wind up very far off course as you approach the airport. If the VOR is at the airport, you’ll be getting closer to the correct course as you approach the field. If the VOR is located away from the field, you’ll be multiplying your error in the improper “twist” of the OBS knob.
Other errors in flying a VOR approach:
- Not setting the OBS precisely
- Not tuning and identifying that you have the right station and that it is working (if the Morse code identifier is removed, then the signal is unreliable)
- Not doing a VOR check every 30 days
- Not doing a VOR check that TEST THE RADIAL YOU ARE USING ON THE APPROACH (VOR errors vary depending what radial you are testing from, it may pass the +/-4 degree check on a VOT, but fail another ground check from a station when testing on the 157 radial (or some random radial), try to conduct multiple checks if you are really shooting VOR approaches).
- Setting the reciprocal heading by accident (you should always have a TO indication when flying towards a VOR and FROM indication when it is at your back to have “positive sensing”.
A tale of two plates……
Take a look at the two plates below going into KARB on a VOR approach. Think to yourself, what OBS setting would I use, would I have a TO or FROM flag depending on what approach I am on (technically both approaches are “from” the VOR right?) But ask yourself do you want to use an OBS setting that gives a FROM or TO indication? Also note the distance from the station when flying the approach to runway 6 (imagine a VOR receiver that was 6 degrees off or more, which it easily could be). Being 6 degrees off with the legal VOR check, plus, a few degrees off from your own twisting and flying could easily put you 4-5 miles off course when making that procedure turn inbound, and you’d really have no idea!
What do you legally need to fly this approach?
Most airplanes have a VOR, and it’s pretty easy to perform a VOR check (date, place, bearing error, signature). So can you fly this approach (assuming your airplane is otherwise legal for IFR)?
Well, see the big note at the bottom that says “DME or RADAR” required. You are going to need some sort of legal DME (foreflight on your iphone doesn’t count) to measure your distance from SVM. A panel mounted GPS would work, or in the absence of that or an old school true “DME” from the SVM vortac, then you would need RADAR. Luckily Detroit has radar that covers this area and to my knowledge rarely ever goes down. You’ll need to have ATC “RADAR IDENTIFY” DIXBO to you and let you know when you are over that fix, so you know when you can start down to your MDA. If on the day of your checkride the examiner asks you to fly this type of approach, you better have a valid and legal way of identifying all of the fixes on the approach (in this case, without DME onboard the plane, ask ATC to “radar identify” DIXBO for you).
“Detroit Approach, Cessna 8MA, negative DME, request you radar identify DIXBO for us on the approach”