VOR/DME approaches

© Hal Stoen, September 10, 2000

VOR/DME approaches differ from the VOR approach in that they have distance (DME) information available. Here is a VOR/DME approach plate for Hutchinson, Kansas.

What's new, or different on this approach plate?

First off, notice that there is no "timing box" in the lower left corner. With distance information available, you can be much more certain of where you are on the approach. Let's look a few items on this approach plate that were not, or were not addressed, on the previous one.

The ATIS frequency, 124.25 is shown, operation is not continuous. The frequency for Hutchinson Approach would be shown on the first plate for Hutchinson, most likely (and indeed true) an ILS approach plate. The Hutchinson Tower and Ground do not operate continuously. The notation "Wichita Radio CTAF" means that the frequency 118.5 is the Common Traffic Advisory Frequency when the Tower is not in operation. The last note "When Control Zone not effective, except for operators with approved weather service, use Wichita altimeter setting." Translation: If the tower is not open, the Control Zone does not exist. Unless you have a certificated weather observer on the ground to take weather observations for you when the Tower is closed, you must use the altimeter setting from the nearest airport, in this case, Wichita. And, of course, if you have to use a remote altimeter setting, the minimums will probably be higher.

On the back of the first approach plate for the airport there would be the information necessary to use this service.

The tallest object in the approach area. In this case, a tower that is 3,049 feet tall.A "spot elevation". The terrain at this point is 1,928 feet, msl.

 

The published minimums for this approach. For a straight-in landing to runway 21, with the tower in operation (Control Zone Effective), the minimums are 458 & 1: 458 feet above the ground (2,000 msl), and 1 statute mile of visibility, day or night. If it is night time, and the Tower is closed, then the minimums bump up to 698 & 2: 698 feet above the ground (2,240msl), and 2 statute miles of visibility.

OK, I understand all of that. Now, how would I go about shooting this approach?

We're going to go through several different ways that this can be done: without radar, with radar, and via a DME arc.

Without radar

You are currently Southwest of the Hutchinson VOR, level at 7,000.

At some point, Center will call you. "Red Baron 123, turn right heading 020, descend to an maintain 5,000". "Right to 020, out of 7 for 5, Red Baron 123." 'Roger Red Baron 123, now proceed direct to the Hutchinson VOR, maintain five." "Direct the VOR, maintain five, Red Baron 123." Nav. 1 should be set to the HUT VOR, and, as long as there are no intersections for the approach that are based on another navaid, #2 can be set to HUT as a backup. Two miles Southwest of HUT Center calls. "Red Baron 123, contact Approach on 124.55". "124.55, good night." "Good evening Approach, Red Baron 123 with you, leveling 5,000, Echo (the current ATIS)." "Good evening Red Baron 123, you're cleared the VOR/DME approach runway 21 into Hutchinson. Proceed direct to the VOR. Descend to and maintain 4,000." "Direct the VOR. Cleared the approach, out of five for four. Red Baron 123." "Roger Red Baron 123. The Tower at Hutchinson is closed for the night. The one hour old altimeter setting for Hutchinson is 29.73, the current altimeter at Wichita is 29.75."

Ah, a little sneaky here. That means that the Control Zone will not be in effect, and it's night time. What are your minimums? Looking at the plate we see:

So, at night, with the Wichita altimeter setting the "Circle-To-Land" minimums apply in this case.

That makes the minimums for this approach 698 feet (agl) and 2 (statute miles visibility).

"Red Baron 123, Hutchinson Approach is closing operations at this time. Make all radio calls on the CTAF, 118.5. In the event of a Missed Approach, contact Denver Center on frequency 118.75. Good night." "Attention all aircraft this frequency, Hutchinson Approach is now closing operations for the day. All traffic arriving and departing Hutchinson use the CTAF, 118.5. Good night." At this point the "TO/FROM" flag flips over to read "FROM". Set the course selector on the HSI to read 033, the outbound radial for the approach, and track it outbound. You are already level at 4,000 and cannot descend any more until Procedure Turn inbound. Now, where to start that procedure turn? The plate states that it must be done within ten miles of Turky, which is 9 miles from the VOR. That makes your outside limit at 19 miles DME from the HUT VOR.

Turky is your FAF (note the Maltese Cross), so you know that you want to be level at 2,500 feet when you get there, and, you want the aircraft to be in an approach configuration. Looking at the chart, it would appear that a couple of miles from Turky, call it 11 DME, would do it. Remember, it's your decision, your call. As long as you remain within your altitude limits, and the approach airspace, no one cares how you make your turn. Some pilots would turn left 90 degrees for 30 seconds, then make a 180 until they intercept the 033 inbound. The DME clicks over from 10.9 miles to 11.0. You start your procedure turn by turning to a heading of 348 degrees. Note the time. One minute later, you make a 180 degree turn to 168 degrees. All turns are Standard Rate turns. At this time, set your course selector on the HSI to read 213 degrees. In about one minute, depending on winds, you should intercept the 033 degree radial inbound.

As you intercept the 033 degree radial, the DME shows 13.5 DME from HUT, 4.5 miles from your FAF of Turky. Now you can descend out of 4,000 for 2,500. And, as a precautionary safety measure, make a blind radio call on the Hutchinson CTAF, 118.5. "Hutchinson Traffic, Red Baron 123 is on the approach into Hutchinson, Procedure Turn inbound." Why? There could be someone taxing out at Hutchinson. He'll be guarding the frequency too. As a matter of fact, he should also announce that fact on the CTAF. Your "blind call" let's him know that there will be landing aircraft, and that he should use caution if he takes the runway before you land. As you approach Turky, approach power should be set, the first notch of flaps should be down. The DME counts downward toward 9.0 miles.

Turky. The DME reads 9.0 miles, the CDI is centered. Drop the gear, start your descent towards 2,240 feet. And, make a radio call. "Hutchinson Traffic, is at Turky inbound on the approach." You hear: "Roger Red Baron 123, Midwest 417 is holding short of the runway, we'll hold for our departure until you land Sir." Hey, a heads-up guy. "Thank you Midwest 417." Level at 2,240 the DME counts down to 7.4 miles when you see the runway. Adjust your position as necessary for landing. "Hutchinson Traffic, Red Baron 123 is on a one mile final, runway 21, Hutchinson." If, when the DME reads 6.0, you cannot see the runway, it is Missed Approach time.

With radar

You are currently North of the Hutchinson VOR, level at 7,000 feet.

Approach Control will vector you for the approach. "Good morning approach, Red Baron 123 level at 7,000, information Tango. "Roger Red Baron 123, fly heading 090, descend to and maintain 5,000." "Out of seven for five, 090 on the heading, Red Baron 123." "Roger Red Baron 123. This will be vectors for the VOR runway 21 approach into Hutchinson." "Roger, Red Baron 123." Approach will give you changing headings until they have you outside of the VOR, and more or less lined up with the 033 degree radial from the HUT VOR. You should have Nav. 1 radio set for the HUT VOR, Nav. 2 as well for a back-up. Your DME, tuned by the #1 Nav. radio, will show distance to the HUT VOR. The CDI on the HSI will be set to 213 degrees, as well as the VOR head on #2. You should be adjusting your power towards your approach power settings. "Red Baron 123, fly heading 190. Intercept the approach on that heading and track it inbound. Descend to and maintain 4,000." "190 on the heading, track the approach inbound, out of five for four, Red Baron 123." You look at the DME, and it displays 16.5 miles.

The CDI on the HSI centers as the DME counts down to 15.0 miles. Fly headings as necessary to track the 033 degree radial. "Red Baron 123, I show you intercepting the radial at this time, you're six miles from Turky. Descend to and maintain 2,500. You're cleared the approach, contact Hutchinson Tower at Turky inbound." "Out of four for 2,500, cleared the approach, Tower at Turky, Red Baron 123."

You are here:Turky is the FAF (Final Approach Fix) for this approach. Level at 2,500, you watch the DME countdown towards 9.0 miles- Turky. At this point the aircraft should be set up completely for the approach. The only item left will be to drop the gear. The DME drops down from 6.1 to 6.0. You are at Turky. Drop the gear. Start your descent out of 2,500 for the MDA, 2,000 feet. "Hutchinson Tower, Red Baron 123 is Turky inbound." "Roger 123, not in sight, cleared to land runway 21." "Cleared to land, 123". Level at 2,000 feet, you watch the DME. When it gets down to 6.0 you must be able to see the runway in order to land. If you see the runway at any time prior to the 6.0 DME readout, you may position the aircraft as necessary and proceed to land. If you do not see the runway at 6.0 DME, you must go Missed Approach.

Via a DME arc

Flying a DME arc is an effective way to join the final approach course. It is also expeditious, as no Procedure Turn is required, even in a non-radar environment.

Note the remarks by the arc. "15 DME Arc, 3,300 No PT." This means that once you are cleared the approach, via the arc, and you are established on a published segment of the DME arc, you may descend to and maintain 3,300, join the final approach course, and fly it inbound, without the Procedure Turn.

"Good morning Approach, Red Baron 123 with you, niner thousand, Romeo" (the current ATIS). "Roger Red Baron 123, fly heading 300 and join the 15 mile arc for the VOR 21 approach into Hutchinson. Once established on the arc, descend to and maintain 3,300." "Heading 300, join the arc. 3,300 once established, Red Baron 123." "Roger Red Baron 123, report intercepting the 033 degree radial." "Report intercepting the 033 degree radial, 123."

On your assigned heading of 300 you watch as the DME counts down towards 15.0. While that is going on, set the course selector on the HSI to 213 degrees, the inbound radial for the approach. The DME reaches 15.1 miles. Turn right 30 degrees. This is just an arbitrary guess on your part, you know that the 300 heading intercepted the arc, therefore you will have to turn right to keep from getting closer to the VOR. Watch the DME, does it stay at 15.0? If it does then maintain your heading. If it increases to 15.1, turn left another 5 degrees. If it goes down to 14.9, turn right another 5 degrees and so on. You know that you will be flying a circle, with a constantly decreasing heading to the left. The only thing that you don't know, is how much turn is required to maintain the 15 mile distance. Flying an arc is an art, not a science. Constantly changing winds, aircraft ground speeds and so on make this maneuver an on-going learning experience for the pilot. Experiment with flying arcs. After a while you will develop a sense about how much of a heading change is required to maintain a given distance.

Established on the 15 mile arc you make your radio call. "Approach, Baron 123 is established on the 15 mile arc, out of niner thousand." "Roger Red Baron 123 out of nine. Report crossing the 040 degree radial." "Report crossing the 040 degree radial, Red Baron 123." You tune Nav. #2 to the HUT VOR, 116.8, and set the OBS on the #2 Nav. display to 040 degrees.

POP quiz. Given your approximate location, and the fact that you have not reached the inbound radial for the approach yet, when you select the 040 degree radial in the Nav. #2 display, which way will the CDI be displaced? Left or right? How about the "TO/FROM" indicator? To, or From? Picture your airplane facing a heading of 040 degrees. The 040 degree radial is to your left, you haven't reached it yet. Therefore, the CDI will be displaced to the left. What about the "TO/FROM" indicator? Given your location, the indicator would read "FROM".

Leveling at 3,300 feet you prepare for the final approach. Power set as appropriate to get you into the flap operating range on the airspeed indicator. Hold off on dropping flaps at this time however, no sense in dragging out the approach. The DME is holding between 14.9 and 15.1. Hey, this flying an arc stuff isn't so hard! Your eye catches the #2 VOR display starting to twitch. The CDI starts drifting in from the left. It centers. "Approach, Red Baron 123 is crossing the 040 degree radial at this time, 15 DME, level at 3,300." "Roger Red Baron 123. You're cleared the VOR runway 21 approach via the 15 mile arc. Report Turky inbound to the Tower, 118.5." "Cleared the approach, Tower at Turky, 123." A couple of minutes later the CDI on the HSI starts to swing towards center. Start your left turn now to intercept the 033 degree radial inbound. If you wait until the CDI centers, you will overshoot the radial. Once established on the 033 radial inbound, descend to and maintain 2,500 feet. About 11 miles DME (2 miles from Turky), drop your approach flaps.

The DME drops to 9.0 miles. You are at Turky. Drop your gear. Start your descent to 2,000 feet. "Hutchinson Tower, Red Baron 123 is Turky inbound." "Roger Red Baron 123. Not in sight, cleared to land runway 21. A Cessna 421B that shot the approach 10 minutes ago reported the bases of the overcast at 2,200 feet, with a visibility greater than 2 miles under the overcast." (What a nice guy that fellow in the 421B was!) "Cleared to land, thanks for the report, Red Baron 123." As predicted, the airport pops into view about two miles out. You are in perfect alignment with the runway and proceed to make a first class greaser onto the surface. Good for you! You just shot a VOR/DME approach using a DME arc. That wasn't so bad, was it?

This ends the tutorial on VOR/DME Approaches.

This narrative, along with aditional content, is available as a CD or an eBook.

For CD information click here. For eBook information click here.

© Hal Stoen, September 10, 2000

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