Audio Panels Demystified

As instructors we are sometimes quite guilty of assuming “everyone knows that”, whatever “that” may be. Just a simple question from a student however can quickly make us realize it’s a false assumption. So it was a question from a student concerning the operation of an audio panel made me realize that it is probably worth offering some explanation about its operation.

The audio panel in question was the KMA 24, probably one of the most common audio panels found in planes.

In an overall view, the KMA 24 audio panel has two rows of buttons, flanked on the left by marker beacon lights and on the right by a rotary knob whose principle function allows the user to select COM 1 or COM 2. The top row of buttons directs the selected audio output to the speaker in the aircraft. The bottom row of buttons directs the selected audio output to your headset.

1. Marker beacon lights are used in many ILS instrument approaches. If the ILS approach has marker beacons (not all of them do), the most common ones are the outer marker (the blue light marked “O”) and the middle marker (the amber light marked “M”). The inner/airway marker (the white light marked “A”) is generally only installed at major airports. Marker beacons emit a 75-Mhz signal. When the aircraft passes over an outer marker, the blue marker beacon light is seen. A middle marker beacon illuminates the amber marker beacon light. In addition, an audible tone may be heard. If you want the audible signal to come through the speaker, press MKR (#9) on the top row of buttons. If you want it to come through your headset, press MKR on the bottom row of buttons.
1. The 75 Mhz signal transmitted by the marker beacons is a carrier frequency. This carrier frequency is modulated into a 400 hz, 1300 hz or 3000 hz signal for the OM, the MM, and the IM respectively.
2. TST - test the marker beacon lights. Pressing this button causes all the marker beacon lamps to illuminate. SENS - the button just to the right of the amber marker beacon lamp selects the sensitivity of the marker beacons. HI allows the marker beacon signal to be detected approximately one mile before passing over the beacon. At this point, if you had HI sensitivity selected, you would want to switch to LO sensitivity. A word of caution concerning the TST button. Bendix King notes that the TST button should not be pushed when the autopilot is coupled on an ILS approach. Some autopilots, including Bendix King models, use the marker beacons to change the sensitivity of the autopilot. Next to the “O” marker beacon lamp is a photoelectric cell which controls the brightness of the marker beacon lamps.
3. TEL – controls audio for a radio telephone. Alternately some KMA 24 audio panels replace the TEL function with HF, for operation with a high frequency transceiver. Note that this function, either TEL or HF, must also be selected on the rotary knob on the right side of the audio panel.
4. 1 COM – controls audio received from COM 1 communications radio. Again, the top row button directs output to the aircraft speaker, and the bottom row button directs it to your headset.
5. COM 2 – controls audio received from COM 2 communications radio.
6. 1 NAV – controls the audio received from the NAV 1 radio. This includes any weather information, such as HIWAS as well as the Morse code IDENT. Many nav radios have a switch on the radio for IDENT. This must be selected in addition to selecting either speaker or headset for the audio.
7. NAV 2 – ditto for the NAV 2 radio.
8. DME – allows you to hear the Morse code identifier for any DME that is co-located with VOR or localizer stations. Most DME receivers have the ability to enter a frequency separately from the nav radios. However the most common method of operation is to remote the DME receiver to either nav 1 or nav 2.
9. MKR – allows you to hear the marker beacon audio signals.
10. ADF – allows you to hear the Morse code identifier of an NDB station. During an NDB approach, most instructors teach their students to keep the Morse code identifier for the NDB on during the entire approach to verify integrity of the signal. Unlike VOR receivers, ADF receivers do not display an OFF flag, so the Morse code is the only way to ensure the data being received by the ADF receiver is valid.
11. AUTO – this is probably the most confusing button for pilots when they first work with the audio panel. The rotary switch on the right side of the KMA 24 can be set for either COM 1 or COM 2. The rotary switch controls the transmission frequency. So if you have COM 1 selected with the rotary switch, when you push the transmit button, you are transmitting on COM 1. The AUTO button allows you to automatically slave the received audio information to whichever frequency you have selected with the rotary switch. By pressing the AUTO button in the bottom row (headset), you will automatically hear the transmissions from either COM 1 or COM 2, depending on which one has been selected by the rotary switch. So with AUTO selected, you may switch back and forth between COM 1 and COM 2 with the rotary switch without having to reselect COM 1 or COM 2 using the push buttons. If you desire to hear audio from the other com radio, you may do so by simply pressing the appropriate button for either speaker or headset. For example you are listening and transmitting on COM 1 but would like to listen to ATIS at the same time. You may do this by putting the ATIS frequency in COM 2 and pressing the COM 2 button for either speaker or headset. Warning – it can be confusing to try to listen to two frequencies at the same time.
12. The rotary switch on the right side is used to select the desired transmitter for the cockpit microphones. COM 1 and COM 2 have been previously discussed. The INT position selects cabin intercom. This allows the crew to address the passengers over the cabin speaker. The EXT position allows the crew to address people on the ramp through an external ramp hailer speaker, if one is installed.

In putting this discussion together, I found a good pilot guide to operation of the KMA 24 audio panel on the Bendix King website. It is a downloadable pdf file, and the web address is

Pilot Guide to the KMA 24 Audio Panel

Goodbye old WINGS, hello new WINGS

The old Wings safety program that we all knew is now officially gone. This has come as a shock to many pilots who relied on it for their flight reviews. In its place however is a new and improved version of the program, one that addresses some of the issues and shortcomings of the old program.

The new WINGS is a web-based program that tracks your training and promotes personal proficiency. The old WINGS program was time based; go to an FAA safety seminar and do the three hours of training. No standard of proficiency was specified. The new WINGS program is based on both knowledge and proficiency. It is modeled on consistent recurrent training to PTS standards, a paradigm that has proven successful in both airline and corporate flying. As with the old program, it is entirely voluntary. In order to participate, you need to have a pilot license and a current medical. Student pilots may participate in the program, but they will not be able to receive credit for training.

Training is broken down into three phases — basic, advanced and master. Completing the requirement for the basic phase will count as a flight review. Within the phases there are core elements and elective elements. Completing the requirements for the basic phase constitutes a flight review.

How do you, both flight instructor and pilot, participate in the new WINGS Pilot Proficiency Program?

• Go to the website (FAASafety.gov) and register. You must hold an FAA license and a current medical.
  
• Complete the pilot profile for the type of training you wish to do. This does not necessarily have to reflect your certificates. It may be tailored to the type of flying you do.
  
• Complete the required and elective training requirements.
  
• Submit your completed credits for validation.
  
• Use the system to track your proficiency.
  

As with the old system, you must fly with an instructor in order to complete your training. Both the flight instructor and the pilot must be registered in order to obtain credit. If the flight instructor is not registered, the flight training must be verified by a registered instructor.

The instructor doing the training must put an endorsement of training in the pilot’s logbook.

“I certify that [pilot], holder of pilot certificate number [number], has satisfactorily demonstrated proficiency in all tasks as outlined in the WINGS Pilot Proficiency Program activity course number [number] on [date].
Name, certificate number, date, signature”

I have made it my goal to do my flight review, which expires in May, by working my way through the Basic phase of the new WINGS Pilot Proficiency Program. This should give me a much better understanding of the program, and I am looking forward to doing it.

Substituting GPS for DME and ADF

I work with a lot of plane owners, and I have found the trend is to install an IFR GPS and skip having a DME in the plane. After all, the IFR GPS can be used in place of DME – right? Yes it can, but you had better have a clear understanding of how that substitution is to be done if you want to stay squeaky clean with the FAA.

The 2007 AIM, section 1-1-19 has information that every pilot flying with an IFR GPS should take the time to read. Specifically 1-1-19(f) talks about the substitution of an IFR GPS for DME or ADF. Before jumping into this discussion, it must be noted that your GPS must have a current database card.

Let’s look at the DME requirements first. Let me offer a caveat up front. I confess to having a difficult time following the AIM numbering scheme. Having said that, I will jump into this discussion, hoping I have the numbers right.

The first point to note is in AIM 1-1-19(f)(5). It says that in order to use the GPS for DME, the course deviation indicator (CDI) must be set to terminal sensitivity. This is normally 1 nm full-scale deflection. In most situations, the GPS receiver will already be in terminal mode. However, if it isn’t, then you will need to manually select terminal mode. To do this with the Garmin 400-500 series, go to the Aux 3 page and select CDI/Alarms.



This will allow you to manually select the CDI sensitivity. Select the 1.00 nm scale.



The caveat here is that you must not forget to restore it to AUTO once you no longer need it forcibly set to 1.0 nm sensitivity.

To manually select the CDI scale for the KLN89B, go to the NAV1 page. Turn the cursor on. Position it on the CDI Deviation Indicator and press CLR until it says CDI scale. Use the small knob to select the 1.0 nm sensitivity (ARM mode). Press CLR to return the display to the CDI Deviation Indicator and turn the cursor off. When the KLN89B is in Approach mode, it is not possible to select a less sensitive scale that the current one. The default sensitivity is 5.0 nm. Unlike the Garmin units, there is no AUTO mode.



The KLN94 CDI sensitivity is selected in the same manner. For both the Garmin and the KLN units, if the sensitivity has been manually set to 1.0 nm, the unit will go to a more sensitivity setting (approach mode), but it will not go to the enroute sensitivity (5 nm) until it has been reset to AUTO (Garmin) or 5.0 nm (KLN).

AIM 1-1-19(f)(c)(2)(b) talks about using GPS to fly a DME arc, and this is the one that is probably most frequently violated, albeit unintentional. It says, in part, with the boldface type from the AIM itself:

“You must select from the airborne database the facility providing the DME arc as the active GPS waypoint.
Note: The only acceptable facility is the DME facility on which the arc is based. If this facility is not in your airborne database, you are not authorized to perform this operation.”

What that means is you can’t just merrily load the approach and fly the arc using the Map page display and the suggested headings provided by the GPS, sequencing along from waypoint to waypoint. You have to keep the DME facility as your active waypoint. It is generally possible to do this and keep the waypoints, including the arc, visible in your Map display.

Let’s look at the VOR/DME-27 into Anoka (KANE) as an example of how to do this.





This approach incorporates a couple of different examples of using GPS for DME. To get started, let’s examine the use of the GPS to fly the DME arc. The first step in doing this is to load the approach into the GPS. By loading the full approach into the GPS, we get most of the waypoints as well as the arc displayed on the Map page. Also note that the GPS is in terminal mode sensitivity.



The problem however is that GEP, the facility that provides the DME information, is not the active waypoint. It is however the MAP waypoint for the hold. We can make it the active waypoint by going into FPL0, highlighting GEP and doing a DIRECT-TO.




By doing this, we still have the waypoints displayed on the Map page, but we have now satisfied the requirement to have the DME facility as the active waypoint. The arc can be flown using the Map for positional awareness and the waypoint distance to keep us within the proper arc distance.



Turning inbound on the final approach course, we are in VLOC mode and GEP is still the active waypoint. Now that we are no longer on the arc, we can go back to using the GPS waypoints. AIM 1-1-19 f(c)(1)(b) states:

“If the fix is identified by a five-letter name which is in the airborne database, you may select either the named fix or the DME facility as the active waypoint.”

This means that the fixes in the approach (TOURI, VOR10 and RW27) may be used in lieu of GEP and the DME distance.



By going to PROC and selecting Activate Vectors-To-Final, we can replace GEP with TOURI, the FAF, and start waypoint sequencing again. But be forewarned; because this is not a GPS approach, you must leave the CDI in VLOC mode so that guidance is being provided by GEP.





Now let’s look at another approach that might trip the unwary user depending on GPS to substitute for DME. Consider the ILS-27 into Anoka.



The trap here lies in the localizer-only approach. If you load this approach from the GPS database, the step-down fix KOGGE will not be one of the waypoints in the approach. This means that you must rely on DME to identify this fix, but the facility providing the DME is the localizer, I-ANE, rather than a VOR. You can get the proper DME distance by doing DIRECT-TO IANE in your GPS. Both the Garmin and the KLN units think IANE is an intersection, but it does give you the proper DME distance for a localizer-only approach. I did talk to Jeppesen about this approach. They do not include waypoints for step-down fixes for localizer-only approaches. However Jeppesen indicated there is some thought as to possibly including them in the future.

When substituting GPS for an ADF, it is not so detailed on instructions. The AIM says the NDB must be selected from the database and the receiver must be in terminal sensitivity. This might lead you to believe you can fly a pure NDB approach using the NDB as the active waypoint in the GPS and placing the unit in OBS (non-sequencing mode). Take the case of the NDB-28 approach for Osceola (KOEO).



By now you are probably asking yourself why would anyone choose to do this when there is a GPS-28 for Osceola? Well, for quite a while there was indeed an approach plate for GPS-28/OEO but there was no corresponding GPS approach in the database. Why? Because of a runway extension, the GPS-28 approach was NOTAM’ed as NOT AUTHORIZED. In this case, you had only one choice – the NDB-28. So trying to conform to the guidelines in the AIM, the NDB-28 approach is loaded. But now you run into yet another problem. AIM 1-1-19 (f)(b)6) says:

“Charted requirements for ADF and/or DME can be met using the GPS, except for use as the principle instrument approach navigation source.”

Now the conundrum – that ancient ADF receiver in your plane hasn’t worked in years. And even if it did work, you know that loading OEO into the GPS as the active waypoint, putting the receiver in OBS mode, and forcing it to terminal sensitivity is going to do a far better job of getting you into Osceola than that old ADF receiver. But unfortunately the AIM seems to say the FAA doesn’t see it that way.

This basically means that you can hold over a compass locator or NDB using GPS, and you can use it to identify a compass locator on an ILS or LOC approach. Returning to the ILS-27 into Anoka, the primary holding fix is GEP. But there is an alternate holding waypoint at the PNM NDB, which is about 30 nm northwest of Anoka.




You can use GPS to substitute for ADF in doing this hold. Again, the receiver must be set to terminal sensitivity. At the MAP waypoint for the ILS-27 into Anoka, the GPS receiver stops sequencing and waits for instructions from the pilot. If you press OBS on the Garmin units, it automatically brings up the waypoint for the published hold, which in this case is GEP. However you don’t want to go to GEP. So instead press DIRECT-TO. The GPS will display the waypoint for the published hold in the DIRECT-TO dialogue box, with the cursor on. All you have to do is put in PNM for the desired waypoint. The DIRECT-TO works on the KLN units as well.



So now you can head off to Princeton (KPNM) and enter the alternate hold. You can either do it by placing the GPS in OBS mode and flying the hold with raw data, so to speak, or you can load the NDB-15 approach at Princeton (KPNM) and go to PNM for the missed approach, since it is the same hold. Personally I would opt for the latter, since it depicts the hold.



To summarize substitution of an IFR GPS for DME and/or ADF:

• Current database card
  
• For use on a DME arc, the active waypoint must be the facility providing the DME
  
• For DME waypoints (other than an arc), if the DME waypoint has an associated name in the database, you may use the database waypoint. If not, the waypoint must be identified using the DME facility as the active waypoint
  
• The GPS may substitute for an NDB or compass locator except if it is the primary navigation source for an instrument approach
  
• For use in lieu of both DME and ADF, the GPS must be in at least in terminal sensitivity (1 nm)
  

So now you have the nuts and bolts of substituting your IFR GPS for DME and/or ADF. Find a friend and go practice this ahead of time. Or better yet, find a good sim with a GPS and go practice these skills. Flying in the soup with a controller issuing rapid-fire instructions is not the time to be figuring out which buttons you need to push to substitute your GPS for DME or ADF.

The Art of Going Missed - Updated

The missed approach may be thought of as a Plan B maneuver. It is normal to anticipate and expect that an instrument approach will result in a beautiful runway emerging from the mist and clag. That’s what we expect to see and our mindset tends to be “It is going to be there.” But sometimes it isn’t – and that’s when we need a Plan B.

DH or MAP point is not the time to be looking down at your approach plate, trying to find the missed approach instructions, during which time the plane will most likely continue to descend. The first part of the missed approach procedure should be firmly fixed in your mind, right alongside DH or the MAP point. You are low to the ground at that point, and you need to start reversing that situation immediately. So pitch up and power up right away. Get started climbing away from what is all-too-firm terra firma. Once you have a positive rate of climb established, then you can attend to other duties – cleaning the plane up and reporting your missed approach.

Many missed approach procedures involve climbing straight ahead to a certain altitude, then executing a turn to go to the waypoint for the hold. With more and more planes being equipped with IFR approved GPS units, it is increasingly common to have the instrument approach loaded in FPL 0, even if it is not a GPS approach. The GPS will automatically sequence through the waypoints in the approach until the missed approach point is reached. At that point automatic sequencing is suspended, and the GPS will wait for input from the pilot.

What happens next is specific to the model of GPS. The Garmin 400/500 series wait for the pilot to press the OBS button, which will bring up the published missed approach waypoint and provide guidance to it. The KLN89B and KLN94 units expect the pilot to press the DIRECT-TO button, which will bring up the waypoint for the published hold. By the way, this works on the Garmin unit too, and has some advantages. More on this later. The trick here is to know when to press either the OBS button or the DIRECT-TO button. The ILS-30 into Air Lake (KLVN) offers a good example.



The missed approach instructions are to climb straight ahead to 1500 feet, then climbing left turn to 2800 feet, to hold at the Farmington (FGT) VOR. The GPS will stop sequencing at the runway threshold. If OBS (or DIRECT-TO) is pressed at this point, the GPS gives guidance from that point to the VOR. But this is not what you want. The secret here is to delay pressing the OBS button until you have completed the climb to 1500 feet. When you press the OBS button after completing the straight-ahead climb, the Garmin 430 will display the magenta track that will take you to the holding fix, as shown below. Notice that the magenta track is offset by the distance required for you to make a standard rate turn to the desired heading.



Sometimes there may be an intermediate waypoint between the missed approach waypoint and the fix for the published hold. My best guess is that this is done to prevent the possibility of a plane hitting an obstacle while executing the missed approach. The GPS-13 at Rochester (KRST) provides an example of this.



The waypoints in FPL 0 for this approach in the Garmin 430W, look like this:



The Garmin 430 will stop automatic sequencing when RW13 is reached. If you press OBS at this point, it brings up the next waypoint in FPL 0, which is POKYI. Since there is no turn involved here, it is okay to press OBS as soon as you start the missed approach. This approach, by the way, is an LPV (precision GPS approach). I have had a Garmin 430W installed in my plane. I received the Garmin 430W/530W trainer CD from Garmin, and it does contain this approach. I will be writing future entries on the Garmin 430W unit.

I mentioned earlier that when the GPS stops sequencing through the waypoints, pressing the DIRECT-TO button is another way of bringing up the waypoint for the hold. Sometimes there is a distinct advantage to doing it this way.

• Press OBS at the MAP point and the Garmin 400/500 series will immediately make the next waypoint in FPL 0 the active waypoint
  
• Press DIRECT-TO at the MAP point and both the KLN and Garmin units will present the next waypoint in FPL 0 in a dialog box with the cursor turned on, so that it can be changed to another waypoint if so desired
  

So when would you ever want to utilize another waypoint for the hold. The ILS-27 into Anoka (KANE) provides a good example. This is the Jeppesen plate for the ILS-27.



Gopher VOR (GEP) is the waypoint for the published hold. However note in the upper left-hand corner of the plan view there is an alternate holding waypoint at the Princeton NDB (PNM). If you had been told to proceed to the alternate holding point, utilizing the DIRECT-TO method of bringing the waypoint for the hold would definitely be the preferred method.

Interestingly enough, the NOS version of the ILS-27/ANE shows the PNM holding point but gives the pilot no clue as to why it is on the approach plate.



To wrap this up, when you are briefing an approach, there are four items that you need to commit to memory.

• The FAF
  
• DH or MDA
  
• How to identify the MAP point
  
• The first part of the missed approach instructions
  

My experience in being a CFII for many years is that it is the last one that most people forget to do.

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
CORDY (IA)
HEBAS
HUPAP (FA)
RWY 13 (MA)
POKYI
RST (MH)

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!

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.

Using an RMI

Those of us who did instrument training before GPS took over, had to learn how to do NDB navigation. An ADF is a very simple instrument. It simply points at the NDB. Follow the needle, and sooner or later you will get to the NDB – or possibly a thunderstorm. But such a seemingly simple instrument has been the source of a great deal of frustration to generations of pilots who had to learn how to use it for navigation. If our instrument instructors were successful in beating it into our heads, we eventually learned how to intercept specific bearings and track towards or away from the NDB in a more or less precise manner. The degree of precision often depended on the degree of wind.

VORs have radials, and NDBs technically have bearings. But to simplify this discussion, I am going to use radials in talking about NDBs. If we wanted to track inbound on the 180° radial towards the station, we learned to turn to an intercept heading, usually 30, 45, or 60° for ease of use. When the head of the ADF needle fell to the intercept angle, we were on the desired radial. If our airplane was really fancy, it had an ADF card that could be rotated. This simplified things for the pilot – more or less. If you remembered and had the time to do so, you could rotate the ADF card to match the aircraft’s heading. By doing this, you didn’t have to calculate intercept angles. When the head of the ADF needle fell to the desired radial, you had made the interception. Suppose you were southwest of the NDB and wanted to intercept the 180° radial and track inbound on it. You could turn to an intercept heading of 045° and also rotate the ADF card to match your heading. The head of the ADF needle would fall, and when it reached the desired reading of 360° (reciprocal of 180°), voila – you were on the desired course.



The ADF with a rotating card was often called the poor man’s RMI. It simplified NDB navigation, but having to constantly rotate the card really added to the pilot’s workload. But what if the card rotated automatically, just like your DG (heading indicator) or HSI. That essentially is what an RMI is. It is a DG with either one or two needles that can be set to respond to either NDBs or VORs. So using an RMI is basically just remembering how you did NDB navigation.

The RMI combines the DG and ADF into one instrument. As you turn, the card moves just as the DG or heading indicator would move.



Recently I was asked about using an RMI for hold entries. So let’s investigate how you use an RMI to get into a hold. To do this, set the RMI to respond to a VOR rather than an ADF. Assume you are tracking north on the 180° radial towards the VOR.



I have marked off the face of the RMI with the lines to determine holding entry for a right-hand hold. If you don’t recall this, please refer to Creating Holding Clearances. Our holding clearance at Podunk VOR was given as:

Hold northeast of PODUNK VOR on the 050° radial, right-hand turns, EFC……

This calls for a teardrop entry. To make this entry, we would turn to a heading of about 020° after passing over the VOR and fly for one minute (if it was timed legs).



Turning right to intercept the inbound course on the 050° radial, the RMI tells us right away that we need to stop the turn momentarily to intercept the radial.



Remember the RMI acts just like an ADF. The head of the needle is going to fall. Right now the plane is on the 40° radial, but we need to intercept the 050° radial. Since the head of the needle will fall, we can stop the turn temporarily on a heading of 200° and wait for the needle to fall. When it gets to 230°, we are on the 050° radial.



Modern RMIs include those that can track two different stations simultaneously and can be independently set to either VOR or ADF. This one is from a King Air panel.



It takes a little bit of readjustment to your thinking, but once you get the hang of it, it’s really a great instrument.