Everything You Ever Wanted to Know about Instrument Approaches
By Marc Sykes (MS)

Learning how to handle instrument approaches safely and efficiently, with the correct phraseology, is one of the toughest aspects of the transition to approach control. This is so partially because of the sheer amount of vocabulary that you need to acquire: precision, non-precision, MVA, MEA, IAF, FAF, PTAC – there are acronyms galore to learn and apply. Additionally, since it's rare for pilots to ask for instrument approaches other than the ILS, students don't get a lot of practice with these more unusual requests. In this article, I'll attempt to define the relevant terms clearly and precisely, and to demonstrate three basic techniques for handling instrument approaches correctly, using specific examples from various Socal TRACONs. I'll also go over the criteria, including factors such as terrain, approach type, direction of flight, and aircraft equipment suffix, that you must consider when deciding which of the three main techniques is most efficient for the controller and/or most expeditious for the pilot.

1. Clearance from an Initial Approach Fix (IAF)

If you've ever flown into LAX, or listened to Socal Approach, you've probably noticed how the approach clearance for aircraft on the CIVET4/PDZ4/MITTS1 is different from those on other approaches, like the SADDE6. For the CIVET4s, you'll simply hear Socal say:

Air Canada 301, after FUELR, cleared ILS runway 25L approach

Why doesn't Socal have to give the full PTAC (position, turn, altitude, clearance) sequence here? The answer can be found after a quick look at the approach plate:

We know that the CIVET4 tells the pilot to cross FUELR at 8,000. Here we see that FUELR is an Initial Approach Fix (IAF) for the ILS approach, with a crossing altitude of 8,000. From here, the pilot has all the information he needs to join the approach. Therefore position is unnecessary (since the pilot hasn't been vectored off the CIVET4 he knows where he is with regard to FUELR); as are turn (since the pilot is already headed direct to FUELR) and altitude (since it's already specified on both the CIVET4 arrival chart and the ILS approach plate). All that's left is clearance; hence the instruction above.

What a lot of Socal students don't realize is that this same technique can be used for any instrument approach – ILS, LOC, VOR, NDB, GPS, it doesn't matter. If the pilot's route takes him to an IAF, or if you can vector him there, and get him to the appropriate altitude before he reaches it, you can clear him this way.

Let's look at a specific example. N527MS, a Cessna 421C Golden Eagle (type M for purposes of TEC classifications), is flying from John Wayne (KSNA) to Palomar (KCRQ). The appropriate TEC route is the CSTL12, which is as follows: V25 V208 OCN, at an altitude of 7,000 feet. Twin Cessna 7MS has requested the VOR-A approach into Palomar tonight. A handy tip on approach nomenclature: an instrument approach can be specific to a particular runway – eg. VOR runway 24 – or it can bear a suffix of A/B/C/D etc., which means it is an approach to the field, not to any particular runway. If an approach course isn't aligned within at least 30 degrees of a particular runway, or if it serves all runways (meaning the pilot will join the traffic pattern and circle to land on the appropriate runway once he has the field in sight), it will have a letter designator. Looking at the VOR-A approach plate, we can see why it bears the A suffix; the approach course is nearly perpendicular to the runway:

The one and only IAF for this approach is OCN, which just so happens to be the last fix on our pilot's flight plan. Looking at the vertical profile at bottom left, we see that the intercept altitude for OCN is 3,000, so as SAN_APP, we can easily make sure he'll meet this restriction:

Twin Cessna 7MS, Socal Approach, good evening, Palomar reporting winds calm, visibility 10 miles, few clouds at 3,100, altimeter 30.08, cross Oceanside at and maintain 3,000, expect VOR-A approach

Once 7MS is close to OCN, you can go ahead and issue the clearance:

Twin Cessna 7MS, cross OCN at or above 3,000, cleared VOR-A approach

Since the pilot is still on his published flight plan, position and turn are both unnecessary; however, we do need to remind him of the intercept altitude for OCN. He'll continue on the approach course until he sees the field, then, at his discretion, join a right downwind for runway 24 or a left downwind for runway 6. Since we're simulating an uncontrolled field, it's up to him to use the weather you gave him to pick the appropriate runway, announcing his intentions on the “traffic” channel at the field (on VATSIM we use the UNICOM frequency, 122.8, for this purpose). As soon as he's established on the approach, send him over to advisory:

Twin Cessna 7MS, change to advisory frequency approved, report IFR cancellation or missed approach this frequency

Although it's obviously easier if the IAF is on the pilot's flight plan, it isn't mandatory if you can vector him there. In our second example, Twin Cessna 7MS is flying from LAX to Gillespie Field (KSEE), using the LAXL16 TEC route: SLI5.SLI SLI148R LAX118R MZB320R MZB, altitude 9,000 feet. He's requesting the GPS approach to runway 17. You pull up the chart and see that the IAF is ROBNN:

This is easy enough except that 7MS' plan as filed doesn't take him anywhere near ROBNN. He'll actually enter SAN_APP's airspace just west of OCN, about 20 miles southwest of ROBNN, as he's establishing on the MZB R-320 inbound. Since that pesky Camp Pendleton airspace is in the way, we can't give him direct ROBNN right away, so we'll keep him on course for a minute and give him some other information he needs to know:

Twin Cessna 7MS, Socal Approach, good evening, Gillespie reporting winds calm, visibility 10 miles, scattered clouds 2,500, altimeter 30.09, expect GPS runway 17 approach

Once he's clear of the restricted airspace we'll send him to ROBNN:

Twin Cessna 7MS, turn left heading 070 direct ROBNN when able, descend and maintain 5,100

Although ROBNN isn't listed on the vertical profile at bottom left, the chart states that the MEA (Minimum Enroute Altitude) between ROBNN and ASIXY is 5,100, so we'll bring 7MS down to cross ROBNN at that altitude to make it easier on him, since the MVAs in the area allow it.

One note of caution: be aware that not all aircraft can fly direct to an intersection – to do so an aircraft would need to be equipped with either an FMS (suffix /E or /F) or a GPS (/G). Most commercial airliners have an FMS, and some general aviation aircraft have a GPS, but you'll find that most GA planes are /A – they can go direct to a VOR as long as they're in range to receive it, and they can intercept a VOR radial in order to find an intersection, but you can't send them direct to an intersection. Of course, since 7MS is requesting a GPS approach, we can pretty safely conclude that he's GPS-equipped. But don't count on a typical general aviation aircraft being able to accept a direct-to routing – check the suffix in the flightstrip before you attempt to issue such an instruction.

Back to 7MS, he's now heading to ROBNN and descending to 5,100. In this case, since you have vectored him off his plan you have to give position, and you also want to remind him of the crossing altitude. Turn is unnecessary, though, since he's heading direct to the IAF. Therefore you can issue a PAC:

Twin Cessna 7MS, 8 miles from ROBNN, cross ROBNN at or above 5,100, cleared GPS runway 17 approach

Easy enough, right? The news gets even better, because most TEC routes are designed to end at the VORs that are most commonly used for instrument approaches: for instance, most San Diego routes end at MZB, OCN, or JLI, while Ontario routes end at POM or PDZ, and so on. So particularly in the case of VOR approaches, usually all you have to do is check the chart to confirm the altitude and IAF, and then make sure the pilot descends in time to meet the intercept altitude, and you're good to go.

But what if this method doesn't work (usually because the IAFs are in impractical locations)? Well, it gets a little more complicated, but not much.

2. Vectoring onto the final approach course

Let's take a look at the approach plate for the ILS to runway 24R at LAX:

Noting that SMO is an IAF for this approach, you might wonder why we don't employ the same logic with the SADDE6 arrivals as we do for the CIVET4s, and simply say, “after SMO, cleared ILS approach runway 24R.” While this is entirely legal to do, there are a few problems associated with it. First of all, notice that flying the full approach means intercepting the localizer at MERCE, 16 miles from the threshold. That's a longer final than most aircraft would need; something more on the order of 10 to 11 miles is preferred in the interests of efficiency. Also, check out the flight path: the aircraft tracks the SMO R-068 outbound, then intercepts the SLI R-330 inbound, and finally intercepts the localizer. But that turn to intercept the localizer is about 100 degrees – might work if you're low and slow in a Cessna 172, but most airliners won't stand a chance at making such a steep turn. Finally, most VATSIM pilots don't carry ILS approach plates onboard since these approaches are usually vectored, so it's not a good bet to assign a full approach (although you can always ask the pilot if he has the plate).

For these reasons, even though it means a few additional instructions, it's much easier for both controller and pilot to vector the aircraft onto the final approach course. From SMO the aircraft will fly a 065 or 070 heading and descend to 2,500, then once abeam HUNDA will receive the full PTAC:

Southwest 240, 6 miles from JETSA, turn right heading 220, maintain 2,500 until established on the localizer, cleared ILS runway 24R approach

Some controllers use different headings, but the four key elements – position, turn, altitude, and clearance – will always be there.

You can use this technique to vector a pilot onto the approach course for any type of approach if the pilot is unable to accept a routing direct to the IAF, or if the IAF is inconveniently located. Case in point: Twin Cessna 7MS is back with us, flying from Palm Springs (KPSP) to Riverside (KRAL) on the PSPL11 TEC: V388 PDZ, 12,000. He's looking for the VOR-A into Riverside :

V388 is going to take 7MS across the approach course right around BOBBE, so sending him to HDF, the only IAF for this approach, isn't all that helpful. We also can't put him directly onto the approach at BOBBE since the MEA on the airway is 5,000 feet. We also note that the Minimum Vectoring Altitudes (MVAs) in the vicinity are around 4,000 feet, and since the intercept altitude for BOBBE is 3,500, that isn't going to work. What we can do, however, is break him off the airway on initial contact, when he's still northeast of DANNL:

Twin Cessna 7MS, Socal Approach, good evening, Riverside reporting winds calm, visibility 7 miles, skies clear, altimeter 30.10, turn left heading 190, descend and maintain 5,000, vectors for the VOR-A approach

The guideline is to vector aircraft to intercept with no more than a 30-degree turn to final, so we'll have to give him a right turn as part of our PTAC when he's near DANNL:

Twin Cessna 7MS, 3 miles from DANNL, turn right heading 240, maintain 5,000 until established, cleared VOR-A approach

He'll now intercept the RAL R-268 inbound, maintain 5,000 until he crosses DANNL, then descend to 3,500 for BOBBE, and then down to the MDA (2,000) until he has the field in sight or crosses the VOR, which is the missed approach point.

Unfortunately, sometimes the art of vectoring gets a bit more complicated than this, particularly in areas with a lot of high terrain. Twin Cessna 7MS has once again refiled and is headed from John Wayne (KSNA) to Van Nuys (KVNY), using the CSTL1 at an altitude of 6,000 feet. The last waypoint on his flight plan is SILEX and he's looking for the ILS approach to runway 16R from there:

Both IAFs (FIM and VNY) are a bit out of the pilot's way from SILEX; remember as well that most VATSIM pilots aren't capable of a full ILS approach. So vectors after SILEX seems to be the way to go:

Twin Cessna 7MS, Socal Approach, good evening, Van Nuys reporting winds 160 at 9, visibility 10 miles, broken clouds 10,000, altimeter 30.08, depart SILEX heading 340, expect ILS runway 16R approach

There's just one problem: the final approach fix is KADIE with an intercept altitude of 4,300, but the MVAs in the area are 5,000 or more. Not only that, the MVAs a bit north of UMBER shoot up to 7,000, so it would be pretty tricky to vector him straight to UMBER at 6,000. So how can we make this work?

The solution lies in knowing when you, as the controller, are governed by the MVAs, and when you're governed by the MEAs. Put quite simply, as long as you're giving 7MS headings to fly, he has to stay above the MVA. But the moment you get him established on an airway, or on an instrument approach course, the MVAs no longer matter and the MEA for that airway/approach segment is all that counts. The MEA from UMBER to KADIE is 4,300 – but (and this is a big but) – we have to keep 7MS at 6,000 until he's established on the localizer.

The easiest way to do this is to break the traditional PTAC into two parts – a technique called T/PAC. First, we'll turn 7MS onto a right base when he's approximately abeam UMBER:

Twin Cessna 7MS, turn right heading 080, vectors ILS runway 16R approach

Once he's within a few miles of the localizer, we'll turn him (the T/ part of our T/PAC) to intercept it – but without descending him and without giving him an approach clearance just yet:

Twin Cessna 7MS, turn right heading 130, intercept the localizer, track it inbound, report established

He should report established when he's about 2 miles south of UMBER. At this point, you can throw that 6,000 MVA out the window – the 4,300 intercept altitude at KADIE is all that matters. Now comes the PAC:

Twin Cessna 7MS, 5 miles from KADIE, cross KADIE at or above 4,300, cleared ILS runway 16R approach

You want to make sure he's got enough room to get down to the intercept altitude before reaching the next fix. In this case, 5 miles should be more than enough distance to lose 1,700 feet. And that's all there is to it! Be sure to master this technique as early as possible, because it's the only way to get an aircraft on the localizer legally (ie. without busting MVAs) at many fields – not just Van Nuys, but also the KAYOH4 arrivals into John Wayne, as well as many of the fields in the San Diego sector of Socal TRACON.

A quick review of the essential requirements for vectoring onto the approach course in instrument conditions (there are some exceptions to these rules if you're in visual conditions and you have the pilot's concurrence, but we don't need to go into them here):

• You must give the aircraft a heading that leaves him no more than a 30-degree turn to intercept the final approach course (allowing a few degrees of “play”; if the final approach course is 161, it's all right to assign a 130 intercept heading).

• The aircraft must intercept the final approach course at least two miles outside of the final approach fix.

• The aircraft cannot descend below the MVA until established on the approach course.

You'll find that the preceding two methods (direct to IAF and vectoring) will get you through nearly any instrument approach situation. However, there are a few rare situations where the IAFs aren't located conveniently and vectoring onto the approach course is difficult or inefficient, and there's one other method you can use to clear aircraft for an approach in those cases.

3. Outbound leg with procedure turn/hold

Let's say 7MS is flying from Ontario to Van Nuys, having filed the ONTL1 TEC route. The route is PDZ V186 VNY. You note in his remarks that he's requesting the VOR/DME-B approach into Van Nuys. You pull up the chart and here's what you see:

The IAFs are FIM, GMN, PURSY, and SAUGS, none of which really work given that he's coming from the southeast. So method #1 is out. You also note that the intercept altitude for PURSY, the final approach fix, is 3,400, but the MVA in that area is 5,000. It would be possible to vector him onto the approach course with a T/PAC, but it would be tricky and require several vectors. Is there an easier way?

Fortunately, yes. There are two important things to note from the chart: first, on the vertical profile, note the arrow moving downward from PURSY with the 335 heading. That means that it's possible to fly an outbound leg (in other words, established on the approach course but flying the reciprocal heading – 335 instead of 155) during which the pilot descends to 4,900. Also note the arrow just south of GRANS intersection with the headings 110 and 290 on either side. That's your cue that this approach allows a procedure turn to be flown. (On the other hand, you will notice that some approach procedures, particularly most ILS approaches, specifically state “Procedure Turn NA [not authorized]” in the vertical profile section of the chart.)

Simply put, if a procedure turn is allowed, this means there's a safe zone within a defined radius of the initial approach fix (in this case 10 nautical miles around PURSY as you can see from the chart) in which a pilot may descend to 4,900 without being fully established on the approach course. To fly this approach, a pilot will cross VNY, intercept R-335 outbound, check his DME readings to see when he passes PURSY (the IAF, which is 5 DME from VNY), then make a 45-degree left turn to heading 290, and begin a descent to 4,900. This heading is held for 30-60 seconds, then he'll make a 180-degree right turn to heading 110. From here he can re-intercept the VNY R-335, tracking it inbound this time (heading 155), and descend to cross PURSY at 3,400, thence to the minimum descent altitude.

The great thing about this style of approach is that the pilot does pretty much all the work on his own – it's a lot easier for the controller than vectoring onto the approach course. The phraseology, however, is a bit different than the standard PTAC. We don't have to worry about vectoring N527MS to VNY because it's on his filed route. The MEA for V186 is 5,000 so he'll have to cross VNY at that altitude. We tell him to join the approach like so:

Twin Cessna 7MS, join the VNY R-335 outbound

Once he's tracking the radial, you issue the approach clearance as follows:

Twin Cessna 7MS, 4 miles from PURSY, cross PURSY at or above 5,000, make procedure turn within 15 DME, do not descend below 4,900 until inbound on the approach, cleared VOR/DME-B approach

Theoretically the DME and altitude restrictions aren't necessary because they're on the chart. However, I find that it's a good CYA move to give them. Many pilots, particularly if they're flying faster aircraft, will end up more than 10 miles from the IAF during the procedure turn, and in that case all bets are off; that 4,900 altitude may not be safe anymore. The smaller circle at the top right of the chart gives the MSA (Minimum Safe Altitude) within a 25-mile radius of the field by quadrants; in the direction in which an aircraft will be traveling on the procedure turn, it is 6,800. Also, some pilots may descend below 4,900 even before becoming fully established on the approach course; again, there are no guarantees of safety if they choose to do this. Giving these restrictions covers you as the controller and also gives the pilot a reminder that you want him to make a nice tight procedure turn if possible – especially important if you have other aircraft holding to join the same approach. Remember that since Class D fields are usually simulated as non-towered on VATSIM, you cannot clear a second aircraft for this approach, nor allow any IFR aircraft to depart from the field, until 7MS has landed and cancelled IFR.

Now that we've mastered the procedure turn, let's move on to the holding pattern. Here, Twin Cessna 7MS is flying from Montgomery Field to Van Nuys, having filed the SANL6 TEC route: MZB293 SLI148 SLI V23 LAX LAX316 SILEX. He's requesting the LDA-C (Localizer Directional Aid) into Van Nuys. An LDA is a localizer that provides directional guidance to the general vicinity of the field (hence the name), but doesn't align with a particular runway. In this case, the LDA for Van Nuys is actually the ILS for runway 8 at Burbank . The approach course happens to pass only a mile or two south of Van Nuys, so aircraft can use the localizer (not the glideslope) to descend to 2600 MSL (1800 feet above the field) and then circle to land when the airport is in sight. Here's the chart; you can see Van Nuys just north of BUDDE intersection:

7MS will be flying R-316 outbound from LAX, and this is not a segment of an airway, but we note from the chart that the MEA is 4,000 along this segment. But – you guessed it – the MVA around SILEX is 3,400, and the intercept altitude is 3,300. Once again, we can't clear N527MS for a straight-in approach from SILEX, and vectoring him onto the localizer, while possible, would be tedious and a bit tricky.

Fortunately, there's another way. Although this approach does not allow a procedure turn (most likely due to the higher terrain both north and south of the approach course), it does allow the aircraft to enter a holding pattern at SILEX in order to lose some altitude and get down to 3,300. There are different ways to enter a hold depending on the direction of travel to the fix, and as a controller you don't need be concerned with this because it's the pilot's responsibility. Nonetheless, in this case, a method called “parallel entry” is preferable. The pilot will cross SILEX at 4,000 (because you'll instruct him to do so), make a left turn to parallel the outbound course (heading 256), maintain that course for 60 seconds, then make a hard 225-degree turn to the left (heading 031) and intercept the inbound course – in this case, the localizer. Below, the dashed line shows the inbound course, the black line is the holding pattern, and the red line shows the parallel entry:

During the outbound leg the pilot can descend to 3,500, and after intercepting the localizer he can continue descent to 3,300. If he's not at 3,300 by the time he reaches SILEX again, he can fly a standard turn in the hold (black line), but this is pretty unlikely.

Again, while this is complicated and work-intensive for him, it's easy for you. The phraseology is exactly the same as with the procedure turn except, since the hold is “anchored” at a specific fix, you don't need to give a DME restriction:

Twin Cessna 7MS, 5 miles from SILEX, cross SILEX at 4,000, do not descend below 3,500 until inbound on the approach, cleared LDA-C approach

It's that simple. Now all you need to do is go out and find some willing prop jockey to test your new skills. Good luck!

Review of the terms:

Minimum Vectoring Altitude (MVA) – minimum altitude you can assign an aircraft that is not established on an airway or instrument approach.

Minimum Enroute Altitude (MEA) – minimum altitude you can assign an aircraft that is established on an airway (MEAs for airways come up in ASRC if you bring up airway IDs) or a segment of a STAR or instrument approach (this changes from segment to segment and is illustrated by an altitude next to each segment of a STAR, and by a descent profile on every instrument approach plate).

Instrument Approach Procedure (IAP) – this can be an ILS, localizer, LDA (localizer directional aid), VOR, GPS, or NDB approach. Although all of these are instrument approaches, only an ILS is termed to be a “precision” approach because it's the only one that offers true vertical guidance (a glideslope). Other IAPs use a series of step-down altitudes, but this isn't considered to be a precision approach. The main difference is that non-precision approaches use Minimum Descent Altitude (MDA), which is expressed in feet above mean sea level (MSL), while precision approaches use Decision Height (DH), which is expressed in feet above ground level (AGL).

Initial Approach Fix (IAF) – any intersection or VOR from which an aircraft can be cleared to execute a full instrument approach. These are clearly marked on every approach plate with the designation “IAF.” There can be as few as one or as many as three or four IAFs for a procedure.

Final Approach Fix (FAF) – as the name would imply, this is the last waypoint (intersection, VOR, or NDB) that the aircraft will cross before beginning the final descent to the MDA (minimum descent altitude) depicted on the chart. Aircraft must always intercept the final approach course before the FAF, and at an altitude no lower than the FAF intercept altitude depicted on the vertical profile.

Minimum Safe Altitude (MSA) – minimum altitude for obstacle clearance that a pilot can safely maintain within a 25-mile radius of a given airport. Expressed on approach plates but not used by controllers; strictly informational for pilots.

Minimum Descent Altitude (MDA) – on a nonprecision (no glideslope) approach, the lowest altitude to which the aircraft may descend, after crossing the FAF, without having the runway in sight. The pilot will descend to the MDA and then try to establish visual contact with the runway; if he fails to do so before reaching the Missed Approach Point (MAP), he must inform the controller and execute the missed approach procedure.

Decision Height (DH) – on a precision (ILS) approach, the lowest altitude, expressed in feet above ground level (AGL), to which the aircraft may descend without having the runway in sight. Upon reaching this altitude, if visual contact is not established, the pilot must inform the controller and execute the missed approach procedure. DH for Category I ILS is 200 feet AGL; for Category II approaches, 100 feet; for Category III (aka. “autoland”) approaches, there is no decision height. The runway equipment, crew, and aircraft must be specially certified to execute Category II and III ILS approaches.

Position, Turn, Altitude, Clearance (PTAC) – used when vectoring an aircraft onto the final approach course; most commonly employed with ILS approaches. Phraseology as follows: “Pacific West 5000, 6 miles from JETSA, turn right heading 220, maintain 2,500 until established on the localizer, cleared ILS runway 24R approach.”

Position, Altitude, Clearance (PAC) – approach clearance for an aircraft that is already established on a segment of an instrument approach course. Phraseology as follows: “Pacific West 5000, 5 miles from KADIE, descend and maintain 4,300, cleared ILS approach runway 16R.”

Acknowledgements: Everything I ever wanted to know about instrument approaches, as well as a lot I probably didn't at the time, I learned from, in no particular order, Bryan Wollenberg, Jim Johnson, Andy Cleeremans, Mark Coldwell, Ian Elchitz, David Hendleman, and Jeff Clark. I dedicate this article to them, with thanks.