Last week we looked at PBN STARs from a charts point of view. This week we finally return to the IFR Flight series, this time enjoying a look at PBN STARs from the piloting side and what different clearances mean. The majority of information in this week's topic comes from the Aeronautical Information Mublication Canada (AIM Canada) section RAC paragraph 9.2.2, the section on PBN STARs.

Introduction
VATSIM Cautionaries
    Discontinuities
    Runway Selection
Standard Procedures
    Straight-ins Only
    Omission of PBN STAR in Approach Clearances
    Cancellation of STAR
PBN STAR Example Image
Table of Clearance Examples and Meanings
PBN STAR Walk Through Example

Introduction

There really isn't all that much to PBN STARs (formerly known as FMS STARs, then known as RNAV STARs), but two prominent circumstances combine to make these obscure. First off, the rules and phraseologies that were introduced were changed, then changed again, and again. For example, an open route could be closed by ATC, then it became mandatory for ATC to vector the aircraft to final, removing the flexibility for both controller and pilot to close such a route, and now that flexibility has been returned to us all. Also, some terminology and criteria have changed over the years, as well some design conventions. These changes left a few remnants of old procedures and meanings floating around and the second problem arose: a lack of a total current picture, at least in some people's minds. This has, for the most part, been settled to a few basic situations. Once these are understood, PBN STARs become a cinch for both ATC and pilots in practice. Speaking of practice, it then also becomes a matter of practicing for the pilot to know how to engage or disengage certain functions on the Flight Management Computer (FMC) so any instructions from ATC can be followed.

VATSIM Cautionaries

This note is primarily intended for pilots in online flight simulation environments. YouTue and other sources can be great for finding tutorials regarding how to set up the FMS on aircraft in flight simulation software. While learning to fly my own aircraft, I found many videos which mentioned how to program the FMS, but almost none of them mentioned anything ATC-related in the process. For example, on an Open STAR (discussed in the previous topic), there is a leg that will typically show as "DISCONINUITY", often "DISCO" or "DISCON" for short, in the FMS. They happily tell you while programming the route on the ground or in the air how to remove a DISCO, but don't explain what it's there for in the first place. As a result, many VATSIM pilots learn to remove these legs without understanding that they are not supposed to remove DISCONTINUITIES until receipt of a clearance from ATC which permits them to do so. If ATC is expecting an aircraft to fly straight ahead but it turns 90° to the right or left, the controller and any other traffic operating nearby will be in for a surprise. If flying offline alone, of course, this doesn't matter.

Similarly, many pilots set up the STAR for a particular runway while still on the ground at the point of departure. Especially when flying long legs, this is not a good procedure. If the weather changes during flight, drastically different winds may exist at the field that weren't there on take-off. Or if the wind is calm, other traffic may dictate the use of a different runway. In either case, the aircraft is no longer configured for an optimum descent path and may get in the way of others. The best practice is to wait until a reasonably late time to set the runway and approach in the FMS. Well prior to Top of Descent (ToD), a pilot should listen to the ATIS if there is one, talk to the controller if there isn't an ATIS running at destination, or get the latest METAR and the intentions of other aircraft online to determine the approach to be flown if there is no controller working arrivals at the destination. Then set up the FMS with the desired runway and approach to get the best out of the FMS.

Again, it's one thing if flying offline, but it's not generally acceptable for one user to negatively affect others while flying online.

Standard Procedures

There are some items that are standard operating procedures for PBN STARs, even though the STAR itself won't specifically state them. Have a look below.

Straight-Ins Only

The PBN STAR is intended to allow the manoeuvring of an aircraft onto the final approach course without the requirement for a procedure turn. Therefore, not only are procedure turns not provided for on a PBN STAR, they are not permitted, either. At one time, the normal interpretation of "Cleared for the ILS RWY 23 approach" meant for the pilot to go over the final approach fix and complete a procedure turn, if one was published. RNAV-based approaches have changed this philosophy as there are no procedure turns designed into them, and even the approaches that use ground-based NAVAIDs are being redesigned so as not to have them. In those days, for a pilot to have authorization to conduct a straight-in approach without a PBN STAR, the clearance must specify "Straight-in ILS RWY 23 approach." When a PBN STAR is being flown, the same clearance, "cleared for the ILS RWY 23 approach" means only a straight-in approach.

Omission of PBN STAR in Approach Clearances

Additionally, a clearance for a straight-in approach without a PBN STAR must have some mention of the transition to be flown. For example, the transition may have been mentioned earlier, such as, "cleared direct LEROS," followed by, "Cleared the straight-in ILS RWY 23 approach". The transition could be part of the approach clearance, such as, "Cleared the straight-in ILS RWY 24 approach via the 9 DME arc transition," or, "Cleared straight-in ILS RWY 23 approach via LEROS." In the case of a PBN STAR, however, ATC need not mention the PBN STAR with the approach clearance. Some of the examples below have the STAR mentioned as the transition, but if the STAR is filed in the flight plan route and the aircraft has not been removed from his flight plan route (via a re-route or a radar vector), ATC may simply issue an approach clearance and the transition, in such a case, is assumed to be the PBN STAR.

In the case an aircraft was removed from the STAR, either because it was rerouted or it was vectored off the STAR path, there are other phraseologies that apply. See below for further.

Cancellation of STAR

Sometimes ATC just can't permit an aircraft to complete a PBN STAR. Typically, this will involve other traffic and timing just isn't working out. While it would, in theory, work to assign times to arrive over the FACF to each aircraft, not every aircraft using a particular airport has an FMS capable of making such fine adjustments to the flight profile, or they may have none at all. Even though some claim to be able to do it (called "4D navigation"), practical experience shows a lot to be worked out for this possibility to be used in real-world ATC. ATC may have to cancel the STAR and provide radar vectors to final well before reaching the termination point of the STAR (were the STAR ends and an Instrument Approach Procedure (IAP) begins). Even though the STAR was filed, and therefore requested, ATC has the authority to cancel it.

How is this done? A controller cancelling a STAR should state the status of the STAR so the pilot knows what to expect. Let's look at two possibilities:

In first case, a likely scenario involves other traffic that the aircraft on the STAR must be vectored around, but the vector will be short and other traffic is unlikely to be a factor later on. In this case, the controller should state the reason for the vector, the heading (or the direction and magnitude of the turn), and state the point on the STAR to which the pilot should expect a clearance when the traffic situation is resolved. This would sound something like this:

Alpha Bravo Charlie, vectors for traffic, fly heading one-two-zero. Expect direct MUVOX in ten miles.

The second possibility is also traffic-related, but perhaps returning the aircraft to self-navigate via the STAR is not a reasonable option. Two possibilities exist here, too: First, radar vectors all the way to join the final approach course, or a re-route to a fix/waypoint associated with an IAP and not the STAR. In either case, the STAR must be cancelled outright and the pilot issued clear direction on what to do now and what to expect later. Some likely phraseologies include:

There is a subtle difference between the two phraseologies mentioned above. In the second case, the pilot is capable of setting the RNAV up to fly directly to the specified fix/waypoint, meaning the FMS will be able to determine the distance remaining for the flight and be able to calculate a descent profile. In the first example, there is no way for the FMS to automatically figure this out, and the pilot may have an expectation based on previous experience, but is unlikely to be able to determine the distance to be flown. As such, a good controller will provide the pilot with an estimate of the distance to be flown to a particular point and offer that to the pilot. So that first phraseology, to be complete, would be:

Alpha Bravo Charlie, STAR cancelled. Fly heading one-two-zero, vectors for traffic. Expect vectors to the ILS RWY 23 Approach. Five zero miles to localizer.

Controllers should note something else, when short-cutting or entirely circumventing a STAR procedure: If significant distance is being "trimmed" from the flight path, this will alter the Top of Descend (ToD) point if the aircraft is in cruise, or will leave the aircraft higher than anticipated if the descent has already begun. If the aircraft is already in descent, suddenly speed brakes will be required, and it's also possible that there is simply no way for the pilot to alter the flight path enough to make up the difference, and this is more complicated the closer the aircraft is to destination when the short-cut is initiated. Pilots who find themselves facing such a clearance may refuse it -- ideally providing the reason so the controller knows the issue and can formulate a better plan for the aircraft.

Example Image

Below, you'll see an out-dated copy of the FUNDY4 Arrival at Halifax International Airport (CYHZ) in beautiful Nova Scotia. Note that this is only one page of the chart -- the transitions from FUNDY and ALLEX have not been included since those paths are the same regardless of which runway will be used. Only the page with the runway paths is presented here. I'll present a few situations, and I'd like you to refer to this diagram to help you interpret the examples I'll give.

Table of Clearance Examples and Meanings

There are a few situations can be encountered, so we'll get right to the possibilities. I'll set up each situation in the first column, give an ATC clearance in the second column, and review what's expected of the pilot upon acknowledgment of each clearance. For all of the following examples in the table refer to the FUNDY 4 PBN STAR above.

PBN STAR Walk Through Example

Let's pretend we're inbound to Halifax from Toronto. Since we're flying a Boeing 767-200 with a lovely FMS, dispatch was nice enough to file a routing which takes us over CETTY, the bedpost fix for the FUNDY 4 Arrival into CYHZ, and filed the FUNDY 4 PBN STAR on our flight plan as well. We're at FL 330 about 150 NM out of Halifax. While the captain flies the plane and monitor's ATC's frequency, the first officer checks the ATIS.

ATIS: "Halifax International Airport information MIKE, weather at 2300z. Winds 210 degrees magnetic at 15 knots. Visibility 1/4 miles in fog. Vertical visibility 200 feet. Temperature 18, dew point 18. Altimeter 2948. IFR approach ILS RWY 23, Category 2 ILS RWY 23 available. Landing and departing RWY 23. Advise ATC on initial contact you have Information MIKE."

Lovely weather, no? Out of Toronto, ATC cleared us "via flight planned route" which, as mentioned earlier in this example, included the FUNDY 4 Arrival. Now we can set up the FMS for the FUNDY 4 for runway 24, since the ATIS told us what to expect for landing. Can we start descent? No. The reason? ATC hasn't yet given us descent clearance. We currently have authorization to fly the lateral portion of the STAR, but no descent clearance means we maintain the last assigned altitude. Since the FMS has already calculated our optimum point for ToD, or Top Of Descent, and we're approaching it rapidly, we ask ATC for lower. At this point, the aircraft is still with Moncton Centre, the facility that feeds arrivals to Halifax Terminal.

Pilot: "Moncton Center, Mainland two two ready for descent"
ATC: "Mainland two two, Moncton, descend one zero thousand, Halifax altimeter two niner four eight"
Pilot: "Mainland two two, descend one zero thousand, altimeter two niner four eight. We'll begin descent in about ten miles"
ATC: "Mainland two two, roger."

Pilot: "Moncton, Mainland two two leaving flight level three three zero for one zero thousand"
ATC: "Mainland two two, roger"

ATC: "Mainland two two contact Halifax Terminal one one niner two"
Pilot: (Always acknowledge a frequency change!) "One one niner two for Mainland two two"

Pilot: "Halifax Terminal, Mainland two two of flight level two zero five for one zero thousand"
ATC: "Mainland two two, Halifax Terminal, Runway 23, Information Mike, altimeter two niner four niner. Cleared ILS Runway Two Three approach"
Pilot: "Cleared ILS Runway Two Three approach, Mainland two two"

Note the reminder from ATC that "Information Mike" is the current information? If a pilot doesn't state the current information letter, or states an old one, the controller must verify that the pilot has it. Sometimes pilots may state it and the controller states it anyway. In all likelihood, this is either just a habit the controller got into, or the controller didn't hear which ATIS code the pilot reported having. It saves a few words by the controller stating it rather than asking what the pilot said and hearing the response.

What can the pilot do with that clearance as issued? Well, the aircraft is still outside MUVOX. The profile for runway 23 was already selected, based on the ATIS information received. Now the pilot has received a clearance for the approach at the end of the PBN STAR transition. Now, the route description in the STAR for runway 23 can be flown, meeting published altitude and speed restrictions along the way. The track leg after DUTIR can be deleted, allowing the aircraft to join the approach procedure (which, while not shown here, also has DUTIR as an IAWP on the approach chart). This allows a smooth transition passing DUTIR and allows the aircraft to fly the ILS. Note: If the pilot wants the Category II ILS for RWY 23, it must be specified, preferably before ATC gives you clearance. If ATC in Terminal and Tower doesn't know an aircraft is flying the Category II, less separation may be applied, possibly allowing aircraft or vehicles in the sensitive areas for the glidepath or localizer antennas, leading to possible fluctuations of one or both for the aircraft while on final in bad weather. Without the clearance stating the CAT II or subsequent approval for the CAT II, a pilot is not authorized to follow CAT II procedures.

While we're trucking on the downwind leg, we hear:

Pilot #2: "Halifax Terminal, Air Canada three three two out of one seven thousand eight hundred for one zero thousand, Information Mike. Request ILS Runway One Four"
ATC: "Air Canada three three two Halifax, cleared the LIRLA Four Arrival Runway One Four, descend eight thousand, altimeter two niner four niner"
Pilot #2: "Fly the LIRLA Four Arrival for Runway One Four, descend to eight thousand on two niner four niner, Air Canada three three two"
ATC: "ACA332, roger"

The LIRLA 4 sets a pilot up for an Open STAR to runway 14 from the east. In this case, the pilot has not received approach clearance. Also, the pilot has been issued an altitude of 8,000. That's the lowest altitude the aircraft can go right now. This could be because ML223 is just leaving 7,000 and the other aircraft will fly over top of you. There may be other issues of which you're not aware leading to that cleared altitude, as well. The important thing is that the pilot here stops descent at 8,000 feet. Also, the heading as depicted on the LIRLA 4 arrival at IGVOP (the DTW for that STAR for Runway 14) must be flown after passing IGVOP and anticipate radar vectors from ATC. No report is necessary after passing the DTW.

PBN STARs have been confusing to many people, including the controllers and pilots who are supposed to know about them. Given the changes to procedures that have occurred in the short time since their inception, it's no real surprise. I think it's pretty well ironed out now as to what the terms to use are, and the expectations of pilot form ATC and vice versa. As always, if there is any doubt, ask ATC for clarification. Have I left any questions in your head after this? Have you come up with a situation that I haven't covered and you'd like to know how to handle it? Please e-mail me at mo@xlii.ca. Any feedback is always welcome. Thanks once again for taking the time to read!