Sunday, January 20, 2008

Barbs, Teardrops, HILO

Sorry for the delay since my last post. I've been busy ...

Procedure turns (PTs) are maneuvers that allow a pilot flying in instrument conditions to reverse direction and, if necessary, loose altitude. There are mainly two flavors of PTs depicted on Instrument Approach Procedures (IAPs) - the barb and the holding pattern (sometimes called Hold In Lieu Of a procedure turn or HILO). While conceptually simple, procedure turns can cause misunderstandings with air traffic control if the pilot is not up to speed on the regulations.

As always, don't use any of the following illustrations for actual navigation.

When flying the NDB version of the MOG NDB or GPS A approach, the procedure turn is required because the pilot must fly over the NDB station to establish his/her location prior to beginning the approach and descending. Knowing where you at the start of this approach procedure is important because there's plenty of terrain around to run into. You'd be cleared to MOG at a certain altitude, cross the station, turn outbound and track the 157˚ bearing from MOG for a minute or two, then turn to a heading of 112˚ for a minute (procedure turn outbound), then turn to 292˚, intercept the 337˚ bearing to MOG, and begin descending.

It's important to note that without GPS, RNAV, or other specialized equipment, you really don't know exactly where you are while flying the procedure turn. You only have positive course guidance when you are flying inbound or outbound from the NDB and you only know exactly where you are when you cross over the NDB or when you descend out of the clouds and obtain sufficient visual references.

The most common procedure turn is the 45˚shown below. Cross the Final Approach Fix and fly outbound for a minute or two (depending on the wind and your aircraft's performance), then turn 45˚ in the direction of the barb and fly for a minute, the do a standard rate 180˚ turn and intercept the inbound course.

Another accepted procedure turn is the 80/260. Once outbound on the approach course, turn 80˚ in the direction of the barb, then immediately turn 260˚ in the opposite direction to intercept the inbound course.

You can also fly a teardrop procedure turn, but it's a little more complicated. Cross the final approach fix and proceed outbound for 1 or 2 minutes (depending on the wind and your aircraft's performance). Then you turn either 30˚, 20˚, or 10˚. How long you fly outbound depends on the offset chosen; 30˚ for 1 minute, 20˚ for 2 minutes, or 10˚ for 3 minutes. When the alloted time is up, make a standard rate turn back to the inbound course, depending on the offset you chose: For 30° turn 210˚, for 20˚ turn 200˚, and for 10˚ turn 180˚. That's a lot to remember, but it gives you added flexibility in how long you want to make the procedure turn last.

On many (most?) procedures where the barb is depicted, the PT is neither required nor expected (more on this later) when you are being vectored by ATC. But if you need to fly the PT, you can maneuver however you want as long as you stay on the same side of the approach course where the barb is depicted. You also must stay within the distance depicted, usually 10 nautical miles from the final approach fix.

Some IAPs depict a holding pattern that can be used for course reversal and I'll refer to these as HILO (Hold In Lieu Of a procedure turn). In these cases, you have to enter and fly the hold as depicted. As you turn inbound in the holding pattern, you'll be established on the approach course. The holding pattern at WINCH (shown below) may or may not be required, depending on how you approach the fix. For RNAV approaches, the Garmin units will ask you if you want to fly the hold when you load the approach, but they don't ask for other types of approaches like VOR, ILS, or LDA approaches.

Often ATC will ask you to "report procedure turn inbound" and many pilots do not understand what this means. "Procedure turn inbound" does not just mean that you've begun your turn to intercept the approach course. It means you have completed your course reversal and you are established on the inbound approach course. Seasoned controllers will often avoid the potential confusion by just asking you to "report established inbound."

When I did my first 135 indoc training several years ago, I was impressed by how Director of Ops cut the Gordian knot when he described whether or not to execute a procedure turn or a HILO on a vectored approach:

"Don't" was the simple answer.

I later expanded that simple answer a bit:
"Don't fly a procedure turn or HILO on a vectored approach without first asking ATC."

When in doubt, ask. That's the most foolproof, all inclusive answer I can offer to the often asked question "When can I or should I do the procedure turn on an approach?" That's the gist of it and if you want to stop reading now, you can.

Still reading? Well for the long answer, let's all turn in our hymnals to 14 CFR 91.175. Buried in this section of the regulations entitled "Takeoff and Landing Under IFR" is a little kernel of wisdom on holding patterns and procedure turns, stuffed in here as if there wasn't any better place. Or were the authors of the regulations just trying to create their own sort of Easter Egg hunt? We may never know, but let's press on.
(j) Limitation on procedure turns. In the case of a radar vector to a final approach course or fix, a timed approach from a holding fix, or an approach for which the procedure specifies “No PT,” no pilot may make a procedure turn unless cleared to do so by ATC.
When using a Garmin GPS unit like the 430, 530, or G1000 to load an approach, especially a non-GPS or non-RNAV approach, it's easy to have a moment of confusion. Let's consider this clearance:
Barnburner 123 is cleared to the Santa Rosa airport, fly heading 310, radar vectors Sausalito, Sausalito 330 radial, BURDE, Santa Rosa 141 radial, COATI, direct. Climb and maintain ...
30 miles out from STS, you tell Oakland Center that you have the latest surface weather observation (ATIS) and you request the STS ILS RWY 32 approach. Center tells you to proceed direct to COATI and to expect the ILS and so you begin briefing the approach.

You load the approach, selecting COATI as the initial approach fix since that was what your clearance contained. When you're done, you see something odd on the flight plan page: Why in the hell is the procedure turn in there?

The high workload of single-pilot flying may cause you to miss the fact that procedure turn is in the flight plan, but looking at the moving map should give you pause.

14 CFR 91.175 is pretty clear that you shouldn't fly the procedure turn in this scenario since you're going to be pretty much aligned with the straight-in approach course. Approaching from the northwest, well that would be different story. So why doesn't the 530W see that you're approaching from the south and figure out that you don't need the procedure turn? Good question ...

Now you could just fly the localizer and ignore the fact that the 530W wants you to turn around after you reach COATI, but then you'll lose the distance and time to each waypoint on the approach. To delete the procedure turn, you'll need to press the FPL (flight plan) button, press the small knob to enter cursor mode, scroll with the large knob to highlight the procedure turn, press CLR, and press ENT twice. A faster and safer solution is to cursor past the procedure turn (or HILO) and press the Direct key, then ENT twice.

In the next installment, I'll discuss vectored approaches with HILO.


eric said...

John, thanks for the great article on this topic! I've got a further question for you, one which we've discussed a bit here at the office to no real satisfactory conclusion. The RNAV (GPS) RWY 16R approach to Paine Field (KPAE) is not the standard GPS 'T' layout - it only has two IAFs depicted, one as HILO and one NoPT from the northwest.

More often than not, Seattle Center controllers clear you direct to EYWOK (the HILO IAF) for the straight-in GPS rwy 16R approach from just about anywhere, including well to the southeast. However, once in a while they will simply clear you to EYWOK for the GPS 16R approach - and not specify that it is straight-in. I suppose this is really a two-part question - first, is 'direct EYWOK' considered 'radar vectors'? Secondly, at what point do you have to turn 'too far' to fly it without the course reversal - 90°? 100°? 135°?

I've heard answers from either end of the opinion scale and I'd be interested to see your take on the matter.

John said...

Hi Eric,

Glad you liked my post. On to your questions:

While I'm not a controller, I know controllers are supposed to adhere to Order 7110.65R when vectoring you, but sometimes a controller can be a little fast and loose, especially if you are doing a VFR practice approach.

My reading of Section 6. Vectoring leads me to believe that "proceed direct EYWOK" is a vector (note the item in parenthesis in bold face was added by me). The following items appear under the chapter on Radar control and the section is entitled "Vectoring." Note that the controller is responsible for specifying a safe altitude for you to maintain and you must be in radar contact.

"e. So as to permit it (the aircraft and pilot) to resume its own navigation within radar coverage."

DIRECT (name of fix), ..."

As to whether a controller can clear you direct EYWOK without you doing the Hold In Lieu Of a procedure turn (HILO), Chapter 5 of the AIM may be of some help. From 5-4-5 Instrument Approach Procedure Charts, paragraph d. Terminal Arrival Area (TAA), emphasis added by me:

"3. The "T" design may be modified by the procedure designers where required by terrain or air traffic control considerations. For instance, the "T" design may appear more like a regularly or irregularly shaped "Y", or may even have one or both outboard IAFs eliminated resulting in an upside down "L" or an "I" configuration. (See FIG 5-4-3 and FIG 5-4-10). Further, the leg lengths associated with the outboard IAFs may differ. (See FIG 5-4-5 and FIG 5-4-6)."

"7. Just as the underlying "T" approach procedure may be modified in shape, the TAA may contain modifications to the defined area shapes and sizes. Some areas may even be eliminated, with other areas expanded as needed. FIG 5-4-10 is an example of a design limitation where a course reversal is necessary when approaching the IF (IAF) from certain directions due to the amount of turn required at the IF (IAF). Design criteria require a course reversal whenever this turn exceeds 120 degrees. In this generalized example, pilots approaching on a bearing TO the IF (IAF) from 300° clockwise through 060° are expected to execute a course reversal. The term "NoPT" will be annotated on the boundary of the TAA icon for the other portion of the TAA."

So if you get vectored to EYWOK and your turn to intercept will exceed 120˚, you're entitled to do the HILO. I think the best thing to do in a situation like this is tell ATC you need to do the course reversal and get their agreement in advance.

If there are any qualified controllers out there who'd like to comment or correct me, please chime in.

Anonymous said...

As a recently retired ATCS, I'd like to add a comment/observation. When being vectored to a section of the approach, the controller expects you to fly the most direct approach available. The only time I ever protected for the PT or HILO was if the clearance issued was "Cleared for the FULL approach". Otherwise I expected the aircraft to intercept the approach and proceed to the FAF.

eric said...

John, excellent! Thanks for spotting that. I'd spent a ton of time in the FAR, but hadn't made it all the way through the AIM to look for that information. Time to add yet another tab to my regs and another item to my GPS approach lesson.

John said...

Glad to help out.

I think hearing the controller's perspective helps to underline that communication is key. Not all (many?) controllers are pilots and so they might not "get the flick" that we have.

For example, a 120 degree intercept angle can be pretty darn challenging. Depending on the vintage of GPS equipment you have on board, extreme intercept angles can be downright dangerous.

So when in doubt, ask or voice your concerns to ATC. The sooner you do it, the better.

Anonymous said...

John - here's an off-topic question. You and others have written about how available runways and airspace are becoming more and more congested. My question is: is it legal for airliners or air taxis to fly VFR if conditions are right for it? You wrote recently about how a line of bizjets were waiting for IFR clearance, but you and your student decided to take off VFR. Is there anything that prevents passenger-carrying operations from flying completely VFR, from takeoff to landing? And would that alleviate runway and airspace congestion? (If this is NOT currently legal, do you think it's a good idea?)

John said...


Most 121 and 135 operators have defined policies about when they can operate under VFR. The important thing here, I think, is that when an aircraft is VFR there is no guaranteed separation from other aircraft except when operating in Class B airspace.

In any event, it's not clear to me that abandoning IFR is going to solve any problems. In fact, it might create more problems than it would solve.

Back in the early days of airline travel, when there was little or no radar coverage, there were a few spectacular crashes. One in 1956 involved the collision of TWA and United Airlines aircraft.

To my mind, congestion and delays don't trump safety.

Joe said...

"14 CFR 91.175 is pretty clear that you shouldn't fly the procedure turn in this scenario since you're going to be pretty much aligned with the straight-in approach course."


I agreed completely with your statement that before preforming a HILO or PT if any doubt exists you should ask ATC or at least make you intentions clear to ATC.

But what part of 91.175 is clear about being cleared direct to a fix on the final allowing you to a proceed directly inbound? While it maybe treated by ATC as a vector it is in fact not a radar vector without a "fly heading xxx" statement from ATC.

Unless ATC gives you a "cleared strait in" approach type clearance, then doubt exists and I don't see 91.175 helping clear things up at all!

Recently AOPA put out a mini course based on a VOR approach that ATC was clearing people directly to the FAF and expecting them to proceed without a PT.

John said...


I can only fall back on my original advice: If you're being vectored or have been cleared direct to an intermediate approach course fix, don't expect to fly a procedure turn or HILO without first clarifying it with ATC.

The regulations are not always very helpful, unfortunately.