This week's topic:
IFR Flight Part 4: Holds
Why Holds Occur
Sequencing
Non-Radar En Route
Weather
Thunderstorms
Waiting Out
Fog
Snow Removal
Restrictions and Shuttles
Holding Clearance Examined
Parts of a Holding Clearance
Expect Approach Clearance Time
Expect Further Clearance Time
Holding Instructions
"No Delay Expected"
General Directions for Holds
Turns: Rate and Direction
Speeds
Timing of Legs
DME Holds
Published Holds
Sequencing: Departing Published Holds
Entering the Hold
Sector 1: Parallel Entry
Sector 2: Offset Entry
Sector 3: Direct Entry
Left-Hand Holds
Reports to ATC
Ever get issued a holding clearance and not quite know what to do? As a controller, I've often wondered about the responses I've received to holding clearances in the real world just how well the pilot understood what I wanted done. One person who suggested I discuss holds indicated that he had flown in the jump seat on some flights in the past and had been asked about some of the phraseologies used by ATC, wondering exactly what they meant. This week, we'll take some holding clearances apart and examine what to do when in receipt of a hold.
There are a number of reasons why ATC might issue a holding clearance. They range from traffic situations to weather and even go a little beyond. In a terminal control environment, ATC has many backups to the equipment they use, including radar and radios, so they have increased flexibility to provide vectors to final and can actually clear multiple aircraft for approaches simultaneously, even to different runways at the same time in many cases. Without any other factors at play, you're not likely to receive a holding clearance around a major airport with terminal control. If you're not operating around one of these airports, you may notice some differences.
At most of the airports in Canada, there is no terminal control service. The heavier-volume airports certainly do have this service, and they account for the majority of aircraft movements, too. But in the case of the lower-volume airports, the level of traffic doesn't warrant the expense of the extra equipment and man-power to provide a true terminal service. The reduction of redundancy in the equipment forces ATC back a step from a terminal control service and one of the first hints of this to a pilot is when a holding clearance is aimed at the aircraft when the one in front just received an approach clearance. At these airports, the only way ATC can ensure safety in all-weather operations is to clear only one aircraft for an approach at a time. This means that if aircraft number two or three or more in the sequence are all getting to the airport in a relatively short period of time, they are all likely to get holding clearances.
Another reason for holding that stems from traffic situations also stems from an environment of even less equipment for ATC. In many areas of the country, particularly around low-volume airports that are further from major cities, ATC not only lacks equipment for providing terminal service, but they may very well lack radar coverage altogether. In VATSIM, it's a little different as radar coverage is unsurpassed. Where ATC wants radar, they can have it, right to the ground. In the real world, things just ain't so. In cases where two aircraft are to pass in opposite directions, ATC may not have a proper non-radar separation standard ensured to provide one aircraft with a clearance to climb or descend through another aircraft's altitude. In this case, the "paper hold" could come in handy. When in receipt of a holding clearance, the pilot is given a clearance limit (see IFR Flight Part 1: Anatomy of an IFR Clearance) and is sort of "stopped" there. Then ATC can issue a climb/descent clearance to the other aircraft with a restriction to make the next available altitude by a geographical point that is clear of the first aircraft's hold. Once 1,000 feet clear of the other aircraft, the paper hold is cancelled and the first aircraft is re-cleared en route. The reason it's called a paper hold in this case is that the intent is to cancel the holding clearance before the held aircraft actually reaches the clearance limit. It's just a technicality, originally written on the paper flight progress strips in use by ATC at the time.
Aircraft may be held up for weather, too. Three cases come readily to mind. If an airport is experiencing nasty weather such as thunderstorms all around it, it does nobody any good to have 30 or 40 airplanes all flying around within 30 miles of an airport waiting for the weather to improve. In this case, aircraft may be issued holding clearances that keep them well clear of a terminal area, typically holding in one or more "stacks". When the weather breaks, aircraft are "peeled off" one or more of the stacks at a time and sent in closer for approach sequencing.
The second case of this involves traffic just waiting for the fog to lift. With airline schedules running dependent on flights getting in and out to make connections, sometimes airliners, in particular, will want to hold and hope the fog clears up enough to permit an approach. Controllers in Atlantic Canada, see this fairly often. They'll discuss the situation with dispatch, and then inform ATC they intend to hold for 20, 30 minutes, sometimes more, and if the weather doesn't improve, they'll request clearance to go elsewhere. In this case, ATC watches RVR (Runway Visual Range) values closely as they do tend to fluctuate over time. Once they get above the minimums a pilot requires for an approach, controllers issue approach clearances as they are able to attempt to aircraft in as quickly as possible before they drop below minimums again.
Winter operations cause holds sometimes, too. If an aircraft is inbound to a runway where snow removal operations are ongoing, or just starting, the pilot may elect to hold for a short time while snow removal equipment is placed on the runway to improve the runway conditions. This could include a couple of passes with a few very large plows or application of sand or urea to improve braking action.
Other applications of holding patterns exist while not strictly being holds, too. If an aircraft is issued an altitude restriction that can't quite made, for example. If ATC were to say, "Cross FRENN at 7,000 or above" and the aircraft is only out of 6,000 by FRENN, it has to enter a holding pattern at FRENN and "shuttle up" to 7,000 before continuing enroute. Advising ATC is necessary in such a case, of course. Hopefully the friendly neighbourhood ATC wouldn't issue a restriction a pilot not likely to make. That's sloppy at best. This would be in case the pilot accepts a clearance with a restriction, but circumstances change or it was misjudged and now the accepted restriction can't quite be made. Many instrument approach procedures to airports nestled in mountainous terrain also contain shuttle descents to confine the aircraft's descent to safe airspace, and the same airports may require "shuttle climbs" to get an aircraft back out.
There are many other reasons why aircraft may hold, but I'll let you think of some. Let's get to the meat of a holding clearance and what a pilot is expected to do.
As with the General Format of IFR Clearances discussed in Part 1 of this series, a holding clearance contains:
An example of a holding clearance? Have a look:
"CVA822 is cleared to the Moncton NDB via direct, maintain 4,000. Hold east, inbound on the localizer. Expect approach clearance at 1605z"
The aircraft is told where to hold, how to get there, how high to hold, how to hold when it gets there, and when to expect an approach clearance. While the first three parts seem pretty straight forward, there is a little more to each of the last two. The Expect Further Clearance time (enroute hold) or Expect Approach Clearance time (awaiting an approach) are said more than just to prevent a pilot from asking when he can expect further. They are also used in the event of a communications failure. Upon reaching the EAC with a comm failure, the pilot has authorization to commence an approach. If holding over a facility or fix used for an approach, the pilot executes that approach. If not, the pilot is to transition to an approach aid or waypoint for an appropriate approach and start an approach upon reaching the facility or waypoint.
In the case of an enroute hold, the EFC is meant for the same communication failure. In this case, the pilot will leave the holding fix and proceed on course. The AIM, RAC 10.6, 3rd paragraph says that pilots are expected to adjust the timing within the limits of the holding pattern to make departure from the fix as close to the specified time as practical. If no routing was given with the Expect Further Clearance statement in the holding clearance, the pilot is to fly the flight planned route. If given a statement such as, "Expect further clearance via direct SUMSPOT VOR then balance of the flight planned route", the pilot is expected to fly that new route instead. Normally, an EFC will be followed by the routing the pilot can expect if it's not the flight plan route or the balance of a STAR if holding on a fix on a STAR.
What does it mean, "Hold east, inbound on the localizer?" ATC has to specify how the pilot is to hold upon reaching the clearance limit. In this example, the controller wants the pilot to set up the holding pattern on the east side of the Moncton NDB, and the inbound track will be the localizer for runway 29, the instrument approach aid for the runway served by the Moncton NDB as its final approach fix. If the hold were to be set up on a VOR radial, ATC would specify which side of the fix to hold on, and the inbound track would be the radial. To read the radial, make sure the "From" flag is visible in the VOR gauge and the OBS is set to read the radial desired. ATC may instruct an aircraft to set up a hold on an NDB and use a bearing as the inbound course. This example might sound like, "... Hold north on an inbound track of 180,..." remembering that to hold on the north side of the NDB and pointing south on the way in will result in a pilot flying an inbound track of 180°.
In some cases where ATC must issue a holding clearance, the controller may not actually expect the aircraft to have to enter the hold. In such a case, ATC may use the term, "No delay expected" in place of the EAC or EFC. This means the aircraft is not expected to actually have to enter the hold and may, in the event of a communication failure only, commence an approach or continue en route as cleared. If communication is still alive, ATC should actually issue a further/approach clearance at least five minutes prior to the aircraft reaching its clearance limit. The pilot, should request further clearance before reaching the clearance limit if ATC doesn't initiate such action.
For aircraft in the hold, IFR separation is provided primarily on the concept of airspace-to-be-protected. For this to occur, the airspace has to be described so the pilot knows what to fly and the controller knows what to protect for that aircraft. And for this to be possible, there are rules for pilots who fly holds. Here's a diagram of what a Standard Holding Pattern looks like:
There are, of course, turns in a hold. Our pilot's bible, the AIM, defines the requirement for turns in section RAC 10.2, paragraph 2. It says, "pilots manually flying the aircraft are expected to make all turns to achieve an average bank angle of at least 25° OR a rate of turn of 3° per second, whichever requires the lesser bank." There are markings on the aircraft's Turn & Bank Indicator that are calibrated to indicate either rate 1 or rate 1/2 turns. Rate 1 is 3° per second, so use this mark if it's there. If it's a rate 1/2 turn coordinator, you're more likely to use the 25° angle of bank. This can normally be measured with that all-important artificial horizon a pilot should be so familiar with in IFR flight. All turns in a standard holding pattern will be to the right once established in the pattern.
Another important aspect of a hold is speed. The size of the airspace to be protected for a hold depends on the speed of the aircraft. As such, there are maximum airspeeds specified for holds, and these are based on altitude. The following table, taken from the AIM RAC 10.7 Speed Limitations applies to aircraft in holding patterns.
| At or below 6,000 ft | |
| Above 6,000 ft up to and including 14,000 ft | |
| Above 14,000 |
Pilots are to advise ATC immediately if they require speeds in excess of those in the table above. This could be because of icing, minimum aircraft performance, or whatever.
With approval from ATC, pilots can fly faster than the above mentioned speeds. After departing the hold, pilots are allowed to resume a normal operating airspeed, giving consideration for other regulations like CARS 602.32 Speed Limitations, ATC restrictions that may have been issued, etc.
The timing of the legs within a hold is important for ensuring the aircraft remains within the prescribed airspace for the hold. AIM RAC 10.6 gives us the rules for holds when it comes to this topic. The "Still Air" time for flying the inbound leg of a holding pattern should not exceed 1 minute if at 14,000 feet or below, or 1.5 minutes if flying above 14,000 feet ASL. Once established in the holding pattern, pilots are expected to make adjustments, considering winds, to the length of time spent in the outbound leg to attempt to accomplish an inbound leg flying time of 1 minute or 1.5 minutes, depending on the altitude as indicated above.
After the initial circuit in the hold, timing of the outbound leg should begin abeam the fix or when established on the outbound heading, whichever occurs later. You are "Abeam" the fix when you are established on the outbound heading (180° from the inbound heading assigned by ATC in the holding clearance) and the fix is 90° to your right (or left if in a left-turn pattern).
Many pilots issued holds will ask for longer legs in the hold to provide for fewer turns over a given time period. ATC will normally approve requests like this, if they can. Traffic situations may dictate otherwise, especially in a non-radar environment, so ATC may not be able to accommodate such requests.
DME holds can be issued to determine inbound and outbound turning points in lieu of timing the turns. This is preferred by many pilots. As part of the holding instructions, ATC may specify the turning points in a clearance such as:
"CVA822 is cleared to CETTY via direct, maintain 10,000. Hold northwest, inbound on the YHZ 292 radial between CETTY and 40 DME. Expect further clearance via the FUNDY6 arrival runway 24 at 2020"
CETTY, in this example, was a published fix for one of the RNAV STARs into Halifax from years ago. It has a distance from the Halifax VOR and was located on the former airway J29 which was the YHZ 292 radial. ATC has specified in this example the distance where to turn inbound. The pilot should now enter the hold using CETTY as the holding fix. Upon reaching CETTY, make a turn to the right. Then continue on the outbound heading until the DME gauge reads 40 DME. At that point, commence a right turn to intercept the YHZ 292 radial and track it inbound to CETTY. Then repeat as necessary until receiving a further clearance from ATC, or, in the event of a communications failure, until 2020z and commence the FUNDY6 RNAV STAR for runway 24. Controllers shouldn't be giving the RNAV STAR to aircraft incapable of the those procedures. More about that in a future topic.
The above example could have been specified on any radial and any DME. For example, ATC could clear a pilot "... to the YHZ 330 radial at 10 DME, to hold between 10 and 20 DME...". Once established inbound on the 330 radial (we'll assume the pilot was already on it or ATC vectored the aircraft to it before reaching 10 DME), the pilot is expected to start the turn to the right to proceed outbound when the DME reads 10 DME, and start the right turn to proceed inbound at 20 DME. Controllers and pilots alike should understand that, during the turn, the aircraft will pass the "marks" as it makes the turn. The pilots should make sure they make the turns at the required rates to limit the distance outside of the specified distances.
For fixes with published holds, ATC may issue a clearance with a slightly different phraseology. For an example of a fix with a published hold, see this diagram, a clip from a Low En Route IFR chart (LO chart):
Looking at the map snippet above, an aircraft cleared to hold at PAULO might hear:
"CVA116 is cleared to PAULO via V310, maintain 8,000, hold as published. Expect further clearance at 1610"
This simply means "use the published pattern so I don't have to waste time getting descriptive about what I want you to do and you don't have to read it all back to me". It also saves the pilot time in the readback, too, since every aspect of a holding clearance must be read back verbatim. The published pattern in this case, as with a standard hold, is also a right-hand pattern, meaning that turns will be made to the right. How do you know? Look at the arrows on the circuit in the diagram. This hold is meant for aircraft proceeding southwest bound (from the upper right corner of the image to the lower left corner of the image) on the airway segment where the fix is published.
Sometimes published holding fixes are used for arrivals to help control the flow closer in to the airport. ATC might issue a clearance that says something like, "Depart PAULO at 1610". If the aircraft has not yet reached PAULO and the time is 1555, the pilot has the option of burning right on in to PAULO and setting up a hold, reducing speed to attempt to make good a time for PAULO of 1610 to be able to proceed past PAULO as cleared without holding, or to do a little of both. Reduce speed so as to do fewer turns in the hold upon reaching PAULO. The hold, in such a case, is only if the pilot reaches the fix prior to the EFC time issued. Pilots should advise ATC of the action taken.
There are different ways of entering a holding pattern depending on which direction you are approaching your clearance limit from. Refer to the diagrams below for the entry, and I'll describe for you the steps. There are three different "sectors" from which to enter a hold.
1. Upon reaching the fix, turn onto the outbound heading of the holding pattern for the appropriate period of time (1 minute or 1.5 minutes, depending on altitude)
2. Turn left to intercept the inbound track or return directly to the fix
3. On the second arrival over the fix, turn right and follow the holding
pattern
1. Upon reaching the fix, turn to a heading that results in a track having an angle of 30° or less from the inbound track reciprocal on the holding side
2. Continue for the appropriate period of time (1 or 1.5 minutes based
on altitude), then turn right to intercept the inbound track and follow
the holding pattern
Sector 3: Direct Entry
1. Upon reaching the fix, turn right and follow the holding pattern
For a holding pattern where left-hand turns are required, the reverse of the above diagrams and instructions applies.
Pilots should make a report to ATC when crossing the fix to enter a holding pattern. The phraseology for this report is simply, "Entering the hold." ATC may also request a pilot to report, "Established in the hold." A pilot should make this report as the fix is crossed after having completed one of the entries as described above.
There. Now when somebody tells you to "hold your horses", you know what to do with them. Any questions, or to report any omissions, please e-mail me at mo@xlii.ca. Any feedback is welcome, whether you like what I've done with the place or hate it. Thanks again!
Sector 1: Parallel Entry 
Sector 2: Offset Entry 