Aviation Topic of the Week
By Michael Oxner, March 21, 2004


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This week's topic:
Who to Call for IFR Clearance

In the past weeks, I have mentioned that I would do a topic on who to call for IFR clearance. Now's the time to get to that issue. I'll remind you that all of the following information relates primarily to Canada. I haven't checked out rules for other regions, but it may very well be similar elsewhere.

Concept
    Responsibility
    FIR vs. CTA
On the Ground
    Table of Stations to Call and How
    When to Call
Departing in Uncontrolled Airspace
IFR Aircraft Departing VFR

Concept

The AIP Canada gives us plenty of rules for flight, both VFR and IFR. For IFR flight, as discussed in several previous topics, a pilot must obtain an IFR clearance from ATC prior to entering controlled airspace. A past topic was also written on the various classes of airspace, so I won't say anything more than restating that Classes A, B, C, D and E all qualify as controlled airspace. If the departure aerodrome is contained within controlled airspace, then an IFR clearance must be obtained prior to take-off. This topic is all about obtaining that all valuable IFR clearance, and more specifically, who and when to call for it.

The IFR ATC unit has the ultimate responsibility for issuance of IFR clearances. An IFR unit could be an Area Control Center (ACC), as for most airports, or it could also be a Terminal Control Unit (TCU), as is often the case at the busier airports. Each TCU has a designated area of responsibility, and some secondary airports lie within that area, even though they aren't the main airport served by the TCU. In such cases, the TCU is the one responsible for issuance of IFR (Flight Information Region) clearances to aircraft operating into and out of these fields. In all other cases, it's the ACC in whose FIR the airport lies.

One side note: There are several cases across the country where an airport lies within the FIR for one ACC, but lies within the CTA (Control Transfer Area) of another, perhaps even a unit in another country. The CTA defines which ATC unit has responsibility for separating IFR traffic, while the FIR defines who is responsible for providing other services, such as alerting services for aircraft overdue on IFR flight plans. In most cases, the FIR and the CTA are the same. I haven't yet found much written anywhere about this combination, but it is appropriate for an aircraft to call the ATC unit within whose CTA the airport lies. For example, have a look at this snippet from an outdated LO (low level enroute) chart depicting the north western portion of New Brunswick. The designation still exists and is not expected to change in the near future.

FIR/CTA Diagram You can see in the diagram at left that the airspace boundary between Moncton and Montreal ACC's is the same for both the FIR and the CTA (top right). The boundary between Moncton and Boston, on the other hand, is a dual boundary. The international boundary serves as the FIR boundary, and Moncton is therefore responsible for flight information in the area of overlap. Boston is the one providing Air Traffic Control services and providing separation there. Because Boston is doing this, it is actually more appropriate for a pilot to talk to Boston Center for IFR clearance out of this area. It gets more convoluted for a number of reasons. The aircraft on the ground at CYSL (St. Leonard), for example, call Quebec Radio for IFR clearance, since CYSL is in their Area of Responsibility (AOR) and they have a DRCO there. QB FIC then calls Moncton for IFR, who must then talk to Boston for clearance. Then the clearance is relayed through Moncton to QB and on to the aircraft. This is all very cumbersome, prone to delays, and quite outdated. The airspace was divided like this several years ago when AFB Loring was active. Now that the base has been shut down and its TCU closed, the airspace still belongs to Boston, even though it's a pain for both sides of the fence. In any case, the unit providing the ATC service is the best one to talk to for IFR clearance.

This next paragraph starts the path into who to call, but it is related to responsibility for issuance of IFR clearances. Typically, an IFR clearance is relayed through another ATS unit. For example, an aircraft will call a tower for IFR clearance, and the tower will then obtain the clearance from the IFR unit and relay it to the aircraft. At many towers across the country, an agreement is in place whereby the tower will issue an IFR clearance to aircraft when they call. Such a clearance will normally contain a SID, flight planned route and a transponder code. This authority is delegated to the tower for the benefit of both units. The tower no longer has to call for each individual aircraft, and the ACC knows exactly what was issued by the tower with no other coordination being necessary. In these cases, the clearance is technically not valid until the IFR unit authorizes the tower to "release" the IFR aircraft. This is something done behind the scenes -- transparent to the user, as they say..

On the Ground

There are all kinds of situations a pilot can find himself in when he's looking for an IFR clearance. The differences between the situations are often very subtle, but make the difference of who to call, when to make the call, and how to call them. Each aerodrome entry in the Canada Flight Supplement will have some details listed in the COM section regarding the frequency to be used in the vicinity of the aerodrome and who to contact. At most aerodromes, the name of the aerodrome (typically derived from the name of the community the aerodrome serves) makes up part of the callsign, and the station listed makes up the rest. For example, if you were to look up CYHZ, you'd see an entry for TWR on 118.4, and that unit would be called "Halifax Tower". Similarly, at this aerodrome there are GND, for "Halifax Ground" and CLNC DEL for "Halifax Clearance Delivery".

Table of Stations to Call and How

So with all the above said, I thought it best to provide a table of who to call, and how, for departing IFR aircraft looking for IFR clearance. Here it is, listed in order of priority. If you don't find the first entry, look for the second. The second one is not there? Look for the third. Continue until you find one of entries in the table that exists, and use the method in the same row for communication. This table is for use when you are on the ground, attempting to get a clearance before getting airborne.

Priority
 Unit/Sub-Unit
 Radiotelephony
 Method(s)
1
 Clearance Delivery
 Clearance Delivery
 Radio Frequency
2
 Ground
 Ground
 Radio Frequency
3
 Tower *
 Tower
 Radio Frequency
4a
 Flight Service Station (on-site) (FSS)
 Radio
 Radio Frequency
4b
 Flight Information Center (FIC) providing RAAS
 Radio
 Radio Frequency (RCO or DRCO)
5
 Area Control Center/Terminal Control Unit
 Center/Terminal
 Radio Frequency (if a PAL is nearby)
6a
 Flight Information Center (FIC)
 -
 Telephone line/Cellular phone
6b
 Area Control Center/Terminal Control Unit
 -
 Telephone line/Cellular phone
 * Normally, an IFR clearance would not be relayed on a TWR frequency. See the text below for more.

For outlying airports, there is often no direct way of communicating with an ATS unit (Air Traffic Services). As in our example flight in the past few weeks, Stephenville, NL (CYJT) has no on-site ATS unit like a TWR or FSS. The entry in the CFS showed a Mandatory Frequency (MF) listed with ARPT RDO, meaning there was a ground station there, but that kind of unit is not used for relaying IFR clearances like the first five units listed above. The next place to call on the list in our example flight is the PAL located near the field there. If there is one nearby, it would be marked on the LO charts, or listed in the CFS under the airport entry's COM section.

When to Call

When to call for IFR clearance isn't always clear. The rule is "prior to entering controlled airspace". The fact is that many airports and ATC units operate differently at different airports with different facilities. Starting from the top of the chart above, a Clearance Delivery frequency is probably the easiest to remember and deal with. Anyplace where a CLNC DEL position is specified will allow for a pre-taxi IFR clearance. This is when a pilot may call for, and receive, an IFR clearance prior to engine start. As mentioned with the towers above, this is normally a "canned clearance" that will include a SID published for the airport. A clearance, time check and altimeter check is typically done here and this allows Ground to concentrate on ground movements without the distraction of delivering IFR clearances. Pilots should tune in and copy details of the ATIS, if one is provided at the airport, prior to calling CLNC DEL, and notify ATC they have the latest information by use of the identifying letter. If the latest information is acknowledged when calling DEL, there is no further need to mention this to succeeding ground stations, like GND and TWR.

If there is no CLNC DEL position published for your aerodrome, look for Ground next. Most often when there is no CLNC DEL frequency, an IFR clearance is withheld until a pilot is actually ready, or at least near ready, to taxi. This is often because the IFR unit can issue a more appropriate clearance if he knows the aircraft will be airborne within a fairly short period of time. In such a case, a pilot should commence engine start-up, and complete checklists and prepare to taxi prior to calling for IFR. Once ready to go, call GND for IFR clearance and state the flight is ready to taxi as well. This will provide ATC with an opportunity to provide a pilot with the least restrictive and most appropriate clearance. If there are any concerns about burning a lot of fuel, or for delay getting airborne due to de-icing fluid application, a good practice would be to call ATC and state when the flight is expected to be ready to taxi before engine start, or before de-icing. They may be better able to advise about anticipated delays, if any, at that time.

Third in the table is Tower. Normally where there is a TWR in operation, GND is in operation as well. It is quite possible that the guy working "airside" is working ground as well, and this is quickly evident when hearing taxi instructions on the TWR frequency (with no aircraft reply heard) or by hearing take-off and landing clearances as well as directions to aircraft (also without replies) while listening to the GND frequency. Normally IFR clearances should not be requested on a TWR frequency, since the tower would also be operating a GND frequency and that is the appropriate place for it.

Fourth and fifth are treated essentially the same, hence the numbering in the list. Flight Service Stations are often located on aerodromes that aren't busy enough to warrant an airport control tower. Using the callsign "radio", these folks are often located in a building resembling a tower with a view overlooking the airfield. In the case of an FIC providing RAAS, the person on the other side of the frequency may be located several hundred miles from the airport and therefore would be unable to see anything there. They have the authority to direct ground vehicles and facilitate aircraft movement information by recording and relaying pilot reports of position and activities. Part of Radio's job is to relay requests for IFR clearances to the IFR unit, and to then relay the IFR clearances received from the IFR unit to the aircraft at the field. The primary reason for the use of on-field personnel in such a case is to ensure that the same person remains informed of the intent of IFR aircraft once becoming airborne. As with the GND section above, a pilot should generally wait until he is ready to taxi before calling for IFR clearance at such an airport. Again, the pilot would be able to call radio to confirm this or to check on the possibility of delays before engine start.

The ACC is sometimes able to talk to aircraft directly over the radio at some airports. Each radio frequency an ACC uses is located somewhere, and these are often located on or near airports. Sometimes these transceivers are reachable by a pilot on the ground. This allows a pilot to talk directly to the controller. Once again, the pilot should be ready to taxi prior to calling for IFR clearance. The controller will often confirm the pilot is ready to go before issuing an IFR clearance. One difference here is that since an IFR clearance is not being relayed, the term "ATC clears" is not required as part of the clearance.

Lastly, if none of the above units are reachable by radio, the pilot's only remaining option may be to call on the phone for an IFR clearance. This may be done via landline before entering the aircraft, or by cellular phone, either before or after entering the aircraft. It is a good practice to be as ready as you can be before calling, since the longer the delay between asking for IFR and getting airborne, the more likely it is that a pilot will encounter some difficulty in obtaining a reasonable clearance. For example, if a pilot must use a landline, he should do all he can before making the call. Do the walk-around (pre-flight inspection) and anything else that can reasonably be done before engine start, then call for IFR clearance. ATC will be interested in knowing how long before the aircraft will be airborne, so an estimate of expected delay will be appreciated by ATC. In the case of cellular phone, service may be available from within the cockpit, meaning that a pilot can make the call as late as if he were using a radio to obtain clearance. The issue here is who to call. I have been the recipient of calls from the FIC in whose AOR the airport lies for a request for IFR clearance relay, and I have also received phone calls directly to the ACC from pilots requesting IFR clearance. Both methods are acceptable, although, as a controller, I'd rather talk directly to the pilot. It's always easier to talk directly to a pilot than to try to talk through someone else.

Departing in Uncontrolled Airspace

If the departure aerodrome lies outside, or below, controlled airspace, it's a slightly different story. A pilot may elect to depart, even in IFR weather, and call for IFR clearance once airborne. As mentioned in a previous topic, all the rules of IFR flight still apply outside controlled airspace. The only difference is that an IFR clearance is not required to operate there. This means a pilot can get in the air and call for IFR clearance directly to the ACC (or through an FSS or FIC if the ACC doesn't have a PAL located nearby) as long as the clearance is obtained before the flight enters controlled airspace. At some airports, controlled airspace overlies the airport, and the difference in altitude between field elevation and the base of controlled airspace may very well prevent such a manoeuver in foul weather.

Also note that all procedures associated with ATF or MF areas still apply, and a departure message must be forwarded somehow to ATC as well, either by radio or by telephone, all as per the usual.

IFR Aircraft Departing VFR

In good weather, the pilot of an IFR aircraft may elect to depart and fly in accordance with VFR until such time as he can receive an IFR clearance. First off, ATC must actually approve such an option before it can be done. The request must be forwarded to the IFR unit in the same manner as would occur for the request for an IFR clearance. What would be the use for this if you have to call ATC anyway? Sometimes ATC can't issue an IFR clearance right away due to other traffic in the area. If the weather permits, and the airspace is a class which permits, ATC may approve a pilot's request to take-off VFR and pick up the IFR clearance when they're clear of the other traffic. Sometimes time is all that's required, but other times the aircraft has to get far enough away that ATC has separation so they can issue a clearance. As implied above, a pilot has to request approval for a VFR departure. If ATC approves it, they should include a time, altitude or location at which to expect an IFR clearance. A discrete transponder code may be issued with the approval, as well.




I hope this topic goes a long way to understanding who and when to call for IFR clearances. Got any questions or comments? By all means, e-mail them to me at moxner@nbnet.nb.ca. Thanks for reading!