ATC Control Methods
    Types of Control
Position Reports
    Published Reporting Points
    Non-Published Reporting Points
    What to Include
    Radar and Position Reports
Speed Changes
    True Airspeed Tolerances
    Mach Number Tolerances
    Time Acceleration in Flight Sim
Altitude Changes
    Altitude Reports
    How to Report Altitudes
    Rules for Use During Altitude Changes
    Climbing/Descending "At Pilot's Discretion..."
    Too Fast While Descending Below 10,000
Minimum IFR Altitudes En Route
    Higher MEA
    What to do if You Don't Make the new MEA on Time
    Lower MEA
Clearances to Enter/Leave Controlled Airspace En Route

You've had a look at IFR clearances and what to expect on departure. Moving on in the series, we look at the en route phase of flight and some guidelines for flying.

ATC Control Methods

ATC provides control service in a couple of different ways: by use of surveillance systems like radar and ADS-B, where they see aircrafts' positions on a screen relative to others, and by Non-Radar Procedures, where they rely on position reports to figure out where aircraft are in relation to each other. Most commonly, aircraft are under some form of surveillance, but the default would be the other end of the spectrum. Aircraft are procedurally separated until in view of surveillance systems, as a sort of fail-safe method of operations.

Position Reports

The AIM, section 8.1 Position Reports, says that "Pilots of IFR and controlled VFR aircraft are required to make position reports over compulsory reporting points specified on IFR charts and, in addition, over any other reporting points specified by ATC." This is the law that tells pilots they must make calls by radio or other methods of communication to provide position information at predetermined places so ATC knows where their aircraft are at any given point within their flight. There are two reasons for this. Separation is one and the other is for alerting services. If ATC doesn't hear an aircraft within a certain time frame after it is expected to make a position report, controllers will start looking for it, starting from its last-known position. That position was known from its last position report.

This information may sound a bit like a history lesson in that some of the ideas seem out-dated, but they are still in use.

In the old days, before INS, RNAV, GPS, etc., pilots flew airways. To establish separation, there were reporting points published on the charts for pilots to report over, and which would allow ATC points of reference to work from. A reporting point is just a fix established in a strategic (or useless) position, and printed on the charts as solid, or filled-in triangles. Many reporting points are non-compulsory, meaning pilots were not required to make a position report over that fix unless requested by ATC. These fixes are drawn as open, or outlined, traingles. For example, see this image:

ATC may also ask for position reports along routes, like a specified DME distance or number of miles along track, or a radial or bearing from a NAVAID. These are usually quite specific, intended for a special purpose, so pilots should pay particular attention to such a request to ensure the report is made promptly. A pilot's request for altitude change or other such clearance likely hangs on ATC receiving the report requested.

So what should be included in a position report? Our trusty AIM has this to say.

Items to include in an IFR position report:

1. Aircraft Identification
2. Position
3. Time (UTC) over the Fix
4. Altitude or Flight Level
5. Type of Flight Plan filed (In this case the letters "IFR")
6. Name of the Next Reporting Point and ETA (UTC again)
7. Name only for the Next Succeeding reporting point
8. Any Additional Infromation requested by ATC or deemed necessary by the pilot.

A position report might look something like this:

"Moncton Center, CVA670 over GRUPI at 1645, FL340, IFR. Estimating YHZ at 1720. YQI next"

As a controller, I never received a position report on the frequency that included the type of flight plan ("IFR" in the above example), and personally, I didn't miss it. Both the pilot and the controller being spoken to know the pilot is IFR. That statement is actually more for the fact that some position reports may be made to non-ATC facilities and relayed to ATC. The names of the next fixes are in there for confirmation of the routing being followed, and the times are required so controllers can cross-check their own estimate of a pilot's prgroess against reports from the pilot to verify information, and often to verify separation from other aircraft. This helps keep the pilot safe and the level of paperwork due to incidents down.

Now that we've talked a little about position reports, we can almost totally dispense with them. As time passed, more and more radar sites came online. These days, space-based ADS-B stands to dispense with them altogether. As controllers can "see" where you are, position reports become almost totally unnecessary, even to the point of being a nuissance, sometimes. Especially in higher traffic levels. The word a pilot wants to hear, whether on departure or checking in with a controller from the enroute perspective, is "Identified". Hearing this word tells a pilot that position reports are no longer required. Only position reports specifically requested by a controller must be made from then until a controller tells you "surveillance services terminated", at which point, the pilot is being told that the flight will no longer be actively monitored on ATC surveillance systems. This could be simply because an aircraft is no longer visible to ATC surveillance, or because the controller is moving on with other tasks and can no longer provide service to the aircraft.

Essentially, this is like a switch. Controllers can switch to surveillance-based separation standards upon informing an aircraft it is "identified" and switch back to provision of procedural separation standards when the informing the pilot that "surveillance services terminated". Similarly, IFR pilots can switch from making position reports to saving that valuable air time on the radio when they are informed that they are "identified", and start making position reports again when the surveillance services are no longer being provided. A standard phraseology for controllers to remind pilots about the requirement to make position reports again is, "resume position reports." This isn't always said to pilots.

I will be doing a topic or two later on to help pilots understand a little better the idea of flying in a procedural environment. It is quite a bit different and pilots really have to pay attention to get the instructions right. Pilot reports become of utmost importance when ATC can't see you.

Speed Changes While En Route

Generally speaking, there are two types of speed measurement used while enroute. Mach Numbers are used by fast, high-flying jets while True Airspeeds are used by aircraft in the lower altitudes and slower turboprops at high altitudes. If you read the article on the Anatomy of an IFR clearance, you may recall speed was mentioned. The speeds to be used by controllers when separating aircraft and for pilots while flying them are those that are provided to controllers in the flight plans filed by pilots and dispatchers. Whether you're looking at TAS or Mach, ATC will be expecting a pilot to operate within a fairly narrow range either side of the flight planned speed. Speeds different from those in the flight plans may be assigned by controllers for separation, but for now, let's talk about the tolerances required.

For True Airspeed, the AIM, paragraph 8.2.2 tells us pilots are expected to operate within 5% of speed filed in the flight plan. If a pilot filed to cruise at 300 knots True, the aircraft may be flown as slow as 285 or as high as 315 without seeking approval from ATC. If the pilot wants to operate outside that +/- 5% range, ATC's approval should be sought. Again, this is True Airspeed (TAS), not Indicated Airspeed. In Flight Simulator, as it applies to VATSIM, aircrafts' Airspeed Indicators (ASI) can be set to show True Airspeed, but that is not the norm for real world aircraft.

As a controller, I have had some pilots ask if this is important in a radar environment where their speeds can be monitored directly. The short answer is, "yes." To demonstrate why, I'll offer a situation I experienced. I had two DH8D (Dash 8 Q400) leaving Moncton (CYQM) for Montreal (CYUL), both planned on the same route at the same altitude. The first was filed at 345 KTAS, the second at 319 KTAS. Upon leveling off at FL240, they were 8 NM apart. I shouldn't have had to look at the aircraft again, in theory. Even taking it to the extreme, the first aircraft could have slowed 5%, now to be operating at 327 KTAS, and the second could speed up by 5%, meaning as much as 335 KTAS. This means an overtake of 8 knots. To close the gap to the minimum separation of 5 NM, this setup means I would have had, in the worst case, 22 minutes to see and do something about it. But as it was, the radar was showing an overtake of 50 knots. When queried, the first pilot said he was early for his gate, so he had brought his speed back to 295, while the second was trying to make up time wasted on the ground and had increased to 345. Both were outside the 5%, but neither mentioned it. If either had asked about a speed change, it would almost certainly get a controller's view to check into the situation, should the controller have not noticed already. This is why a controller should pay attention.

If you're operating on a Mach Number, the AIM, paragraph 8.2.1 gives us the comparable range. For cruise, pilots are allowed to do 0.01 either side of the number you've flight planned, or the speed you're assigned by ATC. Again, anything outside of this narrow range requires ATC approval. A pilot need only make the request to change to a different speed from ATC to prevent a similar situation as described above.

One thing that, unfortunately, cannot be accomplished in the real world is time acceleration. Time can, however, often be compressed in Flight Simulation software. In VATSIM, please make sure you ask ATC about flying at accelerated time rates, since the controller may have traffic nearby that could be affected. Similarly, a pilot should make sure the controller knows before "slowing down the clock" before it happens. Additionally, especially when close to an airport, pilots should either minimize the number of times menus are accessed that pause the simulation, or set the simulator so that it doesn't pause at task switch. The goal is a realistic experience, to the extent possible for pilots and controllers alike, and this is hard to predict or counter when it happens.

Altitude Changes In Flight

The AIM, section 8.3, says "Pilots shall report reaching the altitude to which the flight has been initially cleared. When climbing or descending en route, pilots shall report when leaving a previously assigned altitude and when reaching the assigned altitude." There is no such rule in CARs, but that doesn't mean pilots shouldn't make these reports. Enroute controllers are more likely to want such reports, as terminal controllers are often much busier and unnecessary calls block ATC frequencies.

The AIM goes on to say that on initial contact with an ATC unit, or on change to another frequency with ATC, pilots shall state the assigned cruising altitude and, when applicable, the altitude through which the aircraft is currently climbing or descending. It might sound like these:

    "Moncton Center, CAW108 Flight Level three five zero."
    "Winnipeg Center, CVA822 out of one two thousand, seven hundren for one six thousand."

When reporting climbing or descending through an altitude, report it to the nearest 100-foot increment. This is what ATC will see on the Mode C readout on their radar screen, so it helps to verify the reading. Once an Mode C altitude readout is validated, controllers can use it in the application separation rather than asking for further altitude reports.

There are some rules for climbing and descending, whether climbing out on departure, descending for approach, or just while changing altitudes enroute, in addition to simply reporting altitudes in communication with ATC. In paragraph 8.4 of the AIM, these rules are articulated.

When in receipt of a clearance to climb or descend, ATC will expect a pilot to commence the altitude change promptly upon receipt of the clearance. Now that's not to say ATC can reasonably expect to see an aircraft's Mode C readout change by the time the pilot finishes reading back the clearance. But a pilot should start the altitude change within a short time after receipt of the clearance and not hang up at the previous altitude for ten minutes or forty miles before commencing the climb or descent. Also, the a pilot should endeavor to climb or descend at an "optimum rate consistent with the operating characteristics of the aircraft". If a different operation is desired, such as a "cruise climb" or "cruise descent", a pilot should ask ATC for it with the request to change altitude. This way, ATC will know what to expect from the aircraft. As soon as a pilot reports vacating an altitude, ATC may assign it to the next aircraft. This is why a normal rate should be used unless ATC approves of something else.

Another expression, discussed in a previous topic, used in clearances for climbs and descents is "when ready". When issued a clearance for an altitude change prefixed by this phrase, a pilot may commence the climb or descent, as appropriate, when the pilot wishes. The altitude change should be made at a normal rate for the aircraft type. Note that this is different from the phrase "at pilot's discretion". This second phrase is no longer used in Canada, but still is the US, and American pilots may still request it. The biggest difference with this phrase is that a pilot may temporarily level off without notifying ATC. Controllers should note that American pilots may not understand "when ready", and mistake it for an instruction to climb or descend immediately. In either case, a pilot is not permitted to return to a previously-vacated altitude.

If descending and a pilot finds the aircraft is moving a little too fast to meet the CARS 602.32, Airspeed Limitations, the aircraft may be required to level off to bleed off speed. If this becomes necessary, a pilot should advise ATC as soon as possible. This gives the controller the chance to adjust plans with other, nearby traffic, if necessary. The Airspeed Limitation was discussed in a previous topic which can be accessed by going to the Archives.

Minimum IFR Altitudes

This was already covered in one respect in a previous topic, but that was as it applies to aircraft descending for approaches.

In the case of an enroute aircraft, a pilot may be flying an airway at an altitude that is safe for the current segment, but then, after passing the next fix enroute, the Minimum Enroute Altitude (MEA) rises. The pilot is required to climb to meet the new MEA. In order to accomplish that climb, the pilot must first obtain clearance from ATC. The controller should also be aware of this requirement, and shouldn't find an difficulty granting a clearance if it wasn't already volunteered by the controller ahead of time. The altitude change must be accomplished in such time that the pilot can reach the new MEA for the next airway segment before the fix where the MEA changes.

If the pilot times the climb poorly and can't make the new MEA before the fix where it rises, the pilot is to enter a holding pattern over the fix, inbound on the current track, and "shuttle up" in the hold to the higher MEA before proceeding past the fix.

When the pilot is flying a segment of an airway with a higher MEA and the next segment's MEA is lower, a descent may be desired. The pilot must first request descent from ATC. There is no regulartory requirement to descend to meet the new MEA if it's lower than the pilot already is.

Clearances to Enter/Leave Controlled Airspace

Last thing to discuss for enroute aircraft is the idea of entering or leaving controlled airspace. In VATSIM, I'm not sure if this topic is generally treated with realism or not (although in my division, an attempt is certainly made since it is a part of the realism we strive to provide). It may depend on the controller.

First off, a pilot must determine whether the aircraft is in controlled airspace or uncontrolled airspace. The charts have this laid out -- assuming the pilot has a copy. If unsure, a pilot can ask the friendly neighbourhood Air Traffic Controller. All of the larger airports in Canada are in controlled airspace, so this doesn't pertain to those. At "satellite" airports, or lesser-traveled aerodromes, the border of controlled airspace may lie across a pilot's route.

Assuming the aircraft is in controlled airspace and will be leaving it, ATC may use an expression in their clearance to remind a pilot of that fact. "Maintain 4,000 while in controlled airspace", for example. The expression will also be used if a pilot is in uncontrolled airspace and intends to enter it. In both cases, this serves as a reminder that the pilot is responsible for obstacle and terrain clearance in uncontrolled airspace, and also of the fact that ATC only provides separation from other aircraft in controlled airspace. ATC may issue restrictions to ensure separation exists in controlled airspace with a phrase like, "Exit controlled airspace at seven thousand or above," or, "Enter controlled airspace at 6,000 or below," or something along those lines. ATC should also provide a pilot with traffic information with such a clearance so a pilot can understand why such a statement is being used, and what threat exists in the event that aircraft will pass outside of controlled airspace where separation is not being provided for the pilots involved.

I'm sure there are items that still raise questions here. Please submit any to me through e-mail at mo@xlii.ca. I also am aware that I may not have covered everything that you may want to know about for en route. Let me know and I'll backtrack a little. I'm always ready to receive feedback, positive or negative, to let me know how I'm how I'm doing. Future topics include holding, while enroute and for approaches, and more information on arrivals, as well.