Aviation In Canada

Tuesday, May 31, 2005


If you believe NavCanada's literature, CAATS has been in operation in the Moncton Center for two years. Well, sort of. It has been in operation, but not in all areas. They have been working towards implementation in the rest of the building since then. Last fall, "phase 2" of CAATS was attempted, and it ended in failure. The system wasn't stable when the more intricate parts of arrivals and departures came into play in the low level and terminal airspace within Moncton ACC. Today is the day where CAATS is supposed to make its second attempt in the rest of the building. As I write this at about 5:30 in the morning, they are attempting to make a start to the day with CAATS.

I have been involved in the process this time, since the end of January of this year. I've watched as they've presented various builds of software for evaluation, written procedures for "normal" operation as well as backup plans in case of failure. Will it work this time? I don't know. I'll offer my observations for this time, though.

I believe CAATS has a better chance of survival this time around. The software is reported to be more stable. The processing tasks have been delegated to the various machines in a way which, arguably, makes more sense. The engineers and developers have done a ton of work on the software, and we have done a bunch of revisions on the local "adaptation" to make things look and work better. Management, to their credit, has taken more pains in getting backup equipment and procedures ready.

Because of all of this, I believe it has a better chance. Only time will tell, though. And the clock started ticking in the wee hours of this morning. Because of my involvement in the CAATS project in our building, my time for posting may be limited over the coming week. Here's hoping things go well so that's not the case. I'll update you if anything significant happens. Here's a copy of the NOTAM regarding CAATS installation, just for interest's sake:

0505311300 TIL APRX 0506100500

Monday, May 30, 2005

Conventional STARs

Alas, my vacation is over. I'm back to the working world, despite all but one day of my 12 days of vacation being killed by rain. I'm just happy that I didn't plan to get very far. Tenting in the rain , cold and wind just isn't my idea of camping. On with the show.

A reader made a request for information after a pilot friend of his was nailed by Transport Canada for an issue related to flying a STAR. The AIP Canada details RNAV STARs quite well, but there is hardly any information on conventional STARs, such as those that start at a fix and fly radials or courses, and typically end in radar vectors from ATC to get to the various runway configurations. Now, that having been said, the main gist of the question was related to the requirement or lack thereof for terminal ATC to restate the STAR upon initial contact. I'm sorry to report that I have virtually no information to offer at this point. Here's the background, just to show that I haven't been idle on the topic.

I have many resources to talk to to get the ATC side -- what ATC expects a pilot to do. What I really want is written direction on what a pilot is supposed to do. I also want to see how many other pilots out there are unclear on what to do, to get an idea of how big a problem exists. To date, I haven't enlisted any of the ATC-end resources. In my travels, searching for information, I made use of a contact that found me to help. He made use of some of his contacts, and I stirred some people up with it. Not in a big way, so don't get excited, but I did, according to them, step outside normal channels of communications. Part of their perception, I'm sure, was my simple presence as an NavCanada employee, as opposed to the nature of the question, but they didn't like the way my question was asked. So be it.

What this NavCanada rep in Ottawa told me was that they had identified a gap in the information in this very section already. He said Edmonton ACC had brought this to his attention (now I don't know if CZEG found this and sent it his way, if an incident within CZEG (perhaps this one that started this topic) was the kindling for the fire or what caused CZEG's involvement), and it had all been forwarded to Transport Canada with a clarification request for publication.

We're talking about NavCanada and Transport Canada, so I'm not sure just how long such a clarification will take. But hopefully we'll see something, since it should be in the process of being addressed. For now, I intend to talk to my resources, when I can find them, to get the poop on how these are supposed to be done. Maybe then we'll see if the pilot in the previous situation was in receipt of an improper clearance, if there had been any recent changes to R/T and the use of STARs.

Thursday, May 26, 2005

Something New!

My "vacation" continues, but now that I am taking a day to recover from an all-day, harsh mountain biking trip (who said Prince Edward Island was flat and low-lying?!), I'll write a quick little something.

I noticed as a side bar in the local paper that Air Canada is a co-launch customer with Air France on a cargo derrivative of the Boeing 777, and also that ACA is planning to use the Boeing 787 later as well. I found that kind of interesting after the air carrier seemed to dump North American products for Airbus in the last decade. A319, A320, A321, A330, A340. Really, there aren't many in the Airbus line they aren't flying, and yet they're looking at Boeing planes, now. I'll have to keep watching. I wonder if there are any feelings from their pilots about the new aircraft. When they went with Airbus, I remember several comments over the airwaves from the B727 crews the A320 was replacing, most notably a very gruff, "Unplug it and fly it!"

Also, another sidebar from a few days ago said that WestJet has announced the provision of in-flight TV entertainment on all of its aircraft. I had the pleasure of flying some of their aircraft in recent months, and found that some had already been offering it. I really liked it, personally. I'm a sight-seer, and love to look out the window, but if there is an undercast layer, there isn't much to look at. The TV just seems like a great diversion since you're cooped up in the tube for a couple of hours, or however long your flight is.

My vacation officially ends next Tuesday, so I expect to be back at writing regularly then. I may drop by if the opportunity presents itself. Thanks for stopping by.

Friday, May 20, 2005

Just stopped by...

I'm still on vacation, technically, but thought I'd just drop a note.

I read in the paper a few days ago that Jetsgo formally declared bankruptcy after the courts did not approve their restructuring plan. I think this is good for their potential customers. While I like to see airplanes fly, I don't much like the way Jetsgo was running things, and I'm sure I have at least 17,000 other supporters of my view. Their assets will be sold to cover meager portions of their debt, and from what I understand, they have 10 Fokker 100's on thier books, with the rest of their aircraft being leases. The next, and perhaps scarrier, question is: Who the heck would buy them? I hope it's not a Canadian outfit...

Oh, yeah. I still haven't found out anything great or earth-shattering about the restating of STARs in clearances to inbound aircraft. There's a definite lack of information on conventional STARs in the AIP, while there is more specific information related to RNAV STARs. I'm still looking. I have found items related to practice, but nothing written down.

If I get another opportunity, I'll try to write something in here. In the meantime, feel free to browse back and see the other items I've ranted about in here. I'm always willing to discuss what I've already written. A fresh look is always good. Now for the self-serving part of this post. Feel free to click on the advertisments on the right-hand side. You may have to scroll down to see them. I'm curious to see how this advertisment thing works. Supposedly, if enough people click on the context-sensitive banners, I'll get paid a little for displaying the ads. A higher traffic website would be more capable of generating cash, but, hey, not everyone wants to read what I write. :) If you do click on these, then thanks. If not, I don't blame you.

Monday, May 16, 2005


After I work my night shift tonight, I'm on vacation for approximately 2 weeks. While I don't plan on venturing far, My time at the computer will be limited by all the various things that are planned, so I have to halt the blog publication for that time period. I'm still reachable through e-mail, in case someone has a question or a comment to make, though it may take a day or three for me to read it.

See you in a couple of weeks, if I survive the mountain biking.

Sunday, May 15, 2005

Filing of SIDs in Flight Plans

I know I've already written this in a response to someone, but I feel this is pretty important. Here's why:

SIDs are an ATC procedure used to reduce coordination between ATC units. The concept is that an IFR aircraft has to have an IFR clearance before departure. In the normal process of things, the IFR unit (ACC or TCU) is the one responsible for issuing IFR clearances. But, when a TWR is in operation, a pilot is meant to call Clearance Delivery, or Ground in their absence, for IFR clearance. Since the TWR is not considered an IFR unit, he has to call the IFR unit for each aircraft when they call for clearance. This way, the IFR unit can issue what's appropriate at the time for that aircraft.

This all sounds cumbersome, and indeed is. The solution? Create a standardized departure, so everyone gets the same thing, and both the TWR and the IFR unit know exactly what the aircraft will do. This eliminates the need for coordination between the TWR and the IFR unit on each individual aircraft. Many pilots have commented that they like SID usage since it simplifies the departure briefing -- it's always the same at an airport with only one SID.

SIDs are published for many airports, but this doesn't mean they'll be used every time. An experiment was tried in the Moncton FIR a few years ago attempting to use SIDs with airports served by FSS rather than TWRs. There were innumerable "SID busts", and nobody seems to know why. Every pilot queried about the meaning of the clearance out of the cockpit of the aircraft interprets it correctly -- same as they would at Moncton or Halifax. So why, then, would they bust a SID at Saint John or Fredericton, and the number of SID busts at Moncton and Halifax is almost non-existent? The current belief is related to the fact that these smaller airports are uncontrolled (meaning strictly there is no TWR in operation). There is still a control zone, which extends controlled airspace to the ground. Even funnier about this, if a pilot were given a clearance which included, "maintain 5,000, expect FL200 ten minutes after departure, depart runway 33, climb runway heading for radar vectors," essentially a SID but not stating the SID by name, a pilot has never, in my experience, busted it. I used to use this routinely instead of a SID to accomplish the same thing, and never had an aircraft go astray.

Our systems will normally strip out SIDs in the flight plan route of an IFR aircraft. As such, we will not necessarily know that you or your dispatcher had filed a SID. So if you were to receive a clearance with the phrase "flight plan route", are you supposed to fly the SID? Hard to argue and lose, isn't it? Now if you file this:

CYYG CYYG2 J509 MAIRE MAIRE3 CYUL (SID and STAR numbers not necessarily current)

...and you were cleared, "to the Montreal Trudeau airport via direct Moncton, flight planned route, maintain FL200," would you fly the SID? Effectively, the SID was cut out of your flight plan route by saying "direct Moncton," which is the first point on J509 west of YYG. I've seen it happen on more than one occasion where a pilot in receipt of such a clearance has flown the SID, stating that it was filed as part of their flight plan route. I've also seen more than one pilot fly a SID despite the fact that it wasn't assigned and not filed as part of their route. Some pilots, a very small minority mind you, seem to want to fly them simply because they're published.

So no, SIDs should not be flown unless assigned specifically in the IFR clearance. And SIDs shouldn't be filed as part of the flight plan route.

Saturday, May 14, 2005

Mode C Altitudes

A common misconception is that the altitude reported by a Mode C transponder is the altitude displayed on the altimeter of the aircraft. This is not the case. The Mode C transponder always reports altitude based on 29.92, regardless of what's in the calibration window on the aircraft's instrument. This means the Mode C reports pressure level, not altitude. So if a pilot is flying at 3,000 feet on an altimeter setting of 30.42, he is flying at 3,000 feet, but his mode C is actually reporting an altitude of 2,500. Effectively, the Mode C's altimeter is set a half inch to low, so it will read 500 feet lower than the aircraft actually is.

ATC's radar now takes over. For each area, an appripriate altimeter is fed into the processors to correct Mode C altitudes. For example, over CYQM, the altimeter for the Moncton airport is fed in and used when correcting Mode C readouts on aircraft flying in the Moncton area. Our example aircraft above reports the altitude of 2,500 feet to the radar. The radar processors consider the altimeter difference between standard pressue and station pressure, and correct the Mode C readout to show 3,000 feet.

This process, as you can figure, may lead to some errors. For example, if the actual sea level pressure where you're flying is higher or lower than what the radar processor is using to correct your Mode C, it'll reflect an errant altitude. Just how much depends on the difference, but it is usually not much. In any case, ATC may have given you the same altimeter setting since you're in the same area, so your altitude and Mode C should jive nicely.

The nice thing about it is that it gives a cross check. Redundancy is what makes the Canadian Air Navigation System as safe as it is. Now, this isn't exaclty a Canadian idea, since this is the way things work worldwide, but it is a good idea nonetheless. For example, it helped us catch an error in the weather sequence one evening, that could have lead to serious problems. An aircraft was climbing out of Moncton westbound, cleared up to 12,000 feet. On initial call to the next sector, he was given the local altimeter setting. A few minutes later, he reported level at 12,000. His Mode C readout on the radar showed 11,000. The standard practice is to issue the current altimeter setting and ask the pilot to verify is altitude. The pilot confirmed he was showing 12,000 feet, despite our reading of 11,000. This is something that warrants further investigation, of course. Looking at surrounding weather sequences, it was quickly determined that the altimeter setting he was issued was vastly different from other stations in the area. A call to the FSS involved revealed that a trainee had inadvertently reported the altimeter off by 1 inch, giving our radar processor an invalid altimeter setting to use for correcting Mode C altitudes. Shortly thereafter, a correction was issued (and maybe a good cuff in the back of the head for a trainee) and everything was right in the world again.

Also, this can help ATC detect when a pilot has the incorrect altimeter setting in the window. If a pilot sets the altimeter incorrectly, he'll report reaching an altitude, and this won't show the same as what ATC sees. Then, steps can be taken to ensure the pilot has the correct altimeter. Critical especially when an aircraft is on approach in IMC. If the Mode C actually did report what the pilot was seeing on his altimeter, this level of redundancy would disappear, and ATC would have no chance to catch an error of this type.

It seems a little convoluted until you think of how it works, and suddenly, it seems like a good thing, doesn't it?

Friday, May 13, 2005

Clearance Window of Validity

For this topic, we'll start with controlled airports, those that have a control tower in operation. Quite often, the old "canned clearances" come into play at these airports. We've all heard them, whether applied to us or someone else. They go something like:

"ATC Clears Air Canada one two three to the Toronto Pearson airport via the Moncton two departure, flight plan route, squawk 3101."

This is the basic clearance with a SID involved. What's the period of validity? How long can this clearance hang out there? This answer is quite simple. Indefinitely. Would ATC like to have this out there forever? No, certainly not. But as far as other IFR traffic is concerned, there is no danger. Since the airport is a controlled airport, the aircraft must receive taxi authorization and take-off clearance before he's allowed to become airborne. This means that he should never become an issue for other IFR traffic unexpectedly, so long as everyone on both sides of the radio does their job. Having said that, if you're going to be delayed for a significant time period, advise ATC and let them decide if they want to cancel it and have you call back. It's unlikely the clearance will sound any different in the end.

At uncontrolled airports, things are a little different. The clearance will not necessarily include a SID, even if a SID is published for that airport. Also, the clearance may contain phrases such as, "Do not depart until [time]," or, "clearance cancelled if not airborne by [time]." These are specified by ATC at the time the clearance is delivered to the aircraft (or to the relaying agency like FSS), since the IFR ATC unit has no direct control over the airport surface. An IFR aircraft at an uncontrolled aerodrome may taxi out and take-off without intervention from ATC in the IFR unit, be it a TCU or an ACC. The catch is the surrounding airspace, however.

Control zones exist at many uncontrolled airports. They are meant as an extension of controlled airspace for two reasons. First, to provide IFR ATC with the authority to direct IFR traffic to enable them to provide separation. Secondly, to provide higher weather limits for VFR to improve the chances of "see and be seen" for both the VFR and the IFR aircraft operating within the control zone. If the airport lies within a control zone but has no operating control tower, an IFR aircraft may taxi out to the runway, but he may not get airborne without an IFR clearance. Hence the requirement to ensure an IFR clearance is received, and that it is valid at the time of take-off. If ATC included a phrase such as, "do not depart until 0105", the pilot may taxi out at any time (providing he considers other traffic), but he is not allowed to become airborne until 0105z. Other phrases might include reports from other aircraft or other such actions. For example, "do not depart until Golf Romeo Uniform Bravo reports leaving 4,000". This would mean that until GRUB, probably someone who taxied out and took off just before you, must make the call out of four thousand before you can take-off. And no, seeing a TCAS target with an appropriate altitude is not good enough. The radio report must occur. If you believe GRUB forgot to make the call, ask on the frequency where he is, or ask ATC for further instructions.

Cancellation times work the same way. A phrase like, "clearance cancelled if not airborne by 0110" may be included. This means that you must get airborne before the clock turns to 0110z. This does not, however, mean that you have until 0110 and 59 seconds to get in the air. And this is airborne, not "on the roll". There has been some confusion over these two points in the past.

At an uncontrolled aerodrome that underlies controlled airspace, ATC may not direct the flow of traffic, and this includes even telling a departure which runway to depart, or a heading to turn to after departure. This normally means that IFR traffic doesn't flow very efficiently. If it were a busy airport with IFR traffic, the odds are a control zone would be established. In any case, an aircraft at these aerodromes would be perfectly within his rights to take-off without an IFR clearance, even in IMC. Just remember that you must receive a valid IFR clearance prior to entering controlled airspace. This is where a familiarity with the airspace structure comes in handy, and it is often known well by the pilots who frequent such areas. For example, if controlled airspace begins "above 12,500," an IFR pilot could take-off and fly in IMC at 8,000 feet without an IFR clearance. In fact, if both point of departure and destination underlie controlled airspace, and no part of the flight plan route enters controlled airspace, the flight will never be in receipt of an IFR clearance, since ATC has no authority to direct the flow of traffic in Class G airspace. Note that a pilot must still file a departure message and an arrival message in a timely fashion for the sake of alerting services.

Thursday, May 12, 2005

RNAV STARs in Clearances

The AIP Canada, RAC 9.2 is all the resource you should need for STARs in general, and RNAV STARs in particular. In fact, most of the information in this section is related to RNAV STARs, since conventional STARs are flyable by anyone, by their very definition.

First things first for RNAV STARs. RNAV STARs are not a requirement for any aircraft or pilot to fly. They exist as a means for an aircraft to navigate from the enroute structure of airspace and airways (or "directs") to the approach phase of flight with a minimum of ATC intervention. In the old days, the primary means of transition from the enroute phase of flight to an approach in a terminal area was by radar vectors from controllers. This is still done where RNAV STARs exist, simply because not all the variables can be controlled to the extent necessary to permit each aircraft capable of flying them to do so without ATC's hand.

There are a number of requirements the aircraft must meet in order to be authorized to fly an RNAV STAR. This is why some aircraft, though they seem equipped for it on the surface, never fly them.

Next, the pilot (or dispatch) is expected to file the RNAV STAR in the flight plan if they desire this procedure. As such, it becomes an integral part of the flight plan route, just as much as over a VOR for an airway, or a preferential routing as published. The pilot will receive his clearance at point of departure, and this will normally include the term "flight plan route" in there somewhere. Since the RNAV STAR is part of the flight plan route, the pilot is expected to fly that unless otherwise cleared. This should eliminate the chance of confusion over which STAR if there is more than one, since the STAR expected by ATC would be the one on the flight plan. The RNAV STAR is not generally restated, since it is part of the flight plan route, but will be restated as necessary if the STAR was cancelled, either explicitly or implicitly, and must be reinstated. If ATC clears an aircraft inbound for a STAR down to a new altitude, the aircraft is still expected to make any speed and altitude restrictions published, and descend to the cleared altitude at appropriate points along the STAR routing. For example, if cleared to 4,000, but the RNAV STAR has a "6,000 or above" restriction at PointA, the pilot may not descend below 6,000 until past PointA unless specifically authorized by ATC to descend earlier, but may continue descent to 4,000 once past PointA.

An RNAV STAR is automatically cancelled when ATC assigns radar vectors or when cleared to a fix that is not within with RNAV STAR. If ATC clears an aircraft directly to a fix within the STAR but it circumvents other fixes (for example, if points A, B, C, D and E are in the STAR, the aircraft is between A and B, and ATC clears the aircraft direct to D), ATC will either state something to the effect of, "balance of the route unchanged," or will state the entire route, fix by fix.

These procedures haven't, to my knowledge, changed in a while, but there were a few revisions to the rules when the RNAV STARs first came out a few years back. There were several meetings involving designers, aircraft operators, and the regulator (Transport Canada) to determine the best wordings for clearances and such, and this is how they stand to date.

Wednesday, May 11, 2005

Flight Plan "Window of Validity"

In response to a couple of questions posted recently, this article deals with flight plans and the length of time in which they are valid.

First off, I have yet to see an official figure for the length of time a flight plan is considered valid, or active. I was taught in the ATC world that a flight plan on an IFR aircraft should be held for a period of 6 hours, and that is what I use today at the boards unless I am aware of something that makes the flight plan invalid. For example, I have two flight plans on the same aircraft, one from CYHZ to CYSJ and one from CYSJ to CYFC, but the aircraft landed in CYFC instead of CYSJ on the first leg due to bad weather in CYSJ. Obviously, he can't leave CYSJ for CYFC if he didn't land. If the aircraft is departing an airport without a TWR or FSS (no ATS facility), then the status of the aircraft and the flight plan must be confirmed at some point. Read on...

If the flight plan is has a departure point that is not served by an ATS facility, we go looking for his departure message if we haven't heard from the pilot within one hour of the proposed departure time. This is part of "alerting services". The time frame of 60 minutes is used to give the pilot some flexibility on departure, since not all flights depart on time. The assumption is that if ATC doesn't hear about a flight, in controlled airspace or not, within 60 minutes of the proposed time, the flight may have attempted to get airborne and failed, leaving the pilot in no position to communicate his departure message. In practice, we often end up looking for information on the pilot's movements before the 60 minutes, but that is the standard time for provision of alerting services. At an airport served by an ATS unit, this is less of a concern since a TWR or FSS is based there, and communications with these units is required prior to taxi, and often these guys could look across the field with binoculars to confirm the aircraft is, in fact, safely still on the ground. If a pilot is to be delayed beyond 60 minutes from the proposed time, there is a requirement to contact ATC or FSS and advise of the delay and a new proposed departure time, though this is really only important for aircraft departing airports without an ATS unit. Note that CARS, UNICOM and other such airport services are not connected with NAVCANADA, and are therefore not ATS units. Advising UNICOM that you'll be departing late is not sufficient. ATC will begin a communications search and may initiate search and rescue operations if they haven't heard from you within 60 minutes of your proposed time.

Tuesday, May 10, 2005

Radar Contact

Over the years, I've had the occasion to talk to many aircraft flying outside of radar coverage. Nothing unusual in itself. But there is the odd pilot every now and then who will get ornery if he's not seen on radar. I can appreciate the idea of a watchful eye as much as the next pilot, but sometimes it's kind of funny. These ones will ask, "Do you have me on radar yet?" When I say "no", the most common response is, "Well, I'm showing interrogation on my transponder. Are you sure you don't see me?" Yup. I'm pretty sure.

In the olden days, when radar was scarce, you were more likely to be right in saying ATC could see you. In fact, even now, ATC somewhere might, even if it's not the one you're talking to. For example, in the northwestern portion of the Moncton FIR, if you're flying low enough, Moncton ATC can't see you, but if you're far enough northwest, Boston may be able to. They have radar s that we don't get the data from, so your transponder may be showing interrogation but not from a Moncton radar source. Cross-border sharing agreements are in place, but we are not yet getting the radar data. Other centers across Canada and the US are already sharing radar data, but it's not a high priority on this end of the country right now, apparently.

In any case, there is another possibility. You may not be seen by any civilian radar at all. It might be a radar from a military installation that is interrogating your trusty transponder. If necessary, it may be possible for you to contact these individuals for assistance, or even to relay through civilian ATC to the owners of the radar. Don't count on it, though.

Lastly, there's one more source of interrogation that may be the culprit: TCAS. TCAS on other aircraft do send out signals for replies from transponders, and that's how they "see" other aircraft and receive Mode C altitudes for traffic detection.

So it's not only ATC you're talking to watching you. There are other eyes out there, too.

Monday, May 09, 2005


As mentioned yesterday, my faith in TCAS isn't what some people would carry. I was "lucky" enough to work before the days of TCAS, and have since seen the development of this system through from its introduction to the present state. I've watched aircraft get instructions from TCAS, tell me they're acting on a TCAS resolution, only to find out that the TCAS actually directed the plane back into the traffic. One example was a Dash 8 on departure out of CYYG seeing a target on TCAS that was already below him, and telling us that TCAS advised a descent. Early days of a new piece of equipment.

One of my favorite stories that I experienced personally happened when two regional airlines, always in fierce competition in our skies, were flying into a non-radar environment. At the time, the pilots were used to the fact that we used 10NM between aircraft due to the nature of our equipment in that area. AircraftA was flying at FL240, and on radar was measured at 14NM ahead of AircraftB at FL220, who was 10 knots faster. Given the distance involved, I would have less than 10NM between them by the time they wanted descent, so AircraftB would end up being too close to AircraftA to do anything but work hard to get AircraftA in. AircraftB was fully aware of this, as I found out later. I decided I'd push AircraftA down early to FL210, then let him descend at his discretion beyond this, using radar to establish the vertical separation before I lost the targets. AircraftB, upon hearing my clearance to A, started the following exchange:

"Moncton, AircraftB"
"AircraftB, Moncton?"
"We've been following AircraftA since we left PointA, watching him on TCAS all the way, and we're only 9 miles behind him."
"Sir, my radar shows him 14 miles ahead of you at this point."
"Well, sir, our TCAS only shows 12 miles ahead, and he's only three quarters of the way up the screen, so that's only 9 miles."
"Well, my radar has been flight checked for accuracy, he's showing 14 miles ahead, and we've had a change in equipment in this area and I only need 5 miles between you now."

Anyway, that exchange prompted an experiment that I carried on over the next 5 years or so. I would take opportunities to evaluate when traffic permitted. For example, I would have to aircraft crossing at shallow angles, or even opposing each other on nearly the same track. If my workload permitted in setting it up, and both pilots agreed, I would ask them if they could keep an eye on their TCAS and watch the traffic go by, and give an estimate of their closest point of approach, all the while watching intently with a distance measuring tool displayed on my radar which would give a readout down to 0.1 NM. For the first two years of this unofficial experiment, I got ranges that varied greatly from aircraft to aircraft, and over what I observed on radar. Many of the reported values differed by as much as 50% over what was displayed on my screen, and even more wildly between each other. After the first two years, the discrepancies began to diminish. I assume this was because better equipment became available on some of these aircraft. I stopped the experiment after finding the reported values hardly varied at all over what I was seeing over the next three years.

So TCAS has gained some trust with me, but as much as I will never board an aircraft without a pilot on board, I still wouldn't want to fly in an airliner in skies without a controller watching over my flight.

Sunday, May 08, 2005

Free Flight, Again

In yesterday's post, I may have presented the view that I'm against Free Flight. I am in some ways, but in many senses, I believe that parts of it are good.

Personally, I don't trust TCAS enough, and there are several reasons for this. First off, not everyone will have TCAS, and TCAS will only work well if both involved aircraft (assuming only two) have it. This doesn't account for the Cessna 172's and the PA-31's and other such aircraft that will still frequent many airports that will fall outside the purview of any remaining terminal control units under the theory of Free Flight. There will still be aircraft meeting up with airliners in non-TCAS contexts. I've also seen TCAS give problematic and erroneous directions to the piltos (happily, the pilots disregarded the instructions, knowing full well that they were going against regulations, but also being well informed of the nature of the traffic and the situation). Mind you, this part of my arguement has become much more rare since TCAS first appeared on scene, but it occasionally happens.

Now, the direct routings part, I agree with. We have better displays in the ACCs now than we had 20 or even 10 years ago, and the concept of not knowing where an aircraft is going if the point is beyond the range of the scope has gone by the wayside. We can draw lines on our screens to any point and see exactly what the track would look like. And with the exception of converging routes or opposite direction traffic, these sorts of direct routes often provide enough lateral separation to allow for unrestricted climbs and descents.

The are some issues though. First off, as I mentioned yesterday, a direct route from point A to B isn't always good, considering airspaces involved. Restricted areas and military flying areas exist, some permanent, others activated by NOTAMs. It's clear to me that many pilots are not aware of the restricted airspaces that lie near their flight plan routes, and therefore are prone to asking for routings that go through some of these areas. An ATC two FIRs removed is not likely to be aware of such a block of airspace, and will grant a clearance if it works for him. He is expecting that the pilot will know if it's good or not, and he's only concerned with his traffic picture, which doesn't extend much beyond his area of responsibility.

Secondly, and this is just as important from our perspective as ATC, is that we have been bombarded with information and requests to stop clearing aircraft on direct routings. In the recent past, we've been giving aircraft direct POINTD on a flight plan that has points A, B, C, D, E, F and G in it. This winter, NAVCANADA, the company that runs the Air Navigation System in Canada, produced a video for ATC staff for our recurrent training that had guest speakers -- including an Air Canada captain and a Westjet dispatcher -- that told us not to meddle with their flight plans. They informed us that we weren't helping when we issued these routes, since the dispatchers have to deal with gate times and weather systems that "controllers are not aware of" and therefore saving those extra couple of minutes in the air often means sitting on the tarmac waiting for a gate to open. So the delays are, once again, ATC's fault. As if that wasn't enough, we have a memo on the books now that was spawned by a letter to our unit chief from IATA, the International Air Transport Association, telling us to cease and desist issuing direct routings, for the very same reasons. It seems from our perspective that the airlines are serious about telling us to stop trying to help them.

I understand the nature of long routes of flight and how weather systems can affect flight times. But when a pilot asks for direct A and we clearing him there, we surely can't be blamed for that. Besides, when we issue an initial vector to the flight plan route and the pilot returns with a readback and a request for what we've been giving him all along, it just wastes airtime for both ATC and the pilot. And a pilot can always refuse the direct routings offered, if these things are, in fact, serious as these messages we're receiving seem to be. So I guess I'll just sit back, wait for pilot requests and see what develops.

Saturday, May 07, 2005

Free Flight

There are many aspects of Free Flight that I disagree with. That may not surprise you, since I am an ATC. I agree with direct routings where practical, but one thing that comes to mind right now is restricted airspace.

In today's world, more and more aircraft are quite capable of long range, point-to-point navigation without the use of land-based NAVAIDs and such. As I mentioned in a previous posting, all too many pilots seem to disregard the concept of charts, opting instead to put in waypoints and let the GPS tell us which way to go. It is quite easy, and as someone who loves the little electronic toys, I can't say I blame a pilot for wanting to play with the technology. The problem I'm talking about today is what happens when a pilot enters a waypoint that he wants to go to, but from his present position, he would fly directly through restricted airspace.

This happens routinely in the Moncton FIR, as I'm sure it happens elsewhere. The biggest offender is one of the biggest in the country, our own CYR724. Pilots wishing direct routings for fuel and time savings often ask for direct a particular fix or NAVAID, rather than staying on the flight plan route. Something I understand and appreciate. However, I would hope a pilot would look at his place in the sky and have a look at what lies between him and his destination before pressing "Enter" to ensure he's not flying somewhere he shouldn't. We routinely have to alter the flight plan routes of aircraft to keep them out of this block of airspace. And dispatchers aren't off the hook either, since we often receive flight plans such as "CYFC > CYHZ", which would go right through the northeast corner of it.

I recognize that some of the more advanced systems provide a visual display of restricted areas and they would provide a pilot with a heads up about danger areas and such on the route of flight. But given the number of aircraft we have flying and the level of technology that is in them, and the number and range of types of aircraft we have that need such corrections, it makes me wonder just how successful something like Free Flight would be. If a pilot were to choose his own routings at will, just how well would this work?

I'm not basing retirement plans on the timetables of Free Flight proponents just yet.

Friday, May 06, 2005

Descent at your Discretion, Part II

Yesterday, a response to my post about discretionary descent brought up the rate of descent a pilot should maintain when commencing descent. With a clearance to "Descend at your discretion" the AIP Canada, RAC 8.5.1 says this:

(b) If the phrase "at pilot's discretion" is used in conjunction with an altitude clearance, the change of altitude may be initiated when the pilot decides. When the change is initiated, the pilot will advise ATC. Pilots may temporarily level off at any intermediate altitude; however pilots are expected to advise ATC of any temporary level-off at any intermediate altitude. Vertical navigation is at the pilot's discretion; however adherence to assigned or published altitude crossing restrictions and speeds is mandatory unless otherwise cleared. [MEAs are not considered restrictions; however, pilots are expected to remain above MEAs].

In the paragraph immediately following the above quote, the AIP states, for information's sake, that ATC may assign your altitude to another aircraft as soon as you report leaving it. It further states that control will be based on the pilot following these procedures, and that the pilots are expected to conduct their climbs and descents commensurate with the "normal operating characteristics of the aircraft."

What's normal? Always a good question. A wide range of values would be considered normal. For example, ATC will expect a piston engined aircraft to descend and climb at a lower rate than a jet or turboprop. If you wish a cruise climb or descent, it would be good, as one reader posted, to mention that you are planning a slow climb or slow descent.

One thing that isn't mentioned, and the interpretation is arguably left open, is that once an altitude is vacated, a pilot may not return to it. That is to say, if you're descending, you must descend and not climb. This means that a "descent at your discretion" is not the same as a block altitude. If a pilot wishes to climb again, he must ask for clearance to do so, as ATC may have already cleared another aircraft to descend above you, expecting you to continue descent, or at the worst, to level off where you are.

Thursday, May 05, 2005

"Descent at your discretion..."

A lot of people already know the meaning of the phrase in the title. The question I have today, fishing for comments, relates to a common radio exchange in the Moncton FIR, though I can't say how common it is elsewhere.

Pilot: "Moncton, ACA123 request descent."
ATC: "ACA123, descend to one zero thousand, altimeter two niner eight seven."
Pilot: "Cleared to one zero thousand, ACA123. Confirm that's at our discretion?"

This makes me wonder. First off, when a pilot calls for descent, I assume he's ready for descent, either now or in the next minute or so. And when the same pilot above starts descent from FL350 a mere 100 NM from destination, does he really intend to level off somewhere in the interim? Additionally, why would he ask to confirm that descent is at his discretion, when there was no mention of the term in the clearance issued following his request?

I will often offer descent clearance to a pilot, traffic permitting, of course, before the pilot asks for lower. When I do, I'll state that descent is at pilot's discretion. It saves a radio transmission, keeping the frequency clear for when I want to use it, and gives the pilot the flexibility to commence descent when he's ready. But when a pilot asks for lower, I find it strange that he would ask if his descent clearance he just received would be at his discretion. If the pilot would ask in his request, "request descent at pilot's discretion," this would make a whole lot more sense to me, regardless of when he was asking for it. I would now know what to expect from him.

Is there something I'm missing?

Wednesday, May 04, 2005

Surveillance Approach

Have you ever heard of a surveillance approach? Any idea what it is?

It's an emergency procedure that pretty much has to occur in a pretty nasty situation. A PAR or GCA is the classic, "talk a pilot down," approach where a radar gives a picture to ATC of where an aircraft is in relation to the final approach course and the glidepath with two separate antennas, one scanning the vertical and the other the horizontal. These antennas make rapid passes of the approach area to give a fast refresh rate for the controller, allowing him or her to react quickly to give guidance to a pilot. It's near continual talking to give a pilot the position information he needs to fly a precision approach -- one with glidepath information. They have fallen out of favor and are mostly relegated to the military now, since ILS gives the pilot the same information and it's right in front of his eyes.

The surveillance approach, on the other hand, is a similar kind of tactic but it varies in a few, but significant, ways. First, there is the conspicuous lack of glidepath information. It is done with enroute radars, and therefore the only possible attempt at vertical guidance is through recommended altitudes, typically given at each mile on final. The keeners would recognize that ATC's enroute radars turn comparatively slowly (in Canada, once every 4.8 seconds, in the US I understand that some are as slow as once every 10s, but I stand to be corrected here). This means that another significant difference is the update rate. And last, enroute and terminal ATC don't exactly get regular practice on such a procedure the way a PAR controller would. It's an emergency procedure only, but it is still in the toolbox, should it ever be needed. And it's not meant to be an IFR approach, either, so much as a cloud breaking procedure. Like a PAR, it can't be conducted just anywhere on the fly. Only airports that have reasonable radar coverage are candidates for it. This would include most of the major airports in Canada, but few of the "satellite" airports, except those lucky enough to be near a radar.

If you're instrument equipped and trained, you'd be better off with a real IFR approach. If you're not IFR equipped, you'd be better off maintaining VFR on your own, in my opinion. Also, if you're destination in one that is served by a radar and their weather is bad, don't just go asking for this as a way to get home. Find another suitable field and land to wait out the weather there. An unnecessary surveillance approach will require a declaration of an emergency, and will get you a lot of unwanted attention if your situation wasn't really that bad. Still, it's good to be aware that such a thing exists, should it be one of the few options available.

Tuesday, May 03, 2005

Special VFR

A pilot asked on a forum I monitor about Special VFR. He asked an instructor a question relating to it and a "Day VFR" rating. It's a good thing to clarify.

The rating of Day VFR is not connected with SVFR. SVFR is a rule which provides primarily for a VFR pilot to enter a control zone for the purpose of landing, or departing an airport, all below normal VFR weather conditions. Remembering that the weather minima for VFR inside and outside a control zone are different (check the class of airspace outside the control zone as well), this may not necessarily be a bad thing. For example, Saint John, NB, is a coastal airport and often shrouded in fog. Even as little as 5NM north, it may be wide open CAVU. If the weather permits, departing the zone under SVFR may get the pilot into clear skies beyond. You had better be sure of the area you're flying in and of the weather beyond, though.

It doesn't matter the rating of the pilot. If you're airborne and see a snow squall coming and you need to land, by all means, tell ATC what's going on. Nobody wants a VFR pilot stuck in Instrument Meteorological Conditions (IMC). Far better to inconvenience another airplane or two than to have clean up wreckage and ruin a good section of forest. Also remember that whatever the circumstance, it's the pilot's ass in the plane, not the controller's. He may be mad, and will write up anything that goes against regulations (ATC is required to write up any such occurrences), so be prepared to justify your actions. But if you're in trouble, do what you have to do. Aviate, Navigate, Communicate. Fly your plane and then tell ATC what's going on.

Monday, May 02, 2005


Here we are, in the first part of May. That month where the VFR pilots tend to come out of the woodwork for the summer and fall seasons. The month where the weather tends to become a little more predictable and warmer. The month where aircraft owners tend to begin venturing out for their vacations. Each of these, from an ATC vantage point, increases the workload dramatically, but for the better, overall.

We tend to get busier, but at the same time we tend to see more interesting stuff. The stuff experience is built from. Pilots doing different things, quite possibly brought our way from their home area. Things they were taught that work wherever they're from that just find it a little harder to integrate up here. But mostly, those pilots who feel it unnecessary to bring charts from the local area with them. You know, that extra $15 dollars is just too much to spend. Or the IFR pilot vacationing who won't buy a copy of approach plates, either, hoping for good weather or hoping ATC won't mind giving him the necessities of the approach. Or even hoping for a radar vector to final, wherever he goes. It's neat to hear the surprise in a pilot's voice when you tell him you won't be able to vector him to final since you can't see below 8,000 feet over his destination airport. (I say, "neat", hoping you'll appreciate the frustration we feel and the time it takes from ohter control duties.)

I recognize that the radar covergage isn't indicated on a chart, but many other useful items are. Restricted airspace, busier corridors. Terrain and obstructions. Large bodies of water. The more aircraft that are equipped with GPS (or even handheld units), the more pilots decide they don't need charts. What about a failure of the GPS unit? What do you do then? What if you're in an area wihtout radar coverage and nobody can see you? Would you even know who to call without the charts you should have brought?

"Be prepared" never meant anything to me as a boy scout. I try my hardest to think of everything now. I also consider the fact that I'm ignorant enough not to think of everything, and try to compensate for that, too, as much as I can by bringing what I can that can be modified. Hardly a Macgyver in reality. But we do what we can.

Sunday, May 01, 2005

SIDs at Uncontrolled Airports

This is a continuation of yesterday's post, sparked by the first response. The reader mentioned the use of SIDs at the example aerodrome, CYFC. CYFC, like many others, is uncontrolled. This means, simply, there is no control tower in operation. There is still a control zone which provides controlled airspace from the surface up, meeting the transition areas and the control area extension around the airport, but there is no airport control service provided.

Our experience in the Moncton FIR with SIDs at such airports is dismal, at best. Every operator, at one time or another, has busted a SID. Many private operators will only go there once, and you can almost count on them busting the SID. It's at the point where most controllers will not use a SID in a clearance where separation may be an issue. For example, the SID altitude is 5,000, and they won't use a SID if the departure aircraft is flight planned above 5,000 if there is an overflight at 6,000. Even Air Canada and Jazz, the prime proponents of SID use at these smaller airports, has busted them. The difference is, when an Air Canada pilot makes a mistake, their training division can bring it to the attention of other pilots in their organization to prevent a recurrence. Last year, an Air Canada RJ departing CYSJ assigned a SID took off, then turned left on course. On initial contact, he checked in, climbing only to the SID altitude of 5,000, though. When querried, he confirmed that he had been issued a SID, but, "saw no traffic so we decided to turn on course." A regional airline in our area departed CYFC on a SID, turned on course, and responded, "What's the difference? It's all uncontrolled airspace below 5,000 anyway." As I described above, that's not the case.

Whatever the reason for the SID busts (pilot error, ignorance (not meant in the rude sense), or whatever), the SIDs do get busted at our uncontrolled airports. This is one of the reasons we're reluctant to use them. They very rarely get busted where we have towers in operation. So what's the difference? The clearances are worded the same. The airspace is still Class D or E airspace, where IFR pilots need a clearance. But something just isn't right about SID use at these airports.