Aviation In Canada

Tuesday, August 30, 2005

Not Busy if not Speaking on the Radio

Which side of the radio do you think I'm writing this one about?

The answer is both. I've seen it from both sides: The pilot who thinks because the controller isn't talking on the radio he must not be busy. And the controller who thinks the pilot isn't busy since he hasn't said anything on the radio in a while. I think anyone who stops to think about these myths for even a few seconds can realize that there are many things on both sides of the radio that can prove this to be untrue.

Pilots programming an FMS, perusing weather data, going through a checklist, briefing for a departure or an arrival, setting up instruments, etc. So many tasks and such possibility for inducing a small error if interupted. For example, I once watched a pilot take an unexpected 90° left turn after errantly entering BIMTU instead of BIMKU in the RNAV. He reported that he was interupted in his processes and apologized for the error.

Controllers have hotlines to other ATC units, landlines to other facilities, other controllers in adjacent sectors to coordinate with, and, increasingly, more and more data sensitive systems to work with. Information on aircraft must be coordinated to ensure everyone is operating with the same data, clearances must be issued for relay through other units, and simple planning of traffic flow takes time that is not evident over the radio.

Fortunately, most pilots are aware of controller's having other things to do, and most controllers are aware that pilots are often likewise busy. It's only the odd one out of either bunch that gets impatient and disrespectful. But boy do they stick out of the crowd. So if either side doesn't reply right away, it may not be that they didn't hear the call. A few seconds of patience where possible can go a long way. Emergencies, Ok, fair ball. Get their attention. Otherwise, give 'em a little time.

Monday, August 29, 2005

Transponder Interrogation

Every now and then, a pilot won't believe me when I tell him I don't have him on radar. He'll look at the little light on his is transponder and say, "Well, Moncton, I'm showing interrogation," as if to say, "look a little harder." I have difficulty in seeing why I might try to lie to a pilot and tell him I don't have him on radar since it's most often to my advantage to see an airplane, but anyway, there are several possible explanations as to why you see evidence of interrogation but I don't see you.

First, there is the radar source issue. I have radars across the region. So do other ATC units like adjacent ACCs/ARTCCs and Terminal Control Units. As most people know, the TCUs in Canada are, for the most part, integrated into the parent ACCs now. For example, when you talk to Halifax Terminal, you're talking to someone working within Moncton ACC. They will see the same radar sources that the parent ACC sees. An example where this is not so is a military TCU. These are often located right on the military airfield, and they will normally have their own radar antenna as well. What all this means is that you could be seeing interrogation from a radar antenna that is not fed into the unit that you're talking to, whether it be an ACC and you're receiving interrogation from a military TCU's radar, or the other way around.

Also, TCAS works by broadcasting an interrogation signal and listening for responses, then processing the returns as a direction finding antenna would and calculating range. This means that there is an airborne source for interrogation which may be showing up on your transponder that certainly no ground source will see.

So, showing interrogation doesn't necessarily mean that the ATC unit you're speaking with can see you. Maybe another one can, but that's not necessarily the case, either.

Sunday, August 28, 2005

Misused IF's

A long time ago, in an FIR far, far away, IFs were established. These Intermediate Fixes were placed on the final approach courses of many an approach, typically somewhere around 10NM final, but with some variation. The idea was to allow aircraft with RNAV a certain flexibility, at least when approaching from some directions, to conduct their own navigation to final without the need for DME arcs, procedure turns or ATC intervention in the form of vectors, if ATC were even able to see the aircraft on final on radar. The theory was good, but there seemed to be a lack of direction and some problems started to occur. Well, they weren't problems all that often, but certainly the potential was there. The problems were small, insidious little things that kind of crept up.

These IFs were great when the airplane was coming pretty much straight in already, or even off to the side in what would amount to a base leg, an angle of 90° or so from the FAC. But what about when the angle exceeded that? Many aircraft systems would reject the turn to final in such cases. Especially when the FAC was pretty much a 180° turn from the course inbound to the IF. That didn't stop aircraft from asking for direct to the IF, though. Pilots are pretty clever, and the nav gear became more sophisticated, and this combination had pilots doing some things which were a little unexpected. Many would "project a waypoint" off to the side of the IF, then navigate to the IF and join the FAC from there. Problem is, they'd ask for a clearance to the IF, receive and acknowledge it, leading those crotchety old ATC types to think they would navigate to the IF instead of an imaginary, temporary and unnamed point. The best part is, the ATC would think they could depend on the aircraft's nav gear to take it on a nice, straight track to the IF, since it had the ability, only to find out the aircraft was aiming often around 5NM beside the IF instead of at it. In a terminal environment, ATC could have another aircraft on a vector approaching the fix, planning on the course for direct to the IF for the "self sufficient one", when he only needs 3NM radar separation between them. The unannounced course could have the airplane on the wrong side of his traffic. A little communication could go a long way to alleviate expectations for this one, though.

Another problem occured when the pilots received a clearance for a straight-in approach via an IF. Some pilots, especially those flying into uncontrolled airports, often decided after acknowledging such a clearance to disregard the IF and point directly at the Final Approach Fix, hoping to save a minute or two of flight in the process. Hey, with gas prices in this FIR, anyone can appreciate that. Unfortunately, those darn ATC types would be taken by surprise again, expecting to have that minute to use when issuing a clearance to an aircraft who wanted to take off. Now, the window of validity for the departure was compromised, as was the lateral separation expected when the departure got airborne since the arriving aircraft might be as much as 5NM or so closer to the airport than he should have been when approaching on a base leg style track when he makes the turn to final.

And the last one was a little different, since it often didn't compromise separation. Some pilots, keen on using the advanced nav gear and wanting to set up an FMS to do its thing, would ask for clearances to these IFs from hundreds of miles away. This often meant that those controllers had to ask "down the line", or so to speak: One enroute controller had to ask another, who had to ask another, who often had to relay the request to the controller working the airport in question, who had to send the approval or denial back up the line to the original controller. Many controllers, not wanting to make a pilot wait that long, would often clear the pilot to the requested fix and either tell the next guy on the hand off, or actually forget to tell them. Sometimes the fix requested wasn't associated with the runway in use, which meant the pilot would set up his computers for an approach he might not get. There was even the rare pilot that would get upset about this, and demand an inactive runway saying that it had already been approved for him, since he received a clearance 30 minutes ago or other such arguments. Another tough one to deal with.

Well, the problems, small as they were perceived by some, continued on a daily basis without either side being aware of the other's concerns, since both groups had bigger fish to fry. Unfortunately, for those reading this story, no such thing has happened in this little far away FIR for us to learn from, so we'll have to come up with our own little solutions. Maybe we can solve these issues before they lead to a problem, perhaps even before those in the little imaginary FIR where this story originated.

Saturday, August 27, 2005

Carbon Monoxide Story (with followup)

(Readers of the forums at Aviation.ca will already be aware of the post referred to below. I'm writing about this for the benefit of those who read my blog here, which is mirrored there)

Someone posted a recent experience with Carbon Monoxide in the forums at Aviation.ca. The odorless and colorless gas is an insidious little problem which is difficult to detect, and can have deadly consequences, both directly and indirectly. It's effects are slow and sublime, and can cause death simply by itself but also due to incapacitation which could result in a loss of control. Luckly, the writer survived and landed his plane before anything could happen, evne though his passengers had already suffered too much exposure. His story was written to remind everyone about the existence of such a problem. The reason I'm writing about it is not only due to the story of the experience, but also because a reader added an informative follow-up post with some interesting information about CO exposure that I think we can learn from. Follow the link below to the forum's post (no registration is required, the forum is public) and see just what was written.


Friday, August 26, 2005

"Hot Areas" Mapped Online

One of the many areas in which the Canadian Air Navigation System is concerned with safety involves the large number of warning and restricted areas across the country. There are rocket ranges, military flying areas, and all kinds of other activities. If they're marked as continuously active, then it's pretty easy for a pilot to know they're active (now they just have to look a chart to figure out where they are). A large number of these are, however, not active continuously. They are plotted on charts and NOTAMed active. Many pilots seem to be quite willing to fly into a region without making themselves aware of the NOTAMs. In any case, the US FAA has taken another step that's quite interesting. A reader sent me this release, so I'm copying it here:

An FAA database called the special-use airspace management system
(SAMS) now will tell anyone with Internet access whether any
restricted area, military operations area, military route, or warning
area anywhere in the country is going to be "hot," AOPA said on
Monday. It updates every six minutes, and the schedule is accurate 24
hours in advance. AOPA said it has been lobbying for access to this
information since 2001. SAMS has been in the works for a while, AOPA
said, but it took time for the FAA to coordinate with all the Air
Traffic Control centers to ensure that the data is kept updated.

Interesting read, no? What about the concept, too? I think it's great to have this stuff available, personally, though I'm not sure just who would be surfing the internet while flying a plane...

Thursday, August 25, 2005

Snowbird Crash

It saddens me when I read about any incident regarding the Snowbirds. I feel a certain pride over them, despite having no more connection to them than any other airshow spectator. Because their Canadian? Because they fly airplanes? I don't know.

My biggest fear about the Snowbirds rrests not with the pilots. These guys are enthusiastic, and are true professionals. They analyze their show, plan their every move, and practice hard and often. They know the risks, and yet still push on to give a show for the public, the vast majority of which will never even begin to appreciate what goes into doing such an act, and even the most dedicated to their shows will never *really* know what it's like.

No, my biggest fear is the possibility that one day we won't have them. Someday someone will probably say, "Look, the airplanes are getting too old. Look at how many problems we've had over the last XX years. I'm sorry, we have to stand them down." They've already talked about it in the past. I'm afraid it may only be a matter of time. With each incident like the recent crash, I feel that time gets a little shorter.

I'm extremely pleased that Snowbird 8 survived the incident. Its great to know he's alive and well. I hope his dedication continues, and that the Snowbirds survive as a team just as he did for years to come.

Wednesday, August 24, 2005

Stupidity Recognized

While telling some people about my little injury (mentioned yesterday), I would mention that, "I saw it coming," and yet, "let it happen." Obviously I felt that it may not happen or I would have stopped, right? And yet, even with my little vision, I ended up getting hurt. I started thinking about this when people I spoke to would tell me about their own little stories. "I was cutting shingles while roofing my house and I could see I was doing something stupid and ended up proving it." "I was hammering away in an awkward position I knew was stupid, saw that my thumb was in a bad place and ended up getting confirmation in a painful way."

It's interesting in an aviation sense because I'm sure this feeling comes into play in a lot of human error incidents. Can't you just see a pilot saying, "Looking back, I knew I shouldn't have tried but did it anyway"? I've heard some people, being involved in minor events, saying similar things. That's what judgment is all about, and yet how often is it ignored? What if it was heeded? I wonder how many major events could be avoided by listening to that meek, little voice that suggests against doing something. Think about it for a minute. What has happened to you that you somehow just "knew" would happen but you went ahead and did anyway, only to suffer for it somewhow? Care to post any? Hey, I posted mine.

Saturday, August 20, 2005

Smoke in the Cockpit

Smoke in the cockpit is a serious concern. Few people would argue. I wrote about this a while back, speaking more along the lines of fire detection until fatal crash. This time, I just wanted to write a little entry in the blog about how often it happens.

Like the last time I wrote about this, I refered to Swissair's Flight 111 that piled into the waters just off the coast of Nova Scotia. This very high profile incident scared many people, and sparked a spike of smoke or smoke smells in the cockpits. This is a quite normal reaction when something is brought to our attention in such a nasty way -- people all of a sudden start to question things they may have written off in their minds as, "insignificant until it becomes significiant." Now they may just be a little more aware of the significance. The funny thing is public perception.

Pre-Swissair, an airliner diverting for smoke in the cockpit was just a little filler on the corner of the newspaper's 10th page, or a brief mention on the news but no details mentioned. After Swissair's crash, it was front page news every time for a while, and reporters doing the old, "it's the third time since Swissair's MD11 crashed for the same reason!" or, "It's the fourth airliner to divert to a different airport this month!" I checked our unit log book, the document we make entries in about abnormalities in the operation within our region. In the 8 months leading up to the big Swissair one, there was an average of one airliner declaring smoke in the cockpit or smelling a burning sort of smell in the cabin each week. Most of these either declared an emergency or asked for some kind of handling (have the trucks ready, we're landing now; looking to divert to another airport; or perhaps just mentioning it; whatever) and rarely was a big deal made from any angle. There was no significant increase in the overall rate (yes, there were a few more than usual, but not too many), but the heightened awareness of it all in the media really showed through. And that was just in the Moncton FIR. I have no data for this post from other regions in Canada.

Friday, August 19, 2005

Ultralight Crash in NB in July

The report was recently released about the crash of an ultralight aircraft near Fredericton, NB, on July 20th of this year. The impact site suggested a high angle of impact, while the metallurgical analysis suggested no signs of pre-impact failure. The pilot was flying from CYTN, Trenton, NS, to Ontario. The weather was good at point of departure, and past Moncton, as well, though both Fredericton and Saint John weather at the time were IMC. CFB Gagetown, the closest weather report to the crash site, was also IMC, reporting a 300 foot overcast condition. The "Wag-A-Bond" aircraft was not equipped for IFR flight, and it appears the pilot attempted to descend with the clouds as he encountered them travelling westward, resulting in low altitude, low level flight. This eventually led to the loss of control of the aircraft, as all systems and the airframe appeared to be serviceable prior to the crash.

I find it hard to believe that with all the publicity around such bad weather flying that this could occur these days. There are many well documented accidents, most of them fatal, of what flying into IMC can do to a VFR pilot, or even to a pilot who is IFR trained but not supported by appropriate instrumentation. It's a shame that yet another had to add itself to the pile.

Thursday, August 18, 2005

Aircraft Speed Limits

I'm not exactly sure what made me think of this, but I did a search for it this morning and found that CARs was available online at the Justice Department of the Canadian Government in a searchable format. Anyway, on with the post.

I've had several questions as a controller, most of them off the radio, about the item formally known as the "speed limit order" before CARs came into existence and Air Regs and Air Navigation Orders were the laws of Canadian aviation. The most common question was this: If ATC asks a pilot to "Keep his speed up", does this mean he can exceed 250 knots indicated below 10,000 feet? There are two parts to the answer.

The first part is found in CARs, 602.32. Here's a link to it:

This pretty much says "no". The fact that it is spelled out about the 200 knots below 3,000 within 10NM of a controlled airport and there are no such exceptions for the 250 below 10,000 point says it all. ATC has neither the authority to direct a pilot to exceed 250, nor can they authorize a pilot request to exceed 250 below 10,000. Period.

The second part is where we'll get a bit wishy washy. The simple fact is that ATC can't be proof positive that an airplane is being flown above 250 below 10,000. There are a number of reasons that come together to ensure we can't know. ATC sees only groundspeed on the radar, simply because that's all a radar can track is your velocity relative to itself, firmly fixed to the ground. Next, the difference between true and indicated. You may be at 9,000 feet, indicating 250, but your true airspeed may be in the range of 275 or 280, so your groundspeed would be in the same range -- with a caveat from the following sentence. Next is winds. If you have a 50 knot tailwind, your groundspeed will be much higher, even near sea level where the difference between true and indicated speeds are very small.

ATC can always make a pretty good guess about whether you're over the speed limit or not, but honestly, I don't think there are many controllers out there who care. If you exceed the speed limit and it helps us and other aircraft behind you, we likely won't give it a first thought, let alone a second.

I'll offer this, too, though I'm not 100% certain it's true so take it with a grain of salt. I've been told that the 250 below 10,000 regulation is not a VFR see and be seen issue. I'm told it's an ICAO directive more to do with reducing damage due to birdstrikes, rather than an issue of other traffic. Someday I may actually take the time to try to confirm that, but it won't likely be for a while.

Wednesday, August 17, 2005

Another CF-18 Down

I always hate reading news like this. We lost aonther CF-18 out of Bagotville yesterday morning. Happiy, the pilot survived, was taken to hospital with no word on injuries. The plane, however, has seen better days.

This makes me wonder. I think I read a long time ago that we were originally supposed to receive some 138 F-18s, but never did get that many. The fact that we have already mothballed some of them is interesting enough, but then you look at the number we have lost in operation since then and it makes you wonder. How many do we have left? How long will they last? Is the Canadian government considering these issues and planning ahead? Nobody knows the answer to the second question, though some could offer educated guesses. I'm sure aviation enthusaists out there know the answer to the first one, and know the tailnumbers of the remaining ones (Please post!). The last one, I think we all know the answer to. Someone somewhere is looking at it seriously and having a hard time convincing someone in a position of power to realize that it's something to look at now and not at election time somewhere down the road.

Until then, we can only read of the reports and see the odd CF-18 at an airshow unless we're lucky enough to live close enough to one of the few places these things are stationed at. *sigh*

Here's the news item: http://www.aviation.ca/content/view/1254/117/

Tuesday, August 16, 2005

"Call the tower when you get in."

Many of us while flying have heard the phrase, "After you land, please call the tower." Most of us at some point during flight training, but other times as well on the odd occasion. At Aviation.ca, someone asked in the forum about this directive. Should you call?

One person wrote back that he often didn't call (Often? How often does he get this?), while another wrote in stating with great authority that one should never call the tower under any circumstances. I can't figure out why not.

When the tower asks for this phone call, they're likely trying to find out why you did something, and perhaps give you a reason not to do it again. Sure, the controller may be upset, but more than likely he or she is trying to help you without going further. It may be a way of telling you something (like what was expected of you when this was said, for example) without admonishing you on the radio for all to hear. Or they may be trying to correct a certain type of behaviour without "writing you up". ATC is not a traffic cop, but both pilots and ATC have a responsibility to "write up" anything observed that seems to contravene regulations. They may have witnessed something that was against the rules and rather send some paperwork your way, they may be sticking their neck out to say, "Hey, don't do that again." Why do I say sticking their neck out? Because if something did happen that was wrong, and someone else reports it when they simply asked you to call the tower, they can get in shit for not reporting it themselves.

I'm not trying to say that this is always what happens and you won't get reamed out when you call, but I think if you ever hear this, perhaps you should make the call. The guy who demands that pilots should never, under any circumstances, make that call is likely a problem for more than just ATC in the air and is too arrogant to figure out why. Perhaps too stupid to recognize it, too.

Monday, August 15, 2005

Arguments on the Radio

I've seen it several times over the years, initiated from both sides of the radio. Somebody does something wrong or unexpected, and the "affected party" gets the hair on the back their neck up. Suddenly, a question asked turns into a standoff on the radio. So far, in the 13 years I've been in ATC, I haven't seen anyone win one of these arguments.

The biggest problem I have with arguing over the radio is that it gets people riled up. A lot like road rage. The pilots are put upon at a time when they should be concentrating on flying an airplane. The controller, whose mental abilities are also important, is distracted by the situation while it's happening and afterward, as well. Neither side is where he should be mentally after one of these confrontations. It's a major distraction, and, like I say, doesn't resolve anything at the time. There are always emotions that simply stay either on the top or just under the skin and affect everything that happens for a while afterwards.

Everybody makes mistakes, and sometimes the mistakes cost a little to one side or the other. A real point may exist to be made, but the odds of it being made on a radio seem to be so much slimmer than on any other medium, it seems. Sometimes it's just better for everyone to let it go and let karma do its thing. Maybe the offending party, on whatever side of things, will have already seen the mistake and be thinking about it anyway, so the point really doesn't have to be made. It'll at least save the frustration that is likely to come from a radio confrontation.

Saturday, August 13, 2005


I recently read a post on another aviation related site that had a person speaking of circuits during his flight training. He mentioned how much he enjoyed them, and then how his instructor told him he would eat those words as time went on. I remember feeling similarly during my training, and eating my words later.

I sometimes found myself back then going up for circuits simply because I couldn't get a plane long enough or didn't have the money to take one for a longer time, all in the name of currency. I started to get discouraged, since circuits were boring. Then I met a member of my new extended family when my widowed mother married a widower. He was an instructor in years gone by, and he encouraged me to take advantage of such opportunities. Basically being forced into circuits was an opportunity? Then he explained it to me.

He asked where I trained. CFB Shearwater (CYAW). What's the shortest runway? 5,600 x 200 feet. Have you even landed on something shorter or narrower? No. Try it. Run with markings on your long runway and pretend the runway is shorter and narrower than you're used to. Set yourself some goals and try to fly the plane to them. Instead of looking at an 8,000 foot runway, see if you can think of it as a 1,500 foot runway by use of the right markings. Also, pretend the runway is only 40 feet wide or some other value, by landing on the centerline markings, or other markings, and considering it a failure if you don't track straight. I thought about it. Having a runway nearly 9,000 feet long and 200 feet wide as my usual piece of pavement, I had become very lax about tracking the centerline or "spot landings". That's a good idea, I thought. What if I had to use a shorter runway? Would I be prepared?

So now, the "forced circuits" are actually looked at as an opportunity, with a challenge in it that makes it kind of fun -- or at least proves an important point about my skill level. In fact, most flights I do now I include a couple of touch and goes for practice in these very issues before my final touchdown . I've made the circuits fun again, or at the very least, worthwhile again.

Friday, August 12, 2005

ATC Radar (Digital)

The next generation of ATC radars included some new technology. In this case, the data that was received by the radar antenna was processed by computers and turned into digital data. This way the data could be sent great distances by using modems and satellite links. Now, the ACC's could start spreading radar antennas around without having to man them at each site individually, but could now all operate out of the same building.

The old system in use in Canada, called JETS (Joint Enroute Terminal System) was implemented. This system promised to reduce some workload. By the use of Mode C readouts, controllers no longer had to ask pilots for altitudes on a contunal basis, and could instead ensure on reading is valid and use it from there. This cut down some communication and created some efficiencies with it. Another benefit was data tags. The old systems detected aircraft and displayed them, but even though codes were selectable to an extent, the radar still displayed them (as a single slash if the code was not selected, a double slash if it was selected). The computers involved now could not only display the code, but could also add a data tag showing the controller the aircraft's identification, his altitude and groundspeed. Also, a little two-letter symbol was added just above the target to show who was working the aircraft. This came to our next coordination saving device: A system handoff. Rather than transferring radar identification of a target from one controller to another by using voice ("20 miles west of Moncton is ACA123 at FL240") on a hotline or actually, physically pointing to the target on the receiving controller's screen, a controller could put the target in "handoff mode" which makes it flash on the receiving controller's screen so he knows the airplane is coming his way. A little more savings on communications.

With all the processing power, JETS had its disadvantages. You could only view one radar source at a time, which meant some sectors would constantly switch between sources depending on what airspace they needed to view. Also, in order to provide for a more accurate track on a target, code was introduced for "track smoothing". This worked reasonably for a high speed, enroute target, but was no good for an aircraft on a radar vector to final. The displays we called "time shares" showed analog radar data from nearby sites with digital data superimposed over top of it. It was often seen, especially when an aircraft took a tight turn, that the analog target (what the radar was actually showing) would make the turn, while the digital target (processed by the computers with track smoothing) would continue relatively straight ahead for another sweep or two, then jump to where the target should be. Track smoothing seemed like a good idea, but it was clearly demonstrated that it was not what it was cracked up to be, and ATC had to use 10 NM between targets.

Along came a new system called RAMP. Transport Canada (then operator of the ATC system) built a new system of radar antennas that were designed to be more accurate, totally digital, and included a new processing system in the units that would make use of the data. This system offered a number of advantages over JETS. First and foremost, the systems takes the overall picture from all the radar sources fed into it and "mosaics" them together to make one picture. No more radar source switching. The radar sites themselves all send processed data to the ACCs, so no more complex controls at the sector for the controller. Every gain has it's disadvantages, though, and ATC's weather picture has greatly worsened. The change in wavelength for the primary radar and the digital processing (which means no fine tuning controls for ATC) meant, inadvertently, that the weather display capability was greatly reduced (See previous posts for more on the weather capability).

In any case, the new system was still drawn as a vector display (also mentioned in recent post), and since it was built in the 80's, the computers didn't have much memory. Recent upgrades in the ACC's have led to newer, color, raster displays on 20" square monitors (2048x2048 resolution), much more memory and much more functionality, too.

ATC's radar systems have come a long way over the years. Have I forgotten anything? Want more info on a particular item? By all means, write. I'll see what I can come up with.

Thursday, August 11, 2005

ATC Radar (Light History - Analog)

Don't be put off by the title if you hate history. This is background, more so than anything else.

The term Radar isn't specifically meant for something that rotates and plots targets. It's meant as RADio Detection And Ranging. Strictly speaking, it's the use of radio waves to determine if something's out there, and if so, how far away it is. Naturally in our business, if you find something, you'd like to know where it is to make the information more useful. So now, we add the rotating antenna and measure its azimuth (which direction it's pointing) at any given moment so we know where a return (in the case of ATC radar, a reflection of radiation or a transponder reply) comes from. The antenna emits very short pulses of radiation at rapid intervals, and where the antenna is when the return comes in is known. The rate of pulses given out over a 360° rotation of the antenna is called the Pulse Repitition Frequency (PRF) and the more pulses given out in a single rotation, the more accurate the radar can be in terms of azimuth. You'll notice that long range radars tend to rotate more slowly than short range (compare airway surveillance and ASDE, the very short range, airport oriented radars), and this aids their ability to be accurate at long ranges. The more rapidly a radar rotates, the more quickly a radar image is updated, thereby allowing for a closer-to-real-time plotting of movements. The radar's intended usage is considered at the time of design, and the best compromise of update rate and range required is determined before the system is built.

Another issue for radar is the nature of the display. There are several methods of plotting information on a display. Perhaps you'll recall the old home video game called "Vectrex", or the old-style arcade games of "Battlezone" or the oringial "Asteroids". These were plotted in a vector-based method. Straight lines, single color, each line being comprised of a start and end point (even a dot on the screen had two points, they just happened to be the same). Anyone remembering these will recall how crisp the lines were regardless of direction. Your computer monitor in front of you is drawn in the method called "raster", which simply means the image is drawn on the screen a line at a time, starting from the top left and drawing one line lower on each pass. The downside of this display is the "pixel" effect, where a diagonal line is drawn as a series of blocks, making it look jagged when compared to a true horizontal or vertical line.

The old radars used by ATC were drawn differently again. Though I don't remember a name for it, they were plotted from the center out as returns were gathered. Each pulse of the antenna was drawn on the screen as it was sent, so the azimuth on the screen was tracked in time with the antenna. This is called an analog radar display, since there is no digital conversion of any kind taking place. If the radar received something, it would plot it on the display on the current azimuth at the range determined. There was no computer processing to determine if a return was an actual airplane or background clutter, or weather. If it "saw" something, it showed it to you. There was a mess of switches and knobs that were used to vary any of a number of "filters" (affecting the polarization of the signals, reducing the antenna gain, and so on) that would allow ATC to peer through heavy weather systems to see airplanes and so forth, but it was all controlled by the controller, not a computer.

The big downside of the analog systems is that since there was no digital data returned by the antenna, the range that the data could be transmitted was very limited. This resulted in Terminal Control Units being located at the airport, away from the parent Area Control Centers. I doubt you'll find a terminal controller who worked in the old days hating this fact. The airport was a good place to be for a TCU, and offered a few advantages, too. They could hear their departures, their backup communications were often simple, and they also worked in rooms very near the tower staff, so close working relationships were formed with the individuals on both sides. But not all TCU's are 24-hour operations and when the TCU closed for the night, the parent ACC didn't have access to the data from that radar antenna in many cases, leading to inefficiencies for those flying through the night time.

More tomorrow.

Wednesday, August 10, 2005

ATC Radar (Secondary Surveillance Radar)

We looked at Primary Radar (aka "Skin Paint") yesterday. Now we'll take a look at SSR, or Secondary Surveillance Radar.

SSR is really the mainstay of the ATC system these days, and for many reasons. First off, SSR works by having a radio transmitter that "replies" to "interrogations" it receives, and we pretty much all know these as transmitter-responders, or Transponders. The radar antenna sweeps the sky in much the same way as the PSR antenna does, but instead of emitting a powerful signal and looking for reflected radiation, the radar sends out a small signal on 1030MHz and listens for any transponders to reply to it on 1090MHz. The transponder replies in any of several "modes" which include different information. The SSR reply is received by the radar antenna and the distance is calculated along with the azimuth in the same method described yesterday to determine the position of the aircraft.

This method has several benefits. First, the range is increased since there is no need to detect reflected radiation. Instead, a simple radio signal broadcast from the aircraft is stronger than PSR returns, so the range of SSR is increased 2-3 times over PSR. Next, with the "IDENT" feature, a special code is sent to change the appearance of the target on the radar screen, thereby increasing the controller's confidence of which target is which. Further to that aspect, each transponder responding on what is known as Mode A will transmit a four-digit code. The numbers are octal values (they range from 0-7, giving eight possibilities for each place), giving a total of 4,096 different codes as possibilities. This allows a controller to see what code has been selected by the pilot, making it easier to track a particular aircraft. Mode C is the next greatest advance, in that aircraft so equipped can transmit their pressure altitude (note this is not the altitude indicated on the altimeter) to the radar station, providing an instant readout of altitude to the controller.

All those benefits and then some. In terms of equipment required for the radar antenna, there are advantages as well. Instead of a huge, parabolic antenna, the SSR system needs only a bar, much like what can be seen on ships. This bar still rotates as the other system's antenna does, but it can be mounted on top of a PSR antenna, or by itself as a stand-alone unit. This allows areas that don't warrant a full PSR antenna to be covered by less complex and less powerful antennas in an SSR-only environment. NavCanada, Canada's ATS provider, uses several of these types of stations called ISSRs (Independant SSR) to provide radar coverage over a much greater area than ever before. Using less power (only a radio signal to be transmitted, not needing to be enough to reflect a useful "radar shine" off an airplane), these antennas cost less to operate, too.

More tomorrow...

Tuesday, August 09, 2005

ATC Radar (Primary Surveillance Radar)

I was thinking about radar the other day (considering the weather abilities of our stuff), and I began to wonder what about radar would be interesting to talk about anyway. I honestly can't remember what I knew about radar before I got into ATC, so I thought I'd take a couple posts and write a little about it. I'm not getting into true radar theory partly because I don't know everything about it and partly because I feel some background is good but the truly technical issues are better left to technicians to describe and deal with than for us. Today's post will deal mostly with one type, and I'll continue tomorrow.

The two classes of radar that ATC use are called Primary Surveillance Radar (PSR) and Secondary Surveillance Radar (SSR). Primary radar has nothing to do with its importance, but rather it is the name of the class that deals with reflected radiation. No equipment is necessary on the airplane for this radar to work, and indeed no equipment on the airplane will help this radar in its ability to see an airplane. This is strictly radio waves emitted from the radar antenna and the reflected radiation being picked up by the antenna.

The primary radar antenna is a parabola and is normally encased in a big dome (or "golf ball" on top of some staging. In the old days, and at some locations still, the antenna is not encased and may be recognized by its size. It's a big net of metal, often a frame work rather than a solid sheet, that's bent on both the horizontal and vertical axis so as to focus radiation to a point in the same fashion as a satellite dish focuses signals from a larger area on a smaller area, increasing the gain of the antenna. A larger aircraft will reflect a larger amount of radiation and will be visible to the controller at a greater distance, generally speaking, than a smaller one. The materials an aircraft is made of will make a difference in reflected radiation as well, since metal will reflect more radio waves than some composites will. So generally speaking, the further the aircraft is from a radar antenna, and the smaller the aircraft is, the less radiation is returned to the antenna, so the less likely it will be that the radar can "see" the airplane.

In the case of PSR, the time between the emission of the radio signal and the time that some reflected radiation is received is directly related to the distance between the antenna and the object. Of course, since this is the round trip time, the distance accounted for is twice the actual distance, so the radar has to account for this fact. The azimuth of the antenna is measured continuously, so the direction of the reflected radiation is known as well, thereby allowing the display of a radar hit, or "target", in an appropriate place.

As mentioned earlier, no equipment on the aircraft is read through this method, and therefore altitude is not something can be determined by the simplest of primary radar antennas. The only way altitude can be figured out is to add another antenna that would "sweep" the sky vertically, such as with a "quad radar", those used for precision approach guidance. In this way, a controller can see the vertical axis on one section of the screen as well as the horizontal axis, and both would plot distance. But the average radar antenna used for airport and airway surveillance is incapable of determining an altitude for a given primary radar return.

The antenna doesn't tilt upward, but rather the radiation emitted is more like a triangle if seen from the side, looking from the horizon upward. This leads to a blind spot directly above the antenna, similar to the "cone of ambiguity" over a VOR or NDB. If an aircraft flies very close to the geographical location of an antenna at high altitude, its straight path would seem to curve as it approached the antenna and eventually resume its normal path once it got far enough on the other side. This is due to slant range, similar to DME. It may be nearly right over the antenna, and therefore nearly zero miles from the location, but it's 5 miles up and that distance is also measured simply by the way radar functions. The radar screen would have the target plotted at 5NM from it, and the speed would also appear to shift dramatically as it passed directly over (passing a huge azimuth range in a short time due to the actual horizontal distance being short).

More will follow in the days to come on other types of radar and the changes technology has brought to us.

Monday, August 08, 2005

Canadian Aviation Fun

Here's a little break from the seriousness of things lately. This game, strictly aviation related, and also Canadian. Probably most readers of this post will udnerstand that when the see the airplane involved. Have fun with this little game!


Sunday, August 07, 2005

Canadian ATC Weather Radar, Part II

A couple of responses yesterday prompted this post, which is a little further on the subject brought up yesterday.

I'm not completely sure of the current plans for furthering ATC's weather capabilities. I know there are provisions for displaying "echo tops" to the controller, but that information isn't coming in yet and I don't know where it stands. Currently, we get a separate weather radar feed (original sources include Environment Canada and the US weather service), but this data is displayed on a separate monitor, and therefore little more than just information, since we can't compare it directly with aircraft positions on the radar screen we use. We can look at landmarks and sector boundaries and say that this particular blob of red, which is close to current but not necessarily, is in this general area, but a vector around it is hard to judge at best.

And that's about the extent of our weather information usage, including lightning. What we see is provided for flight information only. We will not, generally, vector an airplane around a blob of weather unless the pilot asks us to. We'll offer vectors, where practical, but the responsibility we have is limited to passing information about what we see, just the same as passing traffic information on a VFR in Class E airspace. If one airplane goes through it, damn near crashes coming out of it, we may very well take further action with the next airplane simply because we have an idea of its effect on flight safety, but until we know something substantial like that, it's only information to provide to the pilots.

Another comment that I received through other channels is important here. Someone poked at me, wonder why ATC would have allowed the aircraft into CYYZ with thunderstorms all around. His question was, "Why did the controllers even let that airplane in there?" He's a truck driver by trade, so I offered him an anedotal situation. I'm in the passenger seat of his truck on a delivery and, on a relatively narrow road, an old bridge comes into view. He plans to cross it. I, as the passenger, say, "I don't think that bridge will hold us. I don't want you to cross it," and asked him how he would feel about that. He said, "Don't tell me how or where to drive." And I said that captured things just about perfectly. It is my job as a controller to give the pilot what he wants to the best of my ability. I must provide him with what information I can to help him make his own decisions, but if he says, "I want to do this," and traffic and regulations permit it, then who am I to tell him, "No"? The pilot has the ultimate authority on what he wants to try. Period.

Saturday, August 06, 2005

Canadian ATC Weather Radar

A number of pilots are flying in Canada without the benefit of weather radar on board. Many of these know that ATC has some capability of weather radar. Even those who have their own on board often ask ATC what they show. The usual response includes some kind of statement denouncing our capabilities.

In the past, the analog radar ATC used had a number of dials and controls that could be used to filter out weather to increase the ability to see aircraft. These same "filters" could also be adjusted to spot weather phenomena better. With Transport Canada's RAMP initiative (Radar Modernization Project), new radars were built and installed, and these units used a different wavelength on the primary radar (the radar which relies on reflected energy to detect aircraft). The changes in the wavelength put together with computer processing of target information changed many things in the controller's presentation, and the weather detection suffered in the process. ATC often sees "blobs" of weather that either isn't there or is not significant from a pilot's point of view, and often will be told about weather when we don't see anything there. Mind you, if the radar covering a particular area doesn't have primary capability, no weather will be shown at all, regardless. And ATC's weather capability is limited to 100 NM from a capable radar anyway, so our weather radar capability is quite limited.

Thankfully, a relatively new addition to ATC's weather displaying ability has made its way across the country in varying stages. I believe Moncton was the last to come online with it (I amy be wrong about that fact, but in any case it was largely due to the implementation of CAATS, our new system, which delayed Moncton's displays). Canadian IFR ATC units now have the ability to display lightning strikes detected by the National Lightning Detection Network. Once each minute the data is updated and displayed, with the source of the lightning detection reported as being accurate to within 500m, or 1/2km, or in nautical terms, about 1/4 NM. This doesn't predict where lightning will strike, but it shows where it has struck, and give ATC an idea of the direction of movement of a system and how much lightning is generated by it, also possibly giving some insight as to whether the system is strengthening or weakening over time.

I know some pilots are already aware of other units' lightning information availability, since a week before Moncton finally received the same information, I had two pilots ask me about lightning data while a heavy set of cells romped through our FIR. Anyway, hopefully this will be able to help ATC plan around thundercells and help pilots steer clear of them. As we've been talking lately, CBs are no place for an airplane to be.

Friday, August 05, 2005

Very Light Jets

Aviation Week magazine published an aritcle on the new segment of aviation that's cropping up, the VLJ, or Very Light Jet. These little jets are in the weight range that is below 10,000 lbs MGTOW, and I believe at least publicly pioneered by the Eclipse 500. 4-6 seats is all you can count on but the performance of most models so far is the Cessna Citation range, with a couple of competitors aiming for higher speeds, closer to Lear Jets. What an interesting thought -- buy yourself a minijet for anywhere from the $3M figure, down to the price tag expected for the Eclipse, a paltry $1.3M.

What does this do for us all? First off, smaller airports might see a little boost in that these jets are often capable of using runways as short as 3,000 feet legally and safely. While many larger jets are capable of landing and taking off on short runways, the big issue is one of failure -- how much runway is needed for a rejected take-off from just below V1? What if the runway surface is contaminated with sluch or snow? Other sorts of what ifs tend to extend legal runway lengths required for the bigger ones, but the little ones may be able to slow down faster, thereby reducing the runway length.

This has potential benefits for the buisness traveller. Those who are often stuck buying full-fare tickets at the last minute, those that spend hours on layovers at airline hub airports, and those who can't fly close enough to destination, even though there is a little airport just over the hill. These jets will be small enough and cheap enough for some business flyers who could otherwise fly themselves to allow them to skip the security delays at major airports and such and get to destination on their own.

Another interesting development is the "Air Taxi" style service. There are a few companies and individuals who now see operators of PA31s and BE100s and the like running small charters, but with the jets, service will be faster, and perhaps cheaper as the hourly rate is liekly to be higher, but the rate for distance flown may end up being cheaper due to the extra speed. There were three operators in the article announcing plans to run this kind of service already with large numbers of airframes on order before they even enter production. They claim they're building their own market and not planning to leech off current charter operations, and their claims are at least plausible at this point. We'll have to see what happens.

The implications for ATC are interesting in this point, too. We are more likely to see less experienced business flyers now instead of professional pilots in the cockpits of the business jets we talk to. Also, regardless of the size of an airplane, it still takes up at least a portion in the skies on radar. Were more of these to be flying around, they still have to be fit in somewhere in the traffic line, and now we're talking about light category for wake turbulence, which means another mile for each of them on the final approach course with many airports servicing a large deal of medium category aircraft.

Personally, I kind of like them -- for now. I can't wait to watch this segment develop as time goes by.

Thursday, August 04, 2005

Aircraft Lightning Strikes

Once again, an aviation occurence brings out the experts (Damn, I hope I'm not lumped into the category I'm demeaning right now). This short comment is about lightning strikes on aircraft.

There are some comments floating around with rampant speculation about whether the Air France A340 was struck by lightning on final or on the runway and what damage may have been done. Some sources say things like, "Aircraft are designed to handle lightning strikes and therefore never suffer damage from them," while others (especially frantic passengers, scared eye-witnesses, and fear-mongering or sensationalistic media moguls) state things like "a lightning strike is always a disaster!" I think we have to look at this one through different colored glasses, people.

There have been many incidents of lightning strikes on aircraft. Sometimes nothing more than burnmarks on the skin are evident, while other times critical systems can be affected. Think about it: Any conductor carrying electricity will dissipate some of it as heat. With a lightning strike, there is a LOT of current to dissipate. Even if no electrical current overloads a system or two on the way through, the heat can fuse parts or have an effect on system operation. This doesn't mean it will, but it can. Also, the simple fact of a system like a radio designed to run on comparatively low voltage (anything compared to the power contained in even a weak lightning bolt is comparatively low) could easily be overloaded or burnt out by a strike. Having said what I have about the possibilities of damage, most aircraft struck by lightning survive to make a landing.

Once again, I stress that we have to let the real investigators do their work and see what they have to say about what happened here, rather than leave it up to the new media who think they are investigative reporters.

Tuesday, August 02, 2005

AFR358 Crash at CYYZ

Of course, it's an aviation incident and it happened in Canada. I have no choice but to make a comment on it, do I? Unlike the myriad of other "experts" who are quite excited to have the opportunity to spout off their opinion of what happened. Well, now that the passengers are all confirmed to have lived, and all the crew survived as well, I'll say this. These experts commenting on the incident on the news are idiots.

Let's look at it: There is a reason why there is a dedicated group of individuals whose sole function is to investigate incidents such as this. Why have them if everyone and their dog has the correct opinion of what happened. There were microbursts in the area. There was water on the runway. Lightning struck the airplane, and killed all power on board, and therefore the hydraulics failed, too. They were landing "extremely fast" and hydroplaned off the runway. So many theories, so few of them comprehensive, even fewer correct. Phooey on them all, damn it! Some newscasters are even pilots themselves, so their opinions are worth more? I think not.

Let's let the real investigators interview the pilots, look at the recorded radar, weather, flight data and voice recorders and come up with the real story. Planting all of these stupid and unnecessary ideas of what's safe and what's not into the public's heads is stupid, and speculation is not helping anyone's job, nor is it helping anyone's view of aviation.

For now, let's, instead, focus on the fact that the crew was apparently quite capable of getting everyone off that plane before it was completely engulfed in fire. This is truly a credit to their training, and their abilities under duress. I can't wait to read the REAL report and see just what actually happened. Until then, I guess I'll have to continue to listen to the speculation of the idiots who think they're experts simply because they were there, or because they have a microphone planted in their faces.

Monday, August 01, 2005

Air Canada's Pilots Time Out

A post in our newpaper today reported that Air Canada had to cancel about 4% of it's flights yesterday with their pilots timing out. Once again, the media runs with a report and makes assumptions without following them up. While the statement from Air Canada wasn't false, it seems to me that there was enough left unsaid that the general public consuming that report will not understand what it's all about.

Airline pilots are not the only ones who "time out". They just happen to do it more quickly than others. Still other groups advance in this list faster than them, but under the Canada Labour Code, I believe most workers are covered to some extent. There is a limit on how much employers can work their employees in a given period and the CLC is but one factor. Many groups have contracts that cover them providing a different limit (less than the CLC) which could be reached earlier. And many of these groups are at least as essential as the passengers would see their pilots being.

ATC, for example, is also governed by it. In a given period, controllers are only allowed to work so many overtime hours before timing out. In a well-staffed unit, this isn't a problem. In a chronically understaffed unit, you start seeing issues. Often pilots and aircraft operators are the only ones who end up knowing about it. They will get notice, often short notice since the understaffing for a particular shift or time period is short notice, or it's just not covered ahead of time when the situation is known for whatever reason. Things like delays at destination, restrictions on altitudes allowed by certain flights or on certain routes. These are often dictated by which "specialty" is affected by the staffing conditions, and therefore which piece of airspace is affected by the staffing. These will often cost airlines and other operators extra in fuel, and sometimes even extra time in flight, which could add up to help cost in pilot's flight times that is the title of this particular post.