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Recently, I was working a B737 inbound to an airport in the maritimes. The pilot asked for a clearance to allow him to proceed directly to an IF to set up for his own navigation to a straight-in approach at a neighbouring sector.

Being an air traffic controller is a little like a triage nurse in an ER -- as you are confronted with a new task, you evaluate it and rate it for priority, then you approach each task based on how urgently it needs to be dealt with. In this case, the other tasks were much higher priority, and the request for the IF was simply pushed down to the point where it didn't get dealt with before the hand-off to the next sector.

When the pilot contacted the next controller, he immediately asked for a 360° turn to accommodate a descent, stating the "previous controller wouldn't let us down." Funny, I thought, when the controller told me this. He asked for lower, and I cleared him to 6,000. I handed him off to the next controller before he left 12,000 so he had plenty of altitude to work through before having to level off (which he never did). So why was he complaining?

I egged the next controller on to ask him about it, feeling a little miffed being blamed for something that I had no part in. When asked, the pilot said, "He didn't clear us direct FIXXX and since we were still going direct the VOR, the computer didn't have us descend in time." In this situation, the VOR was east of the airport and the aircraft and FIXXX were both west. In other words, the pilot had the FMS programmed to fly past the airport, meaning the descent profile was too high to make the approach from 10,000 feet where he was. Had he been cleared direct FIXXX, the profile would have been different, letting the pilot down lower earlier, enabling him to make the approach.

My initial response was a very sarcastic one, so it was good that I wasn't talking to him any more. My thoughts were, "When pilots flew their airplanes, this didn't happen." In fact, the ATIS at this airport advertised the runway he wanted to land in was active, and, in my opinion, he should have been anticipating coming in on that runway (especially since he wanted it), and he should have planned the descent accordingly. By putting the fix into the FMS, the aircraft would have proceeded to that fix, which would have meant he would have been taking a track which would have conflicted with other traffic, so he was right not to program it without a clearance. But to blame me for not "letting him down" in time by not clearing him to an IF is just wrong in my opinion. It seems to me like he's flying the computer, not the airplane.

So, point taken. But it's not always possible to let the computer do all the navigation. What if radar vectors were issued to the airplane? It was just timing that meant he could eventually be cleared to the IF with no other traffic around. How would you program the computer then? Simply put, I would do this again exactly the same way as this situation were I presented with it. My other duties were too high above the IF clearance to warrant taking my attention away from them.

Point taken. And while I now understand a little more about why pilots want to have a clearance to an IF while still 350NM from destination, I still don't accept any responsibility for his poor planning. Nor do I consider a clearance to an IF, especially if it's not the active runway, a priority.

A thread was started in the forums along the lines of today's title, and I had hoped to see a little more discussion on it. The gist of what was said involves the phrases "cleared direct FIXXX", versus, "cleared present position direct FIXXX" and the question was "is there any difference?"

On a related topic, the phrase "Cleared on course", as it relates to departures, for the most part, can be interesting. For example, I spoke last evening with a departure out of an airport in adjacent airspace as he climbed through mine. When the pilot checked in, he said he was "intercepting the on course". The previous controller had coordinated with me to ensure the aircraft could be cleared "on course" versus inbound traffic (to which I said yes), and both of us expected the pilot to proceed on course, as per flight plan route. The difference is where this topic comes in, and how it fits in with the previous topic of discussion.

Changing the fix names to protect the "guilty", the flight plan route was was CYZZ > FIXXA FIXXA8 CYXX". The pilot departed CYZZ, was vectored south for a short time around traffic, then "cleared on course". Both the previous controller and I expected the pilot to fly direct FIXXA, a heading of approximately 090°. Shortly after being cleared on course, the aircraft was handed off to me, and when he checked in, he stated he was "heading to intercept the on course", which by the nature of the transmission said to me that he wasn't going direct FIXXA. When I queried him, he said, "Well we were cleared on course, but we were vectored south, so we're heading back up to the line between CYZZ and FIXXA."

And who can argue? If his flight plan route were V499 FIXXA and he were "cleared on course", he would probably have done something similar and none of us would have said anything. The expectations were different from either side. Had the pilot proceeded direct to FIXXA, in this case anyway, nothing would have been said. Perhaps this is a little something about communication. From our perspective, the "on course" was "wherever you happen to be when we say 'cleared on course' direct FIXXA". From the pilot's, it was "CYZZ direct FIXXA."

The biggest question that arises out of this from my side of things is how is the heading chosen in such a case for the pilot to "intercept the on course"? Is there a standard? 30° to the track? Last evening it was about 10°, and with such a shallow convergence, it would have taken him a long, long time to actually intercept before turning on course. I can see some pilots making the argument, "My heading was a very shallow one which just happened to have me intercept on course right at FIXXA." And I doubt you'd hear a controller say anything to him. But then, all of this ambiguity is one reason I prefer a more concise phraseology than "cleared on course".

Recent posts in another section of this site about spins got me thinking about those nasty little manoeuvers. I remember my spin training well when I was getting my PPL, and still think back fondly of them. I'm not much for theme park rides or roller coasters, but I enjoyed my spin training. Here's one of my stories about them...

It was late in my training when my instructor told me it was time to do some "upper air work". We were in C-GDRL, the oldest C150 in the flight line. It was a 1967 model, and to my memory, was old enough that it didn't have shoulder straps, just lap belts. Also, the one thing that was very different, apart from the yoke that had the tops of the handles joined by a little bar, was that the seats were raised a little above the floor, more so than the others in the line. This afforded the advantage of better visibility over the nose, but it's also what led to the story.

We were at 3,500 feet, and my instructor said to do the checks and then, "show me all about a spin." Checks completed, power off, nose up, rudder right. As we descended, I was watching out the window. Something was odd. We were definitely in a spin, but something didn't look right. I verified everything I could think of, and everything was right. We were spinning. Not fast, not slowly, but at a normal rate. We were descending, but visibility was good and I knew the airplane to know how much I needed to recover and things were going well. Three turns. Four turns. Then my instructor's hand grasped the glareshield in the middle and yelled, "Recover! Recover!" Then it hit me. The difference was simple the higher seating position and how things appeared out the window because of it. It was a standard recovery.

At no point were we in any danger, the way I saw it. I was in control, and fully aware of the ground. Heck, I was looking at it spinning beneath us. Perhaps I did hold the spin too long. Either way, it was interesting, and perhaps the longest spin I had ever done. I lost track of the number of rotations, but the little C150 did just fine, thank you very much. And so did I. My instructor didn't want to spin with me again, though...

The basics of IFR Flight include the need for an IFR clearance. The IFR Clearance is essentially permission for a pilot do something, but it also constitutes a number of requirements that the pilot must adhere to while flying. For example, the complete IFR clearance includes a route (typically the flight plan route) and an altitude. So while a pilot would now be authorized to fly the route and altitude, he is also expected to stick to that route and altitude since other aircraft's clearances would be based on that expectation. The pilot is, of course, free to ask for amendments to the IFR clearance at any time (such as changing altitude or even route, such as asking for "direct to Sumspot").

The IFR clearance must be obtained prior to entering controlled airspace. There are four basic possibilities:

1) The airport is in a control zone and therefore controlled airspace is encountered as soon as the airplane is airborne;
2) The airport underlies controlled airspace;
3) The airport and the initial part of the route is outside controlled airpsace;
4) The departure aerodrome, destination and entire route of flight are outside controlled airspace.

In case one, the IFR clearance must be obtained prior to departure. This is the case at airports with control towers, but control zones also exist at some uncontrolled airports. The idea is that ATC may not issue take-off and landing clearances, but the IFR ATC unit (the Area Control Center) has the authority to direct IFR departures after take-off and restrict the flow of arrivals to at least a certain degree. The CZ also has the effect of raising the VFR weather minima allowing for a better chance of "See and be seen" in the vicinity of the aerodrome.

In case two, there may be controlled airspace above the field (a typical base of controlled airspace in such situations is 2,200 AGL such as an airway or control area extension) while the airport itself is not in controlled airspace. This means that the IFR clearance is not actually required before take-off, but it may be required shortly thereafter. It may be to the point where the aircraft may be required to fly VFR or below controlled airspace at dangerously low altitudes if the IFR clearance cannot be issued right away, and that means it may be better to get the IFR clearance before take-off. If the base of controlled airspace is high enough (say 12,500 for example), the pilot may take-off and complete the initial part of the climb before obtaining IFR clearance. It is important to note that there may be other IFR traffic operating in the area and a call to ATC may be the only way to find that out.

Case three is very similar to the latter portion of Case two's description. The pilot may take-off without the permission of ATC, fly the initial part of the route, and the only required communication is the departure message -- alerting ATC to the fact that the aircraft is airborne. This is done for alerting services as part of the flight planning process. In any case, before the aircraft enters controlled airspace, regardless of altitude, the pilot must call ATC for clearance prior to entering.

The last case, Case four, the pilot may depart, fly in IMC and shoot an approach to landing all without communicating with ATC, since no IFR clearance is required. The only communications with ATC that are required are the departure and arrival messages, and these may even be relayed through FSS or made by telephone after landing in the case of the arrival message. It is wise to make contact with ATC if possible, since they may be aware of other IFR traffic in your area (based on other similar flight plans with their departure and arrival messages also being received).

The big thing is to know what class of airspace you're in. This can be found by checking the appropriate IFR chart (LO charts are for the low level airspace structure and indicate what's below FL180, while HI charts show FL180 and above). As part of the pre-flight planning, the controlled airspace should be reviewed, even if only briefly, to ensure the pilot(s) know where changes to controlled airspace classification take place so they know what's expected of them.

Have you ever flown IFR and been instructed to "establish flight" inbound or outbound on a radial? Chances are that if you only fly IFR in a radar environment, the answer is "no". If you have flown in a non-radar environment, you may have heard of this before.

ATC calls an area where aircraft can't be seen on radar a "non-radar environment". Separation must still be applied in controlled airspace outside of radar coverage, and the way this is done is by "proving" that separation exists. Position reports from aircraft over fixes and NAVAIDs, radials and DME arcs and so forth are used in concert with what we call "separation minima". For example, we say aircraft are separated if they are 1,000 feet apart vertically in airspace where 1,000 feet is sufficient because it meets are separation minimum. Similarly, two aircraft that are on parallel tracks spaced far enough apart are separated because they meet lateral separation requirements. Longitudinally, aircraft on opposite direction tracks that have both reported passing the same NAVAID can be considered separated since we don't protect airspace behind the aircraft. The list goes on.

One the tools in ATC's toolbox is known to us as "OMNI separation". Omni, for those who don't know the abbreivation of VOR, is a short part of that acronym. The idea is that the group of separation minima I'm talking about relies on VORs. ATC can specify radials that have a minimum spacing expressed in degrees depending on the situation to "prove" that aircraft are laterally separated. Since these radials converge at the NAVAID, there is also a distance requirement which says another form of separation must exist (typically vertical) until the aircraft are passing at least 15NM from the facility. Those who fly these kinds of restrictions are also aware that ATC often uses 17DME to prove our 15NM because of known errors in equipment. Perhaps the reason for this could be left to another day?

Anyway, the result of all of this is that a pilot can be instructed to establish flight on a specified radial, while another aircraft is to make a climb from 1,000 feet below the first airplane's altitude to 1,000 feet above it (or the other way around, of course) while established on a specified radial a certain "distance" apart from the first one. The restriction to the climbing aircraft might sound, for example, like this:

Alpha Bravo Charlie maintain one four thousand, make climb from six thousand to eight thousand established on the Sumspot two four zero radial. Not above six thousand til one seven DME.

The intent should be pretty plain. ABC is cleared up to 14,000 feet, but he can't climb above 6,000 until he is at least 17DME from the Sumspot VOR, and established on the 240° radial. He must stay on that radial, much like tracking a VHF airway, until he reaches 8,000. What he would do after that would depend on the context of the situation. For example, ATC may have cleared him directly to some other NAVAID or fix after he reaches 8,000 feet. The altitude range used in the Omni climb or descent may be a lot larger than 2,000 feet, as well, if, for example, both aircraft are climbing or descending.

That's a brief introduction to the principles behind Omni separation, AKA radial climbs and descents. There is, of course, a lot more to it than what's demonstrated here, but the point was merely to introduce a tool in the ATC cabinet that some pilots never, by the nature of their normal routes, encounter.