Thursday, August 20, 2015

Birds on a Schedule

A NOTAM (at some point it stood for NOTice to Airmen, but I think it's just a word now) is a bulletin advising pilots of non-meteorological hazards to aviation: e.g. runway closures, unlighted towers, air traffic control frequency outages, amended procedures, unserviceable navigation equipment or the presence of a nuisance bear at the airport. In Canada a NOTAM begins with the last two digits of the year it was issued, and then has more digits to make it a sequence number. I think the sequence is only unique for that "NOTAM file" -- the major airport under which all the NOTAM in an area are listed. The NOTAM file's four-letter code comes after the number, making the combination unique. After that is the written-out name of the individual airport to which the hazard pertains. After that is a new line, usually starting with the four-letter code for that airport. In fact I originally wrote that it DOES start with that code, but I've just noticed that sometimes they skip it. I wonder if such cases are errors. It's a little disquieting for me to realize this, because it means that one of my shortcuts could miss important information. More on that later. Whether or not the second line starts with an airport code, the rest of the line, and possibly several lines, is an abbreviation-ridden string of text describing the hazard. The last line of a NOTAM shows the period during which the NOTAM is in effect, and it can have three forms. I would have said two forms, but just found many examples like the first one below, where the final line takes the form absent:


Above, the pilot is requested to AMEND her PUBlication, in this case the CFS, because that's the one with a PROcedures section, to add the line about closing flight plans. Perhaps they used to close VFR flight plans automatically at YEG (Edmonton International), or maybe too many people were forgetting so they figured adding an extra line to what is already half a page of dense text on local procedures at the international was the right fix. This NOTAM will go away when the next issue of the CFS becomes current, right now, I think: 00z on the 20th. Also YEG is unsurprisingly in the YEG NOTAM file.

OBST LGT U/S TOWER 542759N 1153430W (APRX 13 NM S AD)
377 FT AGL 4298 MSL
1506171512 TIL 1509181330

Above we see the second form the effective period line can take: a string of numbers representing an exact date and time TIL a second such string. 1506171512 is June 17th 2015 at 1512z. I'm kind of impressed with the precision with which they noted the appearance of this obstacle. I suspect that it reflects the time at which the unserviceability of the light on top of the tower was reported, or entered into the system. The second date and time then is the one at which the NOTAM will no longer be in effect, here September 18th at 1330z. That's 7:30 a.m. on a Friday in Edmonton. I guess they ordered a new lightbulb from somewhere that has 30-day delivery and are going to install it at first light the day after it arrives. Or they told the owner of the tower that if she didn't put a light on top of that thing by Friday morning, they were going to knock it down with a backhoe. Or they just picked an arbitrary day and time for the unlighted obstacle to cease being a hazard. The end time is not a guarantee. Nav Canada just has to issue a cancelling NOTAM if the hazard is gone before then or a replacing NOTAM if the hazard will be there for longer. And this NOTAM does not give the identifier for Swan Hills, although I think it should.

1506042150 TIL APRX 1509041800

Notice that the name of the aerodrome is Edmonton/Cooking Lake and it is a waterdrome, that is a place where you can't take off if your airplane doesn't float. You can sort of land, or at least alight, but that doesn't really work out well. It used to be just called Cooking Lake, but a few years ago they subsumed a bunch of aerodromes into the entries for nearby large ones, such that you have to guess whether a given aerodrome is far enough from the large one to merit its own entry, or whether you have to look it up under the name of the nearby large city. I'm not a fan of the change.

The last line is in the third form it can take, the TIL APRX statement. It means that even if your airplane does float, you're not allowed to use the aerodrome because there isn't enough water in the lake. Because the Edmonton area has not yet perfected weather control, there is no scheduled time for the aerodrome to reopen, but they figure that by noon on September 4th there will probably have been enough rain to use the lake again. They can still cancel or replace this NOTAM with another one, so you'd think there wasn't a big enough difference between the TIL and TIL APRX forms to be worth most of a blog entry, but there's even a question about this on the PSTAR exam you have to take before you're allowed to fly. So they care.

And so now I can reveal the scheduled birds.

1508141530 TIL 1509210659

What ornithomaggedon is going to happen at precisely one minute before one a.m. on the 21st of September? I'm easily amused.

NOTAM are actually a freaking mess. You can't sort them by date or relevance. You have to sift through pages of unlighted towers at 300 agl 10 nm from an aerodrome you're not even landing at in order to find that the one you are planning on using is out of fuel, or has a sinkhole in the middle of the runway. If you want the NOTAM for one airport in an area the "file" system forces you to wade through all the NOTAM for all the airports in that area. And if you're in southern Saskatchewan there are a hundred farm strips in a file. One of my tricks is to load the NOTAM and then hit control-F in my browser and put in the identifier of the aerodrome I'm actually looking for, searching again until I'm back to the beginning and have cycled through all the ones for that aerodrome. Trick doesn't work if the aerodrome you're interested in is the same as the name of the file, and it also doesn't work if the aerodrome identifier is not included in the NOTAM. It's not the distinction between local and FIR NOTAM. All these examples are from the local section. It's not the distance from the airport, because I can find unlighted towers the same distance from an airport, both with and without the identifier. I blame kids these days.

1 comment:

Unknown said...

"NOTAM are actually a freaking mess" ... That sums it up nicely.

Why the need for all the guess-what-this-means abbreviations? That's a hold-over from the day of 200 chars/hour telex systems. There seems little need for all this jargon and coded language in today's hi-tech world.

As for sorting them out to find the Actually Significant Ones... phew good luck. Some sort of rigid categorizing would help though: Some possible section headings: Low Altitdue Hazards / Airways / Airspace Restrictions / Airports ... Something along those lines might help? Most of us could easily ignore the low altitude stuff unless we are crop-dusting or scud running (i.e. non-standard markers on the cable crossing the XYZ river...). Those of us flying VFR could ignore the airways stuff. Etc..

Great post. Thanks