Wednesday, March 18, 2009

Finding the Corners

I have a quick forty minute flight to do, but I haven't checked the weather for a few hours, because I checked out of the hotel this morning and my computer is packed away. I go into the FBO to use their pilot briefing room. They have a dedicated terminal for a proprietary weather briefing system. The US has many different proprietary pilot briefing systems that different FBOs subscribe to. Some of them are great, better than the Nav Canada system, but I haven't learned ever wrinkle of every system. I click something that looks useful on this one, but it tells me this FBO doesn't subscribe to that option. Too useful, I guess. If I have the option I'll just go to the US government system, because I've invested the time to learn my way around it, and it's good.

I don't know the chronology on this, but here's what I suspect happened. The US has long had an online system called DUATS. I wouldn't be surprised if DUATS were originally a teletype service for the airlines, back when the Telex and the DC-3 were first invented. DUATS classic is a highly condensed ALL CAPS code that the cool American pilots with computers were using back when Canadians just called up flight services on the telephone. It's no wonder that commercial services stepped in to offer the Americans easier-to-use services. They must have been expensive, but they were a benefit the competitive American FBOs could offer their customers. In Canada the FBOs didn't have to attract customers (what are you going to do, stay up there forever or land at the only airport in 400 miles?) so no such system arose until Nav Canada put everything on a website. I don't know which website provided flight briefing services first, Nav Canada or NOAA.

I click around the unfamiliar program to find the same products I would get anywhere. Most of these systems are pretty intuitive: you click on things and get METARs and TAFs and pretty pictures. If you're lucky the one you are using has done something clever with the data to give you a graphical route briefing but as far as I can tell, this one just retrieves text forecasts and reports, and a graphic of TFRs, including the oxymoronic "permanent TFRs." The closest TFRs to me are Disneyworld and an airshow up in North Texas, so I'm safe.

Meanwhile the METAR for destination shows me clouds lower than the highest towers in the vicinity of the runway, and low visibility. In fact there's an IFR AIRMET Sierra out for such conditions to persist over a wide area until noon. An AIRMET (it may have been a SIGMET, they're identical in format) warns of a hazardous condition affecting an area. Here's an example, not the one I was looking at, but the same format.

WAUS43 KKCI 182045
CHIZ WA 182045

The first couple lines say which station issued it and when. The third line names this update as Z3, warning of icing conditions until 03Z, occurring in the states listed in the fourth line. Specifically the ice is expected inside an area bounded by lines drawn between the points given: from 20 nm northwest of YQT --hey, I know that one: Thunder Bay--to 80 nm north-northeast of SAW and so on through the airports I don't know, back around the polygon to Thunder Bay.

I'm not positive that the AIRMET covers my destination, as it gives corner points, all airport identifiers, and I can only find two of them on my chart. I'm used to the graphic and am not used to reading the text version of the US style. I may be missing a graphical mode on this system to show me the AIRMETs, like the first page on the NOAA site. In Canada, the boundaries of a SIGMET or AIRMET are given in lat-long coordinates, with directions and distances to airports in parentheses, so you don't need to know where YQT is to find it on your chart.

WSCN34 CWUL 181918
SIGMET A4 VALID 181920/182320 CWUL-
WTN 60 NM OF LN /4808N05156W/45 NE ST JOHNS - /4615N05610W/30 S ST PIERRE.

I would have pulled up the same warning for the Canadian side, but Canada only issues SIGMETs for severe icing. SIGMETs are issued for ICAO-mandated hazardous conditions and AIRMETs for country specific hazards that don't meet SIGMET-nastiness criteria. You can see that the format of the SIGMET above is pretty much like the US one, but with lat-long coordinates and spelled out place names in place of airport identifiers. I like that because I usually have some idea where "Muskoka" or is without looking, but if you don't you can find it on the chart easily. There are so many airports in the US, no one could know them all, so I'm surprised that they don't do the same. Of course, they probably think our system is broken for not plotting the SIGMETs on a map of the country.

There must be a tool I'm not thinking of that I could use to find these airports. I could google them, or otherwise look them up but I'm just sitting at a dedicated planning terminal with my chart. I'll have to go back out to the airplane and get the AF/D. I refresh again and now see that AIRMET Sierra has been extended through to 03Z. That's nine in the evening. Great.

I put off figuring out the AIRMET and check the NOTAMs. The NDB is out of service at my destination and the only other approach there is GPS, which I don't have for IFR approaches. So I'm going VFR if I'm going.

I refresh the destination METAR a few times. It's an autostation so should give frequent updates and I can get a trend. So far that trend is downwards.

Another pilot comes in. I offer him the terminal, but he's just here for coffee. He used to fly Dash-8s, so we chat about Dash-8 anti-ice protection and stall behaviour. I mention my AIRMET issue and he offers to see if he knows the airports. When I pull up the AIRMET it's gone. There isn't even a S3 cancelling the original AIRMET. That must be an artifact of the system. Or don't US SIGMETs end with a cancelling SIGMET, like this.

WSCN34 CWUL 182149

I refresh the METAR and my destination is 3800' scattered. Hey, works for me. Good talking to you. I'm ready to go.


viennatech said...

"There must be a tool I'm not thinking of that I could use to find these airports."

I should wait for David to chime in but just in case he is not available the best tool I know for finding airports by either code or by placement is David's own

Not only can you find out where a particular airport is, you can also use it in reverse to show you airports within range of a landmark and it nicely overlays on google Earth. You can also easily see what it will look like from whatever altitude you like. Not bad for a free tool!

For flying in the US, have you tried AOPA's online flight planner? If you have a DUATS sign in, it does a great job of translating the coded format of weather to graphical format and overlays it on your flight plan. It also can help cross reference the airport codes. I just don't know if either of these will work on a dedicated terminal. YMMV

Sarah said...

I gather you didn't have a laptop, or the FBO didn't offer wireless. I'm sure we all have a bunch of favorite aviation weather sites given the choice. Yes, DUATS is clunky, and should have a teletype soundtrack on the website.

Finding the corners... FA/SIGMET/AIRMETs and the like can be pretty mysterious without graphics. I understand for the US at least there's a wonderful app for the iPhone ( which I'm too cheap to buy for myself - the phone service that is. )

Even as a recreational pilot, I am sorely tempted to buy the aviation wx subscription for my newest toy, a Garmin 396 gps. Is that an option for your company? It's about $50/month if you already have the appropriate Garmin, and does support the US & Canada at that price. To avoid seeming a total shill, I'll refrain from posting a url - you can find it off the garmin site if you wish.

Aviatrix said...

Yes, as you guessed, although perhaps I didn't make it clear in the post, I had access only to the dedicated proprietary system, not the internet. I was hoping that system would have a tool I'd missed to plot or specify lat-long of airports. I wasn't clever enough to record the name of the system, though.

When I have the internet I use the NOAA site, so the "where the heck is this AIRMET?" problem doesn't come up much.

Anonymous said...

One issue that comes up in hanger talk, is "how does one ensure that they leave a paper trail for the FAA that they indeed got a weather briefing and checked the TFRs?"

When I use DUAT,DUATS or talk to a flight briefer I have fulfilled your obligation becuase they have my unique login or a tail number.

If I check the TFRs on the FAA web site, use ADDS or someone's terminal for the weather, there is no proof it was me.

I always "Press one to speak to a briefer" Even if I have gotten the data from ADDS. It's funny to hear some of them just "reading the weather", while others give an actual brief.

That way if there are any issues down the road, there is one less part of the book for them to throw at me. Sure it's double work, but...

When I fly in Canada, I still use ADDs. Then I follow up with call to a briefer who knows all about the weather at places named after animals.

Frank Van Haste said...

OK, here's what you need to do. Go here, print a copy of the map, and keep it in your flight bag. Problem solved.



Aviatrix said...

I had maps. I just couldn't find the specified points. But maybe it was just because of clutter. There aren't very many points on that whole map (which is printing now, thank you). Is that the complete list of identifiers that will be used in US AIRMET/SIGMET?

Frank Van Haste said...

Re: "Is that the complete list of identifiers that will be used in US AIRMET/SIGMET?"

Umm...I believe that it is. Assign confidence factor of 0.95 pending further research.



Sarah said...

Hey, thanks Frank. That map would be nice to have. Now we need to know the scale, so "50 miles SSE" can be interpolated... Or can we? The map projection ( lambert conic? ) would seem to make a consistent scale problematic. Maybe we can approximate, good enough for gummint work.

Frank Van Haste said...


At least it isn't Mercator :-). The copy I have here scales 6 cm from the 30 deg N lat to 40 deg N lat. So that's 6mm per degree, which is 6mm = 60nm more or less. So I'd go ahead and use 1mm = 10nm (or 1/8" = about 30nm if your ruler is unmetric).

Like you said, close enough...



GPS_Direct said...

Thanks for the map! But, while it is certainly helpful, it may not be quite current...

The SAW in the AIRMET is for the Sawyer VOR in Marquette, MI - which is marked MQT on the map.

Also, note that, while Our Airports is a neat site, WX report reference points are (to the best of my knowledge) all high alt VORs, and while many may match an airport, not all will... PXV for instance is only a VOR ID.

I find SkyVector ( since the preview link looks fouled up) to be a better site to search for airports and navaids. Plus, you can look at sectionals, both low and high en-routes, TACs, and more. Though they did take down the VFR flyway charts for some reason...

And of course, the site should (ahem) never be used for actual navigation.