Hacker News Reader

Comment by zackbloom | Hacker News Reader

Unlike the NOTAM outage, a METAR outage will and should actually affect flights. Without weather at your destination it becomes impossible to know if it’s safe to land there. The forecasts (TAF) are actually used more in flight planning, but actual weather is very valuable while enroute, when not close enough to hear weather over the radio from the destination airport.

View on HN

To add some nuance to what other commenters have said, 95%+ of all NOTAMs are useless, telling you about grass that might be mowed, animals that might be present, temporary "obstacles" that you could only hit if you were flying both dangerously and illegally, correcting immaterial typos in the charts, or updates to dubiously helpful information published in the charts (number of hotels in the surrounding area).

Others are potentially useful, but not essential for safe flight. Things like closed taxiways, nonavailability of services at an airport, etc.

And a very few are really critically important. Runway closures, correction to vital chart information, airspace changes, malfunctioning navigation aids.

The FAA's reaction to the NOTAM outage was probably the correct course of action. But make no mistake, the volume of spam NOTAMs combined with the lack of an easy way for a pilot to quickly sort for important NOTAMs makes us all less safe.

> But make no mistake, the volume of spam NOTAMs combined with the lack of an easy way for a pilot to quickly sort for important NOTAMs makes us all less safe.

The system is in desperate need of some modernization, no argument there. The fact that there isn't a simple criticality filed with them that makes it easy to see what will actually impact flight planning (airspace closure / runway closure vs stupid chart updates) is insane.

The idea is probably that is you included a criticality flag, pilots would ignore low priority notices and potentially miss something (like grass being mowed at the time they plan on landing) that could affect them, but is otherwise immaterial for most others.

I can’t say one way or the other, as I’m not a pilot, but that’s the argument I’d make to keep the system w/o priority levels.

As a pilot of single-engine airplanes, I disagree that mowing is useful. I need to look at the runway I'm landing on for obstructions no matter what. The time of year when mowing might occur, I might also have to contend with deer, who are just as hazardous and don't file NOTAMs before grazing near the runway.

The problem is that "criticality" is too binary. A tower light NOTAM might be low-criticality for a fixed-wing airplane pilot flying day VFR, but high-criticality for a helicopter pilot flying at night in IMC.

Similarly, chart updates are very important if you're flying IFR. Going below minimums while in the soup ends... very badly. If somebody's changed the MEA/DA/MDA, you can bet I want to know.

NOTAMs do have keywords to tell you the subject (i.e. airport closure vs tower light), and most briefings will highlight the ones likely to be urgent.

(That said, I'd argue printing out all the tower notams in textual format is somewhat useless. The NEXTGEN FSS briefings are plotting them graphically now, which is an improvement.)

Unrelated to aviation, but I actually find METARs and TAFs are useful for hiking and skiing. I use the altimeter settings for my altimeter when hiking, and knowing the altitude of cloud layers is useful to know what the visibility will be like on the mountain (you have to do a bit of math with the airport elevation and the mountain’s elevation, but hey—it works!).

I like your idea of visibility a lot, and would like to know more. Are you using a barometric altimeter? I use one hiking, but mainly for dead reckoning using an USGS elevation map. I usually just set my altimeter using those maps.

I used METAR for running, or rather to say which days I'm allowed to not run.

I noticed that when the day was long, and I was feeling tired and lazy it was a lot easier to find some excuse why not to run that day. This excuse was often the weather. But on the other hand I didn't want to say no matter the weather I must run, because that is obviously excessive. So I made up a simple "algorithm" to decide if the weather fits the minimums, and if it did I must go and run. And I choose to base it on the measurements from the METAR of the local airport.

Cool idea, what's your algorithm's decision criteria?

I think it was something super simple. Like temperature above X, no percipitation at the moment, no percipitation predicted during the next hour.

(I also remember I was willing to skip running in case of anything “exciting” being reported. Like tornados, or sandstorms or vulcanic ash. Not that any of that was a real possibility.)

In the era before cell-phone internet, being able to call the automated weather reporting station at the nearest airport and have it read out conditions was hugely useful.

For folks who haven't seen what's in a METAR/TAF: https://www.faa.gov/air_traffic/weather/asos/ (By default, clicking a station gives you the abbreviated format; you can select the "decode" radio button and click "update" to translate it into English.)

NOTAMs cover things like runway closures or airspace closures due to hazard, as well as a huge host of other issues.

Stopping takeoffs was absolutely the right move, since they couldn't handle the phone throughput.

Err. NOTAM should also have effected flights. Please don't downplay the safety of airspace.

A pilot can legally land without a METAR, and this happens all the time. The stations can and do go offline. Sometimes they break, especially after a severe storm. Many smaller airfields don't have on-site weather reporting, some others don't have a network connection.

You look at the closest available weather station and you look at the forecasts — human-authored (TAFs) and computer-autored (GFA/MOS). And when you arrive, you look outside at the actual conditions — the windsock, actual flight visibility, etc. If the conditions are worse than expected, you divert to your alternate.

Yep. Not knowing the atmospheric pressure can lead to planes crashing, especially if it's inclement weather.

Wouldn't each airport measure and report the local weather anyways?

Each airport does measure and report the local weather-- that's where METAR data comes from. And busier airports broadcast that data locally, via ATIS or D-ATIS, for pilots in the immediate vicinity to use (either on the ground or on approach to the airport).

That doesn't help a pilot plan ahead for conditions on their route or at their destination, though-- that's where METARs come in.

Are local weather conditions not generally available for all airports at all times?

They are. I've even seen small aircraft pilots call the automated weather line from the cockpit while they're preparing to approach the destination airport.

That automated weather frequency relies on METAR data from the Aviation Weather Service here in the US, and that's where ATC gets their information from as well when they're advising pilots of surface winds when giving landing clearance.

Per the source, 167 airport weather stations are not reporting correctly (either due to a highly unlikely concurrent fault with the stations, or more likely an issue with the system they report to).

Local weather is always used, but that's precisely what is unavailable right now.

You have it backwards, ATIS doesn't pull from METARs... the METAR and ATIS recording are both produced at the same time locally by the local weather observer (usually a controller in the tower), reading raw data directly from the on-field weather station and making manual edits as necessary. The two should match up exactly, but that's because they're both produced by the same process.

If the tower is closed, or it's an untowered field, the system can run in automatic mode. In that case the radio broadcast gets updated every minute, much more frequently than METARs get updated (every hour).

And, if the tower is open, you have to acknowledge the latest ATIS report (by signifying the revision) before you can go.

Yes. And that service is called METAR (METeorological Aerodrome Reports).

>Unlike the NOTAM outage, a METAR outage will and should actually affect flights.

We have mines being blasted to our north in temporarily restricted military airspace - lets just allow pilots to roll the dice?

Reply on news.ycombinator.com