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Comment by woodruffw | Hacker News Reader

The entire world of airline coding (as in "encoding") is fascinating to me: there are all kinds of ancient semi-human-readable formats like ACARS[1] and IATA Teletype[2] that are still pushing data around. Not the mention standard meal codes[3], like BLML for "bland meal" and CLML for "celebration cake meal."

[1]: https://en.wikipedia.org/wiki/ACARS

[2]: https://en.wikipedia.org/wiki/Airline_teletype_system

[3]: https://en.wikipedia.org/wiki/International_Air_Transport_As...

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I've also wondered why cryptically abbrevated things like NOTAMS are still the way they are. It made sense in a teletype/telegraph world where brevity was worth time and money.

From wikipedia, this is a typical NOTAM:

  A1234/06 NOTAMR A1212/06
  Q)EGTT/QMXLC/IV/NBO/A/000/999/5129N00028W005
  A)EGLL
  B)0609050500
  C)0704300500
  E)DUE WIP TWY B SOUTH CLSD BTN 'F' AND 'R'. TWY 'R' CLSD BTN 'A' AND 'B' AND DIVERTED VIA NEW GREEN CL AND BLUE EDGE LGT. CTN ADZ

Likewise METARs (weather reports):

  METAR KTTN 051853Z 04011KT 1/2SM VCTS SN FZFG BKN003 OVC010 M02/M02 A3006 RMK AO2 TSB40 SLP176 P0002 T10171017=

Pilots have to know how to read and understand this stuff. Only justification I can think of is that like mathematical notation, this shorthand, once learned, is unambiguous and conveys meaning better than prose. I don't know if that's really true though.

> Pilots have to know how to read and understand this stuff. Only justification I can think of is that like mathematical notation, this shorthand, once learned, is unambiguous and conveys meaning better than prose. I don't know if that's really true though.

You're correct. It's straightforward for pilots. They can quickly read a NOTAM and understand everything.

Also, it's pretty standard and unambiguous worldwide.

As for the specific example you provided, today is your lucky day! That exact example has been decoded on Wikipedia here: https://en.m.wikipedia.org/wiki/METAR#North_American_METAR_c...

This all seems quite reminiscent of when the US National Weather Service used to issue super-cryptic forecast background summaries, and then slowly non-meterologists started building systems to decode them.

That would be true in an ideal world, but pilots are also only human, so at least some of them will sometimes misread or ignore all that gibberish. To quote Wikipedia:

> In July 2017, Air Canada Flight 759 nearly crashed into four other airliners as it attempted to land on a San Francisco taxiway misidentified as a runway: the adjacent runway was closed but the information was buried in the NOTAM. As a consequence, in September 2018, from the findings during its investigation, the National Transportation Safety Board (NTSB) stated NOTAMs were unintelligible and ignored, and recommended a more effective information presentation for better relevance. NTSB chairman Robert Sumwalt described NOTAMs as "a bunch of garbage that nobody pays any attention to". This led to an ICAO initiative to reform the NOTAM system.

> You're correct. It's straightforward for pilots. They can quickly read a NOTAM and understand everything.

Pretty sure most pilots would disagree. They're a mess.

Yup. Nothing like an AD AP CLSD stuck right in the middle of 53 different unlit tower NOTAMs

I prefer the encoded version of weather, TAF (Terminal Area Forecast). That makes it easier to visually scan down and see how the weather is forecast to change in the terminal area. (Is it improving? Getting worse? Is there a time when the winds change significantly [meaning a frontal passage is happening]?)

Same for a time sequence of METARs, especially when you cross-compare the METARs to the TAF (to know if the forecast is holding or was blown.)

Visually scanning the encoded text of weather is easier. (The entire NOTAM system is a mess, encoded or not.)

Raw TAF and Raw METAR for BOS below:

  KBOS 141129Z 1412/1518 31018G28KT P6SM SKC
    FM141400 31020G30KT P6SM SKC
    FM150200 34014G26KT P6SM SCT070
    FM151100 01009KT P6SM BKN050
    FM151500 04011G18KT P6SM BKN020

  KBOS 141254Z 29020G31KT 10SM FEW050 M05/M13 A3000 RMK AO2 PK WND 29031/1245 SLP157 T10501133
  KBOS 141154Z 31018G28KT 10SM FEW050 M05/M14 A3000 RMK AO2 PK WND 31030/1125 SLP158 60000 T10501139 10006 21050 53003
  KBOS 141054Z 32017G26KT 10SM FEW060 M05/M15 A2999 RMK AO2 PK WND 30028/1020 SLP155 T10501150

Here's Indy's METARs, showing generally good weather with broken clouds, developing into light rain-mist-solid overcast, then heavy rain-mist-overcast, then light rain-mist-broken clouds. (Read from bottom-up.) I'd quickly read that as improving and generally following the TAF (below it), meaning the forecast is probably a good one.

  KIND 141308Z 11013KT 2SM -RA BR BKN006 OVC011 06/04 A2989 RMK AO2 P0002 T00560044 $
  KIND 141254Z 11013KT 1 3/4SM RA BR OVC006 06/04 A2988 RMK AO2 SLP121 P0007 T00560044 $
  KIND 141233Z 11013KT 2SM +RA BR OVC007 05/04 A2989 RMK AO2 P0002 T00500039 $
  KIND 141154Z 11013KT 9SM -RA OVC007 05/04 A2988 RMK AO2 SLP124 P0003 60021 70021 T00500039 10056 20044 55011 $
  KIND 141054Z 09013G22KT 7SM -RA BKN009 BKN055 OVC095 05/03 A2987 RMK AO2 SLP120 P0003 T00500033 $
  KIND 141051Z 10013G22KT 7SM -RA BKN009 BKN021 OVC090 04/03 A2988 RMK AO2 P0003 $

  KIND 141311Z 1413/1518 11013G22KT 2SM -SHRA BR OVC006
    FM141500 13011G21KT P6SM BKN007 OVC015
    FM142200 12011G21KT 5SM -SHRA BR SCT003 OVC009
    FM150300 11013G21KT 2SM SHRA BR OVC006
    FM150700 20012G27KT P6SM OVC009
    FM150900 25010KT P6SM BKN016.

> They can quickly read a NOTAM and understand everything.

lol no. I was a pilot. I think you'd be shocked by how much pilots don't understand in METARs and NOTAMs.

Back in 2004 when I was involved in airtraffic control operations, teletype was still there as backup for the PC based solution. Don't know the status 18 years later By the way the software used was based on win3.1 with a secondary partition with Linux and relevant software which was the secondary option as their audience was not accustomed to Linux UI at the time - that is their words

At this point it's basically historical/a mild hazing ritual. Everyone involved in aviation knows how to read this gibberish, and the next generation damn well better do the same!

Back in the day, it made sense. Say, back in the 60s, these messages were sent over a teletype at maybe 75 baud or less, roughly 10 characters per second. Now the Telex network was billed differently, but by comparison, at the time, domestic long distance rates could be over $1 per minute during the day, so it was on the order of 600 characters/$1. All the abbreviations probably reduce the data transmission by 80-90% over a fully spelled out transmission.

For things like hourly weather reports from every major airport, the abbreviations probably saved $50/hr or more on Telex charges every hour every day at major airports receiving them. That's not to mention the lower latency from getting weather reports sooner or not needing to install more Telex machines to keep up.

You should try having to read several hundred of them before a long-haul duty! Good luck trying to find the runway closure notam buried among the 400 reports of a crane within curvature-of-the-earth viewing range of an airport, or the 300 reports of birds that were once seen near, or somewhere near the runway.

Too hilarious not to share: https://fixingnotams.org/wp-content/uploads/2019/11/Field-Gu...

That's one hell of an interesting read.

I saw a NOTAM about increased bird activity that had a 10 day duration. Thanks NOTAM.

So, as someone learning to fly, I can say that the METAR format is actually pretty quick to learn and the standardization does make it pretty quick to read, effectively acting as a shorthand. I'm not going to say it couldn't be improved, but it's standardized enough, and contains information that's immediately relevant to everything you're doing, so it's something you pick up quick.

The same is not really true of the NOTAMs, at least as far as I can tell. They're much less standardized, being mostly just plain text with weird awkward abbreviations and all caps that make them slower to scan. There's all kinds of mostly irrelevant metadata; and a lot of the time there are so many of them, most of them not really relevant, that it's really easy to lose track of what is important.

So, I don't think there's much pressing reason to change the METAR format, but oh god do they need to reform the NOTAM system, both the format and better filtering for actual relevance.

Note that this is coming from a student pilot, but I've also seen more experienced pilots express similar frustration with NOTAMs.

You answered your own question. Being able to read those things is part a pilot's training and daily job. Complaining about this from the outside is like me critizing Python or something else I have not the slightest clue about.

It's because being standardized is more important than being easy to read.

Now that we can make clients that expand those codes for you, people are working towards a more standardized, more verbose language with a much larger lookup table and computer-friendly separators.

> Pilots have to know how to read and understand this stuff.

Not just regular pilots, but also (here in the EU) operators of drones under A2 classification.

And let me tell you, it sucks, particularly if you're from anywhere else but the US and never heard of units like feet, miles and inches and what they mean outside of "this exists, is only used in the US and that's it" once in school. The only thing in a standard unit there is the temperature, and that I guess is only the case because "0C" is way more obvious as the freezing point of water.

I get it, this dates back to hundreds of years of nautical practice, but everybody else has long since shifted to metric...

> anywhere else but the US and never heard of units like feet, miles

The miles typically used in the USA are not the nautic miles used in aviation.

But what's worse, some air speed indicators show different units than knots (nm/h), depending on the origin of the aircraft mph or km/h.

NOTAMs and METARs are fun, but also the string of characters on a passenger boarding pass, like this one

    M1EWING/SHAUN         E1AAAAA SYDBNEQF 0524 106Y023A0073 359>2180

And for the record, like Python code, the spaces are significant, because the fields have a fixed order and width. (Although there are a couple of places where a field is specified by a number denoting its sized, followed by the contents)

Absolutely hellish indeed. I had to write a parser for some kind of custom IATA PAXLST [0] (passenger list) that was coming from an ancient automated email system and I was dumbstruck by the weirdness of it all while reading the documentation.

    UNB+UNOA:4+SWAIR+NZCS+080708:0545+000000011'
    UNG+PAXLST+SWAIR+ NZCS+080708:0545+11+UN+D:05B'
    UNH+SWCA749+PAXLST:D:05B:UN:IATA'
    BGM+745'
    NAD+MS+++WILLIAMS:JANE '
    COM+41 22 797 2025:TE+41 22 788 4689:FX'
    TDT+20+SW679'
    LOC+125+GVA'
    DTM+189:020322'
    LOC+87+BOS'
    DTM+232:020322’
    DTM+189:020322'
    LOC+92+ATL'
    DTM+232:020322'
    DTM+189:020323'
    LOC+130+SFO’
    DTM+232:020323'
    NAD+DDU+++WINDSOR:ELIZABETH:R'
    ATT+2++F'
    DTM+329:720623'
    LOC+178+NCE'
    LOC+22+ATL'
    LOC+179+MEX'
    LOC+174+FRA’
    NAT+2+CHE'
    RFF+AVF:RXDWWH’
    DOC+P+564SBB41'
    DTM+36+051215'
    LOC+91+FRA'
    DOC+V+VV258DD7'
    DTM+182+021212'
    DTM+36+0421201'
    LOC+91+:::MARSEILLES’
    CNT+42:1'
    UNT+33+SWCA749'
    UNE+1+11'
    UNZ+1+000000011'

[0] https://www.iata.org/contentassets/18a5fdb2dc144d619a8c10dc1...

If you visit an airline on WikiData, they have the FAA, IATA, and ICAO codes pretty well mapped out, but I hadn't ever come across an ACARS entry before. Might be worth mapping out. Example:

https://www.wikidata.org/wiki/Q8731

I have done work integrating real time systems with flight data in all of these encodings and telex for a large intl travel company that does contracts at an airport you have flown at. A lot of legacy systems are using very early web protocols like SOAP or old encodings e.g. Telex messages.

Cryptic codes and abbreviations are surprisingly prevalent in more places than you'd expect. Anyone working with EDI documents in medical or retailers has first hand knowledge.

Certainly. Air transportation just holds particular interest for me, given that the codes and abbreviations reflect historical physical constraints: so-and-so many columns, so-and-so many inches of printable space on a ticket, etc.

(This is also why I find US banking standards interesting[1].)

[1]: https://blog.yossarian.net/2019/12/25/A-shallow-dive-into-th...

Most linters follow the 80 character limit because of the IBM punch card and Unicode and ASCII are also both full of these historical quirks. Many of us deal with these every day. I assume it's the same for people working in the aviation or medical industry

the thing that bugs me the most about all this is all caps

Numerous studies have shown by now that SHOUTING CASE is the slowest to read. Humans read words by their shapes not by individual letters. Capital letters lose the distinctive shapes that their lowercase counterparts often have and thereby also become more ambiguous and error prone

Except that this isn’t really true. Some writing systems lack the ascenders and descenders of the Latin alphabet and reading still happens. Lowercase letters themselves are a late addition to the Latin alphabet. Most readability studies fail the replication test yet they get repeated as if they were scientific facts.

In a sea of lowercase prose, all caps stands out from the rest.

I've always wondered about the IATA meal code CAKE, and what it might have involved.

It sounds like you should take a flight on SAS and find out!

It's a lie.

Add to that (what I understand to be) extortionate data rates for ACARS/ARINC messages, that rival data sent to the Hubble / JWST (if you remember that story from a couple years ago).

UMNR, INFT, CBBG, AVIH, ARNK. Just some off the top of my head.

#3 has RFML - Refugee Meal.

I wonder what that is.

A lot of airlines have done refugee flights at one point or another, so I guess they needed a way to tell the ground crew to load whatever special foods were needed.

What 'special foods' would be needed for refugees?

If they're famine refugees, something like Plumpy'nut[1] maybe. If they're religious refugees, something catering to their religious restrictions. MREs if the refugee operation is being assisted by a military or disaster aid organization. And so forth.

[1]: https://en.wikipedia.org/wiki/Plumpy%27nut

Talking of MREs, some airlines do not allow them as carry on luggage, see https://www.tsa.gov/travel/security-screening/whatcanibring/....

MREs contain a heating packet filled with magnesium pellets and a couple other things, which are used to heat the food when water is added. I'd imagine they don't want those in the cabin, given the gas that is emitted during the heating process.

There's also TBML which is for Tech Bro Meals (soylent, mainly)

Sounds like a backronym

Big Mac Meal.

Bread and water

Given that the only references I can find online appear to be copies of the Wikipedia entry, I’m a bit suspicious.

Two entries were added by an anonymous contributor: CAKE and RFML.

https://en.wikipedia.org/w/index.php?title=International_Air...

It’s a euphemism for Soylent Green.

humble pie

RFML seems from United Airlines, and seems to mean: easy to digest. No egg, no dairy, probably no meat? Its for people from places where food isn't processed or where they had not eaten much for a longer time, so a change in diet content and quantity may be problematic for the passenger.

If you have a citation for that, you should add it to the article.

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