Forum: aviation.stackexchange.com
Tags: <metar><notam><taf>
Title: Why do NOTAMs consist of code instead of plain language?
Question: I'm currently getting thru a PPL course book and I don't understand this. Is there any purpose of sending NOTAMs in this format:  "RWY 08R/26L DUE WIP NO CENTRELINE, TDZ OR SALS LIGHTING AVBL"  instead of plain language  "For runway 08/26, due to work in progress, there is no centreline, touchdown zone or simple approach lighting available"  Why do they force pilots to learn common ICAO abbreviations when they could simply send the text message without encoding it? The same questions goes for TAFs and METARs.

Answers:
sents: text: The NOTAM format is from the time when people still would call the value of individual bits over a phone line.
text: Ok, that may not have happened, but my point is that data transfer was incredibly slow compared to current day standards.
text: Therefore a compact format saved significant transmission time and cost without losing any information.
text: The format didn't change since.
answer_details: author: aviation.stackexchange.com/users/19/DeltaLima
score: 15
sents: text: 1 - It's always been done that way.
text: 2
text: - You'd be surprised
text: how many government computer systems are still using ancient hardware and operating systems.
answer_details: author: aviation.stackexchange.com/users/36690/Steven Brame
score: 5
sents: text: As I understand your question is mainly about line E of a NOTAM, right?
text: Well, this one is in fact meant to use 'plain' English language, in contrast to all other lines, where location and reach as well as type and urgency and duration is encoded.
text: Just, as it already has been mentioned, NOTAMs originate in a time when transmission speed was unimaginable slow by todays standards.
text: So the answer is rather IT related ... stone age IT that is.
text: Standard transmission speed back then was 45 Baud, that's 45 bit per second -
text: with lots of pauses added for feed and other functions, resulting in an effective transmission speed of less than 8 characters per second (*1).
text: Already the lines before line E contain anywhere between 150 to 200 characters, thus requiring some 25 seconds to transmit.
text: The E line you cite is another 60 characters, or 8 seconds.
text: The suggestion made would now increase that to 129 characters or an additional 9 seconds.
text: With no increase in information transmitted.
text: For a rough calculation it may be safe to assume 1 minute of transmission time per NOTAM.
text: That's barley 60 per hour.
text: And 60 is a rather low number of active NOTAMs within the reach of an aerodrome to be kept at hand for its pilots.
text: Keep in mind, there was no internet and instant access to remote data bases at all.
text: Everything had to be transmited ahead of time - and there where people collecting all incoming NOTAMs and filing them into folders (that's what line A supports) to be up to date and ready for flight planing.
text: So short message length was an essential must to make it transmitable.
text: It wasn't until the 1970s that the situation relaxed a bit due faster transmission - still not much, as at the same time air traffic, and related NOTAMs rose in number.
text: The other limit was introduced by early data processing.
text: The E line is limited to 1200 characters at all.
text: This (back then unimaginable hucht) limit was introduced by the size of disk block on the mainframe system used by.
text: 2048 characters was the limit for a whole block, minus some organisational data, minus all other lines, this left 1200 bytes per NOTAM.
text: Since some even needed more, block chaining for up to 12,000 characters was allowed -
text: not realy liked though.
text: Bottom line, abbreviation was a must due the hardware available.
text: At the same time, these abrevations helped in understanding, the very same way we use extreme codified radio sequences for fast exchange and clear interaction.
text: There is no doubt about the meaning, as every day language may create.
text: This might seam strange, but it's like with any other formalized communication.
text: No matter if its about debates in the commons or ATC communication - or in this case NOTAMs.
answer_details: author: aviation.stackexchange.com/users/36468/Raffzahn
score: 5
sents: text: There used to be a good technical reason (transmission time over low-rate modems), so everyone learned how to decode things.
text: That original reason has long since gone away, but nearly everyone affected has already learned the code, so the short-term benefits of changing are minimal--and accrue mainly to new entrants (who have little/no power) whereas the costs would be borne by everyone.
text: There's also a possible "hazing" effect: if the old timers had to go through something unpleasant, then it can become a ritual part of joining the tribe, regardless of what (if any) practical value it has to newbies.
answer_details: author: aviation.stackexchange.com/users/35166/StephenS
score: 3
sents: text: Because the FAA imagines that we are still in the teletype age, and thus believes that every bit of text not actually burned into the the paper scroll (or perhaps we should say every byte of information not transmitted over the wires) is a precious saving of some sort.
text: It's exactly the same misguided reason that airport weather reports (METARS) are still formatted in the near-unintelligible condensed manner as they are.
answer_details: author: aviation.stackexchange.com/users/34686/quiet flyer
score: 1

Summary of the answers:
NOTAMs originate in a time when transmission speed was unimaginable slow by todays standards. At that time abbreviation was essential because of the hardware. No one it seems has yet decided to update things to suit current technology.
The NOTAM format is a remnant of the time when hardware and IT were much older, so communications were much slower and this format helped save money and time. It could also be argued that the coded language cannot be misinterpreted like every-day language can. Also, to some extent, it has become a ritualistic part of becoming a pilot, despite not having practical value.