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Comment by jagrsw | Hacker News Reader

Could the accident be linked to the clarity of radio instructions? I saw a discussion suggesting the DH aircraft might have been unsure about the correct runway to use, C1 or C5.

My aim isn't to critique the English proficiency of non-native speakers, especially those from non-Proto-Indo-European linguistic backgrounds. As a non-native English speaker myself, I understand the challenges.

However, I found it trully hard to comprehend the airport's side of the communications due to heavily accented and unclear pronunciation. Shouldn't there be a greater emphasis on air traffic controllers improving their English skills, since English is lingua franca (pun intended) of aviation.

Or perhaps this is irrelevant, considering aviation's global nature. Are pilots expected to adapt to and understand communications with strong accents?

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> Could the accident be linked to the clarity of radio instructions? I saw a discussion suggesting the DH aircraft might have been unsure about the correct runway to use, C1 or C5.

From my comment in part of the discussion thread[0]:

For the ATC, see:

* https://archive.liveatc.net/rjtt/RJTT-Twr-TCA-Jan-02-2024-08...

* Via: https://www.flyertalk.com/forum/35868205-post57.html

13:13 JL516 continue approach. 14:53 landing clearance. 15:01 readback. 15:13 Japan Coast Guard JA772A taxi instructions. 17:35 fire reported on 34R.

* https://www.flyertalk.com/forum/35868237-post67.html

The recording quality isn't very good, perhaps because of the location of the receiver.

The ATC quality of my local airport (CYYZ Tower) available through LiveATC is much better. I following some flying/pilot Youtubers, and their recordings of ATC are also quite good, so I'm not sure why LiveATC at HND is as statically as it is.

[0] https://news.ycombinator.com/item?id=38839885#unv_38841161

All of these ATC feeds are from SDR stations close by that monitor the same frequencies. Your local airport sounds better because someone has a better SDR rig to receive it. Generally the audio is crystal clear in the cockpit and on the ground — it’s just that the SDR stations don’t have as good antennae as the real systems do.

I’ve always wondered about that. When I hear recordings online they’re often so bad I wonder how there aren’t more issues.

That explains it.

Yep, it's a line-of-sight transmission, so in a way the aircraft has the advantage of being a really, really tall antenna.

The volunteers running the feeds around YYZ are at the airport, IIRC. I'm in Halifax now, and the (single) YHZ feeder has had a really hard time finding a new place to set up after he lost his previous location.

There's a "feed setups" thread (or a whole forum) in the LiveATC forums, it's interesting to see how big or small the feeders' setups are!

I know it’ll be a long time coming but wait for the ATC recordings to come out. They’ll be crystal clear.

Antenna quality is unlikely to be a significant factor in audio quality if the stations are actually somewhat close to the airport. The difference between a very good and very poor antenna is maybe 5-7 dB in the VHF airband, which shouldnt noticeably degrade quality unless you are already at the margins of signal availability. Antenna location is going to make a much, much bigger difference.

In addition to what others have said about the quality, pilots and air traffic controllers communicate using a very restricted vocabulary. They aren’t having free-flowing conversations - ATC issues commands using what’s essentially a spoken domain-specific language, and pilots echo them back. Accent should not be a major issue.

It shouldn't, but it has been many times in the past, OTOH in particular with Spanish speaking pilots or ATC miscommunicating.

Given that JAL516 was a domestic flight, it probably was not the case here though.

> the correct runway to use, C1 or C5.

FWIW, C1 and C5 are not runways, but taxiways leading to the runway.

I learned to fly at St Hubert Airport (CYHU) outside of Montreal, where ATC spoke English to English-speaking pilots and French to French-speaking pilots. I lived in Montreal so I knew enough French to get by, but I could never make out more than a few words at the pace and quality of ATC transmissions plus C152 engine noise -- even in a controlled airspace, not overhearing other planes' instructions is a strange feeling.

But those French-speaking pilots probably heard their own instructions clearer than if they'd been in English.

I was feeling bad because I couldn't understand through the accent, which I consider my failure, not theirs.

But I know one can improve understanding with practice, so maybe pilots are just better at it.

There is a very regular sequence of phrases and that helps an enormous amount. I had little trouble understanding the VASA recording (which is surely lower quality than what was actually hitting the cockpit radios). I had a difficult time getting the word "accident", but the part that mattered operationally "the runway is closed" was entirely clear.

If you ring up ATC and tell them “I’m eating a ham and Swiss sandwich” (an entirely non-standard transmission), you’re very likely to get “say again?” regardless of the quality of the radio link or native English pronunciation and accent.

Even transmitting the ordinary items in a different sequence (altitude, route, code, destination, then frequency rather than the expected destination*, route, altitude, frequency, transponder code) will cause confusion.

* technically, clearance limit, but that's most commonly a destination.

There is a ton of static too, why is that still tolerated?

ATC uses AM radio since it behaves well. Two AM broadcasts on the same frequency add in proportion to their strength. Two FM broadcasts tend to cut into each other randomly.

It's a case of AM being the long-term standard, and also being physically suited to the task.

That static is an artifact of the recording device being on the ground, likely without great line of sight to the transmitting antenna which is also near the ground.

Planes to ATC and planes to other planes don’t really have line of sight issues.

That's just an artifact of the (probably amateur) pickup and recording of the signal. The audio quality in the cockpit and tower is surely much better.

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