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Air Traffic Monitoring => Listener Forum => Topic started by: brendan512 on July 18, 2022, 04:30:13 PM

Title: KORD 27C Curious Go Around 16:35Z today
Post by: brendan512 on July 18, 2022, 04:30:13 PM
Hi All,

Curious about what happened when United 1113 was asked to go around (approx 16:35z) . Something about an aircraft under tow and a system “not liking it?”

Does anyone know what likely happened here?

Title: Re: KORD 27C Curious Go Around 16:35Z today
Post by: frantzy on July 18, 2022, 06:13:38 PM
Here's my interpretation:

At 01:15 into the clip, a service ground tug towing an aircraft (Hughes 5615 if I heard correctly) is cleared to cross rwy 4L on Delta taxiway, which is parallel to / next to 27C.

UAL1113 is told to go around.  They do so but sounded surprised, probably because their landing was going fine and they didn't see any incursion.

As they're being vectored back for landing, the supervisor / other controller offers the explanation they didn't explicitly ask for but probably welcomed (and perhaps their airline would require them to explain, though I'm not an airline pilot so this is pure speculation):  that an automated runway incursion system called for a go-around due to the aircraft under tow (the 5615 tug), which didn't seem like the human controllers or pilots perceived as a threat, but for some reason the automated system did.

If all of the above is true, to me it's a bit like the airplane's traffic collision avoidance system, where the pilots obey a Resolution Advisory, contrary to ATC instructions, and then explain to the controller why once things settle down.   I know KORD is a vast airport with past incursion concerns so I'd bet the warning systems are followed carefully.

Nice find Brendan - I'll be interested to follow if others weigh in to validate or correct my theory.

Title: Re: KORD 27C Curious Go Around 16:35Z today
Post by: diskus on July 19, 2022, 09:26:32 AM
Im trying to find that audio without luck??
Title: Re: KORD 27C Curious Go Around 16:35Z today
Post by: brendan512 on July 19, 2022, 04:01:53 PM
Thanks, @frantzy! Your explanation makes a lot of sense.

Attaching audio and KORD diagram for @diskus and anyone else who would like to weigh in.

01:15 - frantzy false incursion source theory
03:54 - UAL 1113 clearance - fragmented by separate transmission
05:23 - go around
06:10 - explanation

@frantzy, I also noticed that clearance was being given to VV for "crossing traffic" instead of 27C full length. I wonder if something was crossing on Z at the same time and that's what triggered the incursion avoidance system you're describing. Is it possible that activity was taking place on the Ground frequency instead of Tower? I might have a listen even though it seems unlikely/impossible that something so critical would be on a separate frequency.