Re: [SystemSafety] Fwd: Re: Chicago controller halts Delta jet's near-miss....

From: Peter Bernard Ladkin < >
Date: Mon, 22 Jun 2015 07:49:38 +0200

Hash: SHA256

On 2015-06-21 14:58 , Bernd Sieker wrote:
> On 21.06.2015 10:36, Peter Bernard Ladkin wrote:

>> ..... What [Les Chambers] suggest[s] is:

>>> [1] ATC: [call sign] Cleared for takeoff [2] CRW: Cleared for takeoff [call sign] [3] ATC:
>>> [call sign] Affirmative

> The takeoff clearance must also always include the runway; starting somewhere around 2009 ICAO
> phraseology has the runway designation before the "Cleared for takeoff", but that is not
> universally observed. .......
> So, [1] ATC: [call sign] <[further instructions]> <[wind]> [runway designation] Cleared for
> takeoff, [2] <[further instructions]> [runway designation] Cleared for takeoff [call sign]

Yes, you're right - I was modifying Les's suggestion minimally, not delineating correct phraseology. Two points.

  1. ICAO phraseology and US FAA phraseology are by no means identical, although they are similar. I don't seem to have my hand on the FAA phraseology handbooks at present, so I can't check.
  2. Expeditious shortcuts may be taken; Rasmussen's "Migration to the Boundary" (MitB).

At a busy airport, I would have expected ATC: "[call sign] Position and hold RWY XZ" for both aircraft to have been uttered, and in my experience from two decades ago FAA controllers will not necessarily repeat the runway designation if they have already issued such a clearance and can see the aircraft positioned and holding on the designated runway. My mod of Les's suggestion was based on that reasoning.

However, in this case, it seems the controller used the RWY designation and not the call sign. You'd think that was robust, since unambiguous. In particular, since the aircraft were "answering for each other" it is hard to guess what might have helped further.

> Sylvia Wrigley's blog "Fear of Landing" has an interesting page where she has collected some
> known facts (including the relevant snippets from LiveATC) and her own observations:

Good reading!

> As far as we can tell, in this case, [1] is missing the callsign altogether. After both
> acknowledge at the same time, [1] is repeated in a very rapdfire voice.

In my experience, that's normal diction at a busy airport.

It is important to note that cognitive situations like this happen all the time, but almost all of them do not evolve dangerously such as this incident. They are also very hard to investigate if they do. It is difficult to establish with any reliability who understood what when, because people's hindsight into their historical cognitive state is not very reliable.

PBL Prof. Peter Bernard Ladkin, Faculty of Technology, University of Bielefeld, 33594 Bielefeld, Germany Je suis Charlie
Tel+msg +49 (0)521 880 7319

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